Mixed-chain phosphatidylcholine bilayers: structure and properties

Journal Article · Tue Jun 16 00:00:00 EDT 1987 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00386a007· OSTI ID:6021171

Mattai, J; Sripada, P K; Shipley, G G

Calorimetric and x-ray diffraction data are reported for two series of saturated mixed-chain phosphatidylcholines (PCs), 18:0/n:0-PC and n:0/18:0-PC, where the sn-1 and sn-2 fatty acyl chains on the glycerol backbone are systematically varied by two methylene groups from 18:0 to 10:0 (n = 18, 16, 14, 12, or 10). Fully hydrated PCs were annealed at -4 /sup 0/C and their multilamellar dispersions characterized by differential scanning calorimetry and x-ray diffraction. All mixed-chain PCs form low-temperature crystalline bilayer phases following low-temperature incubation, except 18:0/10:0-PC. The subtransition temperature (T/sub s/) shifts toward the main (chain melting) transition temperature (T/sub m/) as the sn-1 or sn-2 fatty acyl chain is reduced in length. T/sub m/ decreases with acyl chain length for both series of PCs except 18:0/10:0-PC, while for the positional isomers, n:0/18:0-PC and 18:0/n:0-PC, T/sub m/ is higher for the isomer with the longer acyl chain in the sn-2 position of the glycerol backbone. The conversion from the crystalline bilayer L/sub c/phase to the liquid-crystalline L/sub ..cap alpha../ phase with melted hydrocarbon chains occurs through a series of phase changes which are chain length dependent. Molecular models indicate that the bilayer gel phases for the more asymmetric PC series, 18:0/n:0-PC, must undergo progressive interdigitation with chain length reduction to maintain maximum chain-chain interaction. The L/sub ..beta../* phase of 18:0/10:p-PC is the most stable structure for this PC below T/sub m/. The formation and stability of the triple-chain structures can be rationalized from molecular models.

• Research Organization: Boston Univ. School of Medicine, MA
• OSTI ID: 6021171
• Journal Information: Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 26:12; ISSN BICHA
• Country of Publication: United States
• Language: English

Related Subjects

550602* -- Medicine-- External Radiation in Diagnostics-- (1980-)
62 RADIOLOGY AND NUCLEAR MEDICINE
ALCOHOLS
AMINES
AMMONIUM COMPOUNDS
CALORIMETRY
CELL CONSTITUENTS
CELL MEMBRANES
CHOLINE
COHERENT SCATTERING
DIFFRACTION
DRUGS
ESTERS
HYDROXY COMPOUNDS
LIPIDS
LIPOTROPIC FACTORS
MATHEMATICAL MODELS
MEMBRANES
MOLECULAR MODELS
MOLECULAR STRUCTURE
ORGANIC COMPOUNDS
ORGANIC PHOSPHORUS COMPOUNDS
PHOSPHOLIPIDS
QUATERNARY COMPOUNDS
SCATTERING
TEMPERATURE EFFECTS
X-RAY DIFFRACTION