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PubMed1997

Free radical transients in photobleaching of xanthophylls and carotenes.

Carotenoids in chloroform and carbon tetrachloride photobleach upon nanosecond laser flash photolysis in two steps: instantaneously and in a second-order reaction. The rate constant for second-order reaction (first-order in a solvent derived radical and first-order in (excess) carotenoid) is largest for carotenes (9.8.10(8) M-1 for beta-carotene), intermediate for hydroxylated carotenoids, and smallest for carbonyl containing carotenoids (1.0.10(8) M-1 S-1 for astaxanthin) in chloroform at 20 degrees C. Near infrared absorbing transients are formed concomitant with photobleaching in chloroform (not detected in carbon tetrachloride). A species formed instantaneously is tentatively identified as either a carotenoid/solvent adduct or an ion-pair. A second species is formed by decay of instantaneously formed species and is identified as the carotenoid radical action. This species is formed in a first-order reaction with a rate constant of approx. 5.10(4) S-1 and absorbing at longer wavelength than the precursor. The lifetime (second-order decay) of the intermediates appears to be longest for the carotenoids with the longest conjugated system. The results indicate that carotenes are better antioxidants than xanthophylls as the carotenes, at least in the present lipophilic solvents, react faster with free radicals.

Carbon Tetrachloride↗
PubMed1988

Influence of source and physical form of xanthophyll pigment on broiler pigmentation and performance.

Two experiments were conducted using 21-day-old, commercial-strain broilers to determine the effect of various commercial pigmentation products on pigmentation and bird performance. Birds received finisher/withdrawal diets that included 8% corn gluten meal or either a 2.5 or 5.0% substitution of gluten meal with Liquid OroGlo5, Dry Oroglo10, or Cromophyl-oro. When birds were slaughtered at either 48 or 51 days of age there were no differences in the birds' breast skin hue (dominant wavelength) or brightness (luminosity). Data indicated similar levels of pigmentation among birds in all treatments. Color intensity (excitation purity) values of shank and breast skin samples suggested that the liquid form of OroGlo was more effective than the dry form in pigmenting broiler skin when both forms were fed at equal calculated levels. Data indicated that actual xanthophyll intake was higher when the liquid source was fed. Body weight gain and feed efficiency among the treatments, in general, indicated that commercial pigment sources can be substituted for corn gluten meal without appreciably altering broiler performance.

Animals↗
PubMed1990

A lack of fluctuation in xanthophyll concentrations in blood in laying hens at night and absence of pigmentation rings in the yolk.

Alternate white and yellow layers in the yolk are described in most textbooks. However, it was impossible to distinguish the presence of these layers when hard-cooked yolks from hens fed commercial type diets were examined. Serum xanthophyll concentrations were measured at different times during a 24-h period. Concentrations did not vary significantly due to time of day.

Animals↗
PubMed2005

Characterization of a nonphotochemical quenching-deficient Arabidopsis mutant possessing an intact PsbS protein, xanthophyll cycle and lumen acidification.

Arabidopsis thaliana plants grown from ethyl methane sulfonate-treated seeds were screened for so-called que mutants, which are affected in non-photochemical energy quenching. Based on video imaging of chlorophyll fluorescence an energy dissipation mutant, que1, was identified, isolated and characterized. Similar to the npq mutants, the que1 mutant showed a drastically reduced capacity for pH-dependent energy dissipation, qE, but without affecting the Delta pH-dependent conformational changes at 535 nm (DeltaA (535)), which have been supposed to be obligatorily correlated with qE and to reflect pH-regulated binding of zeaxanthin to the PsbS protein. Western blot and DNA sequence analysis revealed that neither a reduced expression of the PsbS protein nor a mutation in the PsbS gene was responsible for the missing qE in que1. Measurements of 9-aminoacridine fluorescence quenching showed that the acidification of the thylakoid lumen was also not affected in the mutant. Furthermore, que1 was able to convert violaxanthin to zeaxanthin. However, unusual characteristics of zeaxanthin formation in the mutant pointed at an altered availability of violaxanthin for de-epoxidation. This was further accompanied by a decrease of the photochemical quenching of chlorophyll fluorescence (qP), an increase of the portion of oxidized P700 and a reduction of the electron transport rate. These characteristics indicate changes in the organization of the thylakoid membrane that affect linear electron transport (but not lumen acidification) and the formation of energy dissipation in photosystem II. Preliminary genetic analysis revealed that the phenotype of que1 is related to two different mutations, mapped to the lower arms of chromosomes 1 and 4.

