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排序方式: 共有1273条查询结果,搜索用时 31 毫秒
1.
The amides of Leu5-enkephalin, Met5-enkephalin, and three analogues, D-Ala2,Leu5-enkephalin, (AcO)Tyr1,Met5-enkephalin, and (AcO)Tyr1,D-Ala2,Met5-enkephalin, have been studied by means of 1H NMR spectroscopy in two different solvent systems: Me2SO-d6 and CDCl3. In the latter solvent the peptides were dissolved as complexes with 18-crown-6-ether, a coronand that binds strongly to the NH3+ groups. The crown ether complexation and the apolar solvent were used to simulate the anionic subsite of the receptor and the hydrophobic environment of the receptor cavity, respectively. The very unusual amide proton chemical shifts and their temperature coefficients suggest the presence of folded conformations in CDCl3 for all peptides, consistent with several models of opioid receptors and with the crystal structure of Leu5-enkephalin. The differences among the proposed cyclic conformations of the five peptides may be correlated, in part, with their different biological activity. All peptides in Me2SO-d6 are characterized by complex mixtures of extended fully solvated conformations. 相似文献
2.
3.
A conformational study of the opioid peptide dermorphin by one-dimensional and two-dimensional nuclear magnetic resonance spectroscopy
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Dermorphin, a natural peptide opioid containing a D-Ala2 residue, has been studied in dimethyl sulfoxide (DMSO) solution by means of several one-dimensional and two-dimensional 1H nuclear magnetic resonance (NMR) methods at various fields from 80 to 600 MHz. The combined use of conventional NMR parameters and of nuclear Overhauser effect effects points to an essentially extended structure. This conformation may be, in part, the result of strong interaction of the amide groups with DMSO molecules. 相似文献
4.
T Santantonio E Albore G Angarano G Pastore 《Bollettino della Società italiana di biologia sperimentale》1983,59(7):983-989
Soluble (free) and insoluble (IgG-bound) hepatitis B e antigen (HBeAg) activities in 1,33 M ammonium sulfate solution was evaluated serially in sera from 12 patients with acute type B hepatitis followed up to 60 days. In three cases preclinical sera were available. In patients who showed clinical and biochemical resolution of hepatitis within 60 days, HBeAg free was the prevalent form of circulating HBeAg during the incubation period of disease, then gradually shifting to the IgG-bound form at the onset of jaundice. Finally HBeAg-bound was no longer demonstrable, followed by detection of anti-HBe antibody. On the contrary, in all patients with unresolved hepatitis both HBeAg-free and HBeAg-bound were detected with prevalence of HBeAg-free ratio. These data suggest a striking correlation between synthesis of HBeAg and HBV replication and may indicate that HBeAg-free and IgG-bound ratio reflects the stage and prognosis of acute HBV infection. 相似文献
5.
Lino Piccinini Paola Borella Annalisa Bargellini Cristina Incerti Medici Alessandra Zoboli 《Biological trace element research》1996,51(1):23-30
The purpose of our study was to investigate the relationship between plasma and hair levels of Se, Zn, and Cu, and cancer.
We selected a total of 66 patients affected by either breast (38) or lung (28) cancer. They entered into the study at the
onset of disease, and before any chemical or radiotherapy. Controls were randomly selected among healthy people and were matched
for sex, age, smoking habits, and residence. In the group of breast cancer, a significant decrease in hair Se was found compared
to controls (p<0.01), whereas plasma Se was only slightly decreased. No difference between cases and controls was detected in both hair
and plasma levels of Zn and Cu. Subjects who developed lung cancer were significantly lower in hair Zn (p<0.05) and Cu (p<0.01) than controls, whereas there was no difference with regard to Se. In addition, plasma Cu of these patients was increased
as compared to controls. 相似文献
6.
Summary Two strains of osmophilic yeast which were isolated from honey-comb, produced good yields of erythritol as a main product. These strains were identified as Trichosporonoides sp., 150-5 and 331-1.From the fermentation studies with these strains using glucose and sucrose as substrate, strain 331-1 produced more erythritol as the sole polyhydric product,with trace quantities of glycerol, than strain 150-5. 相似文献
7.
