Changes In Carotenoid Composition Research Articles

Revealing the chemical synergism in coloring tomatoes by Raman spectroscopy

AbstractIn this work, Raman spectroscopy and DFT calculations have been used to identify pigments biosynthesized during the ripening of tomatoes. In situ analysis of the exocarp from tomatoes at six stages of maturation showed Raman bands attributed mainly to carotenes and flavonoids. The Raman spectra of the exocarp in earlier stages (green and breaker) are rich in carotenoids with nine conjugated double bonds, while later stages (light‐red and red) are dominated by ones with 11 conjugated unsaturation. The Raman structural characterization of carotenoids biosynthesized from the phytoene, phytofluene, to β‐carotene is reported for the first time. Changes in carotenoid composition were observed along with the maturation; however, flavonoids/polyphenols that are concomitantly biosynthesized since the green stage presented the same spectral pattern along the process. Here, we present some clues based on Raman spectroscopy of the chemical synergism between carotenoids and flavonoids in coloring tomatoes.

Effect of Ripening Stages and Oven Drying on the Carotenoid Composition of Goji Berry (Lycium barbarum L.) Fruits

In this study firstly, pH, titratable acidity, water soluble solid (°Bx) and carotenoid content of goji berry fruits in three different ripening stages (mature green, intermediately ripe, fully ripe) were determined. Secondly, the fully ripe goji berry fruits were dried at 50, 60 and 70 °C in an oven drying and the changes in carotenoid composition and kinetic parameters were investigated. Thermal degradation of carotenoids in goji berry fruit fitted to the first order reaction model and k, t1/2, Q10 and Ea values were calculated. Changes in the carotenoid composition were observed as a result of the ripening of the fruit. Lutein was found as the predominant carotenoid at mature green goji berry fruit, while zeaxanthin dipalmitate was at intermediately and fully ripe goji berry. Chlorophyll a and b were detected in the mature green fruit but not in the intermediately and full ripe fruit. The results demonstrated that drying temperature is an important factor affecting carotenoid degradation in goji berry fruits and different ripening stages have important effect on the carotenoid content of goji berry.

Involvement of ethylene in color changes and carotenoid biosynthesis in loquat fruit (Eriobotrya japonica Lindl. cv. Algerie)

In loquat (Eriobotrya japonica Lindl cv. Algerie) fruit, despite the non-climacteric ripening behaviour, evidence suggest that ethylene may participate in the regulation of several ripening- and postharvest-related processes. Color changes and carotenoid profile were analyzed in fruit at three developmental stages (breaker, yellow and colored fruits). At early stages, the fruit peel contained phytoene, phytofluene and other typical chloroplastic carotenoids that decreased during ripening, to accumulate β-carotene, violaxanthin and β-cryptoxanthin in mature fruits. In the pulp, carotenoid concentration increased during ripening to become predominant phytoene, followed by β-carotene and β-cryptoxanthin. Expression of the carotenoid biosynthetic genes (PSY, PDS, ZDS, CYCB and BCH) was downregulated in the peel during maturation, but increased in the pulp with the exception of BCH. The involvement of ethylene in the regulation of pigmentation was further evaluated by treating fruits at the three ripening stages with ethylene or its action inhibitor 1-MCP. At breaker fruit, ethylene accelerated and 1-MCP delayed fruit coloration, but the effect was progressively lost as fruit matured. Ethylene and 1-MCP produced different changes in carotenoids content and gene expression in peel and pulp. Application of ethylene enhanced β-carotene content in both tissues whereas β-cryptoxanthin was only stimulated in the pulp. 1-MCP suppressed these changes in carotenoid composition in the pulp but had little effect in the peel. A differential transcriptional level the pulp was more responsive to downregulated gene expression than the peel. Collectively, results indicate that: 1) ethylene is involved in the regulation of pigmentation and carotenoid biosynthesis in loquat fruits, 2) a differential regulation of carotenoid biosynthesis and response to ethylene appear to operate in the peel and the pulp, and 3) β-carotene hydroxylase (BCH) is a key step in the regulation of carotenoid content and composition in both tissues of loquat fruit.

