Formation of carotenoid supramolecular aggregates in nanocarriers monitored via aggregation-sensitive chiroptical output of enantiopure (3S,3'S)-astaxanthin

Imaging of perivascular adipose tissue in cardiometabolic diseases by Raman spectroscopy: Towards single-cell analysis

Perivascular adipose tissue (PVAT) has emerged as a dynamic organ influencing vascular function and cardiovascular health. In this brief review, an overview of the recent research in the investigation of PVAT is presented, ranging from in vivo studies to single-cell methodologies, in particular those based on Raman spectroscopy. The strengths and limitations of each, emphasizing their contributions to the current understanding of PVAT biology were discussed. Ultimately, the integration of these diverse methodologies promises to uncover new therapeutic targets and diagnostic biomarkers, including those emerging from simple Raman spectroscopy-based measurements of alterations in lipid unsaturation degree, invariably associated with PVAT dysfunction.

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

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

Carotenoids are very effectively delivered by albumin to adipocytes. The uptake of carotenoids to the cells occurs in the form of self-aggregates that localize in the vicinity of the adipocyte membrane, as shown by high spatial resolution Raman spectroscopy. The binding of carotenoids to albumin and the mechanism of their transport were elucidated with the help of chiroptical spectroscopies, in tandem with molecular docking and molecular dynamics simulations. In particular, apart from the recognized high affinity pocket of albumin that binds a carotenoid monomer in domain I, we have identified a hydrophobic periphery area in domain IIIB that loosely bounds the self-aggregated carotenoid in aqueous media and enables its easy detachment in hydrophobic environments. This explains the effectiveness of albumins as nanocarriers of carotenoids to adipocytes in vitro.

Exceptionally enhanced Raman optical activity (ROA) of amyloid fibrils and their prefibrillar states

Amyloid fibrils form remarkable, multi-layered chiral supramolecular architectures. The proximity of interacting oscillators in the chiral fibril supramolecules is responsible for the unusual sensitivity of vibrational circular dichroism (VCD) for fibril formation. Surprisingly, up to now, such characteristics have not been shown for ROA, although it displays the same vibrational markers of fibrils as VCD, including the amide I band. Here, we report an exceptionally large enhancement of the ROA signal detected for mature amyloid fibrils and their prefibrillar states. Remarkably, the same ROA signal has been obtained for fibrils of homologous lysozymes and the dissimilar protein, insulin, indicating a possible common enhanced ROA spectrum, analogous to that for VCD for all amyloid fibrils investigated to date. The ROA signal is observed at earlier stages of fibril formation than VCD and provides access to a considerably broader range of vibrations. Further studies are necessary to verify the applicability of ROA for the analysis of amyloid fibrils.