Annalisa Pezzolo Giorgio Gimelli Amnon Cohen Antonella Lavaggetto Cesare Romano Giuseppina Fogu Orsetta Zuffardi 《Human genetics》1993,92(1):23-27
In situ hybridization of a telomeric (TTA-GGG)
n
sequence to metaphases from three cases of ring chromosome, involving respectively chromosomes 4, 16, and 20, showed the presence of the cognate sequences in all three rings. To investigate whether these ring chromosomes originated by telomere-telomere fusion, we determined, by in situ hybridization, whether telomere-associated sequences and/or specific distal sequences were still present in the ring chromosomes. The finding that these sequences were preserved in all the ring chromosomes strongly indicates that they originated by telomere-telomere fusion. All three subjects carrying the ring chromosomes are affected by the so-called ring syndrome, with failure to thrive, minor dysmorphic signs and no major anomalies. The r(4) patient has the ring in mosaic form with a normal cell line and has normal intelligence. The r(16) and the r(20) patients have moderate mental retardation and suffer from seizures. We conclude that the ring syndrome, even in its more severe manifestation, is caused by ring chromosome instability. 相似文献
8.
Anthony John Pastore Alvaro Montoya Manasi Kamat Kari B. Basso James S. Italia Abhishek Chatterjee Maria Drosou Dimitrios A. Pantazis Alexander Angerhofer 《Protein science : a publication of the Protein Society》2023,32(1):e4537
Oxalate decarboxylase from Bacillus subtilis is a binuclear Mn-dependent acid stress response enzyme that converts the mono-anion of oxalic acid into formate and carbon dioxide in a redox neutral unimolecular disproportionation reaction. A π-stacked tryptophan dimer, W96 and W274, at the interface between two monomer subunits facilitates long-range electron transfer between the two Mn ions and plays an important role in the catalytic mechanism. Substitution of W96 with the unnatural amino acid 5-hydroxytryptophan leads to a persistent EPR signal which can be traced back to the neutral radical of 5-hydroxytryptophan with its hydroxyl proton removed. 5-Hydroxytryptophan acts as a hole sink preventing the formation of Mn(III) at the N-terminal active site and strongly suppresses enzymatic activity. The lower boundary of the standard reduction potential for the active site Mn(II)/Mn(III) couple can therefore be estimated as 740 mV against the normal hydrogen electrode at pH 4, the pH of maximum catalytic efficiency. Our results support the catalytic importance of long-range electron transfer in oxalate decarboxylase while at the same time highlighting the utility of unnatural amino acid incorporation and specifically the use of 5-hydroxytryptophan as an energetic sink for hole hopping to probe electron transfer in redox proteins. 相似文献
9.
E. Baldini Osvaldo Facini Fabrizio Nerozzi Federica Rossi Annalisa Rotondi 《Trees - Structure and Function》1997,12(2):73-81
Light partition has been examined and evaluated on five woody species (Olea europaea, Ficus carica, Pittosporum tobira, Hedera helix maculata, Persica vulgaris) in relation to their leaf morpho-histological characteristics, water and chlorophyll contents. Leaf parameters and optical
properties (reflectance, transmittance, absorbance) in PAR, FR and NIR wavebands (400–1100 nm) were preliminarily submitted
to a canonical correlation analysis where lamina thickness and water content showed a leading role in determining all the
optical properties, while chlorophyll, influential in the PAR region, was remarkably effective only in an extreme pigment
situation when green and albino patches of ivy leaves were compared. Transmittance appeared inversely related to lamina thickness
in accordance with the Lambert Beer law. Significant correlations were found also between mesophyll water content and both
transmittance (positive) and reflectance (negative). Olive leaves showed peculiar optical patterns because of the dense and
continuous trichome layer on their abaxial surface.
Received: 3 January 1997 / Accepted: 5 May 1997 相似文献
10.
Annalisa Botta Elizabeth A. Lindsay Vesna Jurecic Antonio Baldini 《Mammalian genome》1997,8(12):890-895
We have constructed a comparative map in mouse of the critical region of human 22q11 deleted in DiGeorge (DGS) and Velocardiofacial
(VCFS) syndromes. The map includes 11 genes potentially haploinsufficient in these deletion syndromes. We have localized all
the conserved genes to mouse Chromosome (Chr) 16, bands B1-B3. The determination of gene order shows the presence of two regions
(distal and proximal), containing two groups of conserved genes. The gene order in the two regions is not completely conserved;
only in the proximal group is the gene order identical to human. In the distal group the gene order is inverted. These two
regions are separated by a DNA segment containing at least one gene which, in the human DGS region, is the most proximal of
the known deleted genes. In addition, the gene order within the distal group of genes is inverted relative to the human gene
order. Furthermore, a clathrin heavy chain-like gene was not found in the mouse genome by DNA hybridization, indicating that
there is an inconsistent level of gene conservation in the region. These and other independent data obtained in our laboratory
clearly show a complex evolutionary history of the DGS-VCFS region. Our data provide a framework for the development of a
mouse model for the 22q11 deletion with chromosome engineering technologies.
Received: 8 July 1997 / Accepted 11 August 1997 相似文献