Abstract
Tethered bilayer lipid membranes (tBLMs) have been known as stable and versatile experimental platforms for protein–membrane interaction studies. In this work, the assembly of functional tBLMs on silver substrates and the effect of the molecular chain-length of backfiller molecules on their properties were investigated. The following backfillers 3-mercapto-1-propanol (3M1P), 4-mercapto-1-butanol (4M1B), 6-mercapto-1-hexanol (6M1H), and 9-mercapto-1-nonanol (9M1N) mixed with the molecular anchor WC14 (20-tetradecyloxy-3,6,9,12,15,18,22 heptaoxahexatricontane-1-thiol) were used to form self-assembled monolayers (SAMs) on silver, which influenced a fusion of multilamellar vesicles and the formation of tBLMs. Spectroscopic analysis by SERS and RAIRS has shown that by using different-length backfiller molecules, it is possible to control WC14 anchor molecules orientation on the surface. An introduction of increasingly longer surface backfillers in the mixed SAM may be related to the increasing SAMs molecular order and more vertical orientation of WC14 at both the hydrophilic ethylenoxide segment and the hydrophobic lipid bilayer anchoring alkane chains. Since no clustering of WC14 alkane chains, which is deleterious for tBLM integrity, was observed on dry samples, the suitability of mixed-component SAMs for subsequent tBLM formation was further interrogated by electrochemical impedance spectroscopy (EIS). EIS showed the arrangement of well-insulating tBLMs if 3M1P was used as a backfiller. An increase in the length of the backfiller led to increased defectiveness of tBLMs. Despite variable defectiveness, all tBLMs responded to the pore-forming cholesterol-dependent cytolysin, vaginolysin in a manner consistent with the functional reconstitution of the toxin into phospholipid bilayer. This experiment demonstrates the biological relevance of tBLMs assembled on silver surfaces and indicates their utility as biosensing elements for the detection of pore-forming toxins in liquid samples.
Highlights
The development of biological membrane models emerged over the past few decades to systematically study fundamental processes at lipid bilayer interfaces, such as the membrane proteins functioning, cell–cell signaling, or protein–membrane interactions.Biomimetic membrane models should provide a simplified system for coherent investigation of the membrane while maintaining the fundamental membrane characteristics, such as membrane fluidity or electrical sealing properties [1]
We explored the effect of different compositions of molecular anchors on the formation of Tethered bilayer lipid membranes (tBLMs) on silver
Spectroscopic analysis by surface-enhanced Raman scattering (SERS) and reflection−absorption infrared spectroscopy (RAIRS) showed that using different-length backfiller molecules, it is possible to control an orientation of WC14 anchor molecules on the surface
Summary
The development of biological membrane models emerged over the past few decades to systematically study fundamental processes at lipid bilayer interfaces, such as the membrane proteins functioning, cell–cell signaling, or protein–membrane interactions.Biomimetic membrane models should provide a simplified system for coherent investigation of the membrane while maintaining the fundamental membrane characteristics, such as membrane fluidity or electrical sealing properties [1]. Tethered bilayer lipid membranes (tBLMs) are considered as a comprehensive experimental platform for membrane biosensors They have been used in various studies ranging from the analysis of biological membrane structure and functions, studies of the membrane–protein and cell–membrane interactions, antigen and antibody binding, applications as biosensors and energygenerating devices [2]. In such biomembrane models, a fluidic lipid bilayer is attached and stabilized on a solid surface via a thin organic layer. Attachment of tBLMs to noble metals allows monitoring of the biologically relevant events with surface-sensitive techniques, including surface plasmon resonance spectroscopy (SPR), measurements with a quartz-crystal microbalance (QCM), surface-enhanced Raman scattering (SERS), and electrochemical techniques, such as electrochemical impedance spectroscopy (EIS) [12,13]
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