Adherent Membrane Research Articles

Traumatic terson syndrome with a peculiar mass lesion and tractional retinal detachment: a case report

BackgroundTo report a case with bilateral Terson syndrome presented with a unique mushroom-like mass lesion on the optic disc along with proliferative vitreoretinopathy and tractional retinal detachment.Case presentationA 33-year-old man was injured during a traffic accident and had diffuse brain swelling and intraocular hemorrhage. Poor vision in both eyes was noted after the patient regained consciousness. B-scan ultrasonography showed extensive vitreous opacity with a posterior vitreous detachment and without obvious retinal detachment. Vitrectomy was performed in both eyes five months after the accident. After clearing up the vitreous opacity, a peculiar pigmented mushroom-like mass lesion was noted in the posterior pole and had severe adhesion to the underneath optic disc. Extensive multilayered peripapillary epiretinal membrane was found covering the posterior pole and led to tractional retinal detachment around the macula. The mass was presumed to be an organized vitreous hemorrhage originated from the optic disc. The extensive and adherent epiretinal membrane together with the mass lesion were removed as much as possible and silicon oil was injected for tamponade. However, in the right eye, the retina redetached under silicon oil, whereas in the left eye, his vision improved to 20/100.ConclusionsTerson syndrome usually has a favorable prognosis but may be complicated by proliferative vitreoretinopathy and tractional retinal detachment. Careful monitoring is warranted and early vitrectomy should be considered in cases suspecting additional pathologies.

An Analysis of Optic Disc Parameters in Patients with Peripheral Retinal Tears Following Acute Posterior Vitreous Detachment: A Cross-Sectional Study.

To investigate association between optic disc parameters analyzed by optical coherence tomography (OCT) and occurrence of peripheral retinal tears in patients with symptomatic posterior vitreous detachment (PVD). This cross-sectional study enrolled 75 patients with symptoms of acute PVD, who were allocated into two groups based on whether a peripheral retinal tear occurred or not. When comparing the average retinal nerve fiber layer (RNFL) thickness (μm) between retinal tear and control groups, it was shown that patients with a retinal tear have a significantly higher (87.18 [95% confidence interval (CI), 84.47 to 89.9] vs 81.14 [95% CI, 77.81 to 84.46], P = 0.005) average RNFL thickness. Furthermore, we observed a significant difference (0.13, 0.06 to 0.22 vs 0.07, 0.04 to 0.1, P = 0.036, Mann-Whitney U-test) in the size of cup volume (mm3) between the tear and control groups, respectively. Linear regression showed a significant decrease (P = 0.029) in average RNFL thickness with increasing age, but without a significant difference between the two groups. There was no statistically significant difference between the tear and control groups in terms of rim area, disc area, and average cup-to-disc ratio. Patients with a higher average RNFL thickness and larger cup volume measured by OCT were more prone to develop a peripheral retinal tear. Increased peripapillary average RNFL thickness due to trauma and subsequent inflammation, possibly related to the more adherent posterior hyaloid membrane to the retina, may also indicate strengthened adhesions in the areas of the peripheral retina where retinal tears occur. OCT analysis of the optic nerve head may be used in everyday clinical practice as a predictor of the development of peripheral retinal tears in patients with symptomatic PVD.

Analysis of Risk Factors for Revitrectomy in Eyes with Diabetic Vitreous Hemorrhage.

