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Query: UNIPROT:P50583 (asymmetrical)
 12,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The thermodynamic and kinetic properties of the most abundant glycated hemoglobin in human blood, HbA1c, have been studied in detail. They display significant differences as compared to normal hemoglobin, HbA0, in that (1) the shape of the oxygen binding curve of HbA1c in the Hill plot is markedly asymmetrical, with a lower asymptote extending up to approximately 40% oxygen saturation, and the oxygen affinity of the T state being tenfold higher than in HbA0; (2) oxygen pulse experiments on HbA1c show a slower rate of ligand dissociation (k = 25 s-1) even at low levels of oxygen saturation, where the T state is largely predominant; (3) kinetics of CO combination to deoxy HbA1c followed by means of stopped-flow experiments reveal the presence of a quickly reacting component, whose fraction increases upon dilution of hemoglobin. These results show that in contrast to what has been stated by other authors, HbA1c displays functional properties markedly different from HbA0. Analysis indicates that glycation of human hemoglobin affects the T quaternary structure, bringing about a more "relaxed" T state and leading to preferential binding to one type of chain (which is unaffected by chloride ions).
J Mol Biol 1988 Sep 05
PMID:Alteration of T-state binding properties of naturally glycated hemoglobin, HbA1c. 318 88

Radiolabelled bovine IgG1, IgG2, SIgA and IgM and heavy-chain specific polyclonal and monoclonal antibodies to these isotypes were employed as models to investigate immunochemical aspects of sandwich enzyme immunoassays (ELISAs). The titration plots obtained by measuring enzyme activity paralleled those obtained when the binding of radiolabelled immunoglobulins to solid-phase capture antibodies was quantitated. As predicted from the Mass Law, the percentage of labelled immunoglobulin which was bound remained constant over the range in which the sandwich ELISA titration was linear on a log-log plot. Also as predicted from the Mass Law, increasing the solid-phase concn of polyclonal antibodies by affinity purification increased the linear region of the log-log ELISA plot and the corresponding region over which a constant percentage of immunoglobulin binding was observed. When used as capture antibodies adsorbed on plastic at equal concns, the best monoclonal antibodies were 1/8- less than 1/16 as effective as their polyclonal counterparts in binding iodinated bovine immunoglobulins; these differences can be directly interpreted to result from an 8 and greater than 16-fold higher functional, relative affinity of the polyclonal reagents. Steric hindrance was shown to occur when symmetrical sandwich ELISAs, i.e. capture and detection antibody are both heavy-chain specific, are used to measure monomeric but not IgM immunoglobulins. The use of an asymmetrical configuration, i.e. anti-Fab antibody-enzyme conjugates, avoids this problem. Symmetrical conjugates based on the avidin-biotin system, horseradish peroxidase or alkaline phosphatase, were less effective than their asymmetrical (anti-Fab) counterparts. Evidence that the lower activity of symmetrical conjugates was due to steric hindrance was illustrated using horseradish peroxidase-antibody conjugates of different sizes. Sandwich assays using affinity-purified, polyclonal solid-phase antibodies and an asymmetrical conjugate were judged to be immunochemically and economically optimal. Using an asymmetrical configuration, the non-linear nature of sandwich ELISA titration plots is the predictable result of changing antibody to antigen ratios in an antibody-limiting system, and not the result of steric hindrance of the detection system.
Mol Immunol 1986 Sep
PMID:The immunochemistry of sandwich ELISAs--I. The binding characteristics of immunoglobulins to monoclonal and polyclonal capture antibodies adsorbed on plastic and their detection by symmetrical and asymmetrical antibody-enzyme conjugates. 349 Dec 98

