title: The effect of calcium on the bilayer stability of lipids from bovine rod outer segment disk membranes.
abstract: The phase behavior of bovine rod outer segment disk lipids has been investigated using freeze-fracture and 31P nuclear magnetic resonance (NMR) techniques. 31P-NMR spectra of isolated disk membranes were taken as a function of temperature between 25 degrees C and 45 degrees C. The 31P-NMR spectrum characteristic of phospholipid bilayers was observed at all temperatures both in the absence of Ca2+ and in the presence of 10 mM and 50 mM Ca2+. A similar study was performed on lipids isolated from the disk membranes. In the absence of Ca2+ only lamellar phase behavior was observed. In the presence of less than 10 mM Ca2+, however, there was a change in morphology to non-lamellar structures. Removal of the Ca2+ caused the system to reassume the lamellar form.
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002417:Cattle; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D005614:Freeze Fracturing; D008051:Lipid Bilayers / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D008854:Microscopy, Electron; D010786:Photoreceptor Cells / Q000378:metabolism*; D012374:Rod Cell Outer Segment / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D013696:Temperature
chemical_list: D008051:Lipid Bilayers; D002118:Calcium