共查询到20条相似文献,搜索用时 15 毫秒
1.
R W Gauldie D Purnell D A Robertson 《Comparative biochemistry and physiology. B, Comparative biochemistry》1977,58(4):389-391
1. Six proteins, haemoglobin (two loci), serum esterase (two loci) and lactate dehydrogenuase (two loci) from two species of jack mackerel, Trachurus declivis and T. novaeselandiae, were compared electrophoretically. All six loci were found to be monomorphic. 2. LDH from red and white skeletal muscle tissue were electrophoretically different, but the red form and the white form were found to be identical in both species. 3. Both species share an electrophoretically identical serum esterase, but each species also has an electrophoretically distinct serum esterase. 4. Both species share an electrophoretically identical haemoglobin, but each species also has an electrophoretically distinct haemoglobin. 5. The otolith iron contents of the two species were compared and found to be identical. 相似文献
2.
Direct observation of ligand colocalization on individual receptor molecules. 总被引:2,自引:0,他引:2
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We have exploited the novel methodology of far-field fluorescence microscopy at the single molecule level to study colocalization of two different ligand molecules on an individual receptor. The use of dual-wavelength single molecule imaging allows discrimination between isolated and colocalized ligands with an accuracy of 40 nm. In the case of very close proximity of the two ligands, below 7 nm, single pair Forster energy-transfer was observed. The latter finding unequivocally demonstrates colocalization of two ligands on an individual receptor. 相似文献
3.
X-ray crystallography shows that translational initiation factor IF3 consists of two compact alpha/beta domains linked by an alpha-helix. 总被引:4,自引:1,他引:3
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The structures of the two domains of translational initiation factor IF3 from Bacillus stearothermophilus have been solved by X-ray crystallography using single wavelength anomalous scattering and multiwavelength anomalous diffraction. Each of the two domains has an alpha/beta topology, with an exposed beta-sheet that is reminiscent of several ribosomal and other RNA binding proteins. An alpha-helix that protrudes out from the body of the N-terminal domain towards the C-terminal domain suggests that IF3 consists of two RNA binding domains connected by an alpha-helix and that it may bridge two regions of the ribosome. This represents the first high resolution structural information on a translational initiation factor. 相似文献
4.
Sequence conservation and region shuffling in an endoglucanase and an exoglucanase from Cellulomonas fimi 总被引:10,自引:0,他引:10
R A Warren C F Beck N R Gilkes D G Kilburn M L Langsford R C Miller G P O'Neill M Scheufens W K Wong 《Proteins》1986,1(4):335-341
Cellulomonas fimi produces an endoglucanase and an exoglucanase which bind strongly to cellulose. Each enzyme contains three distinct regions: a short sequence of about 20 amino acids containing only proline and threonine (the Pro-Thr box); an irregular region, rich in hydroxyamino acids, of low charge density, and which is predicted to have little secondary structure; and an ordered region of higher charge density which contains a potential active site, and which is predicted to have secondary structure. The Pro-Thr box is conserved almost perfectly in the two enzymes. The irregular regions are 50% conserved, and the conserved sequences include four Asn-Xaa-Ser/Thr sites. The ordered regions appear not to be conserved, but the potential active sites both have the sequence Glu-Xaa7-Asn-Xaa6-Thr; they occur at widely separated sites in the two regions. The order of the regions is reversed in the two enzymes: irregular-Pro-Thr box-ordered in the endoglucanase; ordered-Pro-Thr box-irregular in the exoglucanase. The genes for the two enzymes appear to have arisen by shuffling of two conserved sequences and either one or two other sequences. 相似文献
5.
Insulin hypoglycaemia, by acting as a stressor, caused an increase in plasma corticosteroid concentration in sheep. It did not increase jugular haematocrit in splenectomized sheep, but caused an increase, presumably by splenic contraction, in the following sheep: two control, one with one adrenal cortex as its only adrenal tissue, two with denervated spleens, and two splanchnicotomized animals. These preparations showed that insulin hypoglycaemia can cause a splenic contraction in the absence of an increase in plasma adrenaline and after splenic extrinsic denervation. 相似文献
6.
