Organization Of Monolayers Research Articles

PH dependence of daunorubicin interactions with model DMPC:Cholesterol membranes

Mixed monolayers composed of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC):Cholesterol 7:3 prepared by the Langmuir-Blodgett method were used as model membranes to investigate the influence of the anticancer drug daunorubicin (DNR) on the properties of the lipid membrane. The Langmuir monolayer experiments revealed that drug – membrane interactions are pH-dependent. The changes in monolayer organization at subphases of pH 7.4 containing daunorubicin visualized by Brewster Angle Microscopy showed that in the presence of the drug the typical morphology observed for phospholipid layers containing cholesterol was no longer seen. It supports the explanation of the mechanism of the drug incorporation into the layers in terms of the competition between DNR molecules and cholesterol in the layer. Increasing surface pressure with time and increasing value of limiting surface pressure with increasing drug concentration in the subphase confirmed incorporation of the drug into the membranes. The interactions between the lipid monolayer and the drug at pH 5.4 were of electrostatic nature between the negative part of the DMPC molecule and positively charged drug, while at pH 7.4 contribution of interactions of daunorubicin with cholesterol was observed. Large differences of the surface–pressure vs. time plots were observed at both pH values when the DMPC:Cholesterol monolayer was not well organized yet. The voltammograms recorded for DMPC:Cholesterol monolayers transferred from the air-water interface onto gold electrode confirmed the presence of the drug in the lipid layer. Based on the charge of the oxidation-reduction peaks corresponding to the redox processes of quinone-hydroquinone group in daunorubicin, the initial surface concentration of the drug in the membrane and the drug release profile to the solution were evaluated.

Cholesterol strongly affects the organization of lipid monolayers studied as models of the milk fat globule membrane: Condensing effect and change in the lipid domain morphology

The biological membrane that surrounds the milk fat globules exhibits phase separation of polar lipids that is poorly known. The objective of this study was to investigate the role played by cholesterol in the organization of monolayers prepared as models of the milk fat globule membrane (MFGM). Differential scanning calorimetry and X-ray diffraction experiments allowed characterization of the gel to liquid crystalline phase transition temperature of lipids, Tm ~35°C, in vesicles prepared with a MFGM lipid extract. For temperature below Tm, atomic force microscopy revealed phase separation of lipids at 30mN·m−1 in Langmuir–Blodgett monolayers of the MFGM lipid extract. The high Tm lipids form liquid condensed (LC) domains that protrude by about 1.5nm from the continuous liquid expanded (LE) phase. Cholesterol was added to the MFGM extract up to 30% of polar lipids (cholesterol/milk sphingomyelin (MSM) molar ratio of 50/50). Compression isotherms evidenced the condensing effect of the cholesterol onto the MFGM lipid monolayers. Topography of the monolayers showed a decrease in the area of the LC domains and in the height difference H between the LC domains and the continuous LE phase, as the cholesterol content increased in the MFGM lipid monolayers. These results were interpreted in terms of nucleation effects of cholesterol and decrease of the line tension between LC domains and LE phase in the MFGM lipid monolayers. This study revealed the major structural role of cholesterol in the MFGM that could be involved in biological functions of this interface (e.g. mechanisms of milk fat globule digestion).

Self-assembly of tetraalkoxydinaphthophenazines in monolayers on HOPG by scanning tunneling microscopy

