Myasthenia gravis (MG) is a prototypical autoimmune disorder characterized by the presence of pathogenic autoantibodies targeting components at the neuromuscular junction. The classical treatment approach has long relied on broad-spectrum immunosuppressive therapies such as corticosteroids, azathioprine, mycophenolate, tacrolimus, and cyclosporine. While effective in many patients, these agents are associated with significant long-term side effects, delayed onset of action, and often require prolonged use, leading to reduced patient compliance and quality of life. With advances in immunology and molecular biology, novel targeted therapies have emerged that aim to disrupt specific immune pathways involved in MG pathogenesis, offering faster clinical response, improved safety profiles, and potential for sustained remission.

Among the most promising developments are complement inhibitors. The terminal complement pathway plays a central role in the destruction of the postsynaptic membrane at the neuromuscular junction. Eculizumab, a monoclonal antibody that binds to C5 and prevents its cleavage into C5a and C5b, has demonstrated significant efficacy in refractory generalized MG. The REGAIN phase 3 trial showed marked improvements in MG-ADL scores, QMG scores, and quality of life measures compared to placebo.SERBP1 Antibody custom synthesis Despite its success, eculizumab carries a risk of meningococcal infection, necessitating prophylactic vaccination. More recently, ravulizumab, a longer-acting C5 inhibitor, allows for dosing every eight weeks, improving patient convenience. Zilucoplan, a subcutaneous C5 inhibitor, has also shown positive results in phase II trials, with dose-dependent reductions in symptom severity and autoantibody levels.

Another class of emerging therapies targets the neonatal Fc receptor (FcRn), which regulates IgG homeostasis. By blocking FcRn, these agents accelerate the degradation of IgG antibodies, including pathogenic autoantibodies in MG. Efgartigimod, a recombinant Fc fragment with high affinity for FcRn, significantly reduces total IgG levels and improves clinical outcomes in multiple phase II and III trials. Similarly, rozanolixizumab and nipocalimab—both humanized anti-FcRn monoclonal antibodies—have demonstrated rapid IgG reduction and clinical benefit in ongoing phase II and III studies. These treatments offer the advantage of subcutaneous administration and a favorable safety profile, with headache being the most common adverse event.

B-cell-targeted therapies represent another major advance. Rituximab, an anti-CD20 monoclonal antibody, has been used off-label with variable success, particularly in MuSK-positive MG. However, it does not affect long-lived plasma cells, limiting its durability.Survivin Antibody Autophagy Next-generation agents like belimumab (anti-BAFF) and anti-CD19 antibodies are under investigation. Belimumab, approved for lupus, failed to show significant benefit in MG in a phase II trial, possibly due to patient selection or disease heterogeneity. Anti-CD19 agents, which target earlier B-cell stages, may offer greater efficacy and synergy with anti-CD20 therapy.

Other innovative approaches include proteasome inhibitors such as bortezomib, which depletes plasma cells by inducing apoptosis through protein misfolding stress.PMID:35136075 Early reports in refractory MG are encouraging but limited by neurotoxicity risks. Chimeric antigen receptor T (CAR-T) cell therapy is being explored in preclinical models for its ability to eliminate autoreactive B cells and memory populations. Hematopoietic stem cell transplantation (HSCT) has shown remarkable results in severe, refractory cases, achieving complete remission in some patients after intensive conditioning regimens.

Subcutaneous immunoglobulin (SCIG) offers a patient-friendly alternative to IVIG for maintenance therapy, providing sustained IgG levels with fewer infusion-related complications. Finally, antisense oligonucleotides such as Monarsen, which modulate acetylcholinesterase splicing, represent a unique non-immunological strategy aimed at enhancing neuromuscular transmission.

In summary, the therapeutic landscape of MG is rapidly evolving. These novel agents provide more precise, effective, and safer options than traditional immunosuppression. While challenges remain—including cost, long-term safety data, and access—these advancements herald a new era in personalized, mechanism-based management of myasthenia gravis.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com

The regulation of cytoskeleton dynamics is essential for fundamental cellular processes such as migration, division, and differentiation. The YAP-TEAD transcriptional complex responds to cell-cell interactions and substrate mechanics, promoting the expression of focal adhesion (FA) genes that contribute to FA-cytoskeleton stability. This activity is crucial in defining the mechanical properties and function of adult cells. However, its role and regulation in human pluripotent stem cells (PSCs) remain poorly understood. Despite growing in dense colonies, human PSCs exhibit sustained basal YAP-driven transcriptional activity, indicating insensitivity to contact inhibition. This inability to perceive cell-cell contact can be restored by modulating the Tankyrase enzyme, which enhances AMOT-mediated inhibition of YAP. Upon germ layer specification, the YAP-TEAD complex is rapidly inactivated—a necessary step for adjusting PSC mechanical properties in response to physiological substrate stiffness. By demonstrating that YAP-TEAD1 targets key genes involved in cytoskeleton dynamics, our findings suggest that substrate mechanics can direct PSC fate by influencing cytoskeletal organization and intracellular tension. We propose that aberrant activation of the YAP-TEAD1 axis impairs PSC potency by suppressing cytoskeletal dynamics, thereby preventing the shape changes required for phenotypic acquisition.

Introduction

During differentiation and organogenesis, cells undergo dynamic changes in shape and size, which are critical for acquiring new identities. These transitions rely on continuous remodeling of the cytoskeleton, guided by interplay between biochemical and mechanical cues from the extracellular matrix (ECM) or neighboring cells. Gradients in intracellular tension within embryos may regulate Yes-associated protein (YAP), a key mechanotransducer. During fetal heart and liver development, YAP ensures proper cell number through controlled proliferation. Dysregulation of YAP or defects in the mechanosensitive Hippo pathway lead to tissue overgrowth, organomegaly, and even embryonic lethality. YAP functions downstream of the Hippo kinase network, integrating mechanical and biochemical signals to translocate into the nucleus and activate gene programs via interaction with stage-specific transcription factors. Our group previously showed that YAP co-transcriptional activity in breast cancer cells is triggered by cell spreading and reinforces cell-matrix adhesion through focal adhesion assembly. However, recent studies question YAP’s role in maintaining embryonic stem cell (ESC) pluripotency—its depletion has minimal effects, while elevated YAP levels promote somatic reprogramming to pluripotency. Transient YAP overexpression in somatic cells reverses maturation toward tissue-specific progenitors. Substrate mechanics regulate adult progenitor fate and differentiated cell function through YAP. Whether YAP is mechanically regulated in human embryos and PSCs—and whether its transcriptional activity can be harnessed to maintain potency or drive lineage specification—remains controversial. Here, we demonstrate that undifferentiated PSCs sustain YAP-TEAD transcriptional activity insensitive to contact inhibition. Manipulating the Tankyrase-AMOT axis restores contact inhibition of YAP nuclear shuttling. Conversely, ECM stiffening activates YAP-TEAD to regulate PSC mechanical properties by controlling cytoskeletal stabilizing proteins. Precise tuning of YAP-TEAD-induced tension is essential during mesoderm specification to enable timely cytoskeletal reorganization needed for identity acquisition.

