RESUMEN
Supported lipid bilayers (SLBs) are useful structures for mimicking cellular membranes, and they can be integrated with a variety of sensors. Although there are a variety of methods for forming SLBs, many of these methods come with limitations in terms of the lipid compositions that can be employed and the substrates upon which the SLBs can be deposited. Here we demonstrate the use of an all-aqueous chaotropic agent exchange process that can be used to form SLBs on two different substrate materials: SiO2, which is compatible with traditional SLB formation by vesicle fusion, and Al2O3, which is not compatible with vesicle fusion. When examined with a quartz crystal microbalance with dissipation monitoring, the SLBs generated by chaotropic agent exchange (CASLBs) have similar frequency and dissipation shifts to SLBs formed by the vesicle fusion technique. The CASLBs block nonspecific protein adsorption on the substrate and can be used to sense protein-lipid interactions. Fluorescence microscopy was used to examine the CASLBs, and we observed long-range lateral diffusion of fluorescent probes, which confirmed that the CASLBs were composed of a continuous, planar lipid bilayer. Our CASLB method provides another option for forming planar lipid bilayers on a variety of surfaces, including those that are not amenable to the widely used vesicle fusion method.
RESUMEN
Oxidative stress leads to the production of oxidized phospholipids (oxPLs) that modulate the biophysical properties of phospholipid monolayers and bilayers. As many immune cells are responsible for surveilling cells and tissues for the presence of oxPLs, oxPL-dependent mechanisms have been suggested as targets for treating chronic kidney disease, atherosclerosis, diabetes, and cancer metastasis. This review details recent experimental and computational studies that characterize oxPLs' behaviors in various monolayers and bilayers. These studies investigate how the tail length and polar functional groups of OxPLs impact membrane properties, how oxidized membranes can be stabilized, and how membrane integrity is generally affected by oxidized lipids. In addition, for oxPL-containing membrane modeling and simulation, CHARMM-GUI Membrane Builder has been extended to support a variety of oxPLs, accelerating the simulation system building process for these biologically relevant lipid bilayers.
Asunto(s)
Membrana Dobles de Lípidos , Oxidación-Reducción , Fosfolípidos , Fosfolípidos/metabolismo , Fosfolípidos/química , Membrana Dobles de Lípidos/metabolismo , Membrana Dobles de Lípidos/química , Humanos , Membrana Celular/metabolismo , Membrana Celular/química , Simulación de Dinámica Molecular , Modelos MolecularesRESUMEN
Microdomains in lipid bilayer membranes are routinely imaged using organic fluorophores that preferentially partition into one of the lipid phases, resulting in fluorescence contrast. Here, we show that membrane microdomains in giant unilamellar vesicles (GUVs) can be visualized with europium luminescence using a complex of europium III (Eu3+) and tetracycline (EuTc). EuTc is unlike typical organic lipid probes in that it is a coordination complex with a unique excitation/emission wavelength combination (396/617 nm), a very large Stokes shift (221 nm), and a very narrow emission bandwidth (8 nm). The probe preferentially interacts with liquid disordered domains in GUVs, which results in intensity contrast across the surface of phase-separated GUVs. Interestingly, EuTc also alters GM1 ganglioside partitioning. GM1 typically partitions into liquid ordered domains, but after labeling phase-separated GUVs with EuTc, cholera toxin B-subunit (CTxB), which binds GM1, labels liquid disordered domains. We also demonstrate that EuTc, but not free Eu3+ or Tc, significantly reduces lipid diffusion coefficients. Finally, we show that EuTc can be used to label cellular membranes similar to a traditional membrane probe. EuTc may find utility as a membrane imaging probe where its large Stokes shift and sharp emission band would enable multicolor imaging.