We aimed to investigate the risk factors associated with revitrectomy in eyes with diabetic vitreous hemorrhage and to determine the prognosis of these patients at least one year postoperatively. This retrospective case-control study had a minimum follow-up period of one year. Patients were divided into single vitrectomy group (control group, n=202) and revitrectomy group (case group, n=36) for analysis. The indications, number, and timing of revitrectomies were documented. And the revitrectomy group was further divided into two vitrectomies group (n=30) and three or more vitrectomies group (n=6). The best-corrected visual acuity (BCVA) at the last follow-up and the occurrence of neovascular glaucoma (NVG) were compared among the single vitrectomy, two vitrectomies and three or more vitrectomies groups. We conducted a thorough collection of patient data and used univariate and binary logistic regression analyses to identify the risk factors associated with revitrectomy. A total of 197 patients (238 eyes) were included. Thirty-six eyes (15.1%) required revitrectomy with six eyes (2.5%) undergoing three or more vitrectomies during the follow-up period. The median duration of the second vitrectomy was 3 (2-6) months. The indications for a second vitrectomy included 28 eyes (77.8%) of postoperative vitreous hemorrhage and 7 eyes (22.2%) combined with tractional retinal detachment. Patients undergoing three or more vitrectomies had significantly worse postoperative BCVA and a higher incidence of NVG (P<0.01). Fibrinogen> 4 g/L (P<0.001) and preoperative anti-vascular endothelial growth factor intravitreal injection (P=0.015) were independent risk factors for revitrectomy, and glycated hemoglobin A1c (HbA1c)>10% (P=0.049) showed significant difference only in univariate analysis. Patients requiring revitrectomy tended to have higher fibrinogen levels, tightly adhered fibrovascular membranes, higher HbA1c levels, and worse prognoses.

Demixing of homogeneous binary lipid membranes induced by protein inclusions.

We study a model of a lipid bilayer membrane described by two order parameters: the chemical composition described using the Gaussian model and the spatial configuration described with the elastic deformation model of a membrane with a finite thickness or, equivalently, for an adherent membrane. We assume and explain on physical grounds the linear coupling between the two order parameters. Using the exact solution, we calculate the correlation functions and order parameter profiles. We also study the domains that form around inclusions on the membrane. We propose and compare six distinct ways to quantify the size of such domains. Despite its simplicity, the model has many interesting features like the Fisher-Widom line and two distinct critical regions.

Pathomorphological Investigation on Membranous Tracheitis in an Adult Buffalo

Membranous tracheitis is an important pathological condition affecting the trachea in animals, usually associated with immunosuppression. This report describes the pathological findings associated with diphtheric tracheitis in an immunocompromised adult buffalo. A carcass of an adult buffalo, with a history of dyspnea, and a large amount of reddish foam flowing from the mouth and nose, presented for necropsy. Detailed postmortem examination was conducted and representative tissue samples were collected for bacteriological isolation and histopathological examination. Macroscopic examination revealed whitish, pale or red coloured blood mixed heavy froth in lumen of trachea with a tightly adhered greenish colour diphtheritic membrane to mucosa. Lungs showed, circular to irregular shaped blackish suffusions, consolidation, along with thin layer of fibrin covering all the lobes. Microscopic examination revealed fibrinous tracheitis and serofibrinous pneumonia in lungs. Mediastinal lymphnode showed severe lymphoid depletion. Bacteriological isolation from tracheal swab and lungs confirmed the presence of Escherichia coli using VITEK 2 system indicating its role in pathogenesis of diphtheritic membrane formation in presence of immunosupression.

High sensitivity Fabry–Pérot interferometric magnetic sensor based on Fe3O4-doped PDMS composite thin film

A magnetic field sensor based on Fabry–Pérot interferometer (FPI) with soft gold magnetic composite film (GMCF) is proposed and demonstrated experimentally. GMCF is fabricated by Fe3O4-doped polydimethylsiloxane (PDMS) film and adhered thin gold membrane via van der Waals force. Applying an external magnetic field, GMCF can vibrate under magnetic forces and cause a change in the cavity length of FPI and hence modulates the interference spectra. Experimental results indicate that the sensor can achieve maximum sensitivity of 390 pm mT−1 under a linear magnetic field intensity ranging from 0 to 65 mT. The proposed sensor could help with magnetic field detection in complex environments.

Optical Coherence Tomography Angiography Parameters of the Retina in SARS-CoV-2 Recovered Subjects.