Materials and Methods

Human iPSC line DF 19-9-7T (karyotype: 46, XY) was obtained from WiCell (Madison, WI, USA). STENF iPSC line was provided by Prof. I. Koutna (Masaryk University, Brno, Czech Republic). YAP knockout (YAP−/−) and isogenic H9 (WT or CTR) human embryonic stem cell lines were kindly supplied by Miguel Ramalho-Santos and Han Qin. Cells were maintained undifferentiated on Matrigel Growth Factor Reduced (1:100 in DMEM/F12, Corning, NY, USA) in Essential 8™ Medium (Thermo Fisher Scientific, Waltham, MA, USA) supplemented with penicillin/streptomycin (0.5%, VWR). Mesoderm and cardiac differentiation followed Lian et al.’s protocol with minor modifications. Briefly, PSC colonies were dissociated using TrypLE Select (Thermo Fisher Scientific) and re-seeded at 2.0 × 10⁵ cells/cm² onto Matrigel-coated plates in complete medium containing Rock inhibitor Y27632 (2.5 µM, Selleck Chemicals, Houston, TX, USA). After 24 hours, media were replaced daily until confluence. At day 0, media were switched to mesoderm induction medium: RPMI 1640 (Sigma-Aldrich, St. Louis, MO, USA) with penicillin/streptomycin, L-glutamine (2 mM, Biowest, Riverside, MO, USA), B-27 supplement minus insulin (1×, Thermo Fisher Scientific), and CHIR99021 (8 µM, Sigma-Aldrich). At day 2, medium was replaced with RPMI/B-27 minus insulin (+B-27 – Ins) plus IWP-2 (5 µM, Selleck Chemicals). At day 4, medium was changed to RPMI + B-27 minus insulin every other day until beating began. Once beating started, B-27 plus insulin (+B-27 + Ins) was added and refreshed every 2–3 days. Trilineage differentiation assays used a Human Pluripotent Stem Cell Functional Identification Kit (R&D Systems, Minneapolis, MN, USA). Undifferentiated iPSCs/hESCs (0.5 × 10⁵/cm²) were plated and after 48 hours exposed to ectoderm, endoderm, or mesoderm induction media per manufacturer’s instructions. For drug treatments, iPSCs at day 0 of differentiation were treated with Leptomycin B (20 nM, Sigma-Aldrich) for 24 hours before qPCR or immunofluorescence analysis. hESCs were stimulated with jasplakinolide (50 nM, Thermo Fisher Scientific), WNT3A (1 nM, R&D Systems), or XAV939 (10 µM, Absource Diagnostics, Munich, Germany) for 24–48 hours in undifferentiated medium for AFM or RT-qPCR analysis. CAL51 and YAP−/− CAL51 cell lines were cultured as previously described [17]. All cell lines were regularly tested for mycoplasma contamination.

Micropatterned Cell Culture

CYTOOchips™ ARENA glass coverslips (CYTOO, Grenoble, France) with circular micropatterns (140, 225, 500, 1000 µm) were activated with Poly-L-Lysine Hydrobromide (40 g/mL, Sigma-Aldrich) in distilled water (1 mL) for 2 hours at room temperature, then coated with diluted Matrigel (1:100 in PBS) overnight at 37°C. Undifferentiated PSCs (2 × 10⁶ cells/coverslip) were seeded without drying the surface. After 48 hours in complete medium, or medium supplemented with XAV939, cells were analyzed by immunofluorescence. Detailed methods are available in the Supplemental Materials section.

Results

YAP-TEAD1 Axis Controls PSC Mechanics Independent of Cell-Cell Contact

YAP nuclear activity is sensitive to substrate stiffness and negatively regulated by cell-cell contact in many adult cell types. In such cells, nuclear YAP localization occurs on substrates stiffer than 0.5 kPa or 5 kPa. In contrast, human embryonic stem cells (hESCs) and induced pluripotent stem cells (iPSCs) grow in compact, high-density colonies where YAP remains predominantly nuclear despite high cell density (Supplementary Fig. 1a). We cultured iPSCs on micropatterned surfaces allowing precise control of colony size (140, 225, 500, 1000 µm) and cell density, comparing YAP localization to adult human mesenchymal stem cells (hMSCs) and dermal fibroblasts (hNDFs) grown at similar densities. iPSC density inversely correlated with colony area (Fig. 1a), and YAP was primarily nuclear, colocalizing with pluripotency markers NANOG, OCT4, and β-CATENIN (Supplementary Fig. 1b). YAP localization was independent of position within iPSC colonies but affected by density in hMSCs and hNDFs (Fig. 1c, d). Luciferase assay confirmed reduced YAP-TEAD transcriptional activity in dense cultures of adult cells, consistent with nuclear exclusion (Supplementary Fig. 1c). In contrast, PSCs maintained uniform YAP-TEAD activity across all micropatterned colonies regardless of density, as shown by mCherry reporter expression under YAP-TEAD promoter (Fig. 1e). These data indicate sustained YAP activation in PSCs, raising questions about its functional role. We performed chromatin immunoprecipitation followed by sequencing (ChIP-seq) on endogenous YAP in iPSCs, identifying 5,208 unique binding sites, mostly in intergenic and intronic regions (Supplementary Fig. 1d, e; Supplementary Table 1). Bioinformatics analysis revealed novel transcription factors interacting with YAP in PSCs not previously reported in adult cells (Fig. 1f). TEAD1 and TEAD4 motifs were most enriched near YAP peaks (Fig. 1g). Density of TEAD-binding motifs within 500 bp of YAP peaks and co-immunoprecipitation confirmed physical interaction between YAP and TEAD in iPSCs (Fig. 1h). TEAD family accounts for ~78% of YAP co-transcriptional regulation in adult cells. Notably, TEAD proteins remained nuclear regardless of PSC density (Supplementary Fig. 1f). Our previous work showed YAP-TEAD regulates adult cell mechanics by reinforcing ECM interaction [17, 30]. Using atomic force microscopy (AFM), we measured single iPSC stiffness following transfection with YAPS127A (constitutively active via TEAD) or YAP-5SA/S94A (transcriptionally active but unable to bind TEAD), and GFP. Cells overexpressing TEAD-dependent mutant were significantly stiffer (5300 ± 3553 vs. 2466 ± 1666 kPa) than those transfected with TEAD-independent mutant or GFP control (1677 ± 1287 kPa). The TEAD-independent mutant also caused a modest but significant increase in Young’s Modulus (Fig. 1i). Given TEAD1 and TEAD4 play distinct roles in development [31, 32], we asked which isoform drives PSC stiffening after YAP overexpression. We ectopically expressed TEAD1 or TEAD4 in CTR or YAP−/− hESCs. Compared to GFP control (ECTR-GFP = 4170.0 ± 891.7 Pa), TEAD1 overexpression significantly increased Young’s Modulus (ECTR-TEAD1 = 6466.08 ± 1131.70 Pa), while TEAD4 had no significant effect (ECTR-TEAD4 = 4310.21 ± 919.63 Pa). No effect was observed when TEAD1 or TEAD4 were transfected into YAP−/− hESCs (EKO-GFP = 2894.0 ± 308.9 Pa; EKO-TEAD1 = 3056.2 ± 206.9 Pa; EKO-TEAD4 = 2988.1 ± 150.6 Pa) (Fig. 1j). We further probed elasticity across different positions within colonies and found no significant differences between center (Ecentre = 4620 ± 3622 Pa) and edge (Eedge = 4510 ± 3380 Pa) (Fig. 1k). In contrast, confluent adult cells showed significantly reduced mechanics (Econfluent = 8078 ± 4275 Pa vs. Esparse = 17,726 ± 4279 Pa) (Supplementary Fig. 1g). These results suggest YAP-TEAD1 activity supports PSC mechanical properties independently of cell-cell contact.