2D supramolecular organization in monolayers of tetraalkoxydinaphthophenazines, a new group of solution processable organic semiconductors obtained by simple functionalization of indanthrone (6,15-dihydrodinaphtho[2,3-a:2′,3′-h]phenazine-5,9,14,18-tetraone), an old intractable dye, was investigated by scanning tunneling microscopy (STM). Five derivatives with increasing substituent length from butoxy (P-C4) to dodecyloxy (P-C12) were tested. All derivatives show a strong tendency to form ordered monolayers on HOPG graphite via self-assembly which constitute of rows of molecules oriented in one direction. However, local arrangement in this 2D supramolecular organization is strongly dependent on the substituent length. Two tendencies in the structural evolution are observed. For butoxy (P-C4), hexyloxy (P-C6) and octyloxy (P-C8) derivatives increasing substituent length results in the transformation of the structure governed by the conjugated core interactions to the one in which mutual interactions of the alkoxy groups dominate. As a consequence, for P-C8 a very stable 2D structure is obtained with a nearly rectangular 2D unit cell, as a consequence of the alkoxy group interdigitation in two perpendicular directions. With further increase of the substituent length to decyloxy (P-C10) and dodecyloxy (P-C12) a different effect is observed—a directional expansion of the unit cell along the longitudinal axis of the molecules. This is a consequence of structural nonequivalence of the alkoxy groups attached to the same aromatic ring.

Real time acoustic profiling of a live cancerous cell monolayer using QCM

A Quartz Crystal Microbalance (QCM) is a well-established analytical weighing tool that can serve in the monitoring of the viscoelastic properties of a wide range of chemical and biological analytes, as well as investigating adsorption processes occurring at specifically engineered solid–liquid interfaces. More specifically, several recent works have reported the successful QCM-mediated acoustic profiling of various biophysical transformations of cancerous cells (cancer cell profiling). Such a cancer cell acoustic profiling is aimed at characterizing adsorption, adhesion, spreading, and the homeostatic processes of initially suspended cancer cells, seeded onto various chemically engineered nanostructured QCM sensors.The nanostructuration of sensing the QCM electrode surfaces, with well-defined ligand compositions, provides a unique tool for deeply featuring the physico-chemical interaction basis of multi-parameter bio-molecular recognition events. Even individual recognition ones can be tracked to precisely probe the functional behavior of tested cellular systems. In this regard, the well-recognized 2D organization of self-assembled monolayers (SAMs), of alkane-thiolates/disulfides, onto the bare surfaces of metals, such as gold, generates model chemically defined and structured organic surfaces, for cell interaction, when possessing specific ligands, enabling cell attachment and/or interaction.Herein, and in contrast to the most common suspended cell formats, the real-time in situ sensing, and biochemical profiling, of live raw non-processed cell line monolayers (cell monolayer formats) has been demonstrated to be felicitous. This bio-recognition event used a well-defined chemical composition of a cyclic disulfide-based SAM functional layer for QCM electrode nanostructuration/functionalization. This cyclic disulfide-based functional layer also has been shown to provide a robust sensing platform, quite well adapted to the non-planar nature of tested cancer cell monolayers, in a buffered aqueous environment. Corresponding bio-recognition events, for real-time in situ sensing and profiling, of non-suspended cell monolayers, enabled a significant reduction of the signal processing time, while keeping the interacting cells in their native state. As a matter of consequence, this new QCM-relating development may be considered as a significant step milestone, en-route to multiplexed in/ex vivo real-time diagnostics of tissue pathologies.

In vitro and in vivo ocular biocompatibility of electrospun poly(ɛ-caprolactone) nanofibers

Biocompatibility is a requirement for the development of nanofibers for ophthalmic applications. In this study, nanofibers were elaborated using poly(ε-caprolactone) via electrospinning. The ocular biocompatibility of this material was investigated. MIO-M1 and ARPE-19 cell cultures were incubated with nanofibers and cellular responses were monitored by viability and morphology. The in vitro biocompatibility revealed that the nanofibers were not cytotoxic to the ocular cells. These cells exposed to the nanofibers proliferated and formed an organized monolayer. ARPE-19 and MIO-M1 cells were capable of expressing GFAP, respectively, demonstrating their functionality. Nanofibers were inserted into the vitreous cavity of the rat’s eye for 10days and the in vivo biocompatibility was investigated using Optical Coherence Tomography (OCT), histology and measuring the expression of pro-inflammatory genes (IL-1β, TNF-α, VEGF and iNOS) (real-time PCR). The OCT and the histological analyzes exhibited the preserved architecture of the tissues of the eye. The biomaterial did not elicit an inflammatory reaction and pro-inflammatory cytokines were not expressed by the retinal cells, and the other posterior tissues of the eye. Results from the biocompatibility studies indicated that the nanofibers exhibited a high degree of cellular biocompatibility and short-term intraocular tolerance, indicating that they might be applied as drug carrier for ophthalmic use.