This study aims to evaluate retinochoroidal optical coherence tomography angiography (OCTA) parameters in patients recovered from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). This studywas an observational study that included 80 subjects being discharged after having negative reports on the reverse transcription-polymerase chain reaction (RT-PCR) test for SARS-CoV-2 to evaluate OCTA parameters of the retina. The subjects underwent an ophthalmic evaluation that included best-corrected visual acuity (BCVA), intraocular pressure (IOP), color vision (CV), contrast sensitivity (CS), and optical coherence tomography (OCT) parameters. OCTA was done for all patients and was evaluated for foveal avascular zone (FAZ) area, perimeter, and circularity index, and vessel density (VD) in superficial capillary plexus (SCP), deep capillary plexus (DCP), outer retina (OR), outer retina chorio-capillaries (ORCC), chorio-capillaries (CC), and choroid (C) using 3 x 3 mm scans. The OCTA parameters were compared with normative data of the Indian population for various parameters in question. The subjects included 54/80 (67.5%) males and 26/80 (32.5%) females having a mean age of 52.40 ± 15.71 (18-60) years. The systemic evaluation revealed 38.75% of subjects had hypertension, 30% had diabetes, 20% had kidney disease, 5% had tuberculosis, and 3.75% had coronary artery disease.The mean distance BCVA was logarithm of the minimum angle of resolution (LogMAR) (1.17 ± 0.22), mean IOP was 17.0 ± 4.0 mmHg, mean CS was 2.13 ± 0.36, 50.62% of subjects had normal CV on Farnsworth test while 47% had tritanopia, and none of the subjects had red-green CV defect on Ishihara plates. The OCT scan was normal in 90% of eyes while the posterior vitreous detachment was seen in 4% of eyes, broad vitreomacular adhesion in 2.5% of eyes, and the globally adherent epiretinal membrane was seen in 2.5% of eyes. The mean central macular thickness (CMT) measured 245.14 ± 28.41 micrometers. The mean FAZ area measured 0.37 ± 0.15 mm2, the perimeter was 3.28 ± 1.08 mm, and the circularity index measured 0.41 ± 0.10. The average VD in SCP measured 16.06 ± 12.29, in DCPmeasured 9.11 ± 8.75, in ORmeasured 6.38 ± 7.37, in ORCC measured 42.53 ± 12.46, in CCmeasured 25.83 ± 16.31, and in C measured 25.52 ± 17.49. The VD in coronavirus disease 2019 (COVID-19) subjects was significantly lesser than that in the healthy Indian population in all layers except ORCC. The SARS-CoV-2 recovered subjects have a reduced VD in retinochoroidal layersfrom COVID-19, an underlying systemic disease, or both. The CS values fall within normal limits. Several subjects show tritanopia on the Farnsworth test but no red-green CV defect on Ishihara plates.

Interplay of receptor-ligand binding and lipid domain formation during cell adhesion.

Cell adhesion involved in biological processes such as cell migration, immune responses, and cancer metastasis, is mediated by the specific binding of receptor and ligand proteins. Some of these proteins exhibit affinity for nanoscale lipid clusters in cell membranes. A key question is how these nanoscale lipid clusters influence and react to the receptor-ligand binding during cell adhesion. In this article, we review recent computational studies that shed new light on the interplay of the receptor-ligand binding and the formation of lipid domains in adhering membranes. These studies indicate that the receptor-ligand binding promotes coalescence of lipid clusters into mesoscale domains, which, in turn, enhances both the affinity and cooperativity of the receptor-ligand binding in cell-cell adhesion with mobile ligands. In contrast, in the case of cell-extracellular matrix adhesion with immobile ligands, the receptor-ligand binding and the lipid cluster coalescence can be correlated or anti-correlated, depending strongly on the ligand distribution. These findings deepen our understanding of correlations between cell adhesion and membrane heterogeneities.

