Lipid bilayer perturbations induced by simple hydrophobic peptides
Mixtures of tripeptides of the form Ala-X-Ala-O-tert-butyl with 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) bilayers have been used as a model system for studying the influence of hydrophobic peptides on membrane order and dynamic properties by means of deuterium NMR spectroscopy. Tripeptides with X = Ala, Leu, Phe, and Trp have been examined. Lipid /sup 2/H NMR spectra of acyl chain perdeuteriated DMPC ((/sup 2/H/sub 54/)DMPC) show that the addition of peptide disorders the bilayer lipid acyl chains and that the extent of the perturbation increases as the size of the central residue increases. Moment analyses of the spectra indicate that, while the average acyl chain order parameter decreases with increasing central residue size, the order parameter spread across the bilayer (the mean-squared width of the distribution) increases. Lipid segmental /sup 2/H longitudinal relaxation rates, 1/T/sub 1/(i), exhibit a square-law functional dependence on S/sub CD/(i) both with and without the addition of peptide. The addition of peptide causes an increase in the slope of plots of 1/T/sub 1/(i) vs. absolute value S/sub CD/(i)/sub 2/ with little change in the 1/T/sub 1/(i) intercept, indicating a complex modulation of the acyl chain motions. /sup 2/H NMR spectra of Ala-(/sup 2/H/sub 4/)Ala-Ala-O-tert-butyl in DMPC bilayers have both isotropic and powder pattern components that vary as a function of temperature. At 30/sup 0/C the /sup 2/H spin-lattice relaxation time for the labeled Ala residue increase in going from bilayer-incorporated peptide to polycrystalline peptide to polycrystalline Ala x HCl. These experiments provide no information on the location of these peptides in the bilayer. If they protrude into the hydrocarbon core, their disordering influence can be attributed to a direct disruption of acyl chain packing.
- Research Organization:
- Univ. of California, Irvine
- OSTI ID:
- 5559787
- Journal Information:
- Biochemistry; (United States), Vol. 26:19
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
MEMBRANES
CONFORMATIONAL CHANGES
NUCLEAR MAGNETIC RESONANCE
PEPTIDES
BIOCHEMISTRY
ALANINES
DEUTERIUM
NMR SPECTRA
PHOSPHOLIPIDS
SPIN-LATTICE RELAXATION
TEMPERATURE DEPENDENCE
AMINO ACIDS
CARBOXYLIC ACIDS
CHEMISTRY
ESTERS
HYDROGEN ISOTOPES
ISOTOPES
LIGHT NUCLEI
LIPIDS
MAGNETIC RESONANCE
NUCLEI
ODD-ODD NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC PHOSPHORUS COMPOUNDS
PROTEINS
RELAXATION
RESONANCE
SPECTRA
STABLE ISOTOPES
550601* - Medicine- Unsealed Radionuclides in Diagnostics