X-ray diffraction and electron microscope study of phase separation in rod outer segment photoreceptor membrane multilayers

Journal Article · Wed Sep 01 00:00:00 EDT 1982 · Biophys. J.; (United States)

DOI:https://doi.org/10.1016/S0006-3495(82)84514-1· OSTI ID:6516616

Gruner, S M ^[1]; Rothschild, K J; Clark, N A

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1. Princeton Univ., NJ

Phase separation in artificially stacked multilayers of isolated bovine retinal rod outer segment (ROS) membranes has been examined via x-ray diffraction and electron microscopy. Specimens were prepared by isopotential spin drying followed with partial hydration by equilibration against moist gas streams. Upon dehydration, the multilamellar membrane phase assumes a binary phase composition consisting of concentrated protein-containing lamellae interspersed with microdomains of hexagonally packed tubes of lipid in a H/sub II/ configuration. The H/sub II/ lattice is geometrically coupled to the lamellar phase with one set of hexagonal crystal planes co-planar to the local membrane lamellae. The hexagonal microdomains bear a striking resemblance to the ''paracrystalline inclusions'' observed in fast-frozen, intact frog ROS (Corless and Costello, 1981. Exp. Eye Res. 32:217). The lamellar lattice is characterized by an unusually small degree of disorder. Sharp lamellar diffraction with a 120 angstrom unit cell is observed (at near total dehydration) to a resolution of 6 angstrom. A model consistent with the data is that a multilamellar array of ROS disks is stable as long as the external disk surfaces are kept sufficiently far apart. If the distance between the membranes is allowed to shrink below a certain critical value, the disk lipids, spontaneously convert to a nonbilayer phase. This suggests that the structure of the ROS is stabilized by an internal framework that acts to keep the disks apart from one another and from the plasmalemma. Thus, necessity of avoiding phase separations may provide a rationale for the peculiar morphology of the ROS.

• DOE Contract Number: AC02-76EV03120
• OSTI ID: 6516616
• Journal Information: Biophys. J.; (United States), Vol. 39:3
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
CELL MEMBRANES
ELECTRON MICROSCOPY
MOLECULAR STRUCTURE
X-RAY DIFFRACTION
RECEPTORS
CATTLE
RETINA
VISIBLE RADIATION
ANIMALS
BODY
BODY AREAS
CELL CONSTITUENTS
COHERENT SCATTERING
DIFFRACTION
DOMESTIC ANIMALS
ELECTROMAGNETIC RADIATION
EYES
FACE
HEAD
MAMMALS
MEMBRANES
MICROSCOPY
ORGANS
RADIATIONS
RUMINANTS
SCATTERING
SENSE ORGANS
VERTEBRATES
550300* - Cytology