Changes in pigment profile and surface colour of fig (Ficus carica L.) during drying

SummaryIn this study, anthocyanins in three fresh fig varieties (Ficus carica L.) cultivated in Turkey were characterised and quantified by HPLC/DAD and HPLC/MS. In addition, the carotenoid composition of Sarılop and Sarızeybek, yellow fig varieties, was determined, and then the ripening‐ and drying‐related changes in carotenoids and surface colour of figs were monitored during conventional sun‐drying. Four different anthocyanins, cyanidin‐3‐glucoside, cyanidin‐3,5‐diglucoside, cyanidin‐3‐rutinoside (major anthocyanin) and pelargonidin‐3‐glucoside, were identified in samples. Lutein, zeaxanthin, β‐cryptoxanthin and β‐carotene were carotenoids in yellow fig varieties. Approximately 80% of carotenoid compounds in yellow fig varieties degraded at the end of drying (i.e. seventh day). L (lightness), a (redness and greenness) and b (yellowness and blueness) colour parameters were measured by Hunter Lab system. Great changes in carotenoid composition and surface colour were observed at ripening stage on tree. A significant reduction in L and b values that refers to browning in figs was made in the first 3 days of drying process.

Evaluation of colors in green mutants isolated from purple bacteria as a host for colorimetric whole-cell biosensors

The change in carotenoid-based bacterial color from yellow to red can be applied to whole-cell biosensors. We generated several green mutants to emphasize the color change in such biosensors. The blue-green crtI-deleted mutant, Rhodopseudomonas palustris no.711, accumulated the colorless carotenoid precursor, phytoene. Green Rhodovulum sulfidophilum M31 accumulated neurosporene, a downstream product of phytoene. Another green mutant, Rhodobacter sphaeroides Ga, accumulated neurosporene and chloroxanthin, which are both downstream products of phytoene. All green mutants accumulated bacteriochlorophyll a. Photosynthetic membrane obtained from the green mutants all exhibited decreased absorption of wavelength range at 510-570 nm. Therefore, these indicate that the greenish bacterial colors were mainly caused by the existence of bacteriochlorophyll a and the changes in carotenoid composition in photosynthetic membrane. The colors of the green mutants and their wild-type strains were plotted in the CIE-L*a*b* color space, and the color difference (DeltaE*ab) values between a green mutant and its wild type were calculated. DeltaE*ab values were higher in the green mutants than in Rdv. sulfidophilum CDM2, the yellowish host strain of reported biosensors. These data indicate that change in bacterial color from green to red is more distinguishable than that from yellow to red as a reporter signal of carotenoid-based whole-cell biosensors.

Biochemical and Molecular Analysis of Carotenoid Biosynthesis in Flavedo of Orange (Citrus sinensis L.) during Fruit Development and Maturation

Changes in carotenoid content and composition and expression of carotenoid biosynthetic genes were analyzed in the flavedo of sweet orange (Citrus sinensis L. Osbeck, cv. Navelate) fruit during development and maturation. Lutein and all-E-violaxanthin were the major carotenoids in chloroplast-containing tissues. During fruit coloration, phytoene, beta-cryptoxanthin, zeaxanthin, and mainly (9Z)-violaxanthin progressively accumulated, and a large proportion of apocarotenoids was also found in the flavedo of full-colored fruits. We have cloned partial and full-length cDNAs corresponding to genes involved in early condensation and desaturase reactions [phytoene synthase (PSY), phytoene desaturase (PDS), and zeta-carotene desaturase (ZDS)], coupled redox reaction (plastid terminal oxidase), cyclizations [beta-lycopene cyclase (beta-LCY) and epsilon-lycopene cyclase (epsilon-LCY)], hydroxylation [beta-carotene hydroxylase (beta-CHX)], and epoxidation [zeaxanthin epoxidase (ZEP)] and analyzed their mRNA accumulation in the flavedo of fruits during development and ripening as compared with those of leaves. Collectively, the results indicated that PDS gene expression correlated with carotenoid content in developing fruit and that up-regulation of PSY and ZDS genes at the onset of fruit coloration would enhance the production of linear carotenes and the flux into the pathway. The shift from the beta,epsilon-branch to the beta,beta-branch of the pathway that originates the changes in carotenoid composition during fruit coloration may be explained by a down-regulation of epsilon-LCY and by the increase of the beta-CHX transcript.