Contact Inhibition of YAP-TEAD1 Transcriptional Activity Is Restored by AMOT Downstream of Tankyrase

Next, we sought to uncover the molecular mechanism behind YAP restriction in confluent adult/differentiated cells, absent in PSCs. Using PSC-derived cardiomyocytes (Supplementary Fig. 2a) as a model of differentiated cells capable of regulating YAP localization [34] (Supplementary Fig. 2b), we searched for YAP-negative upstream regulators exclusively expressed in the differentiated state. Differentiation was confirmed by downregulation of pluripotency genes and upregulation of early and late cardiac markers (Supplementary Fig. 2c–e), along with Hippo pathway modulation (Supplementary Fig. 2f). Among negative YAP regulators, Angiomotin (AMOT), AMOTL2, DCHS1, and FAT4 were consistently upregulated during cardiac differentiation (Supplementary Fig. 2g). The list of significantly regulated genes in day 0 hESCs versus day 15 cardiomyocytes is provided in Supplementary Table 2. RT-qPCR confirmed upregulation of AMOT, AMOTL2, FAT4, DCHS1, AMOTL1, and NF2 in both day 15 and day 30 cardiomyocytes compared to undifferentiated cells (Supplementary Fig. 3a, b). Parallel immunoprecipitation of endogenous YAP in undifferentiated iPSCs (day 0) and iPSC-derived beating cardiomyocytes (day 15) followed by mass spectrometry identified 146 YAP interactors at day 0 and 76 at day 15, with only ten common to both stages (Fig. 2a). Focusing on the 66 unique interactors in day 15 cardiomyocytes, we identified AMOT as the primary YAP-negative regulator absent in undifferentiated cells (Fig. 2b). AMOTL1 and AMOTL2 were also detected in undifferentiated iPSCs, while FAT4, NF2, and DCHS1 were not found in either condition, likely due to weak or indirect interactions. A schematic of YAP interactomes in iPSCs and cardiomyocytes is shown in Supplementary Fig. 4. The p130-AMOT isoform was recently shown to restrict YAP nuclear presence in adult cells and during PSC neural differentiation [35, 36]. Western blotting revealed accumulation of p130 and p80 AMOT isoforms at day 2, 5, and 15 of cardiac differentiation, paralleled by YAP phosphorylation (Fig. 2c). We next tested whether AMOT could restore YAP sensitivity to cell contacts in PSCs and affect their mechanics. We stably expressed p130-AMOT in YAP-TEAD-mCherry hESCs, achieving twofold mRNA overexpression—similar to threefold increase seen during differentiation (Supplementary Fig. 3b). We also expressed p130-AMOT-Y242/287A (1.8-fold), a mutant unable to bind YAP [36]. Checking mCherry fluorescence, we observed that p130-AMOT re-expression—but not the mutant—reduced YAP-TEAD transcriptional activity in confluent hESCs (Fig. 2d). To confirm AMOT’s role independently, we exploited the fact that Tankyrase regulates p130-AMOT degradation, so Tankyrase inhibitors stabilize AMOT and inhibit YAP [37]. Treating hESCs with XAV939 increased AMOT protein levels and promoted YAP cytoplasmic retention (Fig. 2e). Indeed, XAV939 treatment led to p130-AMOT accumulation in PSC nuclei and reduced both nuclear and cytoplasmic YAP (Fig. 2f). Finally, we measured stiffness in hESCs transduced with p130-AMOT, p130-AMOT-Y242/287A mutant, or treated with XAV939. PSCs with restored p130-AMOT function showed significantly reduced stiffness, consistent with inhibited YAP activity, while the mutant had no effect (ECTR: 2148 ± 837.3 Pa; Ep130-AMOT: 1131 ± 280.7 Pa; Ep130-AMOT-Y242/287A = 2030 ± 224.7 Pa; EXAV939 = 553.6 ± 240.2 Pa; Fig. 2g). Together, these results suggest increased AMOT degradation in PSCs contributes, at least partially, to their reduced ability to regulate YAP via cell-cell contact.

YAP-TEAD1 Control Over Cytoskeleton-Related Genes Mediates PSC Stiffening in Response to Substrate Rigidity

We quantified mCherry fluorescence in YAP-TEAD-mCherry hESCs cultured on soft PDMS-coated surfaces (0.5 kPa), then switched to 2, 20, or 64 kPa substrates (Fig. 3a). YAP-TEAD activity was unaffected by switching from 0.5 to 2 or 20 kPa (mCherry₀.₅kPa = 45.2 ± 3.9%; mCherry₂kPa = 41.6 ± 1.1%; mCherry₂₀kPa = 40.5 ± 1.0%). However, a significant increase in mCherry-positive cells was observed on 64 kPa (mCherry₆₄kPa = 75.5 ± 3.8%, Fig. 3b). These data suggest YAP-TEAD1 activation in PSCs occurs only on very stiff substrates (E > 20 kPa), unlike somatic cells where the threshold is around 0.5–5 kPa [29]. We asked whether this delayed activation altered PSC mechanics. hESCs on 60 kPa were significantly stiffer than those on softer substrates (E₆₄kPa = 2112.26 ± 601.54 Pa; E₂₀kPa = 1239.70 ± 298.57 Pa; E₂kPa = 1170.90 ± 350.33 Pa), which did not differ significantly among themselves. YAP−/− hESCs were significantly softer than isogenic controls and failed to respond to substrate stiffening (E₆₄kPa = 593.74 ± 242.27 Pa; E₂₀kPa = 599.43 ± 149.29 Pa; E₂kPa = 753.52 ± 121.26 Pa), confirming YAP-TEAD1 mediates substrate stiffness-dependent mechanical adaptation in PSCs (Fig. 3c). Cell nanoscale stiffness correlates with F-actin bundle accumulation during breast cancer dissemination [38]. We stained F-actin in control hESCs on increasing stiffness substrates and found higher actin fiber organization paralleled increased stiffness. In contrast, YAP mutant cells showed no actin response to substrate stiffening (Fig. 3d). YAP-depleted cells lost cortical actin and disrupted apico-basal polarity (Fig. 3e). Perinuclear actin caps were disorganized, and monolayer thickness decreased. Reintroducing YAP into knockout hESCs restored F-actin organization similar to isogenic controls (Fig. 3e, Supplementary videos 1–3). This phenotype was recapitulated by treating PSCs with XAV939 (Fig. 3f), which inhibits YAP-TEAD1 and reduces hESC stiffness (see Fig.DSG3 Antibody supplier 2e, f).67469-78-7 Biological Activity As expected, YAP reintroduction restored elastic modulus (ECTR = 2148 ± 873.PMID:35259013 3 Pa; EYAP−/− = 648.7 ± 227.6 Pa; ERESCUE = 1642 ± 317.2 Pa) (Fig. 3g). We next identified YAP-TEAD1 transcriptional targets responsible for PSC mechanics (Fig. 3h). YAP regulates F-actin polymerization genes in murine heart [39]. We performed differential RNA-seq on YAP−/− and isogenic hESCs cultured on soft (0.5 kPa) or stiff (64 kPa, TCPS) substrates. Gene regulation by substrate stiffness increased with stiffness (0.5 kPa: 2299; 64 kPa: 2796; TCPS: 4825) (Fig. 3i), with TCPS and 64 kPa sharing more regulated genes than 0.5 kPa (Fig. 3j). We selected genes annotated for cytoskeleton organization (GO:0007010) physically bound by YAP in iPSC ChIP-seq on TCPS, and significantly regulated in YAP−/− hESCs on stiff vs. soft surfaces. Data from ChIP-seq and RNA-seq are in Supplementary Tables 1, 4 and Supplementary Fig. 5a, b. Matching these with quantitative TMT-MS data on cytoskeleton-bound proteins revealed 266 differentially regulated cytoskeletal proteins (>1.5-fold) in YAP-depleted cells out of 6014 total proteins (Supplementary Table 5). Among them were known cytoskeleton regulators: TRAF2 and NCK-interacting kinase (TNIK) [39], P21 (RAC1) Activated Kinase (PAK1) [40], Thy-1 Cell Surface Antigen (THY1) [41, 42], and Neurofilament Medium [43], upregulated 1.55, 1.54, 1.62, and 1.82 fold respectively. Midline 1 (MID1) [44] was downregulated 1.7-fold in the absence of YAP. Bioinformatics confirmed all identified genes harbor TEAD1-binding sites in enhancers or promoters (Fig. 3l). We hypothesize that altered expression of these key cytoskeletal proteins prevents YAP-depleted PSCs from assembling cortical actin promptly and responding to substrate stiffening. To test this, we forced actin polymerization in YAP-depleted and isogenic hESCs using jasplakinolide [45], then mapped stiffness via AFM. Control cells treated with jasplakinolide became significantly stiffer than untreated controls. However, YAP-deficient cells failed to stiffen (Fig. 3m), confirming that YAP-TEAD1-dependent gene expression is essential for actin-driven mechanical adaptation.

