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排序方式: 共有279条查询结果,搜索用时 359 毫秒
1.
Reactive line-shape narrowing in low-temperature inhomogeneous geminate recombination of CO to myoglobin 总被引:4,自引:0,他引:4
N Agmon 《Biochemistry》1988,27(9):3507-3511
The temporal shift in the near-IR absorption peak of myoglobin (Mb) following flash photolysis of MbCO at cryogenic temperatures appears to be due largely to an inhomogeneous reactive process rather than to relaxation. This conclusion, which follows from a new analysis of the experimental data, is based on the following three points: First, at very low temperatures (60 K) a transient line-narrowing effect can be detected. Second, there is a universal, temperature-independent, correlation between spectral shift and survival probability in the rebinding kinetics, and third, the same quantitative model which accounts for rebinding accounts semiquantitatively for the temporal shift in the peak. A fit to the model indicates that the inhomogeneous broadening of the near-IR peak in myoglobin is 15-20% of the total width. The same rebinding process which governs the loss of intensity of this peak is therefore most likely responsible for the shift in its center wavelength. 相似文献
2.
Vered Barenholz-Paniry Jacob S. Ishay Zvi Grossman 《Bulletin of mathematical biology》1988,50(6):661-679
Rhythmic “circa-second” contrations of larvae of the hornetVespa orientalis, believed to serve as hunger signals, were studied. A considerable degree of coordination among individual larvae, both in
frequency and phase of these contractions, has been observed. The oscillations of singly isolated larvae are of short duration,
non-constant, with increasing intervals in between and there is a substantial variability in the patterns shown by different
larvae. In contrast, the association of two or more larvae leads to enhancement of their periodic behaviour and to (partial)
entrainment. Communication among larvae may perhaps be mediated by the sound pulses (“scratching” noises) which are generated
by these contractions. We have subjected individual and grouped larvae to external sound pulses and were able to demonstrate:
(a) enhancement of rhythmic activity; (b) phase resetting; (c) entrainment to an external oscillator within a range of frequencies;
(d) the existence of a subharmonic mode of entrainment. We propose a simple phenomenologic model to account for these larvae
responses. Our model assumes the existence of an “energy” variable which declines with time but is upgraded, in a phase-dependent
way, by external stimuli.
Based in part on work performed by V. Barenholz-Paniry in partial fulfillment of the requirements for the M.Sc. degree from
the Sackler Faculty of Medicine, Tel Aviv University, 1986. 相似文献
3.
Partial amino acid sequence of porcine elastase II. Active site and the activation peptide regions 总被引:1,自引:0,他引:1
M Vered A Gertler Y Burstein 《International journal of peptide and protein research》1986,27(2):183-190
The partial amino acid sequence of porcine elastase II, isolated from crude trypsin Type II, was determined. The enzyme consists of two polypeptide chains, a light chain composed of 11 residues, and a heavy chain (Mr = 23 500) with four intrachain disulfide bridges; the two chains are held together by one interchain disulfide bond. Elastase II was fragmented into several peptides by chemical cleavages with CNBr at the two methionine residues, 99 and 180 (chymotrypsinogen numbering), and with hydroxylamine at the peptide bond following DIP-Ser195. About 50% of the sequence was determined and the positions of 120 amino acids were located, including the light chain residues and most of the active site residues. The partial sequence shows 64% difference between porcine elastase II and elastase I and only 26% difference between porcine elastase II and bovine chymotrypsin B. 相似文献
4.
