Optimization of headspace solid-phase Microextraction (SPME) for the odor analysis of surface-ripened cheese     

Lecanu L  Ducruet V  Jouquand C  Gratadoux JJ  Feigenbaum A 《Journal of agricultural and food chemistry》2002,50(13):3810-3817

Fifty volatile compounds of surface smear-ripened cheese were detected and identified using headspace solid-phase microextraction (HS-SPME) and vacuum distillation coupled to gas chromatography-mass spectrometry. Changes in the headspace of aroma compounds were monitored over the whole packaging period (47 days) using the HS-SPME method. Initially, the concentration of methanethiol increased before reaching a plateau. This evolution could be linked to the growth of Brevibacterium linens. During the shelf life of cheese, levels of acetic acid and 3-methylbutanoic acid remained constant, whereas butane-2,3-dione, 3-hydroxybutan-2-one, and hydroxypropan-2-one levels gradually declined and acetone and 3-methylbutanol levels dropped sharply to a plateau. Changes in odor could be related to changes of the rind, which behaved as a barrier, strongly influencing the distribution of volatile compounds in the headspace. Using a gas chromatography-olfactometry technique without separation, it was shown that the SPME extract was representative of the cheese odor.  相似文献   

Cigarette smoke contains anticoagulants against fibrin aggregation and factor XIIIa in plasma   总被引：1，自引：0，他引：1  

D K Galanakis  P Laurent  A Janoff 《Science (New York, N.Y.)》1982,217(4560):642-645

Gas-phase, water-soluble components of cigarette smoke cause delayed fibrin self-assembly and prevent fibrin cross-linking by inactivation of factor XIIIa (plasma transglutaminase). These anticoagulant properties of smoke are demonstrable in plasma, suggesting they play a role in the pathophysiology of smoking.  相似文献   

A map of the interactome network of the metazoan C. elegans   总被引：1，自引：0，他引：1  

Li S  Armstrong CM  Bertin N  Ge H  Milstein S  Boxem M  Vidalain PO  Han JD  Chesneau A  Hao T  Goldberg DS  Li N  Martinez M  Rual JF  Lamesch P  Xu L  Tewari M  Wong SL  Zhang LV  Berriz GF  Jacotot L  Vaglio P  Reboul J  Hirozane-Kishikawa T  Li Q  Gabel HW  Elewa A  Baumgartner B  Rose DJ  Yu H  Bosak S  Sequerra R  Fraser A  Mango SE  Saxton WM  Strome S  Van Den Heuvel S  Piano F  Vandenhaute J  Sardet C  Gerstein M  Doucette-Stamm L  Gunsalus KC  Harper JW  Cusick ME  Roth FP  Hill DE  Vidal M 《Science (New York, N.Y.)》2004,303(5657):540-543

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Deep human genealogies reveal a selective advantage to be on an expanding wave front     

Moreau C  Bhérer C  Vézina H  Jomphe M  Labuda D  Excoffier L 《Science (New York, N.Y.)》2011,334(6059):1148-1150

Since their origin, human populations have colonized the whole planet, but the demographic processes governing range expansions are mostly unknown. We analyzed the genealogy of more than one million individuals resulting from a range expansion in Quebec between 1686 and 1960 and reconstructed the spatial dynamics of the expansion. We find that a majority of the present Saguenay Lac-Saint-Jean population can be traced back to ancestors having lived directly on or close to the wave front. Ancestors located on the front contributed significantly more to the current gene pool than those from the range core, likely due to a 20% larger effective fertility of women on the wave front. This fitness component is heritable on the wave front and not in the core, implying that this life-history trait evolves during range expansions.  相似文献   

Helical conformation of alkanes in a hydrophobic cavitand     

Trembleau L  Rebek J 《Science (New York, N.Y.)》2003,301(5637):1219-1220

Alkanes adopt extended conformations in solution that minimize steric interactions and maximize surface area. Folding can reduce the amount of hydrophobic surface exposed to solvent, but sterically unfavorable gauche interactions result. However, we found that the alkyl chains of two common surfactants in aqueous solution adopt helical conformations when bound within a synthetic receptor. The receptor recognizes the helical alkane better than the extended conformation, even though 2 to 3 kilocalories per mole of strain is introduced. The proper filling of space and burial of hydrophobic surface drive the molecular recognition between the receptor and the coiled alkane.  相似文献   

Deep Impact observations by OSIRIS onboard the Rosetta spacecraft   总被引：1，自引：0，他引：1  

