Detection of apolipoprotein B100 early conformational changes during oxidation

Abstract

Conformational changes of human plasma apolipoprotein B100 (apoB) during oxidative modification of low-density lipoproteins (LDL) have been investigated. Emphasis has been put on the early stages of LDL oxidation and the modification of apoB. We have applied two different modes of LDL oxidation initiation in order to approach the problem from different perspectives. To study conformational changes of the protein and the phospholipids surface monolayer, we have applied attenuated total reflection infrared as well as fluorescence spectroscopy. We have found for the first time that conformational changes of apoB occur even in the earliest stages of oxidation process and that those are located predominantly in the beta-sheet regions. The dynamics of changes has also been described and related to different stages of oxidation. After initial increase in particle surface accessibility and mobility, by entering into the propagation phase of oxidation process, LDL surface accessibility and mobility are decreased. Finally, in the decomposition phase of LDL oxidation, as the particle faces large chemical and physical changes, surface mobility and accessibility is increased again. These observations provide new insights into the modifications of LDL particles upon oxidation.