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61.
EMBL-Search: a CD-ROM based database query system   总被引:1,自引:0,他引:1  
This paper describes a system of generally applicable indexfiles provided on the EMBL sequence databases CD–ROM tofacilitate the development offronz–end software to thesequence databases available on this CD–ROM. The indexfiles are used by a new versatile and user–friendly databaseretrieval program for the Apple Macintosh, EMBL–Search,which allows the easy construction of complex database queries.EMBL–Search utilizes cross–reference informationcontained in the databases to support navigation between differentinformation resources. The ability to run EMBL–Searchon a local computer network accessing a shared database CD–ROMmakes its use particularly cost effective.  相似文献   
62.
Crystal structures of four mutants of bovine pancreatic trypsin inhibitor (F22A, Y23A, N43G, and F45A), engineered to alter their stability properties, have been determined. The mutated residues, which are highly conserved among Kunitz-type inhibitors, are located in the rigid core of the molecule. Replacement of the partially buried bulky residues of the wild-type protein with smaller residues resulted in crevices open to the exterior of the molecule. The overall three-dimensional structure of these mutants is very similar to that of the wild-type protein and only small rearrangements are observed among the atoms lining the crevices.  相似文献   
63.
The garnet-type phase Li7La3Zr2O12 (LLZO) attracts significant attention as an oxide solid electrolyte to enable safe and robust solid-state batteries (SSBs) with potentially high energy density. However, while significant progress has been made in demonstrating compatibility with Li metal, integrating LLZO into composite cathodes remains a challenge. The current perspective focuses on the critical issues that need to be addressed to achieve the ultimate goal of an all-solid-state LLZO-based battery that delivers safety, durability, and pack-level performance characteristics that are unobtainable with state-of-the-art Li-ion batteries. This perspective complements existing reviews of solid/solid interfaces with more emphasis on understanding numerous homo- and heteroionic interfaces in a pure oxide-based SSB and the various phenomena that accompany the evolution of the chemical, electrochemical, structural, morphological, and mechanical properties of those interfaces during processing and operation. Finally, the insights gained from a comprehensive literature survey of LLZO–cathode interfaces are used to guide efforts for the development of LLZO-based SSBs.  相似文献   
64.
High-resolution crystal structures of large ribosomal subunits from Deinococcus radiodurans complexed with tRNA-mimics indicate that precise substrate positioning, mandatory for efficient protein biosynthesis with no further conformational rearrangements, is governed by remote interactions of the tRNA helical features. Based on the peptidyl transferase center (PTC) architecture, on the placement of tRNA mimics, and on the existence of a two-fold related region consisting of about 180 nucleotides of the 23S RNA, we proposed a unified mechanism integrating peptide bond formation, A-to-P site translocation, and the entrance of the nascent protein into its exit tunnel. This mechanism implies sovereign, albeit correlated, motions of the tRNA termini and includes a spiral rotation of the A-site tRNA-3' end around a local two-fold rotation axis, identified within the PTC. PTC features, ensuring the precise orientation required for the A-site nucleophilic attack on the P-site carbonyl-carbon, guide these motions. Solvent mediated hydrogen transfer appears to facilitate peptide bond formation in conjunction with the spiral rotation. The detection of similar two-fold symmetry-related regions in all known structures of the large ribosomal subunit, indicate the universality of this mechanism, and emphasizes the significance of the ribosomal template for the precise alignment of the substrates as well as for accurate and efficient translocation. The symmetry-related region may also be involved in regulatory tasks, such as signal transmission between the ribosomal features facilitating the entrance and the release of the tRNA molecules. The protein exit tunnel is an additional feature that has a role in cellular regulation. We showed by crystallographic methods that this tunnel is capable of undergoing conformational oscillations and correlated the tunnel mobility with sequence discrimination, gating and intracellular regulation.  相似文献   
65.
66.
This paper describes the effort of the Marine Aquaculture Section of the Primary Production Department in Singapore and the Institut Francais de Recherche pour l'Exploitation de la Mer in developing adequate facilities for fish nutritional requirement studies in Singapore, and in introducing appropriate nutritional methodology so that results are reliable and accurate. One of the first achievements was the demonstration of homogeneous fish (tropical seabass, Lates calcarifer Bloch) growth response in a newly established tank system before any nutritional experiments were initiated. The application of statistical procedures that take into consideration the power of a test and number of replications required has allowed for more accurate interpretation of results. This can be seen in the results of the first nutritional requirement experiment on the optimal dietary protein level of the seabass at constant energy.  相似文献   
67.