YAP-TEAD1-Driven Cell Stiffening Correlates with Intracellular Tension and Determines Contractility

We investigated whether mechanical properties correlate with tension propagated through FAs via F-actin. We transiently transfected YAP−/− and isogenic Cal51 cells with a Förster Resonance Energy Transfer (FRET) vinculin tension sensor [47]. YAP−/− cells exhibited lower elastic modulus than isogenic controls (Fig. 4a) and higher FRET index, indicating reduced mechanical tension at FAs (Fig. 4b, c). Intracellular tension is transmitted through FAs to the ECM and measurable via traction force microscopy [48]. We seeded Paxillin-GFP YAP−/− Cal51 cells and their isogenic control onto poly-acrylamide gels (15 kPa) embedded with fluorescent microbeads (Fig. 4d). Median stress was calculated from microbead displacement, revealing YAP-depleted cells generated less force than controls (Fig. 4e). These results indicate that soft YAP-depleted cells have reduced intracellular tension and limited capacity to exert force on the ECM.

YAP-TEAD1-Guided Cytoskeleton Remodeling Is Needed for Mesoderm Specification

Cytoskeleton integrity is crucial for PSC [49], MSC [1, 11, 50], and keratinocyte differentiation [51]. We asked whether cytoskeletal changes associated with YAP-TEAD1 inactivation would influence PSC specification. YAP-TEAD-mCherry reporter hESCs undergoing trilineage specification showed a consistent drop in mCherry signal regardless of lineage (ectoderm: 19.04 ± 2.0%; mesoderm: 27.04 ± 5.8%; endoderm: 4.5 ± 1.2%) compared to undifferentiated controls (74.6 ± 5.5%, Fig. 5a). Moreover, YAP mutant cells were more prone to acquire mesoderm and endoderm markers upon stimulation, while ectoderm specification remained unchanged (Fig. 5b). RT-qPCR confirmed YAP involvement in mesoderm lineage, showing increased EOMES and T RNAs in YAP−/− cells (Fig. 5c). We focused on YAP-TEAD1’s role in cytoskeletal remodeling and intracellular tension during mesoderm specification. Comparing F-actin arrangement in CTR and YAP−/− cells before (day 0) and during mesoderm induction (day 2), we observed cortical actin (typical of undifferentiated cells) replaced by stress fibers during specification. Mesoderm-induced cells were significantly smaller and elongated (Fig. 5d). When we triggered mesoderm specification in isogenic and YAP−/− hESCs treated with jasplakinolide, isogenic cells lost ability to express mesoderm markers EOMES, T, and MESP1 (Fig. 5e). YAP−/− cells remained unaffected (Fig. 5f). Transfecting iPSCs with YAPS127A or YAP-5SA/S94A, which differentially regulate tension and stiffness (see Fig. 1j), and inducing mesoderm specification revealed that stiffer YAP-S127A-transfected PSCs showed reduced expression of mesoderm genes EOMES, T, and MESP1, while YAP-5SA/S94A cells showed only reduced T (Fig. 5j and Supplementary Fig. 7a). This result was mimicked by Leptomycin B treatment, which causes YAP nuclear retention (Fig. 5g, Supplementary Fig. 7b). These findings indicate that sustained YAP-TEAD1 activation impedes mesoderm specification by disrupting the fine-tuned cytoskeletal remodeling required for lineage commitment (Fig. 5h).

Discussion

The role of YAP in PSC maintenance and differentiation remains debated [18–21]. Here, we show that YAP-TEAD transcriptional activity is sustained in PSCs and insensitive to contact inhibition, yet promptly repressed during cell specification. Like in adult cells [17], YAP drives PSC stiffening mainly via TEAD1. TEAD-independent transcription also induces mild but significant stiffening, likely due to other transcription factor binding domains in stiffening-related genes. As YAP cannot sense cell-cell contact, PSC colonies remain mechanically homogeneous—a feature distinguishing them from adult cells, which adjust rigidity based on density. Adult cells in dense colonies are softer than sparse ones. YAP-TEAD responsiveness to substrate mechanics also differs: PSCs exhibit delayed sensitivity, with YAP nuclear shuttling threshold above 20 kPa—far higher than in adult cells [12, 28]. This reduced sensitivity to substrate stiffness and cell-cell contact may serve as a protective mechanism against mechanical stress in embryonic cells. Given this unique response, we searched for exclusive upstream regulators absent in pluripotent cells but active in differentiated ones. YAP-TEAD activity decreases during cardiac maturation, enabling cardiomyocytes to restrict YAP nuclear entry [15]. Using PSC-to-cardiomyocyte differentiation, we identified the Tankyrase-AMOT axis as the missing link preventing YAP inhibition downstream of cell-cell contact in PSCs. Tankyrase maintains low AMOT levels in PSCs, preventing AMOT from binding and inhibiting YAP. Ectopic expression of p130-AMOT or pharmacological inhibition of Tankyrase reduced YAP activity and induced cell softening. A similar role for AMOT was reported in PSC neural commitment [36], and Tankyrase inhibitors stabilize AMOT to suppress YAP in tumor cells [37]. However, these inhibitors have broad activities, leaving open the possibility of additional pathways (e.g., Wnt, Akt) being involved. Breast cancer cell stiffening correlates with F-actin bundle accumulation [38]. YAP has been linked to tumor spread and poor prognosis [52], and contributes to gastric cancer cytoskeleton remodeling [53]. Direct regulation of cytoskeletal genes by YAP was suggested in murine heart [54]. We found PSC stiffening in response to physiological substrate rigidity depends on YAP-TEAD1-driven transcription of key cytoskeletal genes. Among them, YAP-TEAD1 represses TNIK, which disrupts F-actin structure and affects ARP2/3 complex activity controlling cortical actin architecture in ESCs [55, 56]. Combined with dysregulation of THY1, PAK1, and MID1 [40, 44], TNIK upregulation in YAP-depleted cells explains their disorganized cytoskeleton, reduced intracellular tension, and impaired contractile force. Alongside established evidence that YAP activation responds to F-actin integrity, our data reveal a positive feedback loop reinforcing cytoskeletal stability through YAP-TEAD1 transcriptional activity. This loop may involve both YAP and its paralog TAZ [57]. Although YAP and TAZ act redundantly in some adult cell types [11], we observed only a slight decrease in TAZ levels on very stiff substrates after YAP depletion. Further studies are needed to clarify TAZ’s role in pluripotent cells. F-actin dynamics are critical for cell differentiation [49–51]. Mesoderm cells are smaller and elongated due to stress fibers, unlike undifferentiated PSCs with regular cortical actin. We show that cytoskeletal remodeling during PSC specification requires YAP-TEAD1 deactivation and can be blocked by increasing intracellular tension or artificially inhibiting actin remodeling (Fig. 6). These findings deepen our understanding of mechanical regulation of PSC phenotype and function, highlighting a specialized mechanosensing mechanism in PSCs in response to ECM stiffness and cell-cell contact.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com

