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Similarity and Specificity of Chlorophyll <i>b</i> Triplet State in Comparison to Chlorophyll <i>a</i> , as Revealed by EPR/ENDOR and DFT Calculations.
摘要： An investigation of the photoexcited triplet state of chlorophyll (Chl) b has been carried out by means of Electron Nuclear Double Resonance (ENDOR), both in frozen organic solvent and in protein environment provided by the Water-Soluble Chlorophyll Protein of Lepidium virginicum. Density functional theory (DFT) calculations have allowed the complete assignment of the observed hyperfine couplings corresponding to the methine protons and the methyl groups, leading to a complete picture of the spin density distribution of the triplet state in the tetrapyrrole macrocycle. The triplet state properties of Chl b were found to be similar in many respects to those previously reported for Chl a, although some specificities have been highlighted. Concerning the spin density distribution, the differences are manly localized on the carbon atoms close to the formyl group which, in Chl b, replaces the methyl group of Chl a.
关键词： EPR/ENDOR,triplet state,DFT calculations,Chlorophyll b,spin density distribution
更新于2025-09-11 14:15:04
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Monitoring of Fluorescence Characteristics of Satsuma Mandarin (Citrus unshiu Marc.) during the Maturation Period
摘要： Monitoring the maturation process of Satsuma mandarin (Citrus unshiu Marc.) by determining the soluble solids (SS) and acid content non-destructively is needed. Fluorescence components potentially offer such means of accessing fruit maturity characteristics in the orchard. The aim of this study was to determine the potential of ?uorescence spectroscopy for monitoring the stage of citrus maturity. Four major ?uorescent components in peel and/or ?esh were found including chlorophyll-a (excitation (Ex) 410 nm, emission (Em) 675 nm) and chlorophyll-b (Ex 460 nm, Em 650 nm),polymethoxy?avones (PMFs) (Ex 260 nm and 370 nm, Em 540 nm), coumarin (Ex 330 nm, Em 400 nm), and a tryptophan-like compound (Ex 260 nm, Em 330 nm). Our results indicated a signi?cant (R2 = 0.9554) logarithmic ratio between tryptophan-like compoundsExEm and chlorophyll-aExEm with the SS:acid ratio. Also, the log of the ratio of PMFs from the peel (ExExEm was signi?cantly correlated with the SS:acid ratio (R2 = 0.8207). While the latter correlation was not as strong as the former, it does demonstrate the opportunity to develop a non-destructive ?eld measurement of ?uorescent peel compounds as an indirect index of fruit maturity.
关键词： ?uorescence,soluble solid and acid ratio,tryptophan-like,chlorophyll-a,chlorophyll-b,polymethoxy?avones,maturity index
更新于2025-09-10 09:29:36