TIMEDB: tumor immune micro-environment cell composition database with automatic analysis and interactive visualization.

Deciphering the cell-type composition in the tumor immune microenvironment (TIME) can significantly increase the efficacy of cancer treatment and improve the prognosis of cancer. Such a task has benefited from microarrays and RNA sequencing technologies, which have been widely adopted in cancer studies, resulting in extensive expression profiles with clinical phenotypes across multiple cancers. Current state-of-the-art tools can infer cell-type composition from bulk expression profiles, providing the possibility of investigating the inter-heterogeneity and intra-heterogeneity of TIME across cancer types. Much can be gained from these tools in conjunction with a well-curated database of TIME cell-type composition data, accompanied by the corresponding clinical information. However, currently available databases fall short in data volume, multi-platform dataset integration, and tool integration. In this work, we introduce TIMEDB (https://timedb.deepomics.org), an online database for human tumor immune microenvironment cell-type composition estimated from bulk expression profiles. TIMEDB stores manually curated expression profiles, cell-type composition profiles, and the corresponding clinical information of a total of 39,706 samples from 546 datasets across 43 cancer types. TIMEDB comes readily equipped with online tools for automatic analysis and interactive visualization, and aims to serve the community as a convenient tool for investigating the human tumor microenvironment.

High-Sensitivity Differential Helmholtz Photoacoustic System Combined with the Herriott Multipass Cell and Its Application in Seed Respiration.

A highly sensitive photoacoustic detection system using a differential Helmholtz resonator (DHR) combined with a Herriott multipass cell is presented, and its implementation to sub-ppm level carbon dioxide (CO2) detection is demonstrated. Through the utilization of erbium-doped optical fiber amplifier (EDFA), the laser power was amplified to 150 mW. Within the multipass cell, a total of 22 reflections occurred, contributing to an impressive 33.6 times improvement in the system sensitivity. The normalized noise equivalent absorption coefficient (NNEA) was 8.64 × 10-11 cm-1·W·Hz-1/2 [signal-to-noise ratio, (SNR) = 1] and according to the Allan variance analysis, a minimum detection limit of 500 ppb could be achieved for CO2 at 1204 s, which demonstrates the long-term stability of the system. The system was applied to detect the respiration of rice and upland rice seeds. It is demonstrated that the system can monitor and distinguish the respiration intensity and respiration rate of different seeds in real time.

A Bibliometric Analysis of the Spatial Transcriptomics Literature from 2006 to 2023.

In recent years, spatial transcriptomics (ST) research has become a popular field of study and has shown great potential in medicine. However, there are few bibliometric analyses in this field. Thus, in this study, we aimed to find and analyze the frontiers and trends of this medical research field based on the available literature. A computerized search was applied to the WoSCC (Web of Science Core Collection) Database for literature published from 2006 to 2023. Complete records of all literature and cited references were extracted and screened. The bibliometric analysis and visualization were performed using CiteSpace, VOSviewer, Bibliometrix R Package software, and Scimago Graphica. A total of 1467 papers and reviews were included. The analysis revealed that the ST publication and citation results have shown a rapid upward trend over the last 3 years. Nature Communications and Nature were the most productive and most co-cited journals, respectively. In the comprehensive global collaborative network, the United States is the country with the most organizations and publications, followed closely by China and the United Kingdom. The author Joakim Lundeberg published the most cited paper, while Patrik L. Ståhl ranked first among co-cited authors. The hot topics in ST are tissue recognition, cancer, heterogeneity, immunotherapy, differentiation, and models. ST technologies have greatly contributed to in-depth research in medical fields such as oncology and neuroscience, opening up new possibilities for the diagnosis and treatment of diseases. Moreover, artificial intelligence and big data drive additional development in ST fields.

Polyarylisocyanides Derived from an Alkyne-Pd(II) Catalyst as Robust Alignment Media with Excellent Enantiodiscimination.

The development of chiral alignment media for measuring anisotropic NMR parameters provides an opportunity to determine the absolute configuration of chiral molecules without the need for derivatization. However, chiral alignment media with a high and robust enantiodiscriminating property for a wide range of chiral molecules are still scarce. In this study, we synthesized cholesterol-end-functionalized helical polyisocyanides from a chiral monomer using a cholesterol-based alkyne-Pd(II) initiator. These stereoregular polyisocyanides form stable and weak anisotropic lyotropic liquid crystals (LLCs) in dichloromethane systems, exhibiting highly optical activities in both single left- and right-handed helices. The preparation process of the media was straightforward, and the aligning property of the LLCs could be controlled by adjusting the concentration and temperature. Using the chiral polyisocyanides, we extracted the residual dipolar coupling for an enantiomeric pair of isopinocampheol (IPC), as well as a number of pharmaceutical molecules, demonstrating excellent enantiodiscriminating properties for a broad range of chiral compounds.