The discovery of novel inhibitors targeting human DNA methyltransferase 3A (DNMT3A) represents a significant advancement in epigenetic drug development. This study reports the identification of two structurally related small molecules—pyrazolone-based inhibitor 1 and pyridazine-based inhibitor 2—from a screening campaign using the Medicines for Malaria Venture (MMV) Pathogen Box, a library of 400 drug-like compounds with known bioactivity against neglected tropical disease pathogens. These compounds exhibit low micromolar inhibition of DNMT3A, with Ki values ranging from 3.7 to 18 µM against AdoMet and 11 to 41 µM against poly dI-dC. Kinetic analysis revealed that both inhibitors follow a mixed-type or uncompetitive inhibition pattern with respect to both DNA and AdoMet, suggesting allosteric binding outside the enzyme’s active site. This mechanism distinguishes them from classical nucleoside-based inhibitors such as decitabine and azacitidine, which function via irreversible incorporation into DNA and active-site blockade.

Importantly, these inhibitors demonstrate high selectivity for DNMT3A over DNMT1 and bacterial DNA methyltransferases. Inhibition assays conducted on full-length DNMT3A, its catalytic domain (DNMT3A_CD), maintenance DNMT1, and the bacterial enzyme M.SssI confirmed that neither compound significantly inhibits M.SssI even at 60 µM, while showing moderate to strong inhibition of DNMT3A. Notably, inhibitor 2 displayed greater selectivity for DNMT3A over DNMT1 compared to inhibitor 1, maintaining this preference even at high concentrations. The observation that both compounds are more potent against the isolated catalytic domain than the full-length protein suggests that the large N-terminal regulatory region may sterically hinder access or alter conformational dynamics required for effective inhibition.PSCA Antibody Cancer

These findings highlight a promising new class of non-nucleoside DNMT3A inhibitors with potential for targeted therapy in cancers characterized by aberrant de novo methylation, particularly acute myeloid leukemia (AML), where DNMT3A mutations are prevalent.Cortactin Antibody Purity By selectively modulating de novo methylation without disrupting maintenance methylation mediated by DNMT1, these agents could reduce off-target toxicity associated with current therapies.PMID:34904792 Furthermore, their allosteric mode of action opens avenues for developing highly specific inhibitors that exploit unique structural features of DNMT3A, including its tetrameric assembly and regulatory domains. Given the extensive analogs already described for these scaffolds, future optimization efforts are well-positioned to enhance potency, pharmacokinetics, and therapeutic index. This work underscores the value of repurposing existing chemical libraries for epigenetic target discovery and paves the way for next-generation DNMT3A-directed therapeutics with improved safety profiles.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com

Sepsis remains a critical challenge in both human and veterinary medicine, demanding rapid and accurate diagnostic tools. Procalcitonin (PCT) has emerged as a highly specific biomarker for bacterial infection and sepsis severity, yet its detection in veterinary species is hindered by the lack of validated assays. Current methods rely on immunoassays using human antibodies, which are not optimized for animal-specific applications. This study presents the development of two novel antibody-free biosensors based on molecularly imprinted polymers (MIPs) for the real-time, label-free quantification of canine and equine PCT using surface plasmon resonance (SPR) technology. The functional monomers dopamine (DA) and norepinephrine (NE) were employed to fabricate MIP films on gold SPR chips. Among them, polynorepinephrine (PNE) demonstrated superior performance due to enhanced binding affinity, selectivity, and lower non-specific adsorption compared to polydopamine (PDA). Optimization of buffer conditions enabled successful calibration of both canine (cPCT) and equine (ePCT) PCT in phosphate buffer, with linear ranges from 25 to 1000 ng mL⁻¹. The PNE-based biosensor achieved limits of detection (LOD) of 15 ng mL⁻¹ for ePCT and 30 ng mL⁻¹ for cPCT, along with excellent reproducibility (CVav% = 4.5% for dog plasma, 11.0% for horse plasma). Notably, the biosensors retained high sensitivity and specificity even in complex biological matrices after surface passivation with mercaptohexanol and mercaptoundecanol, which minimized matrix effects. Cross-reactivity tests revealed that while the cPCT-imprinted MIP showed some recognition of ePCT, likely due to sequence homology, the ePCT-imprinted MIP exhibited high specificity, indicating distinct imprinting behavior driven by PNE’s molecular orientation during polymerization. These findings highlight the potential of PNE-based MIPs as robust, reusable, and cost-effective synthetic receptors for veterinary diagnostics. The developed platform offers a promising alternative to conventional ELISA kits, particularly for equine PCT detection where no specific antibodies are available. Future work will focus on epitope-based imprinting strategies to create universal MIPs capable of detecting PCT across multiple species, paving the way for low-cost, scalable, and field-deployable biosensing solutions in clinical veterinary practice.

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**Performance Evaluation of Polynorepinephrine-Imprinted SPR Biosensors in Animal Plasma Matrices**