Vered Yesodi Shamay Izhar David Gidoni Yona Tabib Nurit Firon 《Molecular genetics and genomics : MGG》1995,248(5):540-546
In petunia, a mitochondrial (mt) locus,S-Pcf, has been found to be strongly associated with cytoplasmic male sterility (CMS). TheS-Pcf locus consists of three open reading frames (ORF) that are co-transcribed. The first ORF,Pcf, contains parts of theatp9 andcoxII genes and an unidentified reading frame,urf-s. The second and third ORFs contain NADH dehydrogenase subunit 3 (nad3) and ribosomal protein S12 (rps12) sequences, respectively. Thenad3 andrps12 sequences included in theS-Pcf locus are identical to the corresponding sequences on the mt genome of fertile petunia. In both CMS and fertile petunia, only a single copy ofnad3 andrps12 has been detected on the physical map of the main mt genome. The origin of theurf-s sequence and the molecular events leading to the formation of the chimericS-Pcf locus are not known. This paper presents evidence indicating that two different mt sequences, related tourf-s and found in fertile petunia lines (orf-h and Rf-1), might have been involved in the molecular evolution of theS-Pcf locus. Southern analysis of mtDNA derived from both fertile and sterile petunia plants suggests that one of theseurf-s related sequences (showing 100% homology tourf-s and termedorf-h) is located on a sublimon. An additional, low-homologyurf-s related sequence (Rf-1) is shown to be located on the main mt genome 5′ to thenad3 gene. It is, thus, suggested that the sequence of events leading to the generation of theS-Pcf locus might have involved introduction of theorf-h sequence, via homologous recombination, into the main mt genome 5′ tonad3 at the region where the Rf-1 sequence is located. 相似文献
5.
Ilana Agmon Tamar Auerbach David Baram Heike Bartels Anat Bashan Rita Berisio Paola Fucini Harly A S Hansen Joerg Harms Maggie Kessler Moshe Peretz Frank Schluenzen Ada Yonath Raz Zarivach 《European journal of biochemistry》2003,270(12):2543-2556
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
6.
Vered Yesodi Shamay Izhar David Gidoni Yona Tabib Nurit Firon 《Molecular & general genetics : MGG》1995,248(5):540-546
In petunia, a mitochondrial (mt) locus,S-Pcf, has been found to be strongly associated with cytoplasmic male sterility (CMS). TheS-Pcf locus consists of three open reading frames (ORF) that are co-transcribed. The first ORF,Pcf, contains parts of theatp9 andcoxII genes and an unidentified reading frame,urf-s. The second and third ORFs contain NADH dehydrogenase subunit 3 (nad3) and ribosomal protein S12 (rps12) sequences, respectively. Thenad3 andrps12 sequences included in theS-Pcf locus are identical to the corresponding sequences on the mt genome of fertile petunia. In both CMS and fertile petunia,
only a single copy ofnad3 andrps12 has been detected on the physical map of the main mt genome. The origin of theurf-s sequence and the molecular events leading to the formation of the chimericS-Pcf locus are not known. This paper presents evidence indicating that two different mt sequences, related tourf-s and found in fertile petunia lines (orf-h and Rf-1), might have been involved in the molecular evolution of theS-Pcf locus. Southern analysis of mtDNA derived from both fertile and sterile petunia plants suggests that one of theseurf-s related sequences (showing 100% homology tourf-s and termedorf-h) is located on a sublimon. An additional, low-homologyurf-s related sequence (Rf-1) is shown to be located on the main mt genome 5′ to thenad3 gene. It is, thus, suggested that the sequence of events leading to the generation of theS-Pcf locus might have involved introduction of theorf-h sequence, via homologous recombination, into the main mt genome 5′ tonad3 at the region where the Rf-1 sequence is located.
Contribution [No. 1581-E (1995 series)] from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel
50 250 相似文献
7.
Michael Chorev Marion Gurrath Vered Behar Stefano Mammi Antonella Tonello Evaristo Peggion 《Biopolymers》1995,36(4):473-484
Bombolitins are five structurally related heptadecapeptides acting at the membrane level able to lyse erythrocytes and liposomes and to enhance the activity of phospholipase A 2(PLA2). In the presence of SDS or phospholipid vesicles bombolitins are able to form amphiphilic α-helical structures and this property seems to be the major determinant of bioactivity. In order to test the model of interaction between bombolitin I and membranes, an analogue was synthesized in which all the lysines were replaced by arginines: ([Arg2,9,12, Ile10] bornbolitin I). The design ofthis sequence allowed the synthesis of a second analogue through a specijic postsynthetic dansylation at the ?-amino group qf a lysine residue replacing the original leucine residue at position 7. The, first analogue was, fiilly characterized by CD and two-dimensional nmr in the presence of SDS or phospholipid vesicles. The peptide, folds into an amphiphilic α-helical confbrrnation with the helical segment spanning the central part of the sequencefrom Ile3 to His16. This behavior is identical to that observed for the native sequence. The replacement of Iysine residues by arginine hus no detectable effect on the conformational prderence of the peptide chain. By CD and fluorescence spectroscopy measurements, the fluorophore-containing analogue [Arg2,9,12, Lys7(?-dansyl)] bombolitin I also folded into the α-helical conformation in the presence of SDS micelles or phospholipid vesicles. In particular, the dansyl fluorophore, which is located approximately in the middle of the apolar surface ojthe amphiphilic helix, is clearly buried in a hydrophobic environment when the peptide is bound to phospholipid vesicles. These findings support the hypothesis that the peptide helices are oriented parallel to the vesicle surface. © 1995 John Wiley & Sons, Inc. 相似文献
8.
