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191.
Sauropod dinosaurs are one of the most conspicuous groups of Mesozoic terrestrial vertebrates. They show general trends towards an overall increase in size and elongation of the neck, by means of considerable elongation of the length of individual vertebrae and a cervical vertebra count that, in some cases, increases to 19 (ref. 1). The long neck is a particular hallmark of sauropod dinosaurs and is usually regarded as a key feeding adaptation. Here we describe a new dicraeosaurid sauropod, from the latest Jurassic period of Patagonia, that has a particularly short neck. With a neck that is about 40% shorter than in other known dicraeosaurs, this taxon demonstrates a trend opposite to that seen in most sauropods and indicates that the ecology of dicraeosaurids might have differed considerably from that of other sauropods. The new taxon indicates that there was a rapid radiation and dispersal of dicraeosaurids in the Late Jurassic of the Southern Hemisphere, after the separation of Gondwana from the northern continents by the late Middle Jurassic. 相似文献
192.
Rolles D Braune M Cvejanović S Gessner O Hentges R Korica S Langer B Lischke T Prümper G Reinköster A Viefhaus J Zimmermann B McKoy V Becker U 《Nature》2005,437(7059):711-715
Because of inversion symmetry and particle exchange, all constituents of homonuclear diatomic molecules are in a quantum mechanically non-local coherent state; this includes the nuclei and deep-lying core electrons. Hence, the molecular photoemission can be regarded as a natural double-slit experiment: coherent electron emission originates from two identical sites, and should give rise to characteristic interference patterns. However, the quantum coherence is obscured if the two possible symmetry states of the electronic wavefunction ('gerade' and 'ungerade') are degenerate; the sum of the two exactly resembles the distinguishable, incoherent emission from two localized core sites. Here we observe the coherence of core electrons in N(2) through a direct measurement of the interference exhibited in their emission. We also explore the gradual transition to a symmetry-broken system of localized electrons by comparing different isotope-substituted species--a phenomenon analogous to the acquisition of partial 'which-way' information in macroscopic double-slit experiments. 相似文献
193.
Victor O. Oria Paul Lopatta Oliver Schilling 《Cellular and molecular life sciences : CMLS》2018,75(13):2291-2301
A disintegrin and a metalloprotease (ADAM) 9 is a metzincin cell-surface protease involved in several biological processes such as myogenesis, fertilization, cell migration, inflammatory response, proliferation, and cell–cell interactions. ADAM9 has been found over-expressed in several solid tumors entities such as glioma, melanoma, prostate cancer, pancreatic ductal adenocarcinoma, gastric, breast, lung, and liver cancers. Immunohistochemical analyses highlight ADAM9 expression by actual cancer cells and associate its abundant presence with clinicopathological features such as shortened overall survival, poor tumor grade, de-differentiation, therapy resistance, and metastasis formation. In each of these tumors, ADAM9 may contribute to tumor biology via proteolytic or non-proteolytic mechanisms. For example, in liver cancer, ADAM9 has been found to shed MHC class I polypeptide-related sequence A, contributing towards the evasion of tumor immunity. ADAM9 may also contribute to tumor biology in non-proteolytic ways probably through interaction with different integrins. For example, in melanoma, the interaction between ADAM9 and β1 integrins facilitates tumor stroma cross talks, which then promotes invasion and metastasis via the activation of MMP1 and MMP2. In breast cancer, the interaction between β1 integrins on endothelial cells and ADAM9 on tumor cells facilitate tumor cell extravasation and invasion to distant sites. This review summarizes the present knowledge on ADAM9 in solid cancers, and the different mechanisms which it employ to drive tumor progression. 相似文献