Mapping the development of cerebellar Purkinje cells in zebrafish.

The cells that comprise the cerebellum perform a complex integration of neural inputs to influence motor control and coordination. The functioning of this circuit depends upon Purkinje cells and other cerebellar neurons forming in the precise place and time during development. Zebrafish provide a useful platform for modeling disease and studying gene function, thus a quantitative metric of normal zebrafish cerebellar development is key for understanding how gene mutations affect the cerebellum. To begin to quantitatively measure cerebellar development in zebrafish, we have characterized the spatial and temporal patterning of Purkinje cells during the first 2 weeks of development. Differentiated Purkinje cells first emerged by 2.8 days post fertilization and were spatially patterned into separate dorsomedial and ventrolateral clusters that merged at around 4 days. Quantification of the Purkinje cell layer revealed that there was a logarithmic increase in both Purkinje cell number as well as overall volume during the first 2 weeks, while the entire region curved forward in an anterior, then ventral direction. Purkinje cell dendrites were positioned next to parallel fibers as early as 3.3 days, and Purkinje cell diameter decreased significantly from 3.3 to 14 days, possibly due to cytoplasmic reappropriation into maturing dendritic arbors. A nearest neighbor analysis showed that Purkinje cells moved slightly apart from each other from 3 to 14 days, perhaps spreading as the organized monolayer forms. This study establishes a quantitative spatiotemporal map of Purkinje cell development in zebrafish that provides an important metric for studies of cerebellar development and disease.

Comparison of the influence of humidity and D-mannitol on the organization of tetraethylene glycol-terminated self-assembled monolayers and immobilized antimicrobial peptides.

We report the use of polarization-modulation infrared reflection-absorption spectroscopy (PM-IRRAS) to characterize the effects of relative humidity (RH) and d-mannitol on the conformations of tetraethylene glycol (EG4)-terminated self-assembled monolayers (SAMs) and immobilized antimicrobial peptides (Cecropin P1 and a hybrid of Cecropin A (1-8) and Melittin (1-18)). These results are used to assess the extent to which d-mannitol can substitute for water in promoting conformational states of the SAMs and oligopeptides similar to those induced by hydration. Our measurements reveal a red shift of the COC asymmetric stretching vibration of the EG4-terminated SAMs with increasing humidity, consistent with a transition from a mixed all-trans/helical (7/2 helix) conformation at 0% RH to a predominantly helical conformation at 90% RH. Significantly, under dry conditions, a thin (2 nm in thickness) overlayer of d-mannitol generated the COC spectroscopic signature of the EG4-terminated SAM measured at high humidity. Comparisons of the effects of humidity and d-mannitol on the secondary structure of the two oligopeptides also revealed both to cause the amide I peak positions, which were measured in dry air (and without d-mannitol) to correspond to α-helical conformations, to undergo red-shifts. The magnitudes of the red-shifts, however, were more pronounced for dry d-mannitol than for high RH, with Cecropin P1 and the hybrid peptide exhibiting amide I peak positions under d-mannitol consistent with bulk aqueous solution secondary structures (random and β-sheet, respectively). These results are discussed in the context of prior reports of the tendency of d-mannitol to form glassy states in the absence of water. Overall, the results presented in this paper support the hypothesis that d-mannitol can substitute, in at least some ways, for the influence of water on the conformational states of biologically relevant molecules at interfaces. The results provide guidance for the design of interfaces for water-free biologics.