Keller HU  Jorda L  Küppers M  Gutierrez PJ  Hviid SF  Knollenberg J  Lara LM  Sierks H  Barbieri C  Lamy P  Rickman H  Rodrigo R 《Science (New York, N.Y.)》2005,310(5746):281-283

The OSIRIS cameras (optical, spectroscopic, and infrared remote imaging system) onboard the European Space Agency's Rosetta spacecraft observed comet 9P/Tempel 1 for 17 days continuously around the time of NASA's Deep Impact mission. The cyanide-to-water production ratio was slightly enhanced in the impact cloud, compared with that of normal comet activity. Dust particles were flowing outward in the coma at >160 meters per second, accelerated by the gas. The slope of the brightness increase showed a dip about 200 seconds after the impact. Dust Afrho values before and long after the impact confirm the slight decrease of cometary activity. The dust-to-water mass ratio was much larger than 1.  相似文献   

Arabidopsis EDS1 connects pathogen effector recognition to cell compartment-specific immune responses     

Heidrich K  Wirthmueller L  Tasset C  Pouzet C  Deslandes L  Parker JE 《Science (New York, N.Y.)》2011,334(6061):1401-1404

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Synthesis and structure determination of the hierarchical meso-microporous zeolite ITQ-43     

Jiang J  Jorda JL  Yu J  Baumes LA  Mugnaioli E  Diaz-Cabanas MJ  Kolb U  Corma A 《Science (New York, N.Y.)》2011,333(6046):1131-1134

The formation of mesopores in microporous zeolites is generally performed by postsynthesis acid, basic, and steam treatments. The hierarchical pore systems thus formed allow better adsorption, diffusion, and reactivity of these materials. By combining organic and inorganic structure-directing agents and high-throughput methodologies, we were able to synthesize a zeolite with a hierarchical system of micropores and mesopores, with channel openings delimited by 28 tetrahedral atoms. Its complex crystalline structure was solved with the use of automated diffraction tomography.  相似文献   

In vitro digestibility of α-casozepine, a benzodiazepine-like peptide from bovine casein, and biological activity of its main proteolytic fragment     

Cakir-Kiefer C  Le Roux Y  Balandras F  Trabalon M  Dary A  Laurent F  Gaillard JL  Miclo L 《Journal of agricultural and food chemistry》2011,59(9):4464-4472

α-Casozepine is a peptide, corresponding to the sequence 91-100 of the bovine α(s1)-casein, displaying anxiolytic activity in the rat. The α(s1)-casein tryptic hydrolysate containing this peptide decreases stress effects after oral administration in various species including man. Therefore, the stability of this peptide toward gastric and pancreatic proteases has been assessed by using pepsin, chymotrypsin/trypsin, Corolase PP, pepsin followed by chymotrypsin/trypsin or pepsin followed by Corolase PP. α-Casozepine was slowly degraded by chymotrypsin, much more sensitive to pepsin and Corolase PP but not completely destroyed after 4 h kinetics. The bonds in the region 91 to 95 of the α-casozepine were totally resistant to hydrolysis by all studied proteases. Surprisingly, a fragment, corresponding to the sequence 91-97 and found in all the hydrolysis media in significant amount, possessed an anxiolytic activity in three behavioral tests measuring this parameter. This peptide could participate in the in vivo activity of α-casozepine.  相似文献   

Biodegradation of 3-chloro-1,2-propanediol with Saccharomyces cerevisiae     

Bel-Rhlid R  Talmon JP  Fay LB  Juillerat MA 《Journal of agricultural and food chemistry》2004,52(20):6165-6169

A novel enzymatic dehalogenating activity of 3-chloro-1,2-propanediol (3-MCPD) with Saccharomyces cerevisiae (baker's yeast) is reported. All bioconversion assays were carried out under aerobic conditions, at 28 degrees C, and the kinetics were monitored. The biodegradation was performed at different pH values (6.2, 7.0, and 8.2), in the presence and absence of glucose, using racemic 3-MCPD at two different concentrations (7.3 micromol/L and 27 mmol/L). Optimal conversion (68%) of racemic (R,S)-3-MCPD at a concentration of 27 mmol/L was achieved after 48 h of reaction time, at pH 8.2, and in the presence of glucose. At a concentration of 7.3 micromol/L, 73% degradation was observed after 72 h, at pH 8.2 and in the absence of glucose. Under the same experimental conditions, the conversion of pure (S)-3-MCPD (85%) was higher than that of the (R)-enantiomer (60%).  相似文献