Organization of Carotenoid Aggregates in Membranes Studied Selectively using Resonance Raman Optical Activity

Abstract

In living organisms, carotenoids are incorporated in biomembranes, remarkably modulating their mechanical characteristics, fluidity, and permeability. Significant resonance enhancement of Raman optical activity (ROA) signals of carotenoid chiral aggregates makes resonance ROA (RROA), a highly selective tool to study exclusively carotenoid assemblies in model membranes. Hence, RROA is combined with electronic circular dichroism (ECD), dynamic light scattering (DLS), molecular dynamics, and quantum‐chemical calculations to shed new light on the carotenoid aggregation in dipalmitoylphosphatidylcholine (DPPC) liposomes. Using representative members of the carotenoid family: apolar α‐carotene and more polar fucoxanthin and zeaxanthin, the authors demonstrate that the stability of carotenoid aggregates is directly linked with their orientation in membranes and the monomer structures inside the assemblies. In particular, polyene chain distortion of α‐carotene molecules is an important feature of J‐aggregates that show increased orientational freedom and stability inside liposomes compared to H‐assemblies of more polar xanthophylls. In light of these results, RROA emerges as a new tool to study active compounds and drugs embedded in membranes.

Efficient delivery of carotenoids to adipocytes with albumin

“…17,63 Importantly, AIRROA yields data only about CAR aggregates, as previously reported. 17,18,28 Therefore, supramolecular (3S,3 0 S)-AXT:BSA complexes, with the molar ratios of CAR to protein 1 : 1 and 3 : 1, were investigated using RR and resonance ROA (RROA) (Fig. 3).…”

“…17,18,23 Thus, ECD and ROA show a rather unique sensitivity to CAR aggregation. 8,[17][18][19]23,28 It has been shown that CARs and their derivatives may aggregate due to their interaction with proteins, 29,30 for example lutein and zeaxanthin form aggregates during interaction with BSA and glutathione S-transferase. 30 In this work, we address the question of the carotenoid transport to cells (adipocytes) via albumins in an in vitro model system.…”

Why Does One Measure Resonance Raman Optical Activity? A Unique Case of Measurements under Strong Resonance versus Far-from-Resonance Conditions

“…Up to now, bisignate or monosignate RROA spectral patterns have been proven to be beneficial in the study of varied molecular systems, including carotenoid aggregates, ,− metal complexes, ,, photoreceptor proteins, ,, and drugs . The sign and magnitude of RROA bands in the SES limit are determined by the ECD resonant transition, where the spectral pattern is similar to that of the parent RR spectrum (except for the sign).…”