Changes in carotenoid composition in different developmental stages of copepods: Pseudocalanus acuspes Giesbrecht and Acartia spp.

Carotenoid contents and composition were studied in three successive developmental groups of copepod populations from the southern Baltic Sea. Samples were collected with >80% prevalence of any one of three developmental groups: (i) nauplii, (ii) copepodids I-III and (iii) copepodids IV-V and also adults of Pseudocalanus acuspes Giesbrecht and Acartia spp. (Copepoda: Calanoida). Samples were collected over the years 1991-1999 from May to September at six sampling sites in the southern Baltic Sea. The carotenoids were analysed by means of reverse-phase high-performance liquid chromatography (RP-HPLC). The mean total carotenoid concentrations (astaxanthin, astaxanthin esters, canthaxanthin and other carotenoid unidentified and derived from the diet) found in three groups of developmental stages for P. acuspes were 556 μg g -1 dry weight (d.w.) in naupliar stages, 791 μg g -1 in copepodids I-III, and 868 μg g -1 in copepodids IV-V and adults. The average carotenoid concentrations in Acartia spp. were 619, 764 and 872 μg g -1 d.w., respectively. Significant changes were observed in the proportion of carotenoids of separate developmental groups. Astaxanthin and canthaxanthin occurred in all developmental groups, with the evident dominance of astaxanthin. However, copepodid groups I-III and especially IV-V including adults, showed an increased proportion of astaxanthin esters. This suggests that astaxanthin is the main active carotenoid in copepod metabolism. It acts most probably as an efficient free radical quencher and may be involved in rapid metabolism of stored lipids in mostly unfeeding young nauplii. The feeding stages (late nauplii and copepodids I-III and IV-V) are evidently able to metabolize this pigment by esterfication and further degradation.

Flesh quality and lycopene stability of fresh-cut watermelon

Abstract Red fleshed watermelons are an excellent source of the phytochemical lycopene. However, little is known about the stability of lycopene in cut watermelon. In this study, lycopene stability and other quality factors were evaluated in fresh-cut watermelon. Twenty melons each of a seeded (Summer Flavor 800) and a seedless (Sugar Shack) variety were cut into 5 cm cubes and placed in unvented polystyrene containers, sealed, and stored at 2 °C for 2, 7, or 10 days. At each storage interval, melons were evaluated for juice leakage, changes in carotenoid composition, color, soluble solids content (SSC), and titratable acidity. Headspace carbon dioxide and ethylene were monitored during storage intervals. Juice leakage after 10 days of storage averaged 13 and 11% for the seeded and seedless melons, respectively. Lycopene content decreased 6 and 11% after 7 days of storage for Summer Flavor 800 and Sugar Shack melons, respectively. β-Carotene and cis lycopene contents were 2 and 6 mg kg−1 for Summer Flavor 800 and Sugar Shack, respectively, and did not change with storage. After 10 days of storage, CIE L∗ values increased while chroma values decreased, indicating a lightening in color and loss of color saturation in melon pieces. Symptoms of chilling injury, such as greatly increased juice leakage, or lesions on cubes, were not seen on the fresh-cut cut watermelon after 10 days storage at 2 °C. Puree pH increased and SSC decreased slightly after storage. Carbon dioxide levels increased and oxygen levels decreased linearly during storage, creating a modified atmosphere of 10 kPa each of CO2 and O2 after 10 days. Fresh-cut cut watermelon held for 7 or more days at 2 °C had a slight loss of SSC, color saturation, and lycopene, most likely caused by senescence.

