Title

The intrinsic pKa values for phosphatidylcholine and phosphatidylethanolamine in phosphatidylcholine host bilayers

ORCiD

David M. Ojcius: 0000-0003-1461-4495

Document Type

Article

Publication Title

Biophysical Journal

ISSN

0006-3495

Volume

49

Issue

2

DOI

10.1016/S0006-3495(86)83655-4

First Page

459

Last Page

468

Publication Date

2-1-1986

Abstract

Potentiometric titrations and surface potential measurements have been used to determine the intrinsic pKa values of both the carboxyl and amino groups of phosphatidylserine (PS) in mixed vesicles of PS and phosphatidylcholine (PC), and also of the amino group of phosphatidylethanolamine (PE) in mixed PE-PC vesicles. The pKa of the carboxyl group of PS in liposomes with different PS/PC lipid ratios measured by the two different methods is 3.6 +/- 0.1, and the pKa of its amino group is 9.8 +/- 0.1. The pKa of the amino group of PE in PE-PC vesicles, determined solely by surface potential measurements, is 9.6 +/- 0.1. These pKa values are independent of the aqueous phase ionic strength and of the effect of the liposome's surface potential due to the presence of these partially charged lipids.