UCMSCs-derived exosomal circHIPK3 promotes ulcer wound angiogenesis of diabetes mellitus via miR-20b-5p/Nrf2/VEGFA axis.

AIMS: Experiments confirmed that circular RNAs contributed to the pathogenesis of diabetic foot ulcers (DFUs). CircHIPK3 was upregulated in type 2 diabetes mellitus (T2DM), but its role in DFU remained unknown. Our study aimed to investigate the regulatory functions of exosomal circHIPK3 and its potential mechanisms in DFU. METHODS: Exosomal size and distribution, marker proteins, and circHIPK3 levels were evaluated by transmission electron microscope, ExoView R200, western blot, and qRT-PCR. Flow cytometry, MTT, Wound healing assays, and tube formation assays were used to assess the roles of exosomal circHIPK3 in high glucose (HG)-treated human umbilical vein endothelial cells (HUVECs). The relationships between Nrf2/VEGFA/circHIPK3 and miR-20b-5p, and between Nrf2 and VEGFA were determined by luciferase reporter assay and RNA immunoprecipitation. We used cell and mice models to investigate the mechanisms of exosomal circHIPK3 under diabetic conditions. RESULTS: CircHIPK3 was significantly upregulated in exo-circHIPK3 rather than exo-vector. Exo-circHIPK3 remarkably inhibited cell apoptosis but promoted cell proliferation, migration, and tube formation in HG-treated HUVECs. Luciferase reporter and RIP assays showed that miR-20b-5p targeted and inhibited Nrf2 and VEGFA, and circHIPK3 acted as a ceRNA of miR-20b-5p to inhibit the binding to its downstream genes Nrf2 and VEGFA. Mechanistically, circHIPK3 promoted cell proliferation, migration, and angiogenesis via downregulating miR-20b-5p to upregulate Nrf2 and VEGFA. However, the overexpressed miR-20b-5p could abolish the promoting effects of circHIPK3 overexpression on cell proliferation, migration, and tube formation under HG conditions. CONCLUSION: UCMSCs-derived exosomal circHIPK3 protected HG-treated HUVECs via miR-20b-5p/Nrf2/VEGFA axis. The exosomal circHIPK3 might be a therapeutic candidate to treat DFU.

LncRNA GNAS-AS1 knockdown inhibits keloid cells growth by mediating the miR-188-5p/RUNX2 axis.

Keloid is a common dermis tumor, occurring repeatedly, affecting the quality of patients' life. Long non-coding RNAs (lncRNAs) have crucial regulatory capacities in skin scarring formation and subsequent scar carcinogenesis. The intention of this study was to investigate the mechanism and function of GNAS antisense-1 (GNAS-AS1) in keloids. Clinical samples were collected to evaluate the expression of GNAS-AS1, RUNX2, and miR-188-5p by qRT-PCR. The proliferation, migration, and invasion of HKF cells were detected by CCK-8, wound healing, and Transwell assays. The expression levels of mRNA and protein were examined through qRT-PCR and Western blot assay. Luciferase reporter assay was used to identify the binding relationship among GNAS-AS1, miR-188-5p, and Runt-related transcription factor 2 (RUNX2). GNAS-AS1 and RUNX2 expressions were remarkably enhanced, and miR-188-5p expression was decreased in keloid clinical tissues and HKF cells. GNAS-AS1 overexpression promoted cells proliferation, migration, and invasion, while GNAS-AS1 knockdown had the opposite trend. Furthermore, overexpression of GNAS-AS1 reversed the inhibitory effect of 5-FU on cell proliferation, migration, and invasion. MiR-188-5p inhibition or RUNX2 overexpression could enhance the proliferation, migration, and invasion of HKF cells. GNAS-AS1 targeted miR-188-5p to regulate RUNX2 expression. In addition, the inhibition effects of GNAS-AS1 knockdown on HKF cells could be reversed by inhibition of miR-188-5p or overexpression of RUNX2, while RUNX2 overexpression eliminated the suppressive efficaciousness of miR-188-5p mimics on HKF cells growth. GNAS-AS1 knockdown could regulate the miR-188-5p/RUNX2 signaling axis to inhibit the growth and migration in keloid cells. It is suggested that GNAS-AS1 may become a new target for the prevention and treatment of keloid.