High irradiance-induced changes in carotenoid composition and increase in non-photochemical quenching of Chl a fluorescence in primary wheat leaves

The effect of acclimation to high irradiance stress (HIS, 250 Wm-2) in wheat leaves grown under three different irradiances was investigated by HPLC analyses of pigments, chlorophyll a fluorescence parameters and photochemical activities of chloroplasts. Significant loss of beta-carotene was observed compared to the xanthophylls in all three types of seedlings exposed to HIS. However, the effect of HIS on neoxanthin and lutein contents was not significant. The loss of partial electron transport (Asc-DCPIP to MV, PSI activity) was less than the whole chain (H2O to MV) and PS II activity (H2O to DCPIP) suggesting that PS I is less susceptible to HIS compared to PS II. The percent of reductions in Fv/Fm and phi PS II were less in plants grown under high irradiance (HI-1, 30 Wm-2 and HI-2, 45 Wm-2) compared to those grown under moderate irradiance (MI, 15 Wm-2). On the other hand, the percent of NPQ increased more in the leaves of HI plants compared to the leaves of MI when exposed to HIS which suggests a more efficient non-radiative dissipation of excess excitation energy in HI plants compared to MI. These observations suggest that plants grown under relatively high irradiance are better adapted to HIS condition.

Survey of Thermal Energy Dissipation and Pigment Composition in Sun and Shade Leaves

A survey was conducted of the magnitude of energy dissipation in photosystem II (expressed as nonphotochemical quenching of chlorophyll fluorescence, NPQ) as well as leaf carotenoid composition of a wide range of different plant species growing in deep shade and/or full sun. Consistently higher levels of the reversible component of NPQ as well as higher degrees of rapidly attainable de-epoxidation of the xanthophyll cycle (VAZ) pool were observed in sun leaves compared to deep shade leaves. It is concluded that these altered features of the xanthophyll cycle allowed sun leaves to dissipate excess energy more effectively over the short term. In addition to the rapid increase in reversible NPQ, shade leaves exhibited a slow further, and sustained, increase in NPQ. In contrast to these deep shade leaves experimentally exposed to high PFDs, understory leaves experiencing highly variable PFD in their natural environment appeared to be able to dissipate excess excitation energy adequately via xanthophyll cycle-dependent thermal dissipation. Furthermore, very consistent trends across plant species were observed for changes in carotenoid composition (pools of carotenes, VAZ, and other xanthophylls) in response to light environment, as long as it is assumed that in some species /^-carotene can be replaced by a-carotene and in a few plant species lutein can be replaced by lactucaxanthin. Sun leaves consistently exhibited much greater levels of VAZ than shade leaves but very similar levels of lutein and neoxanthin (all on a Chi basis) as well as an only slightly higher ratio of total carotenes to the pool of all xanthophylls.

Consequences of chlorophyll deficiency for leaf carotenoid composition in tobacco synthesizing glutamate 1-semialdehyde aminotransferase antisense RNA: dependency on developmental age and growth light

