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Results for “structural variation”

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At least 109 records · Page 6Linked to original sources
PubMed1990

Structural variation in the antithrombin III binding site region and its occurrence in heparin from different sources.

A tetrasaccharide possessing a biosynthetically permissible structural variability in and adjacent to the antithrombin III (ATIII) binding site has been isolated from heparin lyase depolymerized bovine lung heparin by using strong anion-exchange high-pressure liquid chromatography (SAX-HPLC). On the basis of two-dimensional 500-MHz 1H NMR experiments, including phase-sensitive correlated spectroscopy (COSY) and rotating frame nuclear Overhauser enhancement spectroscopy (ROESY), and fast-atom bombardment mass spectrometry (FAB-MS), the primary structure of this tetrasaccharide was unambiguously established as delta UAp2S (1----4)-alpha-D-GlcNp2S6S(1----4)-beta-D-GlcAp(1----4)-alph a-D-GlcNp2S3S6S (where delta UA represents 4-deoxy-alpha-L-threo-hex-4-enopyranosyluronic acid). The 1H NMR ROESY experiment proved to be particularly valuable in offering sequence information. Heparins from a variety of species and tissue sources were examined by oligosaccharide mapping using SAX-HPLC and gradient polyacrylamide gel electrophoresis. Two of these heparins are used as anticoagulants; they are porcine intestinal mucosal heparin and bovine lung heparin. The predominant ATIII-binding site in porcine heparin contained an N-acetylated glucosamine residue. We now report the structure of the predominant ATIII-binding site in bovine heparin as----4)-alpha-D-GlcNp2S6S(1----4)-beta-D-GlcAp(1----4)-alph a-D- GlcNp2S3S6S(1----4)-alpha-L-IdoAp2S(1----4)-alpha-D-GlcNp 2S6S(1----. This study shows the presence of one or both types of ATIII-binding-site variants in all of the heparins that were examined.

Animals↗
PubMedDate not supplied

Species and structural variations affecting pyrethroid neurotoxicity.

Pyrethroids provide fascinating patterns and examples of species selectivity resulting from variations in nerve sensitivity and detoxification rates. Three classification systems are useful in considering pyrethroids: origin, structure, stability and use relative to the natural pyrethrin I; lethal and sublethal or knockdown agents; Types I and II symptoms and nerve action. Pyrethroid-detoxifying esterases and oxidases contribute importantly to the species and strain specificity and provide an opportunity to use inhibitors as synergists for improved effectiveness. Pyrethroids are potent and selective neuropharmacological agents inducing repetitive discharges or conduction block in a variety of sensory and motor nerves and in the CNS. Small structural modifications in the pyrethroid often change the type of action as well as the potency and species specificity. Pyrethroid resistance in selected strains of insect pests may involve a modified and pyrethroid-insensitive target site.

Animals↗
PubMed1986

Structural variations in soluble iron complexes of models for ferritin: an x-ray absorption and Mössbauer spectroscopy comparison of horse spleen ferritin to Blutal (iron-chondroitin sulfate) and Imferon (iron-dextran).

Variations in the turnover of storage iron have been attributed to differences in apoferritin and in the cytoplasm but rarely to differences in the structure of the iron core (except size). To explore the idea that the iron environment in soluble iron complexes could vary, we compared horse spleen ferritin to pharmaceutically important model complexes of hydrous ferric oxide formed from FeCl3 and dextran (Imferon) or chondroitin sulfate (Blutal), using x-ray absorption (EXAFS) and Mössbauer spectroscopy. The results show that the iron in the chondroitin sulfate complex was more ordered than in either horse spleen ferritin or the dextran complex (EXAFS), with two magnetic environments (Mössbauer), one (80%-85%) like Fe2O3 X nH2O (ferritinlike) and one (15%-20%) like Fe2O3 (hematite); since sulfate promotes the formation of inorganic hematite, the sulfate in the chondroitin sulfate most likely nucleated Fe2O3 and hydroxyl/carboxyls, which are ligands common to chondroitin sulfate, ferritin and dextran most likely nucleated Fe2O3 X nH2O. Differences in the structure of the iron complexed with chondroitin sulfate or dextran coincide with altered rates of iron release in vivo and in vitro and provide the first example relating function to local iron structure. Differences might also occur among ferritins in vivo, depending on the apoferritin (variations in anion-binding sites) or the cytoplasm (anion concentration).

