Identification of anthocyanin-flavanol pigments in red wines by NMR and mass spectrometry     

Mateus N  Silva AM  Santos-Buelga C  Rivas-Gonzalo JC  de Freitas V 《Journal of agricultural and food chemistry》2002,50(7):2110-2116

Three newly formed Port wine pigments were isolated by Toyopearl HW-40(s) gel chromatography and semipreparative HPLC. Furthermore, the pigments were identified by mass spectrometry (LC/MS) and NMR techniques (1D and 2D). These anthocyanin-derived pigments showed UV-visible spectra different from those of the original grape anthocyanins. These pigments correspond to malvidin 3-glucoside linked through a vinyl bond to either (+)-catechin, (-)-epicatechin, or procyanidin dimer B3 [(+)-catechin-(+)-catechin]. NMR data of these pigments are reported for the first time.  相似文献   

Identification and synthesis of a novel selenium-sulfur amino acid found in selenized yeast: Rapid indirect detection NMR methods for characterizing low-level organoselenium compounds in complex matrices     

Block E  Glass RS  Jacobsen NE  Johnson S  Kahakachchi C  Kamiński R  Skowrońska A  Boakye HT  Tyson JF  Uden PC 《Journal of agricultural and food chemistry》2004,52(12):3761-3771

After proteolytic digestion, aqueous extraction, and derivatization with diethyl pyrocarbonate or ethyl chloroformate, HPLC-inductively coupled plasma (ICP)-MS, GC-atomic emission detection (AED), and GC-MS analysis of high-selenium yeast stored at room temperature for more than 10 years showed selenomethionine as the major Se product along with substantial amounts of selenomethionine selenoxide hydrate and the previously unreported selenoamino acid having a Se-S bond, S-(methylseleno)cysteine. The identity of the latter compound was confirmed by synthesis. The natural product was shown to be different from a synthetic sample of the isomeric compound Se-(methylthio)selenocysteine. Selenium-specific NMR spectroscopic methods were developed to directly analyze the aqueous extracts of the hydrolyzed selenized yeast without derivatization or separation. Selenomethionine and S-(methylseleno)cysteine were identified by 77Se-1H HMQC-TOCSY experiments.  相似文献   

Antioxidant activity of a proanthocyanidin-rich extract from grape seed in whey protein isolate stabilized algae oil-in-water emulsions     

Hu M  McClements DJ  Decker EA 《Journal of agricultural and food chemistry》2004,52(16):5272-5276

Algae oil-in-water emulsions stabilized with 0.2% whey protein isolate (WPI) at pH 3.0 and 7.0 were chosen to evaluate antioxidant activity of a proanthocyanidin-rich extract from grape seed. In this emulsion system, (+)-catechin and ascorbic acid (620 microM) were found to be prooxidative at pH 3.0 and ineffective at pH 7.0. Grape seed extract was not able to effectively inhibit both lipid hydroperoxides and propanal formation when added to the emulsion at 124 microM. However, increasing the concentration of the grape seed extract to 620 microM resulted in inhibition of both lipid hydroperoxide and propanal formation at pH 3.0 and 7.0. None of the antioxidants tested had any effect on the physical stability of the WPI-stabilized emulsion. The superior antioxidant activity of the grape seed extract is likely due to the presence of oligomeric procyanidins which are better antioxidants compared to their monomeric counterparts.  相似文献   

Carbon exchange of an old-growth eastern hemlock (Tsuga canadensis) forest in central New England   总被引：1，自引：0，他引：1  

Hadley JL  Schedlbauer JL 《Tree physiology》2002,22(15-16):1079-1092

Carbon (C) exchange of an approximately 200-year-old eastern hemlock (Tsuga canadensis L.) forest in central Massachusetts, USA, was estimated from mid-October 2000 through October 2001 based on eddy covariance measurements and statistical modeling from microclimatic data. Measurements were made in 68% of the hours during the year of study, with > 50% coverage in all months except December and August. Data were filtered by wind direction and atmospheric turbulence to remove invalid measurements. Analysis of filtered data showed that photosynthetically active radiation (PAR) was significant in predicting C exchange, except during the winter. Daily minimum air temperature affected C exchange in autumn and winter, whereas time of day, water vapor pressure deficit and air temperature had significant effects on C storage in spring, summer and fall. Most C storage in the stand occurred in April through July and in October 2001, with maximum rates in April and May. Persistent cold weather prevented C storage in December through March. In early spring 2001, C uptake was sensitive to nocturnal frost: daily minimum air temperatures below 0 degrees C reduced C fixation, and minima below -5 degrees C caused its virtual cessation. Soil temperature was a poor predictor of C balance during this period. In August, high soil and air temperatures (averaging 16.7 and 21.1 degrees C, respectively) drove high ecosystem respiration, which approximately balanced C uptake. These patterns show potential for stimulated C storage in hemlock forests in a warmer climate with fewer spring and autumn frosts, but reduced C storage during warmer summers. Estimated annual C storage was 3.0 Mg ha(-1), which is higher than for younger coniferous and deciduous forests during earlier years in the northeastern USA. Long-term data are needed to determine if the estimated high C storage in this hemlock forest is a result of interannual climate variation or an effect of forest composition.  相似文献   