We have developed a selection procedure for mutants obtained by oligonucleotide directed mutagenesis based on asymmetrical A-methylation of GATC-sequences in the duplex DNA. The method involves the construction of gapped duplexes of circular single-stranded phage DNA. An oligonucleotide, complementary to part of the gap except for a single mismatch, is hybridized to the gapped duplex DNA and the remaining single stranded regions are filled-in enzymatically. When the template is undermethylated, the yield of mutants is almost solely dependent on the priming efficiency of the oligonucleotide. The approach was used to introduce an AT----CG transversion in the mut L region of phage lambda. Under optimal conditions, about 50-60% of the transformants were of the mutant genotype. Although situated adjacent to a known nut L mutation, the present mutation was phenotypically silent. The possibility of screening for mutants by means of a coupled, easily detectable marker was also investigated.
Mol Gen Genet 1984
PMID:Oligonucleotide directed mutagenesis: selection of mutants by hemimethylation of GATC-sequences. 609 41

The morphogenesis of bacteriophage lambda proheads is under the control of the four phage genes B, C, Nu3 and E, and the two Escherichia coli genes groEL and groES . It has been shown previously that extracts prepared from cells infected with a lambda C-E- mutant accumulate a gpB polymer, which behaves as a biologically active intermediate in prohead assembly. This gpB activity has been called a preconnector , as it is probably a precursor to the head-tail connector. We now report the partial purification of biologically active preconnectors and the characterization of its structure. In the electron microscope, preconnectors appear as donut -like structures composed of several subunits displaying radial symmetry. Optical filtration of periodic arrays of preconnectors showed that the structure has 12-fold rotational symmetry. Side views of the preconnector reveal that it resembles an asymmetrical dumbell . This information has been used to construct a three-dimensional model of the preconnector . The implications of this structure for prohead shape and function, and for DNA packaging are discussed.
J Mol Biol 1984 Apr 15
PMID:Bacteriophage lambda preconnectors. Purification and structure. 623 91

Electron micrographs show the small (30 S) subunit of Escherichia coli ribosomes lying in a wide range of positions on the specimen support, related by rotation principally around the long axis of the particle. Through correspondence analysis, a multivariate statistical method that distinguishes the major factors accounting for interimage variance, the (aligned) views of the randomly oriented particles were ordered and grouped according to tilt angle. Views so grouped were then averaged and used as input to a three-dimensional reconstruction program. The particle reconstructed from nine averaged projections spanning a 160 degrees rotational range has a resolution of 5 nm in planes perpendicular to the long axis of the particle and approximately 3 nm in the direction of the long axis. It is somewhat asymmetrical and quite compact; its most conspicuous feature is the "platform" that wraps partially around the middle of the subunit.
J Mol Biol 1984 Sep 25
PMID:Three-dimensional reconstruction of the 30 S ribosomal subunit from randomly oriented particles. 638 55

With a view to obtaining a more complete view of the composition and structure of the thick filaments of vertebrate skeletal muscle, we have isolated and characterized two new myofibrillar components, H-protein and X-protein. These were purified by hydroxyapatite column chromatography of an impure C-protein preparation itself made from impure myosin extracted from rabbit back and leg muscles. H-protein is the protein responsible for band H on sodium dodecyl sulphate/polyacrylamide gel electrophoresis of crude myosin. X-protein, although present in such preparations in significant quantities, was not detected previously since it is difficult to resolve from C-protein by sodium dodecyl sulphate/polyacrylamide gel electrophoresis. Physical-chemical parameters have been determined for the new proteins and compared with those of C-protein. The apparent chain weight of H-protein estimated by sodium dodecyl sulphate/polyacrylamide gel electrophoresis is 69,000, whereas that of X-protein (152,000) is only slightly greater than that of C-protein (140,000). The molecular weights of H- and X-proteins determined by sedimentation equilibrium centrifugation show that the molecules contain only a single polypeptide chain. The circular dichroism spectra indicate that the proteins have low alpha-helical contents. Both proteins, particularly H-protein, have a high proline content. Although X-protein is of similar chain weight to C-protein, the two show distinct differences in other properties. The sedimentation coefficient of X-protein is markedly lower than that of C-protein, suggesting X-protein is a more asymmetrical molecule. The amino acid compositions, although broadly similar, also show clear differences. Antibodies to H-protein, X-protein and C-protein have been raised in goats and shown not to cross-react.
J Mol Biol 1983 Nov 05
PMID:H-protein and X-protein. Two new components of the thick filaments of vertebrate skeletal muscle. 641 90

