Optical Imaging of the Nanoscale Structure and Dynamics of Biological Membranes

Abstract

Biological membranes serve as the fundamental unit of life, allowing the compartmentalization of cellular contents into subunits with specific functions. The bilayer structure, consisting of lipids, proteins, small molecules, and sugars, also serves many other complex functions in addition to maintaining the relative stability of the inner compartments. Signal transduction, regulation of solute exchange, active transport, and energy transduction through ion gradients all take place at biological membranes, primarily with the assistance of membrane proteins. For these functions, membrane structure is often critical. The fluidmosaic model introduced by Singer and Nicolson in 1972 evokes the dynamic and fluid nature of biological membranes.(1) According to this model, integral and peripheral proteins are oriented in a viscous phospholipid bilayer. Both proteins and lipids can diffuse laterally through the two-dimensional structure. Modern experimental evidence has shown, however, that the structure of the membrane is considerably more complex; various domains in the biological membranes, such as lipid rafts and confinement regions, form a more complicated molecular organization. The proper organization and dynamics of the membrane components are critical for the function of the entire cell. For example, cell signaling is often initiated at biological membranes and requires receptors to diffuse and assemble into complexes and clusters, and the resulting downstream events have consequences throughout the cell. Revealing the molecular level details of these signaling events is the foundation to understanding numerous unsolved questions regarding cellular life.

Ultrafast Dynamics at Lipid–Water Interfaces

“…In contrast to the model systems discussed above and many others used in fundamental biophysical experiments, biological membranes are composed of a diverse host of species, which vary widely in their charge, shape, polarity, and size. Studying lipid diversity is an active area of research as simulation tools become better equipped for modeling heterogeneous, complex membranes , and as advances in lipidomics quantify the diversity of lipids in cell membranes. − Some of the recent ultrafast work has focused on the effects of increasing levels of heterogeneity and molecular diversity on model membranes. For example, cholesterol has been linked to domain formation, and consequently, recent efforts have focused on understanding the effect of cholesterol on bilayer dynamics. , …”

“…Protein and lipid conformational changes range from nanoseconds to milliseconds, while ion and water molecules fluctuations range from femtoseconds to tens of picoseconds. Many biophysical techniques, including microscopy and NMR spectroscopy, have been deployed to study the dynamics of conformational changes in lipid membranes. ,, Picosecond dynamics, in contrast, have only recently become available to experimental biophysicists. Solvents fluctuate on a picosecond time scale, and one of the primary applications of ultrafast techniques has been solvents and solvent interfaces.…”

Microscope in Dentistry: A Review Article

“…It is a high-resolution microscope with advanced technology to overcome limited resolution found in optical microscopes that are caused by the diffraction of light [68][69][70][71][72][73][74][75][76].…”

Advances in the development of fluorescence probes for cell plasma membrane imaging

“…With this technology, monitoring cell activities, metabolism and cell-to-cell communication on cell surface can be achieved with "naked eyes". Therefore, a numbers of bioanalytical probes and/or imaging agents have been recently developed for visualizing and tracking the behaviors of cell plasma membrane [25,26], and such investigations have contributed and will continue to contribute to future investigating membrane biophysics and cell biology.…”