Resonance Raman optical activity of zeaxanthin aggregates

Abstract

New methods of enhancement in Raman optical activity (ROA) scattering are of great interest. So, previously reported by us, Aggregation-Induced Resonance ROA (AIRROA) may open new opportunities in a field of structural studies of many biologically important compounds. However, the AIRROA phenomenon, reported up until now for astaxanthin and lutein derivatives, requires a deeper understanding and investigation of other carotenoids. Zeaxanthin is a dominant macular pigment that protects human retina against photo-oxidative damage. In this work, we analyse two types of chiral zeaxanthin self-assembly, H and J1, and verify that aggregation process is not enough to enhance ROA signal. Essential for the AIRROA effect is the fact that the electronic circular absorption band of supramolecular species is in proximity with the ROA excitation line. We also compare and analyse the spectral differences between J aggregates of astaxanthin and zeaxanthin, with reference to the AIRROA phenomenon.

Chiral Amplification in Nature: Studying Cell‐Extracted Chiral Carotenoid Microcrystals via the Resonance Raman Optical Activity of Model Systems

“…[7,8] According to this effect, as mall number of chiral units (sergeants) force al arge number of achiral ones (soldiers) to adopt asupramolecular structure and to display an intense chiral signal. [20][21][22][23] Those assemblies also show strong optical activity,g enerated by the non-symmetric layout of molecules through non-covalent interactions (p-p stacking, hydrogen bonding,h ydrophobic effects). [17][18][19] Thec hirality of the model aggregates studied is due to chirality transfer between chiral aCo ra staxanthin (AXT) molecules and achiral bC components,w hich together form am ixed supramolecular chiral system exhibiting resonance-enhanced ROA(RROA).…”

“…[9,10] This kind of chirality amplification has been observed for other supramolecular systems, [11][12][13] such as foldamers, [14] helical nanotubes and columns, [15,16] as well as polymers and copolymers. [20][21][22][23] Nevertheless,R OA spectroscopy is hampered by its low sensitivity because only one photon in ab illion gives rise to the ROAe ffect. On the other hand, aggregates composed of only chiral carotenoids had been studied by us before.…”

“…On the other hand, aggregates composed of only chiral carotenoids had been studied by us before. [20][21][22][23] Those assemblies also show strong optical activity,g enerated by the non-symmetric layout of molecules through non-covalent interactions (p-p stacking, hydrogen bonding,h ydrophobic effects). In detail, the chiral information from ac arotenoid chiral center is imposed on the whole system containing ac hromophore (polyene chain) in the chiral conjugated arrangement.…”

Recent advances in linear and nonlinear Raman spectroscopy. Part XII

“…In this work, they analyzed two types of chiral zeaxanthin self‐assembly, H and J1, and concluded that an aggregation process is not enough to enhance the ROA signal. Essential for the aggregation induced RROA effect is that the electronic circular absorption band of supramolecular species is in proximity with the ROA excitation line . Mensch et al presented the ROA of human α‐synuclein in intrinsically disordered, micelle‐bound α‐helical, molten globule and oligomeric β‐sheet states.…”

“…Essential for the aggregation induced RROA effect is that the electronic circular absorption band of supramolecular species is in proximity with the ROA excitation line. [246] Mensch et al presented the ROA of human α-synuclein in intrinsically disordered, micelle-bound α-helical, molten globule and oligomeric β-sheet states. Alphasynuclein (α-syn) is a 140-residue protein that plays a central role in Parkinson's disease and other neurological disorders.…”