Ligand binding affinity prediction with fusion of graph neural networks and 3D structure-based complex graph.

Accurate prediction of protein-ligand binding affinity is pivotal for drug design and discovery. Here, we proposed a novel deep fusion graph neural networks framework named FGNN to learn the protein-ligand interactions from the 3D structures of protein-ligand complexes. Unlike 1D sequences for proteins or 2D graphs for ligands, the 3D graph of protein-ligand complex enables the more accurate representations of the protein-ligand interactions. Benchmark studies have shown that our fusion models FGNN can achieve more accurate prediction of binding affinity than any individual algorithm. The advantages of fusion strategies have been demonstrated in terms of expressive power of data, learning efficiency and model interpretability. Our fusion models show satisfactory performances on diverse data sets, demonstrating their generalization ability. Given the good performances in both binding affinity prediction and virtual screening, our fusion models are expected to be practically applied for drug screening and design. Our work highlights the potential of the fusion graph neural network algorithm in solving complex prediction problems in computational biology and chemistry. The fusion graph neural networks (FGNN) model is freely available in https://github.com/LinaDongXMU/FGNN.

Mallory-Weiss syndrome in four hemodialysis patients: a case study.

BACKGROUND: Hemodialysis patients are prone to gastrointestinal bleeding, and Mallory-Weiss syndrome (MWS) is one of the causes. Mallory-Weiss syndrome is often induced by severe vomiting, manifests as upper gastrointestinal bleeding, and is self-limited with a good prognosis. However, mild vomiting in hemodialysis patients can lead to the occurrence of MWS, and the mild early symptoms are easy to misdiagnose, leading to the aggravation of the disease. CASE PRESENTATION: In this paper, we report four hemodialysis patients with MWS. All patients displayed symptoms of upper gastrointestinal bleeding. The diagnosis of MWS was confirmed by gastroscopy. One patient had a history of severe vomiting; however, the other three reported histories of mild vomiting. Three patients received the conservative hemostasis treatment, and the gastrointestinal bleeding stopped. One patient underwent the gastroscopic and interventional hemostasis treatments. The conditions of three of the patients improved. Unfortunately, one of the patients died due to the cardia insufficiency. CONCLUSIONS: We think that the mild symptoms of MWS are easily covered up by other symptoms. This may lead to delays in diagnosis and treatment. For patients with severe symptoms, gastroscopic hemostasis is still the first choice, and interventional hemostasis can also be considered. For patients with mild symptoms, drug hemostasis is the first consideration.

TRIM67 Implicates in Regulating the Homeostasis and Synaptic Development of Mitral Cells in the Olfactory Bulb.

In recent years, olfactory dysfunction has attracted increasingly more attention as a hallmark symptom of neurodegenerative diseases (ND). Deeply understanding the molecular basis underlying the development of the olfactory bulb (OB) will provide important insights for ND studies and treatments. Now, with a genetic knockout mouse model, we show that TRIM67, a new member of the tripartite motif (TRIM) protein family, plays an important role in regulating the proliferation and development of mitral cells in the OB. TRIM67 is abundantly expressed in the mitral cell layer of the OB. The genetic deletion of TRIM67 in mice leads to excessive proliferation of mitral cells in the OB and defects in its synaptic development, resulting in reduced olfactory function in mice. Finally, we show that TRIM67 may achieve its effect on mitral cells by regulating the Semaphorin 7A/Plexin C1 (Sema7A/PlxnC1) signaling pathway.

Switched alternative splicing events as attractive features in lung squamous cell carcinoma.

BACKGROUND: Alternative splicing (AS) plays important roles in transcriptome and proteome diversity. Its dysregulation has a close affiliation with oncogenic processes. This study aimed to evaluate AS-based biomarkers by machine learning algorithms for lung squamous cell carcinoma (LUSC) patients. METHOD: The Cancer Genome Atlas (TCGA) database and TCGA SpliceSeq database were utilized. After data composition balancing, Boruta feature selection and Spearman correlation analysis were used for differentially expressed AS events. Random forests and a nested fivefold cross-validation were applied for lymph node metastasis (LNM) classifier building. Random survival forest combined with Cox regression model was performed for a prognostic model, based on which a nomogram was developed. Functional enrichment analysis and Spearman correlation analysis were also conducted to explore underlying mechanisms. The expression of some switch-involved AS events along with parent genes was verified by qRT-PCR with 20 pairs of normal and LUSC tissues. RESULTS: We found 16 pairs of splicing events from same parent genes which were strongly related to the splicing switch (intrapair correlation coefficient = - 1). Next, we built a reliable LNM classifier based on 13 AS events as well as a nice prognostic model, in which switched AS events behaved prominently. The qRT-PCR presented consistent results with previous bioinformatics analysis, and some AS events like ITIH5-10715-AT and QKI-78404-AT showed remarkable detection efficiency for LUSC. CONCLUSION: AS events, especially switched ones from the same parent genes, could provide new insights into the molecular diagnosis and therapeutic drug design of LUSC.