Animals↗
PubMed1994

The relationship between DNA structural variation and activities of P elements in P and Q strains of Drosophila melanogaster.

To characterize the relationship between P element activities and their structures, we cloned P elements from genomic libraries of three isogenic P and Q strains derived from natural populations in Japan. These P elements were mapped with BamHI, AvaII and PstI and were classified by their size. The majority of P elements cloned were classified as either complete or relatively small P elements rather than medium size. The numbers of full length (2.9 kb) P elements per haploid genome of NP280 (P), AK194 (weak P) and WY113 (Q) were at least four, five and one, respectively. However, the 2.9 kb P element of WY113 was thought to be defective since this strain has no transposase activity. In our previous work, we demonstrated that the ORF 3-deleted P element is essential for P cytotype determination in WY113. A similar P element also exists in NP280, and this may have an important role for P cytotype determination in this strain. Two and one copies of the KP element, a deletion derivative of the P element, were found in NP280 and AK194, respectively. One of four complete P elements in NP280 was fully sequenced, and the base sequence was completely identical to that of p pi 25.1 originally derived from the U.S.A. This result is consistent with the notion that these P elements have a relatively recent origin in Drosophila melanogaster.

Animals↗
PubMed2001

Electronic and structural variation among copper(II) complexes with substituted phenanthrolines.

A series of copper(II) complexes with substituted phenanthroline ligands has been synthesized and characterized electronically and structurally. The compounds that have been prepared include the monosubstituted ligand complexes of the general formula [Cu(5-R-phen)(2)(CH(3)CN)](BF(4))(2), where R = NO(2), Cl, H, or Me, and the disubstituted ligand complex [Cu(5,6-Me(2)-phen)(2)(CH(3)CN)](BF(4))(2). The complexes [Cu(5-NO(2)-phen)(2)(CH(3)CN](BF(4))(2) (1), [Cu(5-Cl-phen)(2)(CH(3)CN)](BF(4))(2) (2), [Cu(o-phen)(2)(CH(3)CN)](BF(4))(2) (3), and [Cu(5-Me-phen)(2)(CH(3)CN)](BF(4))(2) (4) each crystallize in the space group C2/c with compounds 1, 2, and 4 comprising an isomorphous set. The disubstituted complex [Cu(5,6-Me(2)-phen)(2)(CH(3)CN)](BF(4))(2) (5) crystallizes in the space group P2(1)/c. Each structure is characterized by a distorted trigonal bipyramidal arrangement of ligands around the central copper atom with approximate or exact C(2) symmetry. The progression from electron-withdrawing to electron-donating substituents on the phenanthroline ligands correlates with less accessible reduction potentials for the bis-chelate complexes.

Copper↗
PubMed1998

Structural variations in nisin associated with different membrane mimicking and pH environments.

Nisin is a membrane active antimicrobial peptide containing unusual dehydrated amino acid residues. The secondary structure of nisin in aqueous solution, membrane mimicking solvents and at various pH values was investigated using circular dichroism. In aqueous solution nisin is largely randomly coiled. In liposomes and at pH 6 and above, however, the presence of a maximum at 195 nm and a minimum at 190 nm was notable and indicative of beta-turn formation in these environments. This change in structure was speculated to result in an increasing unavailability of the site for initial reaction of peptide and membrane at higher pH.

Anti-Bacterial Agents↗
PubMed1983

Structural variation in the named bronchi of the left lung. A morphometric study.