suggests a co-regulation between carotenoid and chlorophyll synthesis; the second emphasizes the Transgenic tobacco (Nicotiana tabacum), with a special role of carotenoids for protection against reduced chlorophyll content of up to less than 10% of light stress. the wild-type level due to a different expression of antisense RNA coding for glutamate 1-semialdehyde Key words: Light acclimation, photoprotection, quantum aminotransferase, were used to study the relationship yield, lutein, xanthophyll cycle. between chlorophyll accumulation and changes in carotenoid composition in developing and mature leaves grown either under low (30 mmol photons Introduction m’2 s’1) or high light (300 mmol photons m’2 s’1). Regardless of the extent to which chlorophyll synthesis Like chlorophylls (Chls), carotenoids of leaves are ubiwas reduced, under low light the ratios of total chloro- quitous structural components of the photosynthetic phyll to carotenoids remained constant. In contrast, apparatus. In higher plants, Chls and carotenoids are under high light the content of carotenoids was elev- bound to specific proteins to form either reaction centre ated relative to chlorophyll and increased further with pigment‐protein complexes or light-harvesting pigment‐ progressive inhibition in chlorophyll synthesis. The protein complexes (LHCs) of photosystem (PS) I and xanthophyll-cycle pigment pool was most strongly PSII (LHCII ). Attempts to ascertain the distribution of increased (up to 18-fold) upon supression of chloro- carotenoids within the multiple pigment‐protein comphyll synthesis. Concurrently to the higher pool sizes plexes by detergent fractionation yielded varying results a higher extent of violaxanthin was converted into between research groups, probably due to distinct isolaantheraxanthin and zeaxanthin and this was found to tion procedures and diVerences in both the growth condibe correlated with a decrease in the quantum yield of tions and plant species. Nevertheless, b-carotene was photosystem II photochemistry. While lutein increased consistently found in the reaction centre/core complexes (up to 3-fold) with decreasing chlorophyll contents in of both PSI and PSII, whereas xanthophylls mainly bind

Carotenoid Pigments and Colour of Hermaphrodite and Female Papaya Fruits (Carica papaya L) cv Sunrise During Post-Harvest Ripening

The predominant carotenoids in extracts of female and hermaphrodite Papaya fruits (Carica papaya L) Solo cv Sunrise were determined by high-performance liquid chromatography on a C18 reversed-phase column using a diode-array detector. Three classes of carotenoids were separated and identified from the papaya extract without saponification; these were xanthophylls, hydrocarbon carotenoids and carotenol fatty acid esters. The xanthophylls were identified as trans-zeaxanthin, cryptoflavin and β-cryptoxanthin; other xanthophyls were detected in very small quantities. The major hydrocarbon carotenoid was identified as lycopene. Carotenol fatty acid esters were identified as carotenol fatty acid esters of β-cryptoxanthin, cryptoxanthin-5,6-epoxide, lutein, zeaxanthin and violaxanthin. There were no qualitative differences among the carotenoid pattern of female and hermaphrodite papaya fruits. Changes in carotenoid composition during ripening in hermaphrodite and female papaya fruits (cv Sunrise) were investigated in three different stages of ripeness. These changes could be shown in terms of Hunter colour values.

Carotenoid catabolism during leaf senescence and its control by light

Abstract Reviews on the biosynthesis, distribution and function of carotenoids in chloroplasts of higher plants and algae are available. However, the data, although limited, on degradation of the pigment during leaf senescence are not integrated. This review is an attempt to summarise the data available so far, generalise them, and address a few unanswered questions in the field. Both Chl and carotenoids degrade during leaf senescence; the latter process, however, is demonstrated in many plant systems to remain relatively stable. Senescence brings about changes in carotenoid composition and causes formation of xanthophyll esters and epoxides in some cases. The esters and free carotenoids are predominantly located in plastoglobuli formed during the process. In the context of compositional changes, the possibility of the operation of the xanthophyll cycle during senescence is discussed. The existing experimental findings suggest the involvement of enzymes for degradation of the pigment. Light is shown to stimulate carotenoid degradation in the background of dark treatment during aging of isolated chloroplasts and plants treated with herbicides. The mechanism of stimulation is mostly explained through the participation of free radicals. In contrast, photoinduced retardation of the pigment loss during leaf senescence is attributed to the action of phytochrome.