Peroxidase-Mimetic Copper-Doped Carbon-Dots for Oxidative Stress-Mediated Broad-Spectrum and Efficient Antibacterial Activity.

Carbon dots (CDs) have recently emerged as antibacterial agents and have attracted considerable attention owing to their fascinating merits of small size, facile fabrication, and surface functionalization. Most of them are involved in external light activation or hybridization with other functional nanomaterials. Herein, we present peroxidase-like Cu-doped CDs (Cu-CDs) for in vitro antibacterial applications. The unique peroxidase-mimicking property of the Cu-CDs was demonstrated by tetramethylbenzidine chromogenic assay, electron paramagnetic resonance spectra, and hydroxy radical probe. Escherichia coli and Staphylococcus aureus were chosen as representative gram-negative/positive models against which Cu-CDs exhibited superior antimicrobial activity even at a dosage down to 5 µg/mL. A possible mechanism of action was that the Cu-CDs triggered a catalytic redox reaction of endogenous H2 O2 and glutathione depletion in the bacteria cells, with subsequent oxidative stress and membrane disruption. This work provides a new strategy for the design of microenvironment-responsive antimicrobial nano-agents.

Interplay of Fusion, Leakage, and Electrostatic Lipid Clustering: Membrane Perturbations by a Hydrophobic Antimicrobial Polycation.

Membrane active compounds are able to induce various types of membrane perturbations. Natural or biomimetic candidates for antimicrobial treatment or drug delivery scenarios are mostly designed and tested for their ability to induce membrane permeabilization, also termed leakage. Furthermore, the interaction of these usually cationic amphiphiles with negatively charged vesicles often causes colloidal instability leading to vesicle aggregation or/and vesicle fusion. We show the interplay of these modes of membrane perturbation in mixed phosphatidyl glycerol (PG)/phosphatidyl ethanolamine (PE) by the statistical copolymer MM:CO comprising, both, charged and hydrophobic subunits. MM:CO is a representative of partially hydrophobic, highly active, but less selective antimicrobial polycations. Cryo-electron microscopy indicates vesicle fusion rather than vesicle aggregation upon the addition of MM:CO to negatively charged PG/PE (1:1) vesicles. In a combination of fluorescence-based leakage and fusion assays, there is support for membrane permeabilization and pronounced vesicle fusion activity as distinct effects. To this end, membrane fusion and aggregation were prevented by including lipids with polyethylene glycol attached to their head groups (PEG-lipids). The leakage activity of MM:CO is very similar in the absence and presence of PEG-lipids. Vesicle aggregation and fusion however are largely suppressed. This strongly suggests that MM:CO induces leakage by asymmetric packing stress because of hydrophobically driven interactions which could lead to leakage. As a further membrane perturbation effect, MM:CO causes lipid clustering in model vesicles. We address potential artifacts and misinterpretations of experiments characterizing leakage and fusion. Additional to the leakage activity, the pronounced fusogenic activity of the polymer and potentially of many other similar compounds likely has implications for antimicrobial activity and beyond.

Design and Development of a New Glucagon-Like Peptide-1 Receptor Agonist to Obtain High Oral Bioavailability.