In order to establish whether or not the named bronchi of the left lung differ structurally from each other, their proportions of cartilage, gland and muscle in normal and chronic bronchitic patients were measured. In the normal subject the lower lobe bronchus contains proportionally more muscle than either the upper lobe bronchus or the segmental bronchi. Its proportion of cartilage is less than that of the main and upper lobe bronchi, and in this respect it is similar to the segmental bronchi. The proportions of gland in the main, upper and lower lobe bronchi are the same. There is no difference between the tissue proportions of the segmental bronchi of the upper and lower lobes. In chronic bronchitics the proportion of gland is increased, and in many cases there is also an increase in muscle. The relatively high proportion of muscle in the lower lobe bronchus is no longer apparent, and its proportion of cartilage is greater than in the normal subject. The main and upper lobe bronchi contain a higher proportion of gland than the lower lobe bronchus and the segmental bronchi. The proportions of the components in the upper and lower segmental bronchi are again similar. It is concluded that in the left lung the tissue proportions of the named bronchi vary. In particular, the normal lower lobe bronchus is characterized by a relatively high percentage of muscle, and a similar cartilage content to the segmental bronchi. Care is therefore needed in selecting airways for morphometric studies.

Aged↗
PubMed1997

The aconitase family: three structural variations on a common theme.

The aconitase family contains a diverse group of iron-sulphur (Fe-S) isomerases and two types of iron regulatory protein (IRP). Structural comparisons have revealed three architecturally distinct variants in which one of the four structural domains is covalently linked at either the amino- or carboxy-terminal end of a single polypeptide or else this domain exists as an independent subunit.

Aconitate Hydratase↗
PubMed1972

Hemoglobin Beta chain structural variation in mice: evolutionary and functional implications.

The Hbb(d) allele at the hemoglobin beta chain locus of Mus musculus is composed of two linked genes, coding for structurally different beta chains, betadmin and betadmaj. Mus caroli has only one beta chain, which combines structural features of both betadmin and betadmaj and thus may be a Lepore type of beta chain. Sequence data suggest that selection may have been important in the evolution of the mouse beta chains.

Alleles↗
PubMed1995

Structural variation of novel alleles at the Hum vWA and Hum FES/FPS short tandem repeat loci.

This paper reports the sequences of novel alleles identified during population databasing studies on the short tandem repeat loci HumvWA and HumFES/FPS. Two HumFES/FPS alleles follow the simple repeat pattern (ATTT)7 and (ATTT)15. Sequence variation corresponding to an A to C transversion occurred in the 5' flanking region in two individuals possessing the designated allele 7. Two HumvWA alleles exhibited compound repeat regions comprising TCTA and TCTG repeat units. Sequence analysis confirmed the putative designation of 11 for a 127 base pair allele. However, a 131 base pair allele, putatively designated as 12, exhibited a more complex sequence. Two different types of repeat unit structures were identified which also exhibited sequence variation in the 3' flanking region.

Alleles↗
PubMed1983

Antigenic and structural variations in the cholera/coli family of enterotoxins.

Recent observations establish the existence of a family of ADP-ribosylating, adenylate cyclase-activating, heat-labile enterotoxins which are structurally, functionally, and immunologically related to the cholera enterotoxin. Despite their overall similarity, it is clear that there are significant structural and immunological differences within the group. These conclusions are supported by extensive experiments comparing the precipitin activity and neutralizing effects of various specific antisera, before and after purification by immunoaffinity chromatography and solid phase immunoaffinity adsorption of common and cross-reactive antibody species, on the various pure enterotoxins. It will be of great importance to determine the full range of the antigenic and structural drift among this family of enterotoxins. The results will have significance in efforts to develop effective broad spectrum antitoxic immunity and also in the development of rapid and reliable techniques for the identifications of enterotoxic enteropathogens.

Antigens, Bacterial↗
PubMed2001

Structural variations and bonding in gold halides: a quantum chemical study of monomeric and dimeric gold monohalide and gold trihalide molecules, AuX, Au2X2, AuX3, and Au2X6 (X = F, Cl, Br, I).