Trans splicing of mRNA precursors in vitro 总被引:32,自引:0,他引:32
Two exon segments from two separate RNA molecules can be joined in a trans splicing process. In trans splicing reactions, an RNA molecule containing an exon, a 5' splice site, and adjacent intron sequences was mixed with an RNA molecule containing an exon, a 3' splice site, and adjacent intron sequences. The efficiency of trans splicing of these two RNAs increased if the two termini of the intervening sequences were paired in a short RNA duplex. However, trans splicing of two RNA molecules with no significant complementarity was also observed. These results strongly suggest that significant secondary structures within intervening sequences could affect the splicing of flanking exons. Similarly, RNAs that are complementary to segments within the intervening sequences could potentially regulate the selection of splice sites. Finally, some organisms might use trans splicing to distribute a single exon to many different mRNAs. 相似文献
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S Ben Jilani S Mzabi-Regaya R Zermani A Chadli 《Archives de l'Institut Pasteur de Tunis》1986,63(4):477-480
The authors present two cases of Cryptococcus neoformans disease in two young persons. Its appears, in the first case, a diffuse ganglionnary and cutaneous lesion with an evolutive meningo-encephalic localization, and in the second case it appears only a meningitic lesion. These two observations are characterized by the apparition of the infection in a immunodepression patient and by an unfavorable evolution in spite of the treatment. 相似文献
9.
In spite of an early history of interaction, progress in thefields of ecology and evolutionary biology during most of thiscentury has been made largely in parallel, with little creativeexchange until the past two decades. In contrast, recent historyin the two fields shows an exciting and productive trend towarda unified effort in understanding the ecological and evolutionaryforces and constraints that together produce the phenomenonof adaptation. Common themes that have drawn the two fieldstogether in the past decade include an intensified appreciationof discontinuities in time and space, an increased awarenessof the interaction of history and mechanism, a greater concernfor tradeoffs and constraints, and a renewed exploration ofthe role of hierarchy in producing pattern. 相似文献
10.
The midbody is an electron-dense structure that forms between two dividing daughter cells, and a midbody remnant is left after completion of cell separation. This structure has been regarded as a piece of cellular debris, but two recent papers suggest an unexpected function for the midbody remnant in promoting an undifferentiated cellular phenotype. 相似文献
11.
A secondary structure has been predicted for the C termini of the fibrinogen β and γ chains from an aligned set of homologous protein sequences using a transparent method that extracts conformational information from patters of variation and conservation, parsing strings, and patterns of amphiphilicity. The structure is modeled to form two domains, the first having a core parallel sheet flanked on one side by at least two helices and on the other by an antiparallel amphiphilic sheet, with an additional helix connecting the two sheets. The second domain is built entirely from β strands. © 1997 Wiley-Liss, Inc. 相似文献
12.
How many EF-Tu molecules participate in aminoacyl-tRNA binding and peptide bond formation in Escherichia coli translation? 总被引:7,自引:0,他引:7
We have observed that two EF-Tu.GTP cycles are required to make one peptide bond during steady-state translation in an accurate and fast poly(U) translation system prepared from Escherichia coli. We have also found that there are two complexes of EF-Tu.GTP bound to one molecule of aminoacyl-tRNA under our experimental conditions. We suggest, on the basis of these data, that aminoacyl-tRNA enters the ribosomal A-site in a pentameric complex together with two EF-Tu and two GTP molecules. When the tRNA is delivered to the ribosome two GTP molecules are hydrolyzed. It is possible that the functional role of such an EF-Tu dimer is related to the function of the two L7/L12 dimers in the large ribosomal subunit. 相似文献
13.
Pickett JM 《Plant physiology》1972,50(3):396-399
The linear (Myers) and nonlinear (Joliot-Kok) models of photosynthesis were used to predict enhancement. With an apparent equilibrium constant of 1000 between the two light reactions, both models predict a minimal enhancement of about 1.0. However, with an equilibrium constant of 5, both models predict a minimal enhancement significantly greater than 1.0. Consequently, with an equilibrium constant of 5, neither model can account for the observed enhancement values of 1.0 near 685 nanometers in Chlorella. Also, with an equilibrium constant of 5, enhancement significantly greater than 1.0 is predicted between two short wavelengths or between two long wavelengths; neither is observed. 相似文献
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We propose a rapid method to determine the primary structure of a protein knowing the sequence of a homologous protein. The method consists in submitting both the reduced and alkylated proteins to an enzymatic or chemical hydrolysis and performing the sequence analysis of the peptide mixtures. The assessment of the unknown sequence and the degree of identity of the two proteins are reached by comparing the two sequence analyses. The sequences of all the possible peptides present in the two mixtures are reconstructed and the differences in the two sequences are determined. If necessary, the differences can be confirmed by performing a mass spectrometric analysis of the two mixtures. We used this procedure on two homologous proteins of known sequence to furnish an application example of the method. 相似文献
16.
