Biomimetic lipid/polymer colorimetric membranes

Abstract

Elucidation of the structure and organization of biological membranes is essential for the understanding of various cellular functions that rely on biochemical processes occurring within membranes, such as response to environmental conditions, signaling mechanisms, cell-cell communication, cell motility, or protein transport. Parameters affecting membrane properties include the molecular composition of the membrane, the structure and fluidity of the lipid bilayer, and the interactions of membrane components with the cell environment. Such membrane properties have been investigated by a variety of analytical and structural methods (1). To better detect and analyze diverse membrane processes, we have recently developed a novel colorimetric lipid assay (2-7). This assay has been used to examine various aspects of membrane biology, including enzymatic cleavage of lipids (2), screening of antimicrobial peptides (3), peptide-membrane interactions (4), ion sensing (5), antibody-epitope recognition (6), as well as assessing the activities of membrane penetrationenhancers (7). This colorimetric platform consists of supramolecular aggregates of physiological lipid molecules embedded within a chromatic polydiacetylenic (PDA) lipid matrix (8). Conjugated polydiacetylenes have been shown to exhibit rapid blue-red colorimetric transitions upon interfacial disruption of the pendant alkyl sidechains (8). Our results have demonstrated that lipid/PDA systems similarly exhibit unique bio-chromatic transitions attributed to specific interfacial perturbation of the incorporated lipid domains. Such interactions indirectly affect the conjugated network of the adjacent PDA framework, thereby inducing colorimetric transitions (2-7).In the present work we probe in detail the structures and organization of the lipid and polymer components within the chromatic particles. In addition, experiments were conducted to evaluate the applicability of the colorimetric system for studying the effects of specific lipid components, such as cholesterol or cardiolipin, upon the rigidity and thermal stability of membranes. Understanding the molecular properties of the lipid/PDA system is essential for evaluation of whether the colorimetric platform can indeed serve as a reliable model for studying cellular membrane processes.

Mechanisms of α-Defensin Bactericidal Action: Comparative Membrane Disruption by Cryptdin-4 and Its Disulfide-Null Analogue

“…Nevertheless, incorporation of cardiolipin into the 30% electronegative lipid bilayer promoted deeper insertion of Crp4 into the membrane and induced liposomal leakage. Such effect could be attributed to the ability of cardiolipin to increase fluidity of lipid bilayers in model membranes (35) and in bacteria (36). In addition, cardiolipin reportedly forms CL-containing lipid domains in E. coli cells (37), leading us to speculate that CL domains may serve as highly charged “gates” to facilitate Crp4 movement into and through lipid membranes.…”

Chromatic response of polydiacetylene vesicle induced by the permeation of methotrexate

“…For diverse membrane processes, colorimetric assay can be adopted for studying enzymatic cleavage of lipids, 1 screening of antimicrobial peptides, 2 membrane-peptide interaction, 3 ion sensing, 4 and assessing membrane penetration enhancers. 6 Recently, many studies have reported about the sensor fabrication using 10,12-pentacosadiynoic acid (PCDA) and its derivatives. 6 Recently, many studies have reported about the sensor fabrication using 10,12-pentacosadiynoic acid (PCDA) and its derivatives.…”

Vaccinia Virus Interactions with the Cell Membrane Studied by New Chromatic Vesicle and Cell Sensor Assays

“…An important question this study aims to address concerns the dependence of membrane interactions of VV upon bilayer makeup and organization. In that regard, the lipid composition of the chromatic lipid/PDA vesicle platform can be easily varied (25). Figures 2 to 5 present experimental results designed to evaluate the extent of bilayer binding, penetration, and membrane fusion of vaccinia virus and examine the relationship between these parameters and lipid constituents in the bilayer.…”

“…Figure 1 depicts the principle of the lipid/PDA vesicle assay for studying membrane interactions. The mixed vesicles comprise both lipid domains, constituting the biomimetic membrane platform interspersed within the PDA matrix that functions as the chromatic reporter for the biological events occurring within the membrane (25). Interactions of viral particles with the lipid/PDA vesicles induce chromatic transformations within the polymer matrix, and analysis of those transformations yield biophysical information on events occurring within the membrane bilayers.…”