The sodium/proton antiporter is part of the pH homeostasis mechanism in Escherichia coli 总被引:30,自引:0,他引:30
D Zilberstein V Agmon S Schuldiner E Padan 《The Journal of biological chemistry》1982,257(7):3687-3691
9.
Jotham Suez Steffen Porwollik Amir Dagan Alex Marzel Yosef Ilan Schorr Prerak T. Desai Vered Agmon Michael McClelland Galia Rahav Ohad Gal-Mor 《PloS one》2013,8(3)
Human infection with non-typhoidal Salmonella serovars (NTS) infrequently causes invasive systemic disease and bacteremia. To understand better the nature of invasive NTS (iNTS), we studied the gene content and the pathogenicity of bacteremic strains from twelve serovars (Typhimurium, Enteritidis, Choleraesuis, Dublin, Virchow, Newport, Bredeney, Heidelberg, Montevideo, Schwarzengrund, 9,12:l,v:- and Hadar). Comparative genomic hybridization using a Salmonella enterica microarray revealed a core of 3233 genes present in all of the iNTS strains, which include the Salmonella pathogenicity islands 1–5, 9, 13, 14; five fimbrial operons (bcf, csg, stb, sth, sti); three colonization factors (misL, bapA, sinH); and the invasion gene, pagN. In the iNTS variable genome, we identified 16 novel genomic islets; various NTS virulence factors; and six typhoid-associated virulence genes (tcfA, cdtB, hlyE, taiA, STY1413, STY1360), displaying a wider distribution among NTS than was previously known. Characterization of the bacteremic strains in C3H/HeN mice showed clear differences in disease manifestation. Previously unreported characterization of serovars Schwarzengrund, 9,12:l,v:-, Bredeney and Virchow in the mouse model showed low ability to elicit systemic disease, but a profound and elongated shedding of serovars Schwarzengrund and 9,12:l,v:- (as well as Enteritidis and Heidelberg) due to chronic infection of the mouse. Phenotypic comparison in macrophages and epithelial cell lines demonstrated a remarkable intra-serovar variation, but also showed that S. Typhimurium bacteremic strains tend to present lower intracellular growth than gastroenteritis isolates. Collectively, our data demonstrated a common core of virulence genes, which might be required for invasive salmonellosis, but also an impressive degree of genetic and phenotypic heterogeneity, highlighting that bacteremia is a complex phenotype, which cannot be attributed merely to an enhanced invasion or intracellular growth of a particular strain. 相似文献
10.
Leeat Keren Ora Zackay Maya Lotan‐Pompan Uri Barenholz Erez Dekel Vered Sasson Guy Aidelberg Anat Bren Danny Zeevi Adina Weinberger Uri Alon Ron Milo Eran Segal 《Molecular systems biology》2013,9(1)
Most genes change expression levels across conditions, but it is unclear which of these changes represents specific regulation and what determines their quantitative degree. Here, we accurately measured activities of ~900 S. cerevisiae and ~1800 E. coli promoters using fluorescent reporters. We show that in both organisms 60–90% of promoters change their expression between conditions by a constant global scaling factor that depends only on the conditions and not on the promoter's identity. Quantifying such global effects allows precise characterization of specific regulation—promoters deviating from the global scale line. These are organized into few functionally related groups that also adhere to scale lines and preserve their relative activities across conditions. Thus, only several scaling factors suffice to accurately describe genome‐wide expression profiles across conditions. We present a parameter‐free passive resource allocation model that quantitatively accounts for the global scaling factors. It suggests that many changes in expression across conditions result from global effects and not specific regulation, and provides means for quantitative interpretation of expression profiles. 相似文献