The molecular structures of all gold mono- and trihalides and of their dimers have been calculated at the B3LYP, MP2, and CCSD(T) levels of theory by using relativistic pseudopotentials for all atoms except fluorine. Our computations support the experimental observation that the relative stability of the monohalides increases from the fluoride toward the iodide, while the stability trend of the trihalides is the opposite. The potential energy surface (PES) of all gold trihalides has been investigated. These molecules are typical Jahn-Teller systems; the trigonal planar D3h-symmetry geometry does not correspond to the minimum energy structure for any of them. At the same time, the amount and character of their Jahn-Teller distortion changes gradually from AuF3 to AuI3. The minimum energy geometry is a T-shaped structure for AuF3 and AuCl3, with a Y-shaped transition-state structure. For AuI3, the Y-shaped structure lies lower than the T-shaped structure on the PES. For AuBr3 and AuI3, neither of them is the global minimum but instead an L-shaped structure, which lies outside the Jahn-Teller PES. This structure can be considered to be a donor-acceptor system, or a closed-shell interaction, with I2 acting as donor and AuI as acceptor. The dimers of gold monohalides have very short gold-gold distances and demonstrate the aurophilic interaction. The dimers of the trihalides are planar molecules with two bridging halogen atoms.

Journal Article↗
PubMedDate not supplied

Phenotypic effects of apolipoprotein structural variation on lipid profiles. III. Contribution of apolipoprotein E phenotype to prediction of total cholesterol, apolipoprotein B, and low density lipoprotein cholesterol in the healthy women study.

The apolipoprotein (apo) E structural locus has been shown to influence concentrations of total cholesterol, apo B, and low density lipoprotein (LDL) cholesterol in population studies. Apo E has six phenotypes resulting from three common alleles at this locus. In the present study, we have typed 473 healthy white women for apo E. At baseline in 1984, all women were premenopausal. To date, 109 of these women have become postmenopausal and are not on hormone therapy. Statistical analyses were done on both pre- and postmenopausal groups to assess the influence of menopausal status in combination with the apo E locus on lipid profile. Nine lipoprotein lipids and apolipoproteins were categorized by three apo E phenotypes: apo E3-2, apo E3-3, and apo E4-3. These were compared in analysis of variance. At baseline, the apo E3-2 phenotype showed the lowest average concentrations of total cholesterol (170 mg/dl), apo B (80 mg/dl), and LDL cholesterol (91 mg/dl), while the apo E4-3 phenotype demonstrated the highest average concentrations of total cholesterol (192 mg/dl), apo B (104 mg/dl), and LDL cholesterol (116 mg/dl) (p less than or equal to 0.0004). Apo E3-3 homozygotes were intermediate on all three quantitative variables. The postmenopausal subset showed the same trends by phenotype, with overall increases in total cholesterol, apo B, LDL cholesterol, and triglycerides, regardless of phenotype. Women who remained premenopausal generally showed smaller increases in these same measures. Our results suggest that, on average, the lower lipoprotein values for the apo E3-2 phenotype are maintained through early menopause despite a worsening of lipid profiles for all women as they age.(ABSTRACT TRUNCATED AT 250 WORDS)

Alleles↗
PubMed1985

The predicted presence of large helical structural variation in yeast HIS4 upstream region is correlated with general amino acid control on the CYC1 gene.

A series of CYC1 constructions in which the upstream promoter portion has been replaced by a variety of HIS4 synthetic fragments has demonstrated that the 5' TGACTC 3' repeat is crucial for conferring amino acid general control. Efficient regulation, however, is obtained only with fragments containing both the repeat and flanking sequences. Analysis of the flanks shows the presence of a 16 nucleotide long sequence composed of alterations of two purines and two pyrimidines between the upstream and downstream repeats. Such a sequence has very large twist angle variations. Homologous sequence are observed in HIS1, HIS3, and in TRP5 upstream regions between copies of the repeat. Sequences which confer special structural characteristics may aid in protein recognition of the promoter region.

