Resonance Raman spectroscopy

Abstract

Resonance Raman spectroscopy may yield precise information on the conformation of, and on the interactions assumed by, the chromophores involved in the first steps of the photosynthetic process, whether isolated in solvents, embedded in soluble or membrane proteins, or, as shown recently, in vivo. By making use of this technique, it is possible, for instance, to relate the electronic properties of these molecules to their structure and/or the physical properties of their environment, or to determine subtle changes of their conformation associated with regulatory processes. After a short introduction to the physical principles that govern resonance Raman spectroscopy, the information content of resonance Raman spectra of chlorophyll and carotenoid molecules is described in this review, together with the experiments which helped in determining which structural parameter each Raman band is sensitive to. A selection of applications of this technique is then presented, in order to give a fair and precise idea of which type of information can be obtained from its use in the field of photosynthesis.

Variation in carotenoid–protein interaction in bird feathers produces novel plumage coloration

“…the extent and position of twisting along the carbon backbone of the molecule [29,50,51]. The n 2 band around 1160 cm 21 is due mainly to stretching vibrations of C-C single bonds coupled with C -H in-plane bending modes [29,32]. The rR bands in the vicinity of n 2 are also sensitive to the position of twisting along the carbon backbone and this constitutes the 'fingerprint region' for the assignment of carotenoid configurations [50].…”

“…Variation in carotenoid -protein interactions M. M. Mendes-Pinto et al 3341 [30,32]. The n 4 band around 960 cm 21 arises from C -H out-of-plane wagging motions coupled with CvC torsional modes that are out-of-plane twists of the carbon backbone [30,32].…”

“…The n 4 band around 960 cm 21 arises from C -H out-of-plane wagging motions coupled with CvC torsional modes that are out-of-plane twists of the carbon backbone [30,32]. If the p-electron conjugated system in the carotenoid is symmetric, as it is in canthaxanthin, the out-of-plane n 4 modes will not be coupled with the electronic transition when the molecule is planar.…”

“…By matching the energy of incident light with the energy of the electronic absorption of a given carotenoid, selective probing of a subpopulation of molecules in a complex mixture may be achieved [28,31], thus allowing structural characterizations in situ. rR spectra of carotenoids are characterized by four distinct bands denoted n 1 through n 4 , whose frequencies vary with the effective conjugation length of the p-electron double bond chain in the molecule, geometric isomeric configuration and degree of distortion [27,29,30,32]. In an analysis of yellow and red-coloured patches of the European goldfinch (Carduelis carduelis), which are pigmented by canary xanthophylls (1,1-carotene-3,3 0 -dione and 3 0 -hydroxy-1,1-caroten-3-one), Stradi et al [11] documented variation in the energy of the strongly allowed S 0 !…”

Localizing and Quantifying Carotenoids in Intact Cells and Tissues

“…In fact, the resonance efect can increase the scatering cross section to exceed any of-resonance Raman scater and, importantly, even rival intrinsic luorescence from the species. RRS thus has profound analytical potential and has been comprehensively reviewed elsewhere for the general life science ield [7] and speciically for applications in photosynthesis [8]. Here, its role in the assessment of carotenoids is examined explicitly.…”