Deuterium isotope effect on the stability of molecules: phospholipids

Journal Article · Thu Apr 25 04:00:00 UTC 1985 · J. Phys. Chem.; (United States)

DOI:https://doi.org/10.1021/j100255a054· OSTI ID:5227299

Guard-Friar, D; Chen, S H; Engle, A S

To examine the deuterium isotope effect on the stability of phospholipids, the phase transition properties of bilayer vesicles, prepared from deuterated phospholipids, were investigated and compared with those of nondeuterated (normal) phospholipids. Three lipids, 1,2-distearoyl-, 1,2-dipalmitoyl-, and 1,2-dimyristoylphosphatidylcholines, were studied. Differential scanning microcalorimetry showed that, unlike a sharp phase transition observed in a nondeuterated lipid, a deuterated lipid exhibits a broad transition which is associated with a lower temperature (t/sub m/) and small enthalpy (..delta..H/sub m/) and entropy (..delta..S/sub m/) of the transition. The magnitude of t/sub m/ in deuterated lipid is 3-5/sup 0/C lower than in the corresponding nondeuterated lipid. Deuteration causes the magnitude of ..delta..H/sub m/ and ..delta..S/sub m/ to be decreased by 14-35%. For each CH/sub 2/ group, the deuterium substitution in general decreases ..delta..H/sub m/, ..delta..G/sub m/ (Gibbs energy), and ..delta..S/sub m/ by 272 J/mol, 15.4 J/mol, and 0.7 J/mol deg), respectively. Steady-state fluorescence polarization (P) measurements have demonstrated that, at a temperature above t/sub m/ (liquid-crystalline phase), deuterated and nondeuterated lipids essentially have a same magnitude of P, while at a temperature below t/sub m/ (gel phase), deuterated lipid has a lower P than nondeuterated lipid. Consequently, deuterated lipid has a lower magnitude of ..delta..P (difference in P below t/sub m/), indicating that the structural differences between gel and liquid-crystalline phase is less profound in deuterated lipids. The melting properties of deuterated and nondeuterated fatty acids corresponding to these three lipids were also examined. 20 references, 3 figures, 1 table.

• Research Organization: New York State Dept. of Health, Albany
• OSTI ID: 5227299
• Journal Information: J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 89:9; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400302* -- Organic Chemistry-- Isotope Effects-- (-1987)
DATA
DEUTERIUM
ENERGY
ENTHALPY
ENTROPY
ESTERS
EXPERIMENTAL DATA
FLUORESCENCE
FORMATION HEAT
FREE ENTHALPY
HYDROGEN ISOTOPES
INFORMATION
ISOTOPE EFFECTS
ISOTOPE ENRICHED MATERIALS
ISOTOPES
LIGHT NUCLEI
LIPIDS
LUMINESCENCE
MATERIALS
MELTING POINTS
NUCLEI
NUMERICAL DATA
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANIC PHOSPHORUS COMPOUNDS
PHOSPHOLIPIDS
PHYSICAL PROPERTIES
POLARIZATION
REACTION HEAT
STABILITY
STABLE ISOTOPES
THERMODYNAMIC PROPERTIES
TRANSITION TEMPERATURE