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Stefan Tholen Martin L. Biniossek Martina Gansz Theresa D. Ahrens Manuel Schlimpert Jayachandran N. Kizhakkedathu Thomas Reinheckel Oliver Schilling 《Cellular and molecular life sciences : CMLS》2014,71(5):899-916
Endolysosomal cysteine cathepsins functionally cooperate. Cathepsin B (Ctsb) and L (Ctsl) double-knockout mice die 4 weeks after birth accompanied by (autophago-) lysosomal accumulations within neurons. Such accumulations are also observed in mouse embryonic fibroblasts (MEFs) deficient for Ctsb and Ctsl. Previous studies showed a strong impact of Ctsl on the MEF secretome. Here we show that Ctsb alone has only a mild influence on extracellular proteome composition. Protease cleavage sites dependent on Ctsb were identified by terminal amine isotopic labeling of substrates (TAILS), revealing a prominent yet mostly indirect impact on the extracellular proteolytic cleavages. To investigate the cooperation of Ctsb and Ctsl, we performed a quantitative secretome comparison of wild-type MEFs and Ctsb ?/? Ctsl ?/? MEFs. Deletion of both cathepsins led to drastic alterations in secretome composition, highlighting cooperative functionality. While many protein levels were decreased, immunodetection corroborated increased levels of matrix metalloproteinase (MMP)-2. Re-expression of Ctsl rescues MMP-2 abundance. Ctsl and to a much lesser extent Ctsb are able to degrade MMP-2 at acidic and neutral pH. Addition of active MMP-2 to the MEF secretome degrades proteins whose levels were also decreased by Ctsb and Ctsl double deficiency. These results suggest a degradative Ctsl—MMP-2 axis, resulting in increased MMP-2 levels upon cathepsin deficiency with subsequent degradation of secreted proteins such as collagen α-1 (I). 相似文献
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198.
In this paper we adopt a principal components analysis (PCA) to reduce the dimensionality of the term structure and employ autoregressive (AR) models to forecast principal components which, in turn, are used to forecast swap rates. Arguing in favour of structural variation, we propose data‐driven, adaptive model selection strategies based on the PCA/AR model. To evaluate ex ante forecasting performance for particular rates, distinct forecast features, such as mean squared errors, directional accuracy and directional forecast value, are considered. It turns out that, relative to benchmark models, the adaptive approach offers additional forecast accuracy in terms of directional accuracy and directional forecast value. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
199.
Klaus Regenauer-Lieb Andrew Bunger Hui Tong Chua Arcady Dyskin Florian Fusseis Oliver Gaede Rob Jeffrey Ali Karrech Thomas Kohl Jie Liu Vladimir Lyakhovsky Elena Pasternak Robert Podgorney Thomas Poulet Sheik Rahman Christoph Schrank Mike Trefry Manolis Veveakis Bisheng Wu David A. Yuen Florian Wellmann Xi Zhang 《地球科学学刊》2015,(1)
Deep geothermal from the hot crystalline basement has remained an unsolved frontier for the geothermal industry for the past 30 years. This poses the challenge for developing a new un-conventional geom... 相似文献
200.
Structure of cytochrome c nitrite reductase. 总被引:1,自引:0,他引:1
O Einsle A Messerschmidt P Stach G P Bourenkov H D Bartunik R Huber P M Kroneck 《Nature》1999,400(6743):476-480
The enzyme cytochrome c nitrite reductase catalyses the six-electron reduction of nitrite to ammonia as one of the key steps in the biological nitrogen cycle, where it participates in the anaerobic energy metabolism of dissimilatory nitrate ammonification. Here we report on the crystal structure of this enzyme from the microorganism Sulfurospirillum deleyianum, which we solved by multiwavelength anomalous dispersion methods. We propose a reaction scheme for the transformation of nitrite based on structural and spectroscopic information. Cytochrome c nitrite reductase is a functional dimer, with 10 close-packed haem groups of type c and an unusual lysine-coordinated high-spin haem at the active site. By comparing the haem arrangement of this nitrite reductase with that of other multihaem cytochromes, we have been able to identify a family of proteins in which the orientation of haem groups is conserved whereas structure and function are not. 相似文献