Structural biology. Up close with membrane lipid-protein complexes     

Whitelegge J 《Science (New York, N.Y.)》2011,334(6054):320-321

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El Niño-like pattern in ice age tropical Pacific sea surface temperature     

Koutavas A  Lynch-Stieglitz J  Marchitto TM  Sachs JP 《Science (New York, N.Y.)》2002,297(5579):226-230

Sea surface temperatures (SSTs) in the cold tongue of the eastern equatorial Pacific exert powerful controls on global atmospheric circulation patterns. We examined climate variability in this region from the Last Glacial Maximum (LGM) to the present, using a SST record reconstructed from magnesium/calcium ratios in foraminifera from sea-floor sediments near the Galápagos Islands. Cold-tongue SST varied coherently with precession-induced changes in seasonality during the past 30,000 years. Observed LGM cooling of just 1.2 degrees C implies a relaxation of tropical temperature gradients, weakened Hadley and Walker circulation, southward shift of the Intertropical Convergence Zone, and a persistent El Ni?o-like pattern in the tropical Pacific. This is contrasted with mid-Holocene cooling suggestive of a La Ni?a-like pattern with enhanced SST gradients and strengthened trade winds. Our results support a potent role for altered tropical Pacific SST gradients in global climate variations.  相似文献   

A late Triassic impact ejecta layer in southwestern Britain     

Walkden G  Parker J  Kelley S 《Science (New York, N.Y.)》2002,298(5601):2185-2188

Despite the 160 or so known terrestrial impact craters of Phanerozoic age, equivalent ejecta deposits within distal sedimentary successions are rare. We report a Triassic deposit in southwestern Britain that contains spherules and shocked quartz, characteristic of an impact ejecta layer. Inter- and intragranular potassium feldspar from the deposit yields an argon-argon age of 214 +/- 2.5 million years old. This is within the age range of several known Triassic impact craters, the two closest of which, both in age and location, are Manicouagan in northeastern Canada and Rochechouart in central France. The ejecta deposit provides an important sedimentary record of an extraterrestrial impact in the Mesozoic that will help to decipher the number and effect of impact events, the source and dynamics of the event that left this distinctive sedimentary marker, and the relation of this ejecta layer to the timing of extinctions in the fossil record.  相似文献   

The status of the world's land and marine mammals: diversity, threat, and knowledge     

Schipper J  Chanson JS  Chiozza F  Cox NA  Hoffmann M  Katariya V  Lamoreux J  Rodrigues AS  Stuart SN  Temple HJ  Baillie J  Boitani L  Lacher TE  Mittermeier RA  Smith AT  Absolon D  Aguiar JM  Amori G  Bakkour N  Baldi R  Berridge RJ  Bielby J  Black PA  Blanc JJ  Brooks TM  Burton JA  Butynski TM  Catullo G  Chapman R  Cokeliss Z  Collen B  Conroy J  Cooke JG  da Fonseca GA  Derocher AE  Dublin HT  Duckworth JW  Emmons L  Emslie RH  Festa-Bianchet M  Foster M  Foster S  Garshelis DL  Gates C  Gimenez-Dixon M  Gonzalez S 《Science (New York, N.Y.)》2008,322(5899):225-230

Knowledge of mammalian diversity is still surprisingly disparate, both regionally and taxonomically. Here, we present a comprehensive assessment of the conservation status and distribution of the world's mammals. Data, compiled by 1700+ experts, cover all 5487 species, including marine mammals. Global macroecological patterns are very different for land and marine species but suggest common mechanisms driving diversity and endemism across systems. Compared with land species, threat levels are higher among marine mammals, driven by different processes (accidental mortality and pollution, rather than habitat loss), and are spatially distinct (peaking in northern oceans, rather than in Southeast Asia). Marine mammals are also disproportionately poorly known. These data are made freely available to support further scientific developments and conservation action.  相似文献   

Suitability of southern grown potato varieties for processing     

William A. Sistrunk  Raymon E. Webb  Julian C. Miller 《American Journal of Potato Research》1954,31(11):360-365

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Re-evaluation of some techniques and their effect on stimulating flowering in four Irish potato varieties in Louisiana     

Aly Ezzat Abdel-Wahab  Julian C. Miller 《American Journal of Potato Research》1963,40(2):53-57

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