Structure of supramolecular astaxanthin aggregates revealed by molecular dynamics and electronic circular dichroism spectroscopy

Abstract

Biomolecular aggregation is omnipresent in nature and important for metabolic processes or in medical treatment; however, the phenomenon is rather difficult to predict or understand on the basis of computational models. Recently, we found that electronic circular dichroism (ECD) spectroscopy and closely related resonance Raman optical activity (RROA) are extremely sensitive to the aggregation mechanism and structure of the astaxanthin dye. In the present study, molecular dynamics (MD) and quantum chemical (QC) computations (ZIndo/S, TDDFT) are used to link the aggregate structure with ECD spectral shapes. Realistic absorption and ECD intensities were obtained and the simulations reproduced many trends observed experimentally, such as the prevalent sign pattern and dependence of the aggregate structure on the solvent type. The computationally cheaper ZIndo/S method provided results very similar to those obtained by TDDFT. In the future, the accuracy of the combined MD/QC methodology of spectra interpretation should be improved to provide more detailed information on astaxanthin aggregates and similar macromolecular systems.

Astaxanthin supplementation enriches productive performance, physiological and immunological responses in laying hens

“…Astaxanthin is a kind of carotene, one of the strongest natural antioxidants, which can effectively eliminate oxygen free radicals in LS-180 Cells [29]. The molecular structure of astaxanthin is composed of many conjugated double bonds, and α -hydroxyketone is composed of ketone group and hydroxyl group at the end of the conjugated double bond chain [30]. These molecular structure characteristics of astaxanthin determine that it has active electronic effect, which can provide electrons to free radicals or attract unpaired electrons of free radicals, so it can play the role of scavenging free radicals and antioxidation.…”

The Astaxanthin Aggregation Pattern Greatly Influences Its Antioxidant Activity: A Comparative Study in Caco-2 Cells

“…The unstable AST aggregates can be stabilized by incorporation into the hydrophobic micro-domain of the DNA/chitosan complex even without the presence of ethanol/water solvent. As the pattern of AST aggregation can be identified by the optical absorbance [31], the aggregation forms of AST that stabilized in the DNA/chitosan nano-system were evaluated by UV-Vis. As shown in (Figure 1A), the yellow nano-suspension (prepared by method 1) had an absorption peak at 388 nm, which was similar to that of the unstable H-aggregates, and it was 92 nm blue shifted relative to AST monomers [26].…”

Recent Trends in Chiroptical Spectroscopy: Theory and Applications of Vibrational Circular Dichroism and Raman Optical Activity

“…The resonance can be conveniently monitored using UV absorption and ECD spectroscopy. This phenomenon is quite difficult to model computationally; nevertheless realistic aggregation and ECD spectral properties could be obtained by a combination of MD and DFT …”