Fabrication of Langmuir–Blodgett thin film for organic vapor detection using a novel N,N′-dicyclohexyl-3,4:9,10-perylenebis (dicarboximide)

The Langmuir–Blodgett (LB) thin film fabrication and gas sensing properties of a novel N,N′-dicyclohexyl-3,4:9,10-perylenebis (dicarboximide) (FY2) is reported in this study. Surface pressure changes as a function of surface area of FY2 molecule at the water surface shows a well organized and stable monolayer with a 22.5mNm−1 surface pressure value for LB film deposition. LB deposition processes is characterized by UV–vis spectroscopy and quartz crystal microbalance (QCM) measurement system. Transfer ratio values are found to be 0.93 for glass and 0.95 for quartz crystal substrate. Gas sensing properties of these LB films against volatile organic compounds (VOCs) such as chloroform, benzene, toluene and ethyl alcohol are studied using the QCM technique. The FY2 LB film sensor sensitivities are calculated for chloroform, benzene, toluene and ethyl alcohol, 5.32×10−4, 3.52×10−4, 1.32×10−4 and 1.16×10−4Hzppm−1, respectively. LB films are more sensitive to chloroform than other vapors and the response of the LB films to chloroform is fast, large and reversible. Associated limits of detection are found to be between 1.12×104 and 5.17×104ppm for these organic vapors. The novel FY2 material is promising as a vapor sensing device at room temperature.

Surface Selection Rule of Infrared Diffuse Reflection Spectrometry for Analysis of Molecular Adsorbates on a Rough Surface of a Nonabsorbing Medium

The surface selection rule (SSR) for discussing the molecular orientation in a thin film adsorbed on a rough surface is determined by analyzing a surface monolayer by defining the angle of incidence and polarizations. As the standard sample, a highly organized self-assembled monolayer (SAM) on a rough alumina surface is employed. By introducing crossed-Nicol polarizers in the incident and detection paths, the specular reflection and diffuse reflection components are readily separated. To fully understand the spectra of the SAM, a new idea is proposed that the incidental light can be excluded from the discussion when the angle of incidence is small, which is named the pseudotransmission (pd-Tr) model. Another important idea is that a part of a spectrum is degraded in the signal-to-noise ratio by the suppression of incidental light on the rough surface via a deconstructive interference, which can experimentally be revealed by the crossed-Nicol measurements of single-beam spectra depending on the angle of incidence. Through the experiments of all the combinations of polarizations and angles of incidence, the pd-Tr model and the light suppression are found to be an important base to fully understand the SSR of molecular adsorbates on a rough surface of a nonabsorbing medium.

Scaffold Architecture Controls Insulinoma Clustering, Viability, and Insulin Production

Recently, in vitro diagnostic tools have shifted focus toward personalized medicine by incorporating patient cells into traditional test beds. These cell-based platforms commonly utilize two-dimensional substrates that lack the ability to support three-dimensional cell structures seen in vivo. As monolayer cell cultures have previously been shown to function differently than cells in vivo, the results of such in vitro tests may not accurately reflect cell response in vivo. It is therefore of interest to determine the relationships between substrate architecture, cell structure, and cell function in 3D cell-based platforms. To investigate the effect of substrate architecture on insulinoma organization and function, insulinomas were seeded onto 2D gelatin substrates and 3D fibrous gelatin scaffolds with three distinct fiber diameters and fiber densities. Cell viability and clustering was assessed at culture days 3, 5, and 7 with baseline insulin secretion and glucose-stimulated insulin production measured at day 7. Small, closely spaced gelatin fibers promoted the formation of large, rounded insulinoma clusters, whereas monolayer organization and large fibers prevented cell clustering and reduced glucose-stimulated insulin production. Taken together, these data show that scaffold properties can be used to control the organization and function of insulin-producing cells and may be useful as a 3D test bed for diabetes drug development.

