Izvorni znanstveni članak
Molecular Dynamics of Surface Lipids in Human Serum Lipoproteins Studied by ESR
; Ruđer Bošković Institute, University of Zagreb, Croatia
Greta Pifat ; Ruđer Bošković Institute, University of Zagreb, Croatia
Slavko Pečar ; J. Stefan Institute, University of Ljubljana, Slovenia
Milan Schara ; J. Stefan Institute, University of Ljubljana, Slovenia
Human serum lipoproteins were investigated using electron spin resonance in order to study the molecular dynamics of the surface phospholipid monolayer. Two different nitroxides were incorporated in LDL, HDL2 and HDL3: MeFASL(10,3), with the paramagnetic doxyl group located near the phospholipid surface of the particle, and MeFASL(2,11) where the doxyl group penetrates deeper into lipoprotein interior. The results indicate that the rotational correlation time rc of MeFASL(2,ll) is similar in all three particles, suggesting fast nonrandom motion in this nearly isotropic region of the monolayer. On the other hand, the rotational correlation time of MeFASL(10,3) is different in different lipoproteins. The theoretical analysis of this phenomenon reveals structural changes and dynamical constraints in the phospholipid surface of different lipoproteins when fatty acid esters are incorporated into these particles. At the same time, the rotational correlation time of MeFASL(10,3) does not indicate any influence of protein components on the mobility constraints in the surface domains of different lipoproteins. These results support the recently published observation against any long-lived lipid-protein interactions occurring on the nanosecond time scale.
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