The light-harvesting bacteriochlorophyll-protein complex B850 has been isolated from two species of purple bacteria, Rhodopseudomonas palustris and Chromatium minutissimum. Absorption and fluorescence spectra at 20 degrees and--196 degrees C of this complex were registered. Second derivatives of the absorption spectra, Stepanov's relation and computer curve analyses in terms of asymmetrical Gaussian components show that absorption spectra consist of five and fluorescence spectra--of three components. These components were analysed in terms of exciton interaction among bacteriochlorophyll molecules. Data obtained were used for building-up of the molecular model of the complex.
Mol Biol (Mosk)
PMID:[Molecular organization of bacteriochlorophyll in the light-converging B850 complex of purple bacteria]. 647 67

Double-headed aspirin [bis(3,5-dibromosalicyl)fumarate] selectively cross-links hemoglobin molecules between Lys 82 beta 1 and Lys 82 beta 2 and increases solubility of deoxy-Hb S (Walder et al., J. Mol. Biol., 141:195, 1980 and Kikugawa et al., J. Biol. Chem., 257:7525, 1982). We reacted this reagent with the mixture of Hb A and Hb S and the mixture of Hb S and Hb York (beta 146His replaced by Pro). Cross-linked asymmetrical hybrid hemoglobins (alpha 2 beta - beta S and alpha 2 beta Y - beta S) were produced in high yields in addition to the cross-linked parent hemoglobin molecules. Results on electrophoresis, gel electrofocusing, ion exchange column chromatography, mechanical stability and oxygen binding properties showed that the cross-linked asymmetrical hybrid hemoglobins had properties intermediate between those of the cross-linked parent hemoglobins. Oxygen affinities of the cross-linked asymmetrical hybrids were not affected by the addition of 2,3-diphosphoglycerate (DPG) or inositol hexaphosphate, probably due to the presence of a fumaryl group at the DPG binding site.
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PMID:Formation of cross-linked asymmetrical hybrid hemoglobins by double-headed aspirin. 666 87

The dependence of the slopes of normalized Perrin plots on the excitation wavelength was established. It was shown that the cause of this effect is the anisotropy of the Brownian rotation of proteins, which must be regarded as asymmetrical particles with specific, but not random, orientation of tryptophan with respect to the main axes of the macromolecule. These findings were analysed on the basis of the rotational depolarization theory of such systems, applied for the case when bands of two absorption oscillators overlap as it is for oscillators 1La and 1Lb in the longest wavelength absorption band of tryptophan. It was shown that anisotropy of Brownian molecular rotation is one of the factors that determines the form of the polarization spectrum. The difference of the polarization spectrum of proteins from that of tryptophan, extrapolated to the infinite viscosity, is determined by energy transfer processes in proteins.
Mol Biol (Mosk)
PMID:[Polarization of the intrinsic fluorescence of proteins. I. Factors determining the form of the polarization spectrum]. 679 45

A hydrogen-bonded complex of diphenylhydantoin (DPH) and 9-ethyladenine (EtAd) crystallizes from 2,4-pentanedione with the asymmetrical unit consisting of two DPH molecules, one EtAd molecule, and one solvent molecule. The crystal structure was solved by direct methods and refined to a residual of R = 0.054. Structure determination reveals that one DPH hydrogen-bonds to EtAd in a Watson-Crick scheme while the second DPH N(3)--H bonds to EtAd N(3) to form a 2:1 DPH-EtAd complex. Comparisons are made with barbiturate-adenine complexes and with an earlier postulation of a 1:1 DPH-EtAd complex derived from NMR and IR data. The 2,4-pentanedione molecule adopts the keto-enol configuration with an asymmetrical intramolecular hydrogen bond.
Mol Pharmacol 1983 Mar
PMID:Hydrogen bonding interaction of diphenylhydantoin and 9-ethyladenine. 683 97


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