Titaniumcarboxonitride layer increased biocompatibility of medical polyetherurethanes

Polyetherurethane (PEU) is in use for blood-contacted devices because of its excellent mechanical properties. However, poor hemocompatibility of the hydrophobic material required surface modification or endothelialization. To increase the biocompatibility of PEU, the polymer was coated with a titaniumcarboxonitride [Ti(C,N,O)] layer by a plasma-activated chemical vapor deposition (PACVD) process. Biocompatibility of titaniferously coated PEU was verified using static and dynamic cell culture techniques. Titaniferous coating significantly improved proliferation and mitochondrial activity of human endothelial cells on PEU. These cells captured significantly less mononuclear cells and platelets. Under shear stress for up to 72 hours, titaniferous coating increased endothelial cell adhesion, spreading, and cell density to form an organized monolayer covering the whole luminal surface of vascular PEU grafts. In summary, coating of PEU surfaces with Ti(C,N,O) might be a promising strategy to improve the biocompatibility of biomedical biomaterials.

Role of squalene in the organization of monolayers derived from lipid extracts of Halobacterium salinarum.

We have studied interfacial compressibility and lateral organization in monolayer configurations of total (squalene containing) and polar (squalene-devoid) lipid extracts of Halobacterium salinarum NRC-1, an extremely halophilic archaeon. Pressure-area isotherms derived from Langmuir experiments reveal that packing characteristics and elastic compressibility are strongly influenced by the presence of squalene in the total lipid extract. In conjunction with control experiments using mixtures of DPhPC and squalene, our results establish that the presence of squalene significantly extends elastic area compressibility of total lipid extracts, suggesting it has a role in facilitating tighter packing of archaeal lipid mixtures. Moreover, we find that squalene also influences spatial organization in archaeal membranes. Epifluorescence and atomic force microscopy characterization of Langmuir monolayers transferred onto solid hydrophilic substrates reveal an unusual domain morphology. Individual domains of microscopic dimensions (as well as their extended networks) exhibiting a peculiar bowl-like topography are evident in atomic force microscopy images. The tall rims outlining individual domains indicate that squalene accumulates at the domain periphery in a manner similar to the accumulation of cholesterol at domain boundaries in their mixtures with phospholipids. Taken together, the results presented here support the notion that squalene plays a role in modulating molecular packing and lateral organization (i.e., domain formation) in the membranes of archaea analogous to that of cholesterol in eukaryotic membranes.

Functionalization of biodegradable magnesium alloy implants with alkylphosphonate self-assembled films

Mg and Mg-alloys are promising materials for biodegradable implants. In order to slowdown the Mg-alloy (AZ91D) degradation and enhance its biocompatibility, the alloy surface was modified with alkylphosphonate self-assembling films. The binding configuration and the structural organization of alkylphosphonate monolayers on the Mg-alloy surface were investigated using contact angle measurements, FTIR, and XPS. Combination of FTIR and XPS data indicated the presence of several different bonding modes (mono-, di-, and tri dentate) of phosphonate head groups with the alloy surface. The existence of well organized and ordered self-assembled alkylphosphonate monolayers with good barrier protecting properties in a physiological solution is a key step in the development of biocompatible Mg-alloy implants.

Properties of long alkyl-chained resorcin[4]arenes in bilayers and on the Langmuir trough

Two resorcinarenes and one cavitand having 10-(decylthio)decyl side chains were studied by using both a planar bilayer conductance voltage clamp device and a Langmuir trough. The former detects the presence of pore formation in a phospholipid bilayer and the latter probes the aggregation behavior of the amphiphiles as a monolayer. The Langmuir trough behavior of these amphiphiles showed that higher polarity head groups dominated organization, but as the head group polarity decreased, monolayer organization was dominated by the four side chains. Among the three, i.e., resorcinarene, octamethyl resorcinarene, and cavitand, only the methylated head group derivative formed ion-conducting pores in bilayers.