PURPOSE: Semaglutide is the only oral GLP-1 RA in the market, but oral bioavailability is generally limited in range of 0.4-1%. In this study, a new GLP-1RA named SHR-2042 was developed to gain higher oral bioavailability than semaglutide. METHOD: Self-association of SHR-2042, semaglutide and liraglutide were assessed using SEC-MALS. The intestinal perfusion test in SD rats was used to select permeation enhancers (PEs) including SNAC, C10 and LCC. ITC, CD and DLS were used to explore the interaction between SHR-2042 and SNAC. Gastric administrated test in SD rats was used to screen SHR-2042 granules with different SHR-2042/SNAC ratios. The oral bioavailability of SHR-2042 was studied in rats and monkeys. RESULT: The designed GLP-1RA, SHR-2042, gives a better solubility and lipophilicity than semaglutide. While it forms a similar oligomer with that of semaglutide. During the selection of PEs, SNAC shows better exposure than the other competing PEs including C10 and LCC. SHR-2042 and SNAC bind quickly and exhibit hydrophobic interaction. SNAC could promote monomerization of SHR-2042 and form micelles to trap the monomerized SHR-2042. The oral bioavailability of SHR-2042 paired with SNAC is 0.041% (1:0, w/w), 0.083% (1:10, w/w), 0.32% (1:30, w/w) and 2.83% (1:60, w/w) in rats. And the oral bioavailability of SHR-2042 matched with SNAC is 3.39% (1:30, w/w) in monkeys, which is over 10 times higher than that of semaglutide. CONCLUSION: We believe that the design and development of oral SHR-2042 will provide a new way to design more and more GLP-1RAs with high oral bioavailability in the future.

GBAP1 polymorphisms (rs140081212, rs1057941 and rs2990220) contribute to reduced risk of gastric cancer.

Aim: This study was designed to evaluate the contribution of GBAP1 variants to gastric cancer (GC) risk in a Chinese Han population. Methods: The genotypes of GBAP1 polymorphisms were detected using the Agena MassARRAY platform. Logistic regression analysis was used to calculate odds ratios (ORs) and 95% CIs. Results: GBAP1 rs140081212 (OR = 0.51, p = 4.50 × 10-07), rs1057941 (OR = 0.48, p = 1.19 × 10-08) and rs2990220 (OR = 0.46, p = 7.34 × 10-09) contribute to reduced GC risk, especially gastric adenocarcinoma. Interestingly, the contribution of GBAP1 variants to GC susceptibility was associated with age, sex, BMI, smoking and drinking. Conclusion: This research suggested that GBAP1 polymorphisms might provide a protective effect against GC occurrence in a Chinese Han population.

Electrocardiogram evolution of acute anterior ST-segment elevation myocardial infarction following pericarditis.

Electrocardiogram is a powerful tool for differentiating acute ST-segment elevation myocardial infarction (STEMI) and pericarditis. However, an unusual ECG presentation of the simultaneous occurrence of the two conditions has not been reported previously. In this article, we report a case of ECG evolution of acute anterior STEMI following pericarditis with pericardial effusion (PE) and find that QRS complex widening in ECG lead with maximal ST-segment elevation is also applicable for identifying STEMI even in patients with prior pericarditis. Undoubtedly, our case can help prevent emergency physicians from making incorrect diagnoses and administering inappropriate treatments.

Polysaccharide from Salviae miltiorrhizae Radix et Rhizoma Attenuates the Progress of Obesity-Induced Non-Alcoholic Fatty Liver Disease through Modulating Intestinal Microbiota-Related Gut-Liver Axis.

Non-alcoholic fatty liver disease (NAFLD) is the most prevalent chronic liver disease worldwide, thus treatments for it have attracted lots of interest. In this study, the Salviae miltiorrhizae Radix et Rhizoma (SMRR) polysaccharide was isolated by hot water extraction and ethanol precipitation, and then purified by DEAE anion exchange chromatography and gel filtration. With a high-fat-diet-induced obesity/NAFLD mouse model, we found that consumption of the SMRR polysaccharide could remarkably reverse obesity and its related progress of NAFLD, including attenuated hepatocellular steatosis, hepatic fibrosis and inflammation. In addition, we also reveal the potential mechanism behind these is that the SMRR polysaccharide could regulate the gut-liver axis by modulating the homeostasis of gut microbiota and thereby improving intestinal function.

Roles of Beclin1 protein expression in cervical cancer: a meta-analysis and bioinformatics analysis.

Beclin1 is a key regulator of a family of autophagy-related proteins. The aim of our study was to elucidate the clinicopathological and prognostic significance of Beclin1 expression which is a positive regulator of autophagy in cervical cancer. The results showed that a total of 2682 patients were enrolled in 21 case-control studies. The results showed that, as for Beclin1 expression, significant differences were found in cervical cancer vs. normal cervical tissues (p<.00001) and cancer tissues with vs. no lymph node metastasis (p<.00001); tumour diameter no less than vs. less than 4 cm (p=.001), myometrial invasion depth no less than vs. less than 1/2 and FIGO I vs. II (p=.02); relationship between Beclin1 expression and prognosis of cervical cancer (p=.03). Kaplan-Meier's plotter showed that Beclin1 expression was negative. It was associated with overall, post-progressive and distant metastatic survival. According to the Oncomine database, Beclin1 mRNA expression in cervical cancer tissues was higher than that in normal tissues. Cox multivariate showed that lymph node metastasis and TNM stage were important factors affecting the survival time of patients. Beclin1 expression can be used as an indicator of prognosis in patients, and provide methods and ideas for prevention and treatment.

