RESUMEN
In nature, plants and some bacteria have evolved an ability to convert solar energy into chemical energy usable by the organism. This process involves several proteins and the creation of a chemical gradient across the cell membrane. To transfer this process to a laboratory environment, several conditions have to be met: i) proteins need to be reconstituted into a lipid membrane, ii) the proteins need to be correctly oriented and functional and, finally, iii) the lipid membrane should be capable of maintaining chemical and electrical gradients. Investigating the processes of photosynthesis and energy generation in vivo is a difficult task due to the complexity of the membrane and its associated proteins. Solid, supported lipid bilayers provide a good model system for the systematic investigation of the different components involved in the photosynthetic pathway. In this review, the progress made to date in the development of supported lipid bilayer systems suitable for the investigation of membrane proteins is described; in particular, there is a focus on those used for the reconstitution of proteins involved in light capture.
Asunto(s)
Materiales Biomiméticos/síntesis química , Suministros de Energía Eléctrica , Transferencia de Energía , Membrana Dobles de Lípidos/química , Proteínas del Complejo del Centro de Reacción Fotosintética/química , Proteínas del Complejo del Centro de Reacción Fotosintética/efectos de la radiación , Materiales Biomiméticos/efectos de la radiación , Diseño de Equipo , Luz , Membrana Dobles de Lípidos/efectos de la radiaciónRESUMEN
A novel poly(amino acid methacrylate) brush comprising zwitterionic cysteine groups (PCysMA) was utilized as a support for lipid bilayers. The polymer brush provides a 12-nm-thick cushion between the underlying hard support and the aqueous phase. At neutral pH, the zeta potential of the PCysMA brush was â¼-10 mV. Cationic vesicles containing >25% DOTAP were found to form a homogeneous lipid bilayer, as determined by a combination of surface analytical techniques. The lipid mobility as measured by FRAP (fluorescence recovery after photobleaching) gave diffusion coefficients of â¼1.5 µm(2) s(-1), which are comparable to those observed for lipid bilayers on glass substrates.
Asunto(s)
Membrana Celular/química , Cisteína/análogos & derivados , Membrana Dobles de Lípidos/química , Polímeros/química , Ácidos Polimetacrílicos/química , Cisteína/química , Modelos Moleculares , Conformación Molecular , Fosforilcolina/análogos & derivados , Fosforilcolina/química , Polimerizacion , Propiedades de SuperficieRESUMEN
Interrogating individual molecules within bio-membranes is key to deepening our understanding of biological processes essential for life. Using Raman spectroscopy to map molecular vibrations is ideal to non-destructively 'fingerprint' biomolecules for dynamic information on their molecular structure, composition and conformation. Such tag-free tracking of molecules within lipid bio-membranes can directly connect structure and function. In this paper, stable co-assembly with gold nano-components in a 'nanoparticle-on-mirror' geometry strongly enhances the local optical field and reduces the volume probed to a few nm(3), enabling repeated measurements for many tens of minutes on the same molecules. The intense gap plasmons are assembled around model bio-membranes providing molecular identification of the diffusing lipids. Our experiments clearly evidence measurement of individual lipids flexing through telltale rapid correlated vibrational shifts and intensity fluctuations in the Raman spectrum. These track molecules that undergo bending and conformational changes within the probe volume, through their interactions with the environment. This technique allows for in situ high-speed single-molecule investigations of the molecules embedded within lipid bio-membranes. It thus offers a new way to investigate the hidden dynamics of cell membranes important to a myriad of life processes.
Asunto(s)
Membrana Dobles de Lípidos/química , Espectrometría Raman , Ácidos Grasos Monoinsaturados/química , Oro/química , Nanopartículas del Metal/química , Fosfatidilcolinas/química , Compuestos de Amonio Cuaternario/químicaRESUMEN
By forming lipid bilayers within SU8 patterns, between interdigitated electrodes, we have demonstrated that it is possible to manipulate charged membrane components using low applied voltages over relatively short time scales. Two distinct patterns were studied: a nested "fish trap" which served as a molecular trap, and a diffusion aided Brownian ratchet which operated as a molecular pump. By reducing the size of the structures we have demonstrated that large applied fields (>200 V/cm) can be achieved on-chip, using low applied potentials (<13 V). By using ac fields applied orthogonal to the direction of desired motion, the molecular pumps provide a voltage independent method for moving charged components within lipid membranes over large distances. The reduced scale of the trap structures compared to those previously used in our laboratory has led to over a 10-fold decrease in the operational time require for charge build-up, from 16 h down to 1.5 h. The observed benefits of scaling means that these systems should be suitable for the on-chip separation and manipulation of charged species within supported lipid membranes.