Significance of the Amide Functionality on DOPA-Based Monolayers on Gold

The adhesive proteins secreted by marine mussels contain an unusual amino acid, 3,4-dihydroxyphenylalanine (DOPA), that is responsible for the cohesive and adhesive strength of this natural glue and gives mussels the ability to attach themselves to rocks, metals, and plastics. Here we report a detailed structural and spectroscopic investigation of the interface between N-stearoyldopamine and a single-crystalline Au(111) model surface and an amide-absent molecule, 4-stearylcatechol, also on Au(111), with the aim of understanding the role of the amide functionality in the packing, orientation, and fundamental interaction between the substrate and the monolayer formed from an aqueous environment by the Langmuir-Blodgett technique. The organization of monolayers on gold was observed directly and studied in detail by X-ray photoelectron spectroscopy (XPS), contact angle measurements (CA), surface-enhanced Raman spectroscopy (SERS), infrared reflection-absorption spectroscopy (IRRAS), and atomic force microscopy (AFM). Our study shows that within the monolayer the catecholic oxygen atoms are coordinated to the gold surface, having a more perpendicular orientation with respect to the aromatic ring and the apparently tilted alkyl chains, whereas the amide functionality stabilizes the monolayer that is formed.

Spontaneous and dense assemblies of nanoparticles within micro-channels by the bubble deposition method

We explore the potential of the bubble deposition method (BDM) for the specific monolayer organization of spherical and anisotropic NPs onto microstructured surfaces. These structurations cannot be only explained by the classical interactions between nano-objects and substrates but mainly by a combination of the drying front peculiar to the BDM with lithographically patterned substrates. Extended up to the integration of SWNT, this approach represents a simple, efficient, nano-object independent and potentially useful route for nanometric device realization.

Highly ordered structural organization of organic semiconductor monolayers on HOPG and Au(111) — STM studies of alkylphenyl N-substituted perylene diimide at liquid–solid interface

Scanning tunneling microscopy was used to investigate self-organization in mono- or multilayers of an organic semiconductor used for the fabrication of n-channel field effect transistors, namely N,N′-bis(4-n-butylphenyl)-perylene-3,4:9,10-tetracarboxylic-diimide (4-n-BuPh-PTCDI). Two types of substrates were used: HOPG and reconstructed Au(111). All investigations were performed at liquid–solid interface in a trichlorobenzene solution. Monolayers deposited directly on the HOPG show a brick-wall organization with individual molecules lying flat on the substrate surface (the planes of aromatic cores being parallel to this surface). Monolayers obtained by controlled dissolution of a previously deposited multilayer show a different 2D organization in which individual molecules are in the edge-on position i.e. stand perpendicular to the substrate surface with their long axis parallel to it. This finding clearly demonstrates the effect of the upper-lying layers on the first monolayer which changes the balance in the molecule–substrate and molecule–molecule interactions, leading to a rotation of the molecules in the first layer. A very similar structure of densely packed molecules, oriented perpendicular to the substrate, is also found for the monolayer deposited on the Au(111) surface.

Impact of the Spacer on the Condensing Effect of Fluorinated Chains Investigated by Grazing Incidence X-ray Diffraction on Ultrathin Langmuir Monolayers