Operation of the Xanthophyll Cycle in Non-Stressed and Stressed Cells of Dunaliella salina Teod. in Response to Diurnal Changes in Incident Irradiation: A Correlation with Intracellular β-Carotene Content

Summary Changes in carotenoid composition were monitored on a diurnal basis in cells of Dunaliella salina Teod. grown outdoors, under natural irradiance in mass culture. Stressed cells contained approximately four times more, β-carotene than non-stressed cells. The net change in β-carotene content however, was similar for both treatments and correlated closely with changes in photon flux density during the diurnal cycle. Xanthophyll levels were higher in stressed cells suggesting that excess light was not the only factor involved in stimulating carotenoid accumulation, although xanthophyll content increased in nonstressed cells to a level similar to that of stressed cells, with increasing photon flux density. Light-response curves of zeaxanthin and β-carotene formation displayed a biphasic nature in stressed cells. In nonstressed cells however, zeaxanthin formation was rapid and the descending light-response curve showed little change in net zeaxanthin levels. High β-carotene-containing cells had substantial amounts of zeaxanthin and levels of this carotenoid remained higher in stressed cells throughout the diurnal cycle. Changes in intracellular β-carotene occurred coincident with operation of the xanthophyll cycle during the diurnal period. Non-stressed and stressed cells showed similar de-epoxidation of the xanthophyll cycle at peak photon flux denisty. Although non-stressed cells formed more β-carotene and zeaxanthin in response to increasing irradiance, stressed cells formed β-carotene and zeaxanthin more rapidly i.e. at lower photon flux density. Zeaxanthin formation in stressed cells occurred as a consequence of violaxanthin de-epoxidation. By comparasion, zeaxanthin production in non-stressed cells occurred by two probable mechanisms: 1, by rapid de-epoxidation of violaxanthin and 2, a slow but continuous de novo synthesis which increased the total zeaxanthin pool.

Carotenoid composition and its relationship to chlorophyll and D1 protein during leaf development in a normally senescing cultivar and a stay-green mutant of Festuca pratensis

Chlorophyll and carotenoid were measured with reference to the developmental gradient along the expanding fourth leaf of Rossa, a normally yellowing cultivar of Festuca pratensis , and of a mutant genotype Bf993 which is unable to degrade pigments and associated thylakoid proteins during foliar senescence. Although pigment levels were highest in the central, mature portion of the leaf, there were nevertheless readily detectable amounts of chlorophyll and carotenoid even in basal tissues enclosed in the sheaths of older leaves. Carotenoid compositions were the same in all the tissues except the senescent tissue at the leaf tip. Here chlorophyll to carotenoid ratio decreased in Rossa but along the young leaf tissue of this genotype and throughout the leaf of Bf993 this ratio was constant. Amounts of D1 protein, associated with the Photosystem II reaction centre, were correspondingly retained to a somewhat greater extent in senescing tissue of Bf993 but surprisingly, given the expression of the genetic lesion in a delayed senescence, amounts of the protein were lower in young tissue from the stay-green mutant than in the normal genotype. When the leaf of Rossa was allowed to senesce until the entire blade was yellow there were marked changes in carotenoid composition, and chlorophyll degradation products accumulated. Any increase in zeaxanthin was slight and there was no evidence to suggest operation of a xanthophyll cycle.

Carotenoid Components in Soybean Seeds Varying with Seed Color and Maturation Stage

The difference in carotenoid components among various color types of soybean seeds, and the changes in carotenoid composition during seed development were examined by reverse-phase high-performance liquid chromatogrphy (HPLC). Lutein was the major carotenoid component in seed extracts from the common yellow soybean and from a variety having a black seed coat. Green soybean seeds contained several xanthophylls in addition to lutein. None of the mature soybean seeds contained β-carotene, a part from a trace amount being detected in a local variety of green soybean. The total carotenoid and lutein contents were higher in green soybeans than in the yellow types, and the estimated total amount of carotenoids correlates with that of chlorophylls. The thylakoid membrane residue in the plastids of green soybean had lost its functional lamella structure. Immature soybean seeds contained a green-vegetable type of carotenoids including α- and β-carotene. The amount of β-carotene decreased more rapidly than that of l...

