AFM for structure and dynamics of biomembranes

Abstract

We review structure and dynamic measurements of biomembranes by atomic force microscopy (AFM). We focus mainly on studies involving supported lipid bilayers (SLBs), particularly formation by vesicle rupture on flat and corrugated surfaces, nucleation and growth of domains in phase-separated systems, anesthetic-lipid interactions, and protein/peptide interactions in multicomponent systems. We show that carefully designed experiments along with real-time AFM imaging with superior lateral and z resolution (0.1 nm) have revealed quantitative details of the mechanisms and factors controlling vesicle rupture, domain shape and size, phase transformations, and some model biological interactions. The AFM tip can also be used as a mechanical transducer and incorporated in electrochemical measurements of membrane components; therefore, we touch on these important applications in both model and cell membranes.

Atomic Force Microscopy Force Mapping in the Study of Supported Lipid Bilayers

“…[1][2][3][4][5][6] In AFM imaging, a tip at the end of a cantilever is raster-scanned across an area of interest, and the cantilever's deflection for example, is used as feedback to adjust the height of the cantilever base relative to the sample surface. In this way, heterogeneities on the sample can be distinguished via relative differences in the actual heights of the region's domains or from chemical differences that still effectively cause the cantilever base to adjust its height.…”

Distribution of cooperative unit size of amphiphilic molecules in the phase coexistence region in Langmuir monolayers

“…There is a rapidly growing number of direct observations of gel and fluid clusters in binary lipid mixtures by atomic force microscopy (AFM) [29,30]. There are, however, vast differences between the observed cluster sizes and shapes depending on the type of the measurement, the construction, and thermal history of the sample.…”

Surface-Dependent Differences in the Adsorption of Pancreatic and Microbial Ribonucleases Visualized by Atomic Force Microscopy

“…The study of the physical adsorption of proteins on different surfaces helps to reveal the peculiarities of their functioning in contact with the cell membrane and other biological substrates and contributes to the understanding of the role of interphase phenomena in biological processes 2,4,5 . Along with the study of adsorption, methods of atomic force microscopy are widely used to study the local structure of the cell membrane and artificial bilayer structures, as they allow one to obtain a valuable information about conformational changes in lipid membranes when interacting with different biomolecules to detect subtle structural features of the lipid layers and to estimate their morphometric parameters [6][7][8][9] .…”