Intramolecular hydrogen bonding in cardiolipin.
Fourier transform infrared (FT-IR) spectroscopy was used to determine whether intramolecular hydrogen bonding between the C-OH and P-OH groups exists in beef heart cardiolipin (CL) or in hydrogenated beef heart cardiolipin (18:0-CL) as compared to the synthetic 2'-deoxy analogue of cardiolipin (16:0-dCL). Such intramolecular hydrogen bonding would provide a structural basis for proton conduction on the molecular level. In aqueous dispersions at 20 degrees C, both 18:0-CL and 16:0-dCL exist in the gel phase as bilayers with gel to liquid-crystalline transitions (Tm) at 61 and 56 degrees C, respectively, whereas the unsaturated CL exists in the non-bilayer (hexagonal II) state. Evidence for intramolecular hydrogen bonding of the C-OH group in aqueous dispersions of 18:0-CL is provided by the large increase in Tm observed on changing the aqueous medium from H2O to D2O but specific hydrogen-bonded C-OH...PO2- species cannot be identified because water molecules also compete for the PO2- binding sites. However, C-OH...PO2- hydrogen bonds can be identified in dry films of the sodium salt of 18:0-CL or in CCl4 solution. In contrast, such hydrogen bonds cannot be formed in the deoxy analogue (16:0-dCL) indicating that the central C-OH group in 18:0-CL could provide a structural basis for proton conduction, involving the phosphate groups.
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Steacie Institute for Molecular Sciences, National Research Council of Canada, Ottawa.
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D000641:Ammonia / Q000737:chemistry; D000818:Animals; D002251:Carbon Tetrachloride / Q000737:chemistry; D002308:Cardiolipins / Q000737:chemistry*; D002417:Cattle; D005583:Fourier Analysis; D006860:Hydrogen Bonding; D006863:Hydrogen-Ion Concentration; D046911:Macromolecular Substances; D009206:Myocardium / Q000737:chemistry; D010712:Phosphatidic Acids / Q000737:chemistry*; D012643:Selenium / Q000737:chemistry; D012964:Sodium / Q000737:chemistry; D013055:Spectrophotometry, Infrared; D013696:Temperature; D015032:Zinc / Q000737:chemistry
D002308:Cardiolipins; D046911:Macromolecular Substances; D010712:Phosphatidic Acids; D000641:Ammonia; C070054:2'-deoxycardiolipin (diphosphatidyl-1,3-propanediol); D012964:Sodium; D002251:Carbon Tetrachloride; D012643:Selenium; D015032:Zinc