The transition from controlled buffer environments to real-world biological samples is a crucial step in validating biosensor reliability. This study evaluates the performance of polynorepinephrine (PNE)-based molecularly imprinted polymer (MIP) biosensors in canine and equine plasma, assessing their applicability under clinically relevant conditions. Initial experiments revealed a significant matrix effect in untreated blank plasma, where non-specific interactions led to elevated background signals despite negligible binding of common serum proteins like albumin. To mitigate this issue, a surface passivation strategy was implemented using medium-short aliphatic thiols—mercaptohexanol and mercaptoundecanol—covalently immobilized onto the PNE film. This modification significantly enhanced hydrophilicity and reduced unspecific protein adsorption, resulting in a nearly tenfold decrease in background noise. Following passivation, calibration curves were established by spiking recombinant cPCT and ePCT into pooled species-specific plasma at concentrations ranging from 25 to 1000 ng mL⁻¹. After filtration and 1:10 dilution in TBST buffer, the biosensors demonstrated linear responses across the tested range. For equine PCT, the sensor maintained a high correlation coefficient (R² = 0.985), with LOD and LOQ values of 15.0 ± 0.6 ng mL⁻¹ and 50.0 ± 1.9 ng mL⁻¹, respectively—comparable to performance in buffer. In contrast, canine PCT detection in plasma showed a reduced slope and higher LOD (30.SERPINE2 Antibody Description 0 ± 0.9 ng mL⁻¹) and LOQ (99.5 ± 3.2 ng mL⁻¹), suggesting greater interference from canine plasma components. However, the R² value remained strong at 0.992, confirming reliable quantification. Reproducibility was consistently high, with average coefficients of variation below 12%. These results demonstrate that the PNE-MIP biosensors can effectively detect PCT in complex plasma matrices when properly passivated, making them suitable for clinical use. Importantly, the improved signal-to-noise ratio enables accurate measurement even at low analyte levels, which is essential for early sepsis diagnosis.ASC Antibody custom synthesis Furthermore, the sensors exhibited long-term stability, remaining functional after storage at 4 °C for over six months.PMID:34663196 This durability, combined with reusability over hundreds of cycles, underscores their practicality for routine veterinary testing. The ability to bypass the need for species-specific antibodies also reduces costs and turnaround time. These findings validate the biosensors’ robustness and readiness for integration into point-of-care systems, offering a transformative approach to sepsis monitoring in veterinary clinics.

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**Advantages and Clinical Implications of PNE-Based MIP Biosensors for Veterinary Sepsis Diagnosis**

The development of polynorepinephrine (PNE)-based molecularly imprinted polymer (MIP) biosensors marks a pivotal advancement in veterinary diagnostics, particularly for sepsis detection through procalcitonin (PCT) analysis. Unlike traditional immunoassays that depend on expensive, unstable, and species-limited antibodies, these biosensors utilize synthetic receptors engineered via molecular imprinting, offering unmatched advantages in cost, stability, and versatility. PNE emerges as an ideal functional monomer due to its redox-active catechol group, enabling self-polymerization and strong adhesion to diverse surfaces, including gold SPR chips. More importantly, PNE-derived MIPs exhibit superior analytical performance: they achieve higher binding affinity, lower non-specific adsorption, and better reproducibility than those derived from dopamine (DA). This translates into detection limits as low as 15 ng mL⁻¹ for equine PCT and 30 ng mL⁻¹ for canine PCT—levels competitive with or surpassing commercial ELISA kits. A key innovation lies in the surface passivation step using thiol compounds, which effectively minimizes matrix effects in plasma, allowing reliable quantification in real samples without extensive sample pre-treatment. The biosensors show excellent linearity and precision in both buffer and plasma, with CVav% values well within acceptable clinical thresholds. Crucially, the ePCT-imprinted sensor demonstrates exceptional specificity, indicating that PNE facilitates selective cavity formation tailored to the equine protein structure. This is especially significant given the absence of validated anti-equine PCT antibodies. Moreover, the sensors are reusable and stable for extended periods, reducing operational costs and enabling high-throughput screening. From a clinical perspective, these biosensors provide a rapid, label-free, real-time method for assessing sepsis severity in dogs and horses—conditions where timely intervention drastically improves survival rates. They represent a major leap toward accessible, affordable, and accurate diagnostics in veterinary medicine, bridging the gap between research tools and clinical utility. Future applications may include integration into portable devices or microfluidic platforms, supporting decentralized testing in field clinics and mobile veterinary units. Ultimately, this technology paves the way for a new generation of antibody-free biosensors capable of addressing unmet diagnostic needs across animal species.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com

This study presents a comprehensive investigation into the inhibitory mechanism of 5-methoxy-2-mercaptobenzimidazole (5-M-2-MB) on tyrosinase, utilizing multiple biophysical and computational approaches. The compound demonstrated potent inhibition with an IC50 value of 60 ± 2 nM, indicating high efficiency. Kinetic analysis revealed that 5-M-2-MB acts as a reversible and competitive inhibitor, with a Ki value of 80 ± 1 nM. This suggests that the inhibitor competes directly with the substrate for binding at the active site of tyrosinase without permanently altering enzyme structure.

Fluorescence quenching experiments showed that 5-M-2-MB significantly reduces the intrinsic fluorescence of tyrosinase through a static quenching mechanism, implying the formation of a non-fluorescent complex between the inhibitor and the enzyme. The Stern-Volmer analysis confirmed temperature-dependent quenching behavior, supporting the static model. Furthermore, the binding constant (KA) and number of binding sites (n) were determined to be approximately 1.45 × 10³ L/mol and 1.49, respectively, indicating a single dominant binding site on the enzyme surface.

ANS-binding assays revealed that 5-M-2-MB increases the hydrophobicity of tyrosinase, suggesting conformational changes upon inhibitor binding. This was corroborated by a blue shift in the fluorescence emission maximum, which reflects alterations in the microenvironment around tryptophan residues. Thermodynamic parameters derived from the Van’t Hoff equation indicated that the interaction is spontaneous (negative ΔG), exothermic (negative ΔH), and driven primarily by hydrogen bonding and hydrophobic interactions (positive ΔS).

Energy transfer analysis based on Förster theory confirmed non-radiative energy transfer from tyrosinase to 5-M-2-MB, with a calculated distance (r = 2.51 nm) less than the critical Förster distance (R₀ = 3.12 nm). This supports close proximity between the donor and acceptor during complex formation. Molecular docking simulations further validated these findings, showing that 5-M-2-MB binds deeply within the active site cavity of tyrosinase, forming hydrogen bonds with Thr-308, Glu-356, and Asp-357, and hydrophobic interactions with Trp-358 on the A chain. These specific interactions stabilize the inhibitor-enzyme complex and hinder substrate access.BMPR-II Antibody Purity

Importantly, no significant effect was observed on dopaquinone stability when 5-M-2-MB was added, confirming that the inhibition occurs primarily through direct enzyme targeting rather than product interference.OGT Antibody custom synthesis Collectively, this work provides strong evidence that 5-M-2-MB functions as a highly effective, reversible, competitive tyrosinase inhibitor through precise molecular interactions involving both polar and non-polar forces.PMID:35122574 These insights offer a solid foundation for the rational design of novel anti-browning agents and potential therapeutic applications in hyperpigmentation disorders.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com

The roots of Lindera glauca, a traditional medicinal plant used in East Asian herbal medicine, have been the focus of extensive phytochemical investigations due to their rich content of bioactive natural products. In this study, nine new compounds were isolated from the methanol extract of L. glauca roots, including cyclopentanone A (1), subamolides F and G (2 and 3), secosubamolide F (4), rupestonic acids J–L (5–7), and linderaguaianols A and B (8 and 9). Among them, compound 1 stands out as a rare example of a five-membered cyclopentane ring fused to a ten-carbon aliphatic side chain, a structural motif previously unreported in natural products. Its molecular formula was determined as C₁₇H₂₈O₃ via (+)-HRESIMS, showing four degrees of unsaturation. The ¹H NMR spectrum revealed two terminal olefinic protons (δ 4.92, d, J = 10.0 Hz, Ha-16; δ 4.98, d, J = 17.2 Hz, Hb-16), one sp³ methine proton (δ 2.51, m, H-2), three methoxyl protons (δ 3.86, s, H₃-17), and multiple methylene signals indicating a long aliphatic chain. Comprehensive spectroscopic analysis, including ¹H–¹H COSY, HSQC, and HMBC correlations, established the planar structure of 1. Notably, the linkage between the side chain and C-2 was confirmed by the COSY correlation between H-2 and H₂-7. HMBC data further revealed that a ketone carbonyl is at C-1 and an oxygenated quaternary carbon at C-3. The NOESY experiment showed a cross peak between H-2 and CH₃-3, suggesting they are on the same face, thus establishing relative stereochemistry. To determine absolute configuration, ECD calculations were performed for the 2S,3R enantiomer, which matched well with experimental data, confirming the structure as (2S,3R)-cyclopentanone A. This compound represents the first natural product featuring a cyclopentane core with such a complex side chain, highlighting its structural uniqueness and potential for novel biological activity.