Absorption↗
PubMed2005

Identification of a carotenoid oxygenase synthesizing acyclic xanthophylls: combinatorial biosynthesis and directed evolution.

A carotenoid desaturase homolog from Staphylococcus aureus (CrtOx) was identified. When expressed in engineered E. coli cells synthesizing linear C(30) carotenoids, polar carotenoid products were generated, identified as aldehyde and carboxylic acid C(30) carotenoid derivatives. The major product in this engineered pathway is the fully desaturated C(30) dialdehyde carotenoid 4,4'-diapolycopen-4,4'-dial. Very low carotenoid yields were observed when CrtOx was complemented with the C(40) carotenoid lycopene pathway. But extension of an in vitro evolved pathway of the fully desaturated 2,4,2',4'-tetradehydrolycopene produced the structurally novel fully desaturated C(40) dialdehyde carotenoid 2,4,2',4'-tetradehydrolycopendial. Directed evolution of CrtOx by error-prone PCR resulted in a number of variants with higher activity on C(40) carotenoid substrates and improved product profiles. These findings may provide new biosynthetic routes to highly polar carotenoids with unique spectral properties desirable for a number of industrial and pharmaceutical applications.

Carotenoids↗
PubMed2004

Violaxanthin de-epoxidase, the xanthophyll cycle enzyme, requires lipid inverted hexagonal structures for its activity.

Bilayer-forming lipids were shown to be ineffective in sustaining the enzymatic activity of violaxanthin de-epoxidase. On the other hand, non-bilayer-forming lipids, regardless of their different chemical character, ensured high activity of violaxanthin de-epoxidase, resulting in conversion of violaxanthin to zeaxanthin. Our data indicates that the presence of lipids forming reversed hexagonal structures is necessary for violaxanthin de-epoxidase activity and this activity is dependent on the degree of unsaturation of the fatty acids. The significance of the reversed hexagonal phase domains in the conversion of violaxanthin into zeaxanthin in model systems and in the native thylakoid membranes is discussed.

Chromatography, Thin Layer↗
PubMed2002

Low-temperature-induced accumulation of xanthophylls and its structural consequences in the photosynthetic membranes of the cyanobacterium Cylindrospermopsis raciborskii: an FTIR spectroscopic study.

The effects of the growth temperature on the lipids and carotenoids of a filamentous cyanobacterium, Cylindrospermopsis raciborskii, were studied., The relative amounts of polyunsaturated glycerolipids and myxoxanthophylls in the thylakoid membranes increased markedly when this cyanobacterium was grown at 25 degrees C instead of 35 degrees C. Fourier transform infrared spectroscopy was used to analyze the low-temperature-induced structural alterations in the thylakoid membranes. Despite the higher amount of unsaturated lipids there, conventional analysis of the v(sym)CH(2) band (characteristic of the lipid disorder) revealed more tightly arranged fatty-acyl chains for the thylakoids in the cells grown at 25 degrees C as compared with those grown at 35 degrees C. This apparent controversy was resolved by a two-component analysis of the v(sym)CH(2) band, which demonstrated very rigid, myxoxanthophyll-related lipids in the thylakoid membranes. When this rigid component was excluded from the analysis of the thermotropic responses of the v(sym)CH(2) bands, the expected higher fatty-acyl disorder was observed for the thylakoids prepared from cells grown at 25 degrees C as compared with those grown at 35 degrees C. Both the carotenoid composition and this rigid component in the thylakoid membranes were only growth temperature-dependent; the intensity of the illuminating light during cultivation had no apparent effect on these parameters. We propose that, besides their well-known protective functions, the polar carotenoids in particular may have structural effects on the thylakoid membranes. These effects should be exerted locally--by forming protective patches, in-membrane barriers of low dynamics--to prevent the access of reactive radicals generated in either enzymatic or photosynthetic processes to sensitive spots of the membranes.

Carotenoids↗