Langmuir monolayers of double perfluoroalkyl(alkyl) chain amphiphiles fitted with a monomorpholinophosphate polar head, [C(n)F(2n+1)(CH(2))(m)O](2)P(O)[N(CH(2)CH(2))(2)O] (di(FnHm)MP with n = 6, 8, or 9; and m = 1 or 2), were investigated by surface pressure (π)/molecular area (A(0)) compression isotherms for temperatures ranging from 15 to 50 °C, and by grazing-incidence X-ray diffraction (GIXD) at 25 °C. Ultrathin monolayers were obtained for these short surfactants. Though the hydrocarbon spacer is short, it has a remarkable impact on the monolayer's organization. At 25 °C, whereas di(F8H2)MP monolayer presents a liquid expanded (LE)/liquid condensed (LC) transition, simply replacing one CH(2) by a CF(2) in the latter compound's structure at constant chain length, i.e. shortening the spacer from 2 to 1 CH(2) (as in di(F9H1)MP), suppresses the LE phase. At 25°, GIXD established that for both di(F8H2)MP and di(F9H1)MP, the chains form an hexagonal lattice in the LC phase. The collective tilt of the two compounds is close to zero. The lattice of the dense phase can be compressed, as assessed by the continuous linear decrease of the d spacing with increasing pressure. This indicates that the azimuthal distribution of the molecular tilts is progressively reduced upon compression. The d value for di(F9H1)MP is significantly lower than that of di(F8H2)MP, providing evidence for strong condensing effect of the fluorinated chains. Molecular areas were determined directly from the compression curves and also from the X-ray data, the latter allowing reconstruction of the compression isotherms. The calculated lattice compressibilities are ~30% and 50% of the macroscopic compressibilities for di(F9H1)MP and di(F8H2)MP, respectively. Comparison with the experimentally determined isotherms shows that the monolayer of di(F9H1)MP is more stable than that of di(F8H2)MP. The enthalpies and entropies determined for di(F9H1)MP and di(F8H2)MP, derived from the Clausius-Clapeyron equation, confirm that the observed transitions are both of the LE/LC type, although the triple point temperatures are strikingly different (27 °C vs -18 °C); this large difference further illustrates the stabilizing effect of the fluorinated chains. Disorder is hindered by the fluorinated chains and facilitated by a hydrocarbon spacer when larger than 1 CH(2).

Lanthanide-Based NMR: A Tool To Investigate Component Distribution in Mixed-Monolayer-Protected Nanoparticles

Gd(3+) ions, once bound to the monolayer of organic molecules coating the surface of gold nanoparticles, produce a paramagnetic relaxation enhancement (PRE) that broadens and eventually cancels the signals of the nuclear spins located nearby (within 1.6 nm distance). In the case of nanoparticles coated with mixed monolayers, the signals arising from the different coating molecules experience different PRE, depending on their distance from the binding site. As a consequence, observation of the signal broadening patterns provides direct information on the monolayer organization.

Interactions of the antifungal mycosubtilin with ergosterol-containing interfacial monolayers

Mycosubtilin, an antimicrobial lipopeptide produced by Bacillus subtilis, is characterized by strong antifungal activities. The molecular mechanisms of its biological activities on the membranes of the sensitive yeasts or fungi have not yet been clearly elucidated. Our purpose was to mimic the mycosubtilin interactions with these membranes using various Langmuir monolayers. Since the major sterol of yeasts or fungi is ergosterol, the interactions of mycosubtilin with monolayers constituted by ergosterol, DPPC/ergosterol or DPPC/sphingomyelin/ergosterol were examined at different initial surface pressures (Πi). Plotting the mycosubtilin-induced surface pressure increases versus Πi allowed to determine that the exclusion pressures of mycosubtilin from these different monolayers is higher than the surface prevailing within the biological membranes. However, this behavior was lost when mycosubtilin was interacting with ergosteryl acetate-containing monolayers. This suggests the involvement of the sterol alcohol group in the mycosubtilin interactions within membranes. Furthermore, the behavior of mycosubtilin with stigmasterol, similar to that observed with ergosterol, differs from that previously observed with cholesterol, suggesting a role of the alkyl side chain of the sterols. The adsorption of mycosubtilin to ergosterol monolayers induced changes in the lipopeptide orientation at the air–water interface as revealed by polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS). Moreover, imaging the air–water interface by Brewster angle microscopy (BAM) indicates that mycosubtilin induced changes in the organization and morphology of monolayers containing pure ergosterol with the appearance of small condensed dots, suggesting again that the target of mycosubtilin might be the ergosterol present in the membranes of the sensitive yeasts or fungi.