Mechanism of Radical Cation Formation from the Excited States of Zeaxanthin and Astaxanthin in Chloroform

From: Photochemistry and Photobiology | Date: March 1, 2006| Author: | Copyright information

ABSTRACT

The C-40 xanthophylls zeaxanthin and astaxanthin were confirmed to form radical cations, Car^sup .+^, in the electron-accepting solvent chloroform by direct excitation using subpicosecond time-resolved absorption spectroscopy in combination with spectroelectrochemical determination of the near-infrared absorption of Car^sup .+^. For the singlets, the S^sub 2^(1B^sub u^^sup +^) state and most likely the S^sub x^(3A^sub g^^sup -^) state directly eject electrons to chloroform leading to the rapid formation of Car^sup .+^ on a timescale of ~100 fs; the lowest-lying S^sub 1^(2A^sub g^^sup ...

Read all of this article with a FREE trial to HighBeam Research

Related newspaper, magazine, and trade journal articles from HighBeam Research

(Including press releases, facts, information, and biographies)

Protection of photosynthesis against ultraviolet-B radiation by carotenoids in transformants of the cyanobacterium Synechococcus PCC7942
; ...have been elucidated, but little is known about how carotenoids alleviate UV-B stress exerted on the cell and on...obtained in which either the amounts of the endogenous carotenoids 3-carotene and zeaxanthin were increased or the...parameters to evaluate the protective effect of carotenoids in the ...
Femtosecond Spectroscopy of Native and Carotenoidless Purple-Bacterial LH2 Clarifies Functions of Carotenoids
; ...suggested that the bound carotenoids may enhance EET between...proposed by Razi Naqvi that carotenoids may induce enhanced relaxation...conversion" (2). Absorption of carotenoids in the visible region is...the ground state, So (1^sup 1^A^sup -^^sub g^ ), to...singlet state, S^sub 1^ ...
Singlet molecular oxygen quenching ability of carotenoids in a reversemicelle membrane mimetic system
; ...Molecular Oxygen Quenching Ability of Carotenoids in a Reversemicelle Membrane Mimetic...of singlet molecular oxygen O^sub 2^(^sup 1^Delta^sub g^) by seven natural and three synthetic carotenoids (CAR) with different substituent patterns...hexane and water. Because O^sub 2^(^sup 1^Delta^sub g^,) ...
Carotenoids from Red Palm Methyl Esters by Nanofiltration
; ...technology to separate the carotenoids from the methyl esters...ranged from 0.5 to 10 Lm^sup -2^h^sup -1^, and rejection...is its high content of carotenoids and tocopherols. Carotenoids, which impart the distinctive...contains 500-700 ppm of carotenoids (0.5-0.7 gL^sup -1^) ...
Kinetics of ^sup 14^C Distribution After Tracer Dose of ^sup 14^C-Lutein in an Adult Woman
; ...feasibility study where we dosed a normal adult woman with ^sup 14^C-lutein (125 nmol, 36 nCi ^sup 14^C), dissolved in olive oil (0.5 g/kg body weight...and urine were collected for 2 wk post-dose. The ^sup 14^C contents in plasma, urine, and feces were measured...
Don't count out "other" carotenoids; they may offer big health bonus.
; ...500 members of the carotenoid family. Carotenoids are what give fruits and vegetables...Green leafy vegetables are also rich in carotenoids, but the yellow and orange pigments are masked by chlorophyll.) About 10% of carotenoids are converted to vitamin A in the body...
Carotenoids Protect Health.
; More than 500 specific carotenoids (pronounced ka-ROT-e-noyds) have...cryptoxanthin, and lycopene. Originally, carotenoids were regarded as important only...colored plant extracts--later termed carotenoids--could convert biologically to...
Carotenoids: functions and degradation. (Cover Story)
; Some carotenoids seem to inhibit certain types of tumours, but is it the carotenoids themselves or their degradation products that are responsible? Carotenoids are important constituents of most foods and act as colouring agents, additives or...
As beta-carotene promise fades, focus turns to other carotenoids.
; ...to a family of natural plant chemicals called carotenoids. Carotenoids give fruits and vegetables their yellow, orange...even more abundant chlorophyll. The most common carotenoids in blood and tissues are alpha-carotene, beta...
Oxidative Conversion of Carotenoids to Retinoids and Other Products1,2
; ABSTRACT In vertebrates, provitamin A carotenoids are converted to retinal by [beta...determines whether provitamin A carotenoids are converted to vitamin A or circulated in the body as intact carotenoids. We have found that a high fat...