Amino Acids↗
PubMed2000

Genetic influence on the structural variations of the abnormal prion protein.

Prion diseases are characterized by the presence of the abnormal prion protein PrP(Sc), which is believed to be generated by the conversion of the alpha-helical structure that predominates in the normal PrP isoform into a beta-sheet structure resistant to proteinase K (PK). In human prion diseases, two major types of PrP(Sc), type 1 and 2, can be distinguished based on the difference in electrophoretic migration of the PK-resistant core fragment. In this study, protein sequencing was used to identify the PK cleavage sites of PrP(Sc) in 36 cases of prion diseases. We demonstrated two primary cleavage sites at residue 82 and residue 97 for type 1 and type 2 PrP(Sc), respectively, and numerous secondary cleavages distributed along the region spanning residues 74-102. Accordingly, we identify three regions in PrP(Sc): one N-terminal (residues 23-73) that is invariably PK-sensitive, one C-terminal (residues 103-231) that is invariably PK-resistant, and a third variable region (residues 74-102) where the site of the PK cleavage, likely reflecting the extent of the beta-sheet structure, varies mostly as a function of the PrP genotype at codon 129.

Brain Chemistry↗
PubMed1996

The relationship between structural variation and dysgenic properties of P elements in long-established P-transformed lines of Drosophila simulans.

Ten lines of Drosophila simulans were investigated with respect to P activity, P susceptibility and the number and structure of their P copies, eight years after transformation with the P element. All 10 were found to have reached a steady state. They exhibited varying levels of P activity (from 0 per cent to 96 per cent GD sterility) and, with the exception of one line, were not P-susceptible. In contrast with P element behaviour in D. melanogaster: (i) no relationship was found between the molecular pattern of P copies in a line and its ability to induce or to repress P expression in D. simulans; (ii) peculiar P element derivatives were observed in this species; (iii) the average number of P copies per genome was only half of that in D. melanogaster. This may result from transposon-host genome interactions, which lead to a low invading power of the P element in D. simulans.

Animals↗
PubMed1992

Alkylphosphocholines: influence of structural variation on biodistribution at antineoplastically active concentrations.

Hexadecylphosphocholine (HPC) and octadecylphosphocholine (OPC) show very potent antitumor activity against autochthonous methylnitrosourea-induced mammary carcinomas in rats. The longer-chain and unsaturated homologue erucylphosphocholine (EPC) forms lamellar structures rather than micelles, but nonetheless exhibits antineoplastic activity. Methylnitrosourea was used in the present study to induce autochthonous mammary carcinomas in virgin Sprague-Dawley rats. At 6 and 11 days following oral therapy, the biodistribution of HPC, OPC and EPC was analyzed in the serum, tumor, liver, kidney, lung, small intestine, brain and spleen of rats by high-performance thin-layer chromatography. In contrast to the almost identical tumor response noted, the distribution of the three homologues differed markedly. The serum levels of 50 nmol/ml obtained for OPC and EPC were much lower than the value of 120 nmol/ml measured for HPC. Nevertheless, the quite different serum levels resulted in similar tumor concentrations of about 200 nmol/g for all three of the compounds. Whereas HPC preferably accumulated in the kidney (1 mumol/g), OPC was found at increased concentrations (400 nmol/g) in the spleen, kidney and lung. In spite of the high daily dose of 120 mumol/kg EPC as compared with 51 mumol/kg HPC or OPC, EPC concentrations (100-200 nmol/g) were low in most tissues. High EPC concentrations were found in the small intestine (628 nmol/g). Values of 170 nmol/g were found for HPC and OPC in the brain, whereas the EPC concentration was 120 nmol/g. Obviously, structural modifications in the alkyl chain strongly influence the distribution pattern of alkylphosphocholines in animals. Since EPC yielded the highest tissue-to-serum concentration ratio in tumor tissue (5.1) and the lowest levels in other organs, we conclude that EPC is the most promising candidate for drug development in cancer therapy.

Animals↗