Membranrand

Membranrand, literally the membrane edge, is a term used in German-language biology to denote the boundary or edge of a biological membrane, such as the plasma membrane surrounding a cell or the membrane surrounding organelles. It is commonly employed in microscopy and descriptive cell biology to refer to the line where the lipid bilayer ends and adjacent cellular structures begin, including membrane-associated proteins, cytoskeletal attachments, or membrane folds.

Biological membranes are primarily composed of a phospholipid bilayer with embedded proteins, cholesterol, and other lipids. At the Membranrand, lipid packing can become less tight and curvature can increase, which can influence membrane tension, pore formation, and trafficking events such as endocytosis and exocytosis. The edge can be stabilized by cytoskeletal linkages and membrane scaffolds, as well as by proteins that induce curvature, such as BAR-domain proteins in eukaryotes. The Membranrand thus plays a role in shaping the membrane and coordinating interactions with the cytoskeleton and the external environment.

In research and imaging, the Membranrand is observed in electron micrographs of membrane fragments and in fluorescence or super-resolution images of labeled membranes, particularly in studies of vesicle formation, fusion, and membrane remodeling where the rim delineates a boundary or region of interest.

Etymology and usage: Membranrand is a term encountered in German-language literature to describe the boundary of a membrane. In English-language texts, the concept is usually expressed with more general terms such as boundary, rim, or edge of the membrane.