Secosubamolide F: A Potent iNOS Inhibitor with Anti-Inflammatory Potential

Among the isolated compounds, secosubamolide F (4) emerged as the most promising candidate for anti-inflammatory drug development. It was isolated as a colorless oil with the molecular formula C₁₉H₃₀O₄, confirmed by (+)-HRESIMS. The ¹H and ¹³C NMR data closely resembled those of secolincomolide A but differed by the presence of a terminal alkyne and an additional methoxy group. Key HMBC correlations from OCH₃-3 (δ 3.30) to C-3 and from H-15 to C-16 and C-17 confirmed the location of these functional groups. The optical rotation measurement yielded [α]²⁵ +44.2° (c 0.186, CHCl₃), consistent with the 3S configuration observed in related compounds like secoisolancifolide. The double bond geometry was assigned as E based on the coupling constant (J = 7.6 Hz) of H-6 (δ 7.09, t). Compound 4 demonstrated significant inhibition of nitric oxide (NO) production in LPS-stimulated RAW264.7 cells, with an IC₅₀ value of 1.73 ± 0.18 μM—superior to the positive control indomethacin (IC₅₀ = 24.0 ± 0.36 μM). Furthermore, Western blot analysis revealed that compound 4 dose-dependently suppressed iNOS protein expression in a concentration range below 10 μM. Molecular docking studies indicated that secosubamolide F binds stably within the iNOS active site, forming hydrophobic interactions with TRP188, ALA191, MET349, PHE363, and TYR483, and a hydrogen bond with PRO344. These findings suggest that secosubamolide F acts as a potent and selective iNOS inhibitor, making it a valuable lead compound for further optimization in anti-inflammatory drug discovery.

Subamolides F and G: Enantiomeric Butyrolactones with Rare Structural Features

Two new butyrolactone derivatives, subamolide F (2) and subamolide G (3), were isolated from the root extract of L. glauca.PRKAR2B Antibody Technical Information Subamolide F (2), a pale yellowish liquid, exhibited a molecular formula of C₁₈H₂₈O₅ based on (−)-HRESIMS data. Its NMR spectra revealed a terminal alkyne proton (δ 1.94, s, H-17), three methoxyl groups (δ 4.14, s, H₃-18), and a characteristic diol system. HMBC correlations confirmed the attachment of the side chain to C-2 and identified a hydroxylated quaternary carbon at C-2 (δ 104.2), suggesting a vicinal diol between C-2 and C-6. Despite being obtained as a racemate, chiral-phase chromatography separated two enantiomers: (+)-subamolide F (2a) and (−)-subamolide F (2b), marking the first reported case of enantiomeric butanolides. The absolute configuration of 2a was tentatively assigned as 2S,6R based on ECD calculations, while 2b was assigned as 2R,6S. Subamolide G (3), lacking the hydroxyl groups at C-2 and C-6, was derived from 2 through deoxygenation. Its ¹H NMR data were similar to those of 2, except for the absence of OH signals. ECD calculations for the 2S enantiomer of 3 showed excellent agreement with experimental data, confirming its absolute configuration as 2S. The presence of a terminal alkyne in 2 and a terminal double bond in 3 indicates a biosynthetic pathway involving oxidation and reduction steps. These findings expand the chemical diversity of butanolides and provide insights into their biosynthesis, particularly in the context of stereochemical complexity and enantiomer formation.

Rupestonic Acids J–L: New Sesquiterpenoid Lactones with Defined Stereochemistry

Three new sesquiterpene lactones—rupestonic acids J (5), K (6), and L (7)—were isolated from L. glauca roots. Rupestonic acid J (5) was obtained as an oily solid with molecular formula C₁₆H₂₂O₃, confirmed by (+)-HRESIMS. Its NMR data closely matched those of rupestonic acid I (12), differing only by a methoxyl signal at δ 3.77 (s, H₃-12). HMBC correlation from H₃-12 to C-12 confirmed its attachment. ECD analysis showed identical spectral patterns to rupestonic acid I, allowing assignment of absolute configurations as 4S, 7R, and 10S. Rupestonic acid K (6) was isolated as a white amorphous powder with molecular formula C₁₅H₂₀O₄. The key difference from rupestonic acid I was the presence of an oxygenated quaternary carbon at C-10 (δ 84.2) and a single methyl signal (δ 1.30, s), indicating replacement of a hydrogen by a hydroxyl group. HMBC correlations from CH₃-10 to C-1, C-10, and C-9 supported this assignment. NOESY experiments revealed cofacial relationships among CH₃-4/Ha-2 and CH₃-10/Ha-2, assigning them as α-oriented. ECD similarity to 5 and 12 confirmed the absolute configuration as 4S, 7R, 10R. Rupestonic acid L (7), a yellowish oil, had molecular formula C₁₅H₂₂O₄.27-O-Demethylrapamycin MedChemExpress It shared a [6,6] bicyclic skeleton with 6 but featured an acrylic acid moiety and an epoxide ring.PMID:35112472 HMBC correlations confirmed the positions of CH₃-10, CH₃-5, and the acrylic group. NOESY data showed H-8/H-5 and OH-6/H-5 were on the same face, and no NOE between OH-6 and CH₃-5/CH₃-10 suggested they were β-oriented. ECD calculations confirmed the absolute configuration as 1S, 5S, 6R, 8S, 10R. These compounds represent structurally diverse and stereochemically defined sesquiterpenoids with potential bioactivity.

Linderaguaianols A and B: Guaiene-Type Sesquiterpenes with Divergent Double Bonds

Two new guaiane-type sesquiterpenes, linderaguaianol A (8) and linderaguaianol B (9), were isolated from L. glauca roots. Both compounds share the molecular formula C₁₅H₂₆O₂, confirmed by (−)-HRESIMS. Their structures were elucidated using detailed 2D NMR analysis, revealing a typical [5,7] bicyclic guaiane skeleton. Linderaguaianol A (8) displayed a double bond between C-4 and C-5, confirmed by HMBC correlations from CH₃-4 to C-4 and C-5, and from H₂-6 to C-5. Mo2(AcO)₄-induced CD analysis showed a positive Cotton effect at 312 nm, indicating the 11S configuration according to Snatzke’s rule. ECD calculations supported the configurations at C-1 (1S), C-7 (7R), C-10 (10S), and C-11 (11S). Linderaguaianol B (9) differed by having the double bond between C-1 and C-5, confirmed by HMBC correlations from H-10 to C-1 and C-5, and from CH₃-10 to C-1. Mo2(AcO)₄-induced CD showed a positive Cotton effect at 317 nm, confirming C-11 as S. ECD calculations validated the configurations as 4S, 7R, 10S, and 11S. These two compounds represent a rare pair of enantiomeric or diastereomeric guaianes with distinct double bond positions, offering insight into the biosynthetic flexibility of this class of terpenoids. Their isolation highlights the structural richness of L. glauca and provides leads for further pharmacological evaluation.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com

Macroplastics are the dominant form of plastic pollution in river systems by mass, posing significant threats to aquatic ecosystems. These large plastic fragments, typically exceeding 5 mm in size, contribute to a wide array of environmental issues, including harm to aquatic life, increased flood risks due to blockages in drainage systems, and adverse impacts on human livelihoods dependent on healthy rivers. Despite their growing recognition as an environmental hazard, research on riverine macroplastics remains underdeveloped compared to other fields such as marine plastic pollution or microplastic studies. Current methods for quantifying macroplastic presence vary widely across regions and lack standardization, making comparative analysis difficult. While passive sampling, net sampling, visual observation, and remote sensing techniques are commonly used, each method has limitations related to spatial coverage, detection accuracy, and representativeness.

