First investigations of two important components of low density lipoproteins by Raman spectroscopy: the cholesteryl linoleate and arachidonate

Abstract

A first study of the vibrational behavior of the cholesteryl linoleate and arachidonate is performed by Raman spectroscopy. The cholesteryl linoleate and arachidonate are two important components of the low density lipoproteins (LDL). At first time, we present a comparative study in the spectral range 1400–3200cm−1 between the cholesteryl linoleate and the cholesteryl alkanoates in two phases: polycrystalline and isotropic liquid. In the spectral range 1600–1700cm−1 the vibrational behaviors of the CC stretching mode and the CO stretching mode are revealed to be two privileged witnesses of the material organization of this molecule in comparison with the cholesteryl alkanoates. In the range 2700–3200cm−1, the influences of the existence of two additional CC double bonds in the alkyl chain for the cholesteryl linoleate in regard of the cholesteryl alkanoates are studied. In the second part, in order to underpin the interpretations of the Raman spectra and knowing that the cholesteryl arachidonate possesses four CC double bonds in the alkyl chain, we show the Raman spectra of the cholesteryl arachidonate in isotropic liquid phase in the same spectral ranges. A comparison with the cholesteryl linoleate in isotropic liquid phase is performed.