Mosyak L Georgiadis K Shane T Svenson K Hebert T McDonagh T Mackie S Olland S Lin L Zhong X Kriz R Reifenberg EL Collins-Racie LA Corcoran C Freeman B Zollner R Marvell T Vera M Sum PE Lavallie ER Stahl M Somers W 《Protein science : a publication of the Protein Society》2008,17(1):16-21
Aggrecanases are now believed to be the principal proteinases responsible for aggrecan degradation in osteoarthritis. Given their potential as a drug target, we solved crystal structures of the two most active human aggrecanase isoforms, ADAMTS4 and ADAMTS5, each in complex with bound inhibitor and one wherein the enzyme is in apo form. These structures show that the unliganded and inhibitor-bound enzymes exhibit two essentially different catalytic-site configurations: an autoinhibited, nonbinding, closed form and an open, binding form. On this basis, we propose that mature aggrecanases exist as an ensemble of at least two isomers, only one of which is proteolytically active. 相似文献
17.
Ohsumi TK Flaherty JE Evans MC Barocas VH 《Biomechanics and modeling in mechanobiology》2008,7(1):53-62
Tissue equivalents (TEs), formed by entrapping cells in a collagen gel, are an important model system for studying cell behavior.
We have previously (Barocas and Tranquillo in J Biomech Eng 117:161–170, 1997a) developed an anisotropic biphasic theory of
TE mechanics, which comprises five coupled partial differential equations describing interaction among cells and collagen
fibers in the TE. The model equations, previously solved in one or two dimensions, were solved in three dimensions using an
adaptive finite-element platform. The model was applied to three systems: a rectangular isometric cell traction assay, an
otherwise- acellular gel containing two islands of cells, and an idealized tissue-engineered cardiac valve leaflet. In the
first two cases, published experimental data were available for comparison, and the model results were consistent with the
experimental observations. Fibers and cells aligned in the fixed direction in the isometric assay, and a region of strong
fiber alignment arose between the two cell islands. For the valve problem, the alignment predicted by the model was generally
similar to that observed experimentally, but an asymmetry in the experiment was not captured by the model. 相似文献
18.
Thermostability of double-stranded deoxyribonucleic acids: effects of covalent additions of a psoralen 总被引:7,自引:0,他引:7
We have carried out a thermodynamic study on the effects of covalent additions of the psoralen derivative HMT, 4'-(hydroxymethyl)-4,5',8-trimethylpsoralen, on the stability of double-stranded deoxyoligonucleotides. This was done with two systems. The first was a double-stranded DNA formed by two non-self-complementary oligonucleotides, 5'-GAAGCTACGAGC-3' and 5'-GCTCGTAGCTTC-3', where we site specifically placed an HMT molecule on the thymidine residue in oligonucleotide 5'-GAAGCTACGAGC-3' as either a furan-side monoadduct or a pyrone-side monoadduct. The second was a double-stranded DNA formed by a self-complementary oligonucleotide, 5'-GGGTACCC-3', where we placed an HMT molecule on the thymidine residue of each strand as a furan-side monoadduct or cross-linked the two strands with an HMT molecule linked to the two thymidines. We found that HMT cross-linking of the two strands stabilizes the double helix formed by 5'-GGGTACCC-3', as one might expect. Less predictable results were that the monoaddition of a psoralen stabilizes the double helix formed by the two non-self-complementary oligonucleotides by as much as 1.3 kcal/mol as a furan-side monoadduct and 0.7 kcal/mol as a pyrone-side monoadduct at 25 degrees C in 50 mM NaCl. In contrast, the monoaddition of a psoralen on each of the two thymidines in the double helix formed by 5'-GGGTACCC-3' destabilizes the helix by 1.8 kcal/mol at 25 degrees C in 1 M NaCl. This destabilization arises from an unfavorable enthalpy change (8.6 kcal/mol) and a favorable entropy change (23 cal/K X mol) due to the two HMT molecules at the centers of each strand.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
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20.
An algorithm for associating the features of two images. 总被引:12,自引:0,他引:12
G L Scott H C Longuet-Higgins 《Proceedings. Biological sciences / The Royal Society》1991,244(1309):21-26
In this paper we describe an algorithm that operates on the distances between features in the two related images and delivers a set of correspondences between them. The algorithm maximizes the inner product of two matrices, one of which is the desired 'pairing matrix' and the other a 'proximity matrix' with elements exp (-rij2/2 sigma 2), where rij is the distance between two features, one in each image, and sigma is an adjustable scale parameter. The output of the algorithm may be compared with the movements that people perceive when viewing two images in quick succession, and it is found that an increase in sigma affects the computed correspondences in much the same way as an increase in interstimulus interval alters the perceived displacements. Provided that sigma is not too small the algorithm will recover the feature mappings that result from image translation, expansion or shear deformation--transformations of common occurrence in image sequences--even when the displacements of individual features depart slightly from the general trend. 相似文献