The transport dynamics of macroplastics in rivers are influenced by multiple interrelated factors, including material properties (density, shape, polymer type), hydrological conditions (flow velocity, turbulence, flood events), wind effects, and interactions with in-channel obstructions like vegetation, rocks, and infrastructure.PHYHD1 Antibody Autophagy Floating macroplastics, often composed of low-density polymers like polyethylene and polypropylene, are primarily transported along the water surface. Suspended macroplastics, which remain mid-column due to near-neutral buoyancy, can be carried by turbulent flows during high discharge events. Riverbed macroplastics, typically denser materials like PVC or PET, move as bedload and may become buried in sediments. Riverbank accumulations result from direct dumping or deposition during floods. Each transport mechanism presents unique challenges for monitoring and management.

Despite recent advances, critical knowledge gaps persist. There is limited understanding of how macroplastic degradation affects transport behavior, particularly how weathering alters density and shape over time. The influence of temperature on chemical leaching and plastic breakdown remains poorly quantified. Moreover, the role of organic matter, such as instream wood, in modifying macroplastic accumulation patterns is not fully explored. Existing models fail to integrate these complex processes into a cohesive framework. Without standardized protocols and global data sharing, it is difficult to develop accurate predictive tools or effective mitigation strategies.

To address these challenges, future research must prioritize three key areas: enhanced field monitoring using advanced technologies such as drones, sonar, GPS tracking, and automated image analysis; the establishment of globally harmonized sampling methods and data-sharing platforms; and the integration of laboratory experiments with field observations to better understand physical and biological interactions.10025-99-7 Molecular Weight A robust riverine macroplastic budget—defining inputs, storage, transformation, and outputs—is essential for guiding targeted management.PMID:34432556 Such a framework would enable policymakers and practitioners to implement science-based interventions at appropriate scales.

A multilayered management strategy is proposed to tackle macroplastic pollution effectively. First, reducing the supply of plastics entering rivers through source control, product redesign, and policy enforcement is paramount. Second, improving removal efficiency via strategic placement of collection devices that leverage natural flow dynamics, while minimizing ecological disruption, is crucial. Third, ensuring responsible post-removal treatment—such as recycling, safe disposal, or energy recovery—completes the cycle. This integrated approach, grounded in improved scientific understanding and collaborative action, offers a pathway toward sustainable river health and resilience in the face of escalating plastic pollution.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com

Bioorthogonal reactions have emerged as indispensable tools in chemical biology, enabling selective labeling and modification of biomolecules within complex biological environments, including living cells. Among these, strain-promoted inverse electron demand Diels–Alder cycloadditions (SPIEDAC) between tetrazines and strained alkenes or alkynes stand out due to their exceptional reaction speed and compatibility with live-cell applications. When combined with genetic code expansion (GCE), this approach allows site-specific incorporation of noncanonical amino acids (ncAAs) into proteins, facilitating residue-specific fluorophore attachment in mammalian cells. Despite significant progress, challenges remain regarding the stability and reactivity of these ncAAs under physiological conditions. Notably, some previously reported ncAAs exhibit instability post-conjugation, primarily through β-elimination, leading to loss of fluorescence signal. This study introduces four newly designed SPIEDAC-reactive ncAAs that are structurally incapable of undergoing β-elimination, thereby enhancing product stability. Additionally, we developed a fluorescence flow cytometry-based FRET assay to quantitatively assess reaction kinetics directly inside living cells. The assay enables real-time monitoring of labeling efficiency, reaction rate, and product stability under physiologically relevant conditions. Our results reveal that while certain compounds show superior kinetic performance, others demonstrate greater resilience over time—highlighting the importance of evaluating bioorthogonal reactions under actual cellular environments rather than relying solely on in vitro data.IRF2BP1 Antibody custom synthesis This work underscores the necessity of considering long-term exposure effects and host-specific factors when optimizing ncAAs for in vivo applications. We identify TCO-E as a highly effective candidate with fast kinetics and excellent stability, surpassing even established analogs like TCO*-A and BCN. Furthermore, we demonstrate that structural modifications such as urea linkage or lactam formation can significantly influence both reactivity and stability.M6903 Autophagy These findings provide critical insights for future design principles in ncAA development and offer a robust platform for systematic evaluation of new bioorthogonal probes in living systems.

The synthesis of the four novel ncAAs—AmTCO-E, AmTCO-A, TCO*N, and TCO*C-E—is based on strategic modifications to eliminate β-elimination pathways. Unlike traditional carbamate-linked trans-cyclooctenes, AmTCO-E and AmTCO-A utilize a urea linkage, which stabilizes the conjugate against hydrolytic cleavage. TCO*C-E replaces the carbamate with an amide bond, further reducing susceptibility to elimination.PMID:35144597 TCO*N incorporates a lactam ring at the C3 position, ensuring that even if β-elimination occurs, the fluorophore remains tethered to the protein backbone. Each compound was synthesized via a modular route involving trans-cyclooctenol intermediates followed by functional group transformations. Purified ncAAs were validated using NMR and mass spectrometry. In cellulo experiments revealed that AmTCO-E exhibits the fastest observed rate constant (kOn > 20,000 M⁻¹s⁻¹), though its initial EFRET-MAX is modest (~0.6), suggesting potential pre-reaction instability. In contrast, TCO-E displays high kOn (~15,000 M⁻¹s⁻¹) and near-maximal EFRET-MAX (0.8), indicating both rapid labeling and strong educt stability. BCN and TCO*-A show comparable rates (~10,000 M⁻¹s⁻¹) but differ in product stability: TCO*-A undergoes significant signal decay over time due to β-elimination, whereas BCN remains stable. TCO*linker-A reacts more slowly (kOn ~6,000 M⁻¹s⁻¹) yet maintains high EFRET-MAX and minimal degradation. TCO*N and TCO*C-E are slow but stable, confirming the effectiveness of structural design in preventing payload loss. Importantly, in vitro measurements diverged from in cellulo observations: BCN showed negligible labeling in purified EGFP assays, suggesting decomposition in bacterial systems. Moreover, TCO-E and TCO-A underwent spontaneous isomerization in E. coli cultures, with up to 95% conversion of TCO-A from trans to cis form. These discrepancies emphasize the limitations of in vitro models and validate our in cellulo FRET assay as a more accurate predictor of performance in living cells. Overall, this study establishes a framework for rational ncAA design and provides a powerful tool for identifying optimal candidates for live-cell imaging and functional proteomics.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com

Product Name :
T-cell-specific surface glycoprotein CD28 homolog