Faculty Collaboration Database

Lipid exchange between mixed micelles of phospholipid and triton X-100. Biochim Biophys Acta 1999 Feb 04;1417(1):144-56

Date

03/17/1999

Pubmed ID

10076043

DOI

10.1016/s0005-2736(98)00254-5

Scopus ID

2-s2.0-0033060851 (requires institutional sign-in at Scopus site)   14 Citations

Abstract

If phospholipase catalyzed hydrolysis of phospholipid dissolved in a detergent mixed micelle is limited to the phospholipid carried by a single micelle, then hydrolysis ceases upon exhaustion of that pool. However, if the rate of phospholipid exchange between micelles exceeds the catalytic rate then all of the phospholipid is available for hydrolysis. To determine phospholipid availability we studied the exchange of 1,2-dioleoyl-sn-glycero-3-phosphocholine between mixed micelles of phospholipid and non-ionic Triton detergents by both stopped-flow fluorescence-recovery and nuclear magnetic resonance-relaxation techniques. Stopped-flow analysis was performed by combining mixed micelles of Triton and phospholipid with mixed micelles that contained the fluorescent phospholipid 1-palmitoyl-2-(12-[{7-nitro-2-1, 3-benzoxadiazo-4-yl}amino]dodecanoyl)-sn-glycero-3-phosphocholine (P-2-NBD-PC). The concentration dependence of fluorescence recovery suggested a second-order exchange mechanism that was saturable. The true second-order rate constant depends on the specific mechanism for exchange, which was not determined in this study, but the rate constant will be on the order of 106 to 107 M-1s-1. Incorporation of 1-palmitoyl-2-(16-doxylstearoyl)phosphatidylcholine into micelles increased the rate of proton relaxation and gave a limiting relaxation time of 1.3 ms. The results demonstrate that phospholipid exchange was rapid and that the phospholipid content of a single micelle did not limit the rate of phospholipid hydrolysis by phospholipases.

Author List

Thomas MJ, Pang K, Chen Q, Lyles D, Hantgan R, Waite M

Author

Michael J. Thomas PhD Professor in the Pharmacology and Toxicology department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Fluorescence
Hydrolysis
Kinetics
Lipids
Magnetic Resonance Spectroscopy
Micelles
Octoxynol
Phosphatidylcholines
Phospholipases
Phospholipids
Spin Labels