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Comparison of lipid/gramicidin dispersions and cocrystals by Raman scattering
- Source :
- Biochemistry. 26:557-562
- Publication Year :
- 1987
- Publisher :
- American Chemical Society (ACS), 1987.
-
Abstract
- Gramicidin crystals, dimyristoylphosphatidylcholine (DMPC)/gramicidin dispersions, and DMPC/gramicidin cocrystals were examined by Raman scattering to determine lipid/gramicidin stoichiometries and lipid organization. Calibrations of the choline (716-cm-1) and tryptophan (756-cm-1) peaks indicate that the cocrystals contain two lipids for each gramicidin monomer, a result confirmed by chemical analyses of washed crystals. In dispersions with high lipid/gramicidin ratios (e.g., 25:1), the lipid is ordered but becomes increasingly disordered as the gramicidin content is increased. Paradoxically, the DMPC/gramicidin cocrystals have highly ordered lipids that possibly contain no gauche bonds at all, despite their low lipid/gramicidin ratio. In addition, the polypeptide amide I peak position near 1670 cm-1 is found to be independent of the lipid/gramicidin ratio in the complexes and may indicate a beta-helix-type secondary structure at all ratios. However, the amide I peak broadens significantly at low lipid/gramicidin ratios and broadens still further in the cocrystals, suggesting that protein-protein interactions may induce band-broadening distortions of the polypeptide structure.
- Subjects :
- Protein Conformation
Molecular Conformation
Analytical chemistry
Peptide
Spectrum Analysis, Raman
Models, Biological
Biochemistry
Choline
chemistry.chemical_compound
symbols.namesake
Phosphatidylcholine
polycyclic compounds
Protein secondary structure
chemistry.chemical_classification
Gramicidin
Tryptophan
technology, industry, and agriculture
Kinetics
Crystallography
Monomer
chemistry
Liposomes
symbols
lipids (amino acids, peptides, and proteins)
Crystallization
Dimyristoylphosphatidylcholine
Stoichiometry
Raman scattering
Subjects
Details
- ISSN :
- 15204995 and 00062960
- Volume :
- 26
- Database :
- OpenAIRE
- Journal :
- Biochemistry
- Accession number :
- edsair.doi.dedup.....c5b761db490c2f199da83b9709de393d