To resolve the molecular basis of the coloration mechanism of alpha-crustacyanin, we used (13)C-labeled astaxanthins as chromophores for solid-state (13)C NMR and resonance Raman spectroscopy of [6,6',7,7']-(13)C(4) alpha-crustacyanin and [8,8',9,9',10,10',11,11',20,20']-(13)C(10) alpha-crustacyanin. We complement the experimental data with time-dependent density functional theory calculations on several models based on the structural information available for beta-crustacyanin. The data rule out major changes and strong polarization effects in the ground-state electron density of astaxanthin upon binding to the protein. Conformational changes in the chromophore and hydrogen-bond interactions between the astaxanthin and the protein can account only for about one-third of the total bathochromic shift in alpha-crustacyanin. The exciton coupling due to the proximity of two astaxanthin chromophores is found to be large, suggesting that aggregation effects in the protein represent the primary source of the color change.

A mixture of oligosaccharides produced by b-galactosidase using lactose as a substrate was fractionated according to degree of polymerization using gel filtration, followed by high-pH anion-exchange chromatography. The fractions obtained were analyzed using monosaccharide analysis, methylation analysis, mass spectrometry, and NMR spectroscopy. Twelve novel non-reducing oligosaccharides were characterized, namely,

A three-part strategy has been developed to study molecular interactions in biological systems at the atomic level. First, isotopically labeled carotenoids and retinoids are prepared by organic total synthetic schemes with labels at predetermined atomic positions and combinations of positions. Subsequently, the labeled compounds are incorporated in the biological system. Finally, the system is studied by isotope sensitive spectroscopic techniques.In this paper, the synthesis of 10-fold 13 C-labeled retinal palmitate and b-carotene acrustacyanin carotene for nutritional studies is discussed. Also, the scheme to label the end positions of astaxanthin and canthaxanthin with 13

A modular synthetic scheme has been developed for the synthesis of 13 C-labeled naturally occurring visual pigment chromophores; 3,4-didehydroretinal, 3-hydroxyretinal, and 4-hydroxyretinal. These compounds can now be made with Ͼ 99%13 C enrichment at any position or combination of positions. We used the common C 10 +C 5 +C 5 scheme for the syn-