Abstract 5847: Normal mammary epithelium of BRCA1 mutation carriers demonstrates increased susceptibility to cell plasticity

Abstract Background: Epithelial-mesenchymal transition (EMT) in breast cancer drives tumor invasion, metastasis and drug resistance. BRCA1 mutation carriers have a high risk for developing aggressive basal-like triple-negative breast cancers with EMT characteristics. It has been described that normal mammary epithelium of BRCA1-mutation carriers is comprised of aberrant luminal progenitor cell population resembling basal-like breast cancer cells. Yet, the role of BRCA1 in regulating epithelial cell plasticity in normal mammary gland remains largely obscure. Aim: Here, we used patient-derived normal and cancer organoid cultures from BRCA1-mutation carriers and noncarriers, to examine the effect of the BRCA1 mutation background on epithelial cell plasticity and the susceptibility to EMT. Methods and results: Mammary organoids were established from normal or cancer mammary tissues obtained from consenting patients undergoing lumpectomy or mastectomy. Isolated cells were plated in adherent basement membrane extract (BME) drops and overlaid with optimized organoid culture medium. EMT regulation in breast cancer is usually studied using cell lines and murine models. To determine the possibility to study EMT on patient-derived organoids, organoid culture media was optimized and established organoids were exposed to TGFβ to induce EMT. Morphological and phenotypic alterations were characterized using immunolabeling and visualization with confocal microscopy. Breast cancer organoids induced with TGFβ demonstrated EMT-like changes including the downregulation of E-Cadherin and upregulation of N-Cadherin. Moreover, breast cancer organoids showed typical cytoskeleton rearrangements. Here, the transformation from cortical actin into stress fibers formed in dedifferentiated mesenchymal cells, was visualized with actin staining. However, normal mammary organoids behaved differently. The cytoskeleton of BRCA-wild type (noncarriers) normal mammary organoids was not affected by the treatment. Curiously, normal mammary organoids derived from BRCA1-mutation carriers demonstrated EMT like changes upon exposure to TGFβ. To further determine mechanisms facilitating cell plasticity in BRCA1-mutation carriers, single cell RNA sequencing analysis on BRACA1-mutation carriers and noncarriers derived organoids is ongoing. Conclusion: The results suggest that BRCA1 germline mutation predisposes normal mammary epithelium dedifferentiation due to increased susceptibility to EMT. Citation Format: Rakefet Ruth Ben-Yishay, Naama Herman, Vered Noy, Eyal Mor, Aiham Mansur, Dana Ishay-Ronen. Normal mammary epithelium of BRCA1 mutation carriers demonstrates increased susceptibility to cell plasticity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5847.

Efficacy of a fine fiber film applied with a water-based lotion to improve dry skin.

Dry skin can trigger eczema that affects>10% of the US population. Dressing films have been developed to improve diseased skin, but there is limited knowledge about their effects, especially for dry skin-related symptoms. We developed an electrospinning method that creates a coating film, called a fine fiber (FF) film, characterized by the production of a transparent, thin, flexible, and adherent membrane on the skin surface. The aim of this pilot study was to examine the effects of the FF film on dry skin. Three treatments (lotion only, lotion with the FF film, and lotion with an alternative film) were designed to treat subjects with rough skin on their lower legs. Twenty-four females were enrolled and used either a water-based lotion U or a petrolatum-based lotion P and the FF film for 2 weeks followed by a regression phase for 1 week. Skin hydration and roughness scores were assessed as were the subjects' perceptions of the effects. When the FF film was applied with lotion U, skin hydration was significantly improved even after 1week, accompanied by a significant improvement of skin roughness and an increase in skin hydration by the end of the regression phase. An evaluation of moisture permeability suggested that the FF film, especially with lotion U, performed as a semipermeable membrane with optimal moisture healing effects on dry skin. The FF film together with a water-based lotion is a promising treatment to quickly improve dry skin conditions.

Cutaneous diphtheria in a patient just returned from Tahiti

During a mission in French Polynesia, a man in his 50s presented with multiple lesions on his legs that resembled little bubbles. Two weeks later, after his return to Toulon, France, the patient had numerous and painful lesions on his legs and right hand, with fibrinous ulcerations covered by an adherent membrane. The patient did not report any specific risk activities during the mission (e.g. contact with animals, poor hygiene, intravenous drug use). Clinicians suspected a Staphylococcus aureus infection with toxin production.

Descemet Membrane Endothelial Keratoplasty and Goniosynechialysis in Iridocorneal Endothelial Syndrome: Surgical Perspective and Long-Term Outcomes.

