Acid dissociation constants of diphytanylglycerolphosphorylglycerol-methylphosphate, and diphytanylglycerolphosphorylglycerophosphate and its deoxy analog

摘要: Abstract Acid dissociation constants of 2,3-diphytanyl- sn -glycero-1-phosphoryl- -3′-glycero-1′-methylphosphate (PGP-Me), the major phospholipid in extreme halophiles (Halobacteriaceae) , and demethylated -3′-glycero-1′-phosphate (PGP) its deoxy analog -glycero-1-phosphoryl-1′-(1′,3′-propanediol-3′-phosphate) (dPGP), were calculated by an original mathematical procedure from potentiometric titration data methanol/water (1:1, v/v) found to be as follows: for PGP-Me (and presumably PGP), p K 1 =3.00 2 =3.61; PGP, 3 =11.12; dPGP, =2.72, =4.09, =8.43. High-resolution 31 P NMR spectra intact benzene/methanol or aqueous dispersion showed two resonances corresponding P-OH groups, each which exhibited a chemical shift change pH range 2.0–4.5, acid =p =3.2; no further ionization (p ) was detected at higher values 5–12. The present results show that titrates dibasic 2–8, but above 8, it tribasic acid, formed hydrolysis methyl group during with KOH. Calculation concentrations ionic molecular species PGP-Me, PGP dPGP function dianionic predominate 5–9, covering optimal growth Halobacteriaceae. are consistent concept hydroxyl central glycerol moiety is involved formation intramolecular hydrogen-bonded cyclic structure polar headgroup, imparts greater stability form 5–9 facilitates lateral proton conduction process diffusion along membrane surface halobacterial cells.