Changes in Carotenoid Composition in Senescing Leaves of Hordeum vulgare L. cv. Dyan

Summary Changes in carotenoid composition were monitored during senescence of the primary leaf of seedlings of Hordeum vulgare L. cv. Dyan. Senescence occurred due to the normal course of leaf development or was induced by incubation of attached leaves in darkness, or by incubation of detached leaf segments in either continuous light or darkness. Carotenoid and abscisic acid levels were monitored in the same tissue extracts, prepared from either attached leaves or detached leaf segments, throughout the course of foliar senescence. The results obtained show that the increase in endogenous levels of abscisic acid, induced by senescence, correlated with enhanced epoxidation of the xanthophyll cycle, i.e., increased conversion of zeaxanthin to antheraxanthin and all- trans -violaxanthin. Additionally, an increase in abscisic acid levels occurred concomitant with a decrease in all- trans -violaxanthin and 9′- cis -neoaxanthin, suggesting an apparent 1:1 relationship on a molar basis. It is therefore proposed that enhanced abscisic acid production, due to foliar senescence, arises from fluctuations in carotenoid turnover. Evidence is also presented to suggest that abscisic acid production and xanthophyll cycle turnover are not independent reactions in the process of leaf senescence.

Changes in Carotenoid Composition and Photosynthesis in Sorghum under High Light and Salt Stresses

Summary The effect of high light stress and salt stress, individually and in combination, was investigated in the leaves of Sorghum bicolor (1.). High light treatment at 5°C and 20°C caused an increase in zeaxanthin and a decrease in violaxanthin contents. Decreases in β-carotene were also observed, which was followed by increased formation of 5,6-epoxide-β-carotene. Violaxanthin + antheraxanthin + zeaxanthin (total) was not the same in control and stressed plants. Salt stress (no photoinhibition) also resulted in the formation of zeaxanthin but it was significantly less than that observed in the high light stressed plants. Neoxanthin content showed a slight decrease, while 5,6-epoxide lutein increased under salt stress. Changes in the xanthophyll cycle (violaxanthin + antheraxanthin + zeaxanthin) were reversed during recovery after photoinhibition. The CO2 assimilation rate and fluorescence Fv/Fm ratio were measured in intact leaves and isolated chloroplasts, respectively, from control and stressed plants. Formation of zeaxanthin and degradation of β-carotene are apparently involved in protection against photoinhibition.

Changes in the native carotenoid of bacterial pigment-protein complexes

Changes in the carotenoid pool of the photosynthetic membrane of Rhodospirillum rubrum caused parallel changes in the carotenoids of light-harvesting and reaction-center complexes. Thus, whereas complexes purified from exponentially growing cultures contained spirilloxanthin and several of its colored metabolic precursors at comparable levels, only spirilloxanthin was detected in preparations derived from stationary-phase cultures, and in both cases the carotenoid composition of the isolated complexes was similar or identical to that of the intact membrane. The differences between the antenna pigments of stationary and exponential cultures were reflected in the circular dichroism spectrum and in the bacteriochlorophyll fluorescence excitation spectrum of the intact membrane, since both optical activity and singlet-singlet energy transfer to bacteriochlorophyll are specific for complex-bound carotenoids. The changes in carotenoid composition that were induced by oxygen in cultures of Rhodobacter capsulatus were accompanied also by parallel changes in the pigments of both the core and the peripheral antenna complexes of this microorganism. In both species of purple bacteria, the variations of pigment pattern did not appear to influence to any significant extent the protective function of carotenoids, as assayed by following the photodestruction of antenna bacteriochlorophyll in aerobic suspensions of isolated membrane vesicles. The similar carotenoid composition of the intact membrane and the antenna may be simply explained by the limiting size of the pigment pool (all pigmented carotenoids that are present become complex-bound). However, to account for the carotenoid variability of the R. rubrum reaction center, which is less abundant in the membrane than some carotenoids, it seems necessary to assume that there are no significant differences among the binding affinities of the complex for the available pigments.

カボチャの調整，凍結ならびに凍結乾燥貯蔵によるカロチノイド組成の変化

カボチャの調整，凍結ならびに凍結乾燥貯蔵によるカロチノイド組成の変化