Microphase separation in low density lipoproteins - Evidence for a fluid triglyceride core below the lipid melting transition

Citation
M. Pregetter et al., Microphase separation in low density lipoproteins - Evidence for a fluid triglyceride core below the lipid melting transition, J BIOL CHEM, 274(3), 1999, pp. 1334-1341
Citations number
42
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Biochemistry & Biophysics
Journal title
JOURNAL OF BIOLOGICAL CHEMISTRY
ISSN journal
0021-9258 → ACNP
Volume
274
Issue
3
Year of publication
1999
Pages
1334 - 1341
Database
ISI
SICI code
0021-9258(19990115)274:3<1334:MSILDL>2.0.ZU;2-C
Abstract
The structural organization of the neutral lipid core in human low density lipoproteins (LDL) was investigated in physicochemically defined, distinct human LDL subspecies in the density range of 1.0244-1.0435 g/mg evaluation of the core lipid transition temperature, chemical composition, and the beh avior of spin-labeled core lipids. Calorimetric studies were performed on m ore than 60 LDL preparations, and the transition temperature, which varied between 19 and 32 degrees C, was correlated to the chemical composition and revealed a discontinuity at a critical cholesteryl ester to triglyceride r atio of approximately 7:1. For electron spin resonance studies, several LDL preparations were probed with spin-labeled cholesteryl esters and triglyce rides, respectively In LDL with a high triglyceride content, both labels ex hibited similar mobility behavior. In contrast, in LDL with only small conc entrations of triglycerides, the behavior of labeled cholesteryl esters and labeled triglycerides differed distinctly. The cholesteryl esters were str ongly immobilized below the transition temperature, whereas the triglycerid es remained fluid throughout the measured temperatures These results sugges t that the critical cholesteryl ester to triglyceride mass ratio of 7:1 cor responds to two concentric compartments with a radial ratio of 2:1, where t he liquid triglycerides occupy the core, and the cholesteryl esters form th e frozen shell. At higher triglyceride contents, the triglyceride molecules insert into the cholesteryl ester shell and depress the peak transition te mperature of the LDL core, whereas at lower triglyceride contents, excess c holesteryl esters are dissolved in the core.