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Thermodynamics of mixing of phosphatidylserine/phosphatidylcholine from measurements of high-affinity calcium binding.

Abstract：

:A simple model system is described that allows measurement of equilibrium Ca2+ binding to multilamellar vesicle mixtures of palmitoyloleoylphosphatidylserine (P,O-PS) and dimyristoleoylphosphatidylcholine (MO,MO-PC). The constraint of the chemical equilibrium among aqueous Ca2+, hydrated P,O-PS/MO,MO-PC, and Ca(PS)2, together with measurements of the Ca2+ concentration in equilibrium with defined PS/PC ratios, enables the determination of the thermodynamic activity of the lipids. The activity coefficient of dilute P,O-PS in PC is analyzed in terms of the partial molal free energy to transfer P,O-PS from an environment of PS to an environment of PC. This study of P,O-PS/MO,MO-PC, by comparison with the earlier study of P,O-PS/P,O-PC [Feigensen, G.W. (1989) Biochemistry 20, 1270-1278], reveals that the excess partial molal free energy to transfer P,O-PS from P,O-PS to P,O-PC is -0.7 kcal mol-1. This free energy change arises in part from the favorable transfer of the negatively charged phosphoserine headgroup from an environment of negative charges to an environment of zwitterions. The contribution of acyl chain mismatch to the partial molal free energy to transfer P,O-PS from P,O-PS to MO,MO-PC is found to be approximately +0.7 kcal mol-1. This value is much larger than that of the excess partial molal free energy of mixing in isotropic solutions of linear hydrocarbons that differ in chain length or unsaturation.

journal_name

Biochemistry

journal_title

Biochemistry

authors

Swanson JE,Feigenson GW

doi

10.1021/bi00488a013

subject

Has Abstract

pub_date

1990-09-11 00:00:00

pages

8291-7

issue

36

eissn

0006-2960

issn

1520-4995

journal_volume

29

pub_type

杂志文章

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