The purpose of this study was to report the long-term outcomes of Descemet membrane endothelial keratoplasty (DMEK) with goniosynechialysis in eyes with iridocorneal endothelial syndrome with an emphasis on the surgical technique. This was a retrospective series of 5 eyes of 5 patients undergoing a DMEK procedure at a tertiary eye care institute by a single surgeon. Modifications in the standard surgical technique, including the release of peripheral anterior synechiae, peripheral descemetorhexis, the release of adherent membranes, maneuvers in the anterior chamber with or without cataract extraction were logged. Long-term outcomes of the surgery in these patients are reported. Five DMEK procedures were performed in 5 eyes of 5 patients. The average age of the patients was 48.2 ± 10.8 years, and the donor was 55.2 ± 3.2 years with a mean endothelial cell density (ECD) of 2784.6 ± 231 cells/mm 2 . After a mean follow-up period of 29.6 months (24-41 mo), all the 5 grafts remained clear; the mean BCVA at the last follow-up was 0.18 ± 0.17 logarithm of the minimum angle of resolution with a mean ECD of 1086.2 ± 338 cells/mm 2 with a 61.1% reduction in ECD. intra ocular pressure was normal in all the cases. None of the patients had graft detachments that required rebubbling, and all eyes had a clear graft at the last follow-up. DMEK can be performed successfully in a case with iridocorneal endothelial syndrome with good visual outcomes with modifications to the surgical technique, including peripheral anterior synechiae release and minimizing surgical manipulation.

Autoinducer Analogs Can Provide Bactericidal Activity to Macrolides in Pseudomonas aeruginosa through Antibiotic Tolerance Reduction

Macrolide antibiotics are used in treating Pseudomonas aeruginosa chronic biofilm infections despite their unsatisfactory antibacterial activity, because they display several special activities, such as modulation of the bacterial quorum sensing and immunomodulatory effects on the host. In this study, we investigated the effects of the newly synthesized P. aeruginosa quorum-sensing autoinducer analogs (AIA-1, -2) on the activity of azithromycin and clarithromycin against P. aeruginosa. In the killing assay of planktonic cells, AIA-1 and -2 enhanced the bactericidal ability of macrolides against P. aeruginosa PAO1; however, they did not affect the minimum inhibitory concentrations of macrolides. In addition, AIA-1 and -2 considerably improved the killing activity of azithromycin and clarithromycin in biofilm cells. The results indicated that AIA-1 and -2 could affect antibiotic tolerance. Moreover, the results of hydrocarbon adherence and cell membrane permeability assays suggested that AIA-1 and -2 changed bacterial cell surface hydrophobicity and accelerated the outer membrane permeability of the hydrophobic antibiotics such as azithromycin and clarithromycin. Our study demonstrated that the new combination therapy of macrolides and AIA-1 and -2 may improve the therapeutic efficacy of macrolides in the treatment of chronic P. aeruginosa biofilm infections.

Cargo sorting at the trans-Golgi network at a glance.

The Golgi functions principally in the biogenesis and trafficking of glycoproteins and lipids. It is compartmentalized into multiple flattened adherent membrane sacs termed cisternae, which each contain a distinct repertoire of resident proteins, principally enzymes that modify newly synthesized proteins and lipids sequentially as they traffic through the stack of Golgi cisternae. Upon reaching the final compartments of the Golgi, the trans cisterna and trans-Golgi network (TGN), processed glycoproteins and lipids are packaged into coated and non-coated transport carriers derived from the trans Golgi and TGN. The cargoes of clathrin-coated vesicles are chiefly residents of endo-lysosomal organelles, while uncoated carriers ferry cargo to the cell surface. There are outstanding questions regarding the mechanisms of protein and lipid sorting within the Golgi for export to different organelles. Nonetheless, conceptual advances have begun to define the key molecular features of cargo clients and the mechanisms underlying their sorting into distinct export pathways, which we have collated in this Cell Science at a Glance article and the accompanying poster.