In Escherichia coli, (GpC)n sequences cloned into plasmid DNA molecules are deletion-prone with the occurrence of both short (<2 bp) and long (>2 bp) deletion events. These repetitive tracts can be stabilized by interrupting the strict monotony of the repetition with a variant dinucleotide sequence. The stabilization of short deletion events that is mediated by the variant sequence is completely lost in E. coli mismatch repair-deficient strains. In contrast, this repair pathway has no influence on the frequency of occurrence of long deletion events, even in sequences containing the variant repeat. These results lead us to propose two distinct models to account for short and long deletions within repetitive sequences in E. coli. Furthermore, this study reveals that the deletions occur preferentially at the end of the repeat sequence that is distal with respect to the origin of replication.  相似文献   
68.
The UL20 gene product of pseudorabies virus functions in virus egress.   总被引:11,自引:10,他引:1       下载免费PDF全文
The UL20 open reading frame is positionally conserved in different alphaherpesvirus genomes and is predicted to encode an integral membrane protein. A previously described UL20- mutant of herpes simplex virus type 1 (HSV-1) exhibited a defect in egress correlating with retention of virions in the perinuclear space (J. D. Baines, P. L. Ward, G. Campadelli-Fiume, and B. Roizman, J. Virol. 65:6414-6424, 1991). To analyze UL20 function in a related but different herpesvirus, we constructed a UL20- pseudorabies virus (PrV) mutant by insertional mutagenesis. Similar to HSV-1, UL20- PrV was found to be severely impaired in both cell-to-cell spread and release from cultured cells. The severity of this defect appeared to be cell type dependent, being more prominent in Vero than in human 143TK- cells. Surprisingly, electron microscopy revealed the retention of enveloped virus particles in cytoplasmic vesicles of Vero cells infected with UL20- PrV. This contrasts with the situation in the UL20- HSV-1 mutant, which accumulated virions in the perinuclear cisterna of Vero cells. Therefore, the UL20 gene products of PrV and HSV-1 appear to be involved in distinct steps of viral egress, acting in different intracellular compartments. This might be caused either by different functions of the UL20 proteins themselves or by generally different egress pathways of PrV and HSV-1 mediated by other viral gene products.  相似文献   
69.
The effects of acute and subchronic stress upon discrete cholecystokinin (CCK) and Substance P (SP) neuronal systems have been studied. Adult male rats were exposed to foot-shock stress for periods of 2, 4, 10, 30 or 60 min, immediately following which they were decapitated; brains were rapidly removed and frozen, and subsequently microdissected and extracted. CCK and SP were determined by RIA. In the olfactory tubercule, stress had no effect upon CCK content, but induced a rapid depletion of SP. In the prefrontal cortex, increased CCK concentrations were found following 30 min of stress exposure. In the medial septum, foot-shock led to a rapid increase in CCK content, and to a similar but delayed change in SP levels. A rapid rise in CCK concentrations was also seen in the lateral septum, but no stress effect whatsoever upon SP occurred in this structure. In the dentate gyrus, CCK exhibited a biphasic responsiveness to stress, while SP levels were increased only at the later time intervals. These data demonstrate that discrete CCK and SP neuronal systems are responsive to stress, and thereby support a functional role for these peptides in the processing of neural and hormonal signals by the CNS.  相似文献   
70.
Summary Activities of the lactate dehydrogenase within the periportal zone and within the perivenous zone in the first layer of hepatocytes adjacent to terminal hepatic venules and the remainder of the perivenous parenchyma of the liver acinus were measured using a Lowry technique during a full 24-h cycle (08.00-08.00) in untreated adult male Wistar rats kept under 12 h of light and 12 h of darkness, scotophase 18.25-06.25. In all three regions studied a broad first maximum was recorded between 10.00 and 22.00 with the peak value at 16.00 and a high and narrow peak at 24.00. Zonal and intrazonal heterogeneity of the lactate dehydrogenase were retained during the full day and night cycle. The regions displayed individual dynamic changes in enzyme activity.Supported by the Deutsche Forschungsgemeinschaft (Hi 318/21)  相似文献   
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