Heat-induced redistribution of disulfide bonds in milk proteins. 1. Bovine beta-lactoglobulin     

Creamer LK  Bienvenue A  Nilsson H  Paulsson M  van Wanroij M  Lowe EK  Anema SG  Boland MJ  Jiménez-Flores R 《Journal of agricultural and food chemistry》2004,52(25):7660-7668

Changes in the structure and chemistry of beta-lactoglobulin (beta-LG) play an important role in the processing and functionality of milk products. In model beta-LG systems, there is evidence that the aggregates of heated beta-LG are held together by a mixture of intermolecular non-covalent association and heat-induced non-native disulfide bonds. Although a number of non-native disulfide bonds have been identified, little is known about the initial inter- and intramolecular disulfide bond rearrangements that occur as a result of heating. These interchange reactions were explored by examining the products of heat treatment to determine the novel disulfide bonds that form in the heated beta-LG aggregates. The native protein and heat-induced aggregates were hydrolyzed by trypsin, and the resulting peptides, before and after reduction with dithiothreitol, were separated by high-performance liquid chromatography and their identities confirmed by electrospray ionization mass spectrometry. Comparisons of these peptide patterns showed that some of the Cys160 was in the reduced form in heated beta-LG aggregates, indicating that the Cys160-Cys66 disulfide bond had been broken during heating. This finding suggests that disulfide bond interchange reactions between beta-LG non-native monomers, or polymers, and other proteins could occur largely via Cys160.  相似文献   

Physical and mechanical wood properties of 14 timber species from Northeast Mexico   总被引：1，自引：0，他引：1  

Artemio Carrillo  Miriam Garza  María de Jesús Nañez  Fortunato Garza  Rahim Foroughbakhch  Sadoth Sandoval 《Annals of Forest Science》2011,68(4):675-679

Background  

Thornscrubs are a vegetation type from Northeast Mexico, consisting of 60 to 80 tree and shrub species that are used for a wide range of constructive, decorative and energy purposes. However, basic research of the physical and mechanical wood properties are still needed to establish additional uses and, thereby, increase their value in the timber industry.  相似文献   

The evolution of modern eukaryotic phytoplankton   总被引：1，自引：0，他引：1  

Falkowski PG  Katz ME  Knoll AH  Quigg A  Raven JA  Schofield O  Taylor FJ 《Science (New York, N.Y.)》2004,305(5682):354-360

The community structure and ecological function of contemporary marine ecosystems are critically dependent on eukaryotic phytoplankton. Although numerically inferior to cyanobacteria, these organisms are responsible for the majority of the flux of organic matter to higher trophic levels and the ocean interior. Photosynthetic eukaryotes evolved more than 1.5 billion years ago in the Proterozoic oceans. However, it was not until the Mesozoic Era (251 to 65 million years ago) that the three principal phytoplankton clades that would come to dominate the modern seas rose to ecological prominence. In contrast to their pioneering predecessors, the dinoflagellates, coccolithophores, and diatoms all contain plastids derived from an ancestral red alga by secondary symbiosis. Here we examine the geological, geochemical, and biological processes that contributed to the rise of these three, distantly related, phytoplankton groups.  相似文献   

Comment on "A persistent oxygen anomaly reveals the fate of spilled methane in the deep Gulf of Mexico"     

Joye SB  Leifer I  MacDonald IR  Chanton JP  Meile CD  Teske AP  Kostka JE  Chistoserdova L  Coffin R  Hollander D  Kastner M  Montoya JP  Rehder G  Solomon E  Treude T  Villareal TA 《Science (New York, N.Y.)》2011,332(6033):1033; author reply 1033

Kessler et al. (Reports, 21 January 2011, p. 312) reported that methane released from the 2010 Deepwater Horizon blowout, approximately 40% of the total hydrocarbon discharge, was consumed quantitatively by methanotrophic bacteria in Gulf of Mexico deep waters over a 4-month period. We find the evidence explicitly linking observed oxygen anomalies to methane consumption ambiguous and extension of these observations to hydrate-derived methane climate forcing premature.  相似文献   

Importance of chip selection and elaboration process on the aromatic composition of finished wines     

Rodríguez-Bencomo JJ  Ortega-Heras M  Pérez-Magariño S  González-Huerta C  González-San José ML 《Journal of agricultural and food chemistry》2008,56(13):5102-5111

The evolution of volatile compounds extracted from wood while being macerated for 1 month with four different commercial chips (different geographical origins and toasting degrees) was studied. Furthermore, the effect of the microoxygenation process between alcoholic and malolactic fermentation also was studied. The wood volatile compounds in wines macerated with the four types of chips evolved in the same way. However, the amounts of compounds extracted depended on the type of chip used. There were differences in the levels of vanillin, cis-whiskey lactone, furfural, trans-isoeugenol, and cis-isoeugenol in wines in accordance with the type of wood chips (French or American), and the last two compounds along with 5-methyl furfural presented differences that were directly related to the toast level. However, no effects of microoxygenation treatment on the extraction of volatile compounds extracted from chips were observed. Therefore, the results obtained in this study highlight the importance of chip selection on the aromatic characteristics of finished wines.  相似文献