Complicated corneal ulceration in cats: diagnosis and treatment outcomes of 80 cases (2014-2018)

The study describes the most common clinical and endoscopic findings associated with complicated corneal ulcers in cats and evaluates the short-term outcomes after surgical interventions. Eighty client-owned cats of different breeds with corneal ulcers were included. Cats were clinically evaluated to initially determine corneal abnormalities. Endoscopic examination of the corneas was performed to determine anterior and posterior segments’ abnormalities. Non-healing superficial ulcer was treated by superficial keratectomy and deep stromal ulcers were treated using conjunctival flaps. Corneal sequestrum were treated by partial keratectomies and conjunctival flaps. Anterior synechiae were treated via peripheral iridectomy and separation of the adhesion between the iris and the inner cornea. Symblepharon were treated by removal of the adhered conjunctival membrane from the cornea. Unresponsive endophthalmitis was treated surgically by exenteration. Outcomes after surgical managements of selected corneal abnormalities were assessed clinically and endoscopically. Non-healing superficial ulcer, deep stromal ulcer with descemetocele, endophthalmitis, symblepharon, corneal sequestration and anterior synechiae with secondary glaucoma and corneal scarring were the recorded complications of corneal ulcer. FHV-1 was a common etiologic factor of corneal ulceration. Persistent corneal scars of varying shape and size developed in cats with deep stromal ulcer, anterior synechiae, and corneal sequestration. Domestic shorthaired and Persian cats were the most predisposed breeds to FHV-1 infection and subsequent corneal ulceration. Management of patients with corneal ulcer would prevent serious complications. No age or sex predisposition to complicated corneal ulceration in cats was noticed.

Cis-interaction of ligands on a supported lipid bilayer affects their binding to cell adhesion receptors

Cell adhesion on a supported lipid bilayer (SLB) functionalized with ligand proteins is a widely-used cell-mimetic model for the study of the trans receptor-ligand interaction that mediates the adhesion, and has been shown to play an important role in unravelling the molecular players in cell adhesion. Experimental studies of such cell-SLB adhesion systems often assume that there is no cis interactions between the ligands. An important question remains whether the cis-interaction affects the trans receptor-ligand interaction. Using a statistical-mechanical model and Monte Carlo simulations with biologically relevant parameters, we find that the attractive cis-interaction of strength 1 kBT between adjacent ligands on the SLB can lead to an amplification of both the affinity and cooperativity of the receptor-ligand binding, thereby facilitating the phase separation within the adhering cell membrane. In contrast, the adhesion system is less sensitive to the repulsive cis-interaction between adjacent ligands on the SLB. Our results suggest that the ligand-ligand cis-interaction should be carefully considered in the cell-SLB adhesion experiments.

Epidemiology of Diphtheria in Yemen, 2017-2018: Surveillance Data Analysis.

BackgroundAs a consequence of war and the collapse of the health system in Yemen, which prevented many people from accessing health facilities to obtain primary health care, vaccination coverage was affected, leading to a deadly diphtheria epidemic at the end of 2017.ObjectiveThis study aimed to describe the epidemiology of diphtheria in Yemen and determine its incidence and case fatality rate.MethodsData were obtained from the diphtheria surveillance program 2017-2018, using case definitions of the World Health Organization. A probable case was defined as a case involving a person having laryngitis, pharyngitis, or tonsillitis and an adherent membrane of the tonsils, pharynx, and/or nose. A confirmed case was defined as a probable case that was laboratory confirmed or linked epidemiologically to a laboratory-confirmed case. Data from the Central Statistical Organization was used to calculate the incidence per 100,000 population. A P value <.05 was considered significant.ResultsA total of 2243 cases were reported during the period between July 2017 and August 2018. About 49% (1090/2243, 48.6%) of the cases were males. About 44% (978/2243, 43.6%) of the cases involved children aged 5 to 15 years. Respiratory tract infection was the predominant symptom (2044/2243, 91.1%), followed by pseudomembrane (1822/2243, 81.2%). Based on the vaccination status, the percentages of partially vaccinated, vaccinated, unvaccinated, and unknown status patients were 6.6% (148/2243), 30.8% (690/2243), 48.6% (10902243), and 14.0% (315/2243), respectively. The overall incidence of diphtheria was 8 per 100,000 population. The highest incidence was among the age group <15 years (11 per 100,000 population), and the lowest incidence was among the age group ≥15 years (5 per 100,000 population). The overall case fatality rate among all age groups was 5%, and it was higher (10%) in the age group <5 years. Five governorates that were difficult to access (Raymah, Abyan, Sa'ada, Lahj, and Al Jawf) had a very high case fatality rate (22%).ConclusionsDiphtheria affected a large number of people in Yemen in 2017-2018. The majority of patients were partially or not vaccinated. Children aged ≤15 years were more affected, with higher fatality among children aged <5 years. Five governorates that were difficult to access had a case fatality rate twice that of the World Health Organization estimate (5%-10%). To control the diphtheria epidemic in Yemen, it is recommended to increase routine vaccination coverage and booster immunizations, increase public health awareness toward diphtheria, and strengthen the surveillance system for early detection and immediate response.