Looking into mobility in the Covid-19 'eye of the storm': Simulating virus spread and urban resilience in the Wuhan city region travel flow network.

Recent urban and regional studies have focused on identifying positive spillover effects from intensifying flows of people in city region networks. However, potential negative spillover effects have lacked attention. The article addresses this research gap focusing on the negative spillover effects represented by Covid-19 contagion in the Wuhan regional travel flow network, China. Drawing on central place theory and central flow theory, Covid-19 spatial spread simulation scenarios are explored using a combined micro-level epidemic compartment model and urban network approach. It is found that not only centrally positioned primate but secondary cities are highly risk exposed to contagion. In addition, these cities have enhanced transmission capacity in a balanced, well-connected travel flow network, whereas a centralised or locally clustered network would be more spread resilient. Both hierarchical position and horizontal flows are found relevant for explaining Covid-19 uneven spread and for informing mobility interventions for a potential future outbreak.

Protease-Activated Receptor 2 (PAR-2) Antagonist AZ3451 Mitigates Oxidized Low-Density Lipoprotein (Ox-LDL)-Induced Damage and Endothelial Inflammation.

Oxidized low-density lipoprotein (ox-LDL)-induced endothelial dysfunction plays an important role in the initiation and development of cardiovascular diseases, especially atherosclerosis (AS). Protease-activated receptor 2 (PAR-2) is a receptor for inflammatory proteases. However, the biological function of PAR-2 in endothelial cells and the pathophysiological process of AS are still unknown. In the current study, we found that treatment with ox-LDL increased the gene and protein expressions of PAR-2 in EA.hy926 endothelial cells. Interestingly, we found that antagonism of PAR-2 with its specific antagonist AZ3451 could ameliorate ox-LDL-induced lactate dehydrogenase (LDH) release. Treatment with AZ3451 considerably improved the mitochondrial function by restoring the mitochondrial membrane potential and increasing the levels of intracellular adenosine triphosphate (ATP). Also, we found that AZ3451 attenuated ox-LDL-induced expression and production of pro-inflammatory cytokines such as interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and interleukin-8 (IL-8). Treatment with AZ3451 also mitigated the expression of matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9). Notably, our results demonstrated that the presence of AZ3451 alleviated ox-LDL-induced expression of the endothelial cell adhesion molecules vascular cell adhesion molecule-1 (VCAM-1) and intercellular cell adhesion molecule-1 (ICAM-1). Mechanistically, we found that AZ3451 attenuated ox-LDL-induced activation of nuclear factor-κB (NF-κB) by reducing the levels of intracellular NF-κB p65 and the luciferase activity of NF-κB promoter. Based on these findings, we conclude that PAR-2 might become a novel therapeutic target for the treatment of AS.

Hidden complexity in membrane permeabilization behavior of antimicrobial polycations.

A promising alternative to classical antibiotics are antimicrobial peptides and their synthetic mimics (smAMPs) that supposedly act directly on membranes. For a more successful design of smAMPs, we need to know how the type of interaction with the membrane determines the type of membrane perturbation. How this, in turn, transfers into selectivity and microbial killing activity is largely unknown. Here, we characterize the action of two smAMPs: MM:CO (a copolymer of hydrophobic cyclooctyl subunits and charged ß-monomethyl-α-aminomethyl subunits) and the highly charged poly-NM (a homopolymer of α-aminomethyl subunits). By thorough characterization of vesicle leakage experiments, we elucidate complex membrane perturbation behavior in zwitterionic or negatively charged vesicles. Vesicle leakage data does not entirely agree with the growth inhibition of microbes. Our ensemble of advanced membrane permeabilization approaches clarifies these discrepancies. Long cumulative leakage kinetics show that the two smAMPs act either by transient leakage or by rare stochastic leakage events that occur at charge neutralization in the sample. We determine the strengths of individual leakage events induced by the smAMPs in membranes of various compositions. These strengths indicate changes in leakage mechanism over time and concentration range. Thus, our sophisticated analysis of vesicle leakage experiments reveals a fine-tuned flexibility in membrane permeabilization mechanisms. These details are indispensable in judging and designing membrane-active compounds.