Molecular Biomechanics Controls Protein Mixing and Segregation in Adherent Membranes.

Cells interact with their environment by forming complex structures involving a multitude of proteins within assemblies in the plasma membrane. Despite the omnipresence of these assemblies, a number of questions about the correlations between the organisation of domains and the biomechanical properties of the involved proteins, namely their length, flexibility and affinity, as well as about the coupling to the elastic, fluctuating membrane, remain open. Here we address these issues by developing an effective Kinetic Monte Carlo simulation to model membrane adhesion. We apply this model to a typical experiment in which a cell binds to a functionalized solid supported bilayer and use two ligand-receptor pairs to study these couplings. We find that differences in affinity and length of proteins forming adhesive contacts result in several characteristic features in the calculated phase diagrams. One such feature is mixed states occurring even with proteins with length differences of 10 nm. Another feature are stable nanodomains with segregated proteins appearing on time scales of cell experiments, and for biologically relevant parameters. Furthermore, we show that macroscopic ring-like patterns can spontaneously form as a consequence of emergent protein fluxes. The capacity to form domains is captured by an order parameter that is founded on the virial coefficients for the membrane mediated interactions between bonds, which allow us to collapse all the data. These findings show that taking into account the role of the membrane allows us to recover a number of experimentally observed patterns. This is an important perspective in the context of explicit biological systems, which can now be studied in significant detail.

Super-Resolving Membrane Geometry and Lipid Packing in Living Cells

Membrane geometry and lipid packing actively contribute to the self-organization of reactions at the plasma membrane. However, obtaining quantitative measurements of membrane geometry and lipid packing in living cells remains, indisputably, a non-trivial task. Here, we combine fluorescence lifetime imaging and 3D stimulated emission-depletion microscopy to simultaneously visualize membrane topography (with 2.5+/-0.9 nm axial localization accuracy) and lipid packing at the adherent membrane of living cells.

Unique Properties of Tightly Docked Membranes Prior to their Fusion

Membrane merger through fusion is essential in myriad of processes including neurotransmission and viral infection. Although there are various classes of fusion proteins, they are believed to catalyze membrane fusion through a common pathway. Despite the importance of understanding of this process, the exact mechanisms underlying steps immediately before the first bilayer disruption remain uncharacterized. Here, we characterized mechanism leading to a change in lipid arrangement in membranes arrested in a state that precedes hemifusion. Such tightly adhering membranes with a distance of <1 nm are known from cryo-electron microscopy as fusion intermediates of trafficking organelles, mitochondria, or during cell entry by enveloped viruses. With the use of an in vitro reconstitution system consisting of lipid vesicles with SNARE proteins, we demonstrate formation of a metastable, divalent cation-independent, and protein-free membrane-membrane interface characterized by increased thickness. Furthermore, we confirm that structural rearrangements in the membranes are arising due to membrane intrinsic properties by performing all-atom molecular dynamics simulations of double-membrane systems at varying distances. In turn, we would like to propose that increase in membrane thickness arises by dehydration-driven lipid headgroup tilting leading to lateral area shrinkage that results in increased bilayer thickness visible in experiments.