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1.
α-

New results obtained from a two-dimensional sequence analysis of the small heat shock protein (shsp) family are described. It is confirmed that the conserved C-terminal α-crystallin domain is essentially made of β-strands, most probably two groups of β-strands separated by a large loop. A direct correspondence between the putative β-strands that have been identified in shsps and the seven β-strands of a classical immunoglobulin-like fold is proposed. The hypothesis that the shsp family could belong to the immunoglobulin superfamily (IgSF) is consistent with the ubiquitous distribution and the multifunctional properties of the crystallins that are now emerging.  相似文献   

2.
Synthesis of methyl

-Ribose was converted into methyl and this, on tin-mediated allylation, gave a mixture of the 2-O-allyl and 3-O-allyl derivatives which were separated by chromatography. The more polar isomer was characterised as the 3-O-allyl derivative after conversion via

(which was also synthesised from

) into the known

. Methyl

was converted into methyl

via methyl

.  相似文献   

3.
Determination of

A simple, rapid and sensitive two column-switching high-performance liquid chromatographic (HPLC) method with ultraviolet detection at 210 nm has been developed for the determination of

(AY4166, I) and its seven metabolites in human plasma and urine. Measurements of I and its metabolites were carried out by two column-switching HPLC, because metabolites were classified into two groups according to their retention times. After purification of plasma samples using solid-phase extraction and direct dilution of urinary samples, I and each metabolite were injected into HPLC. The calibration graphs for plasma and urinary samples were linear in the ranges 0.1 to 10 μg ml−1 and 0.5 to 50 μg ml−1, respectively. Recoveries of I and its seven metabolites were over 88% by the standard addition method and the relative standard deviations of I and its metabolites were 1–6%.  相似文献   

4.
5.
Process for the isolation of preparative quantities of

Specific enzymes were used to hydrolyse sugarbeet pulp to facilitate the isolation of

in preparative amounts. The feruloylated arabinose disaccharide was purified by chromatography on Sephadex LH-20 and Bio-Gel P-2 and the structure confirmed by NMR and UV spectroscopy and high-performance liquid chromatography.  相似文献   

6.
7.
Manual and automated determination of

This paper describes the determination of

and its metabolite (E)-5-(2-bromovinyl)uracil in urine. The method involves sample clean-up by liquid-liquid extraction with ethyl acetate followed by high-performance liquid chromatographic (HPLC) analysis. The sample preparation may be performed either manually or automatically using a Zymark Py-robotic system. The chloro analog of the parent compound, CV-araU, is used as the internal standard. As low as 0.1 μg of analyte per ml of urine can be measured. This sensitivity is adequate for pharmacokinetic studies but could be improved quite easily if necessary.  相似文献   

8.
9.
C, N CP MAS and high resolution multinuclear NMR study of methyl

Four new derivatives of methyl

were studied by 1H, 13C, 15N NMR in CDCl3 solutions and by 13C, 15N NMR in the solid state. The replacement of one aryl substituent by another has no influence on the proton and carbon chemical shifts within the sugar moiety, in solution. The differences in 13C chemical shifts Δ = δliquid - δsolid are significant for C-3 (deshielding of -3.4 to -3.8 ppm), C-5 and OMe but not observed for C-2, where the ureido substituent is linked, thus indicating that this fragment of the structure is rigid. The values of Δ in 15N chemical shifts of N-3′ are -2.3 to -2.8 ppm (increase of shielding in the solids); the effect of replacement of substituent at aromatic ring is larger than the contribution of intermolecular H-bond interaction. The values of 15.5–16.1 Hz for 1JC-1′-N and 21.2–21.5 Hz for 1JCO-N indicate that the two C---N-3′ bonds are of significant double bond character.  相似文献   

10.
Preparation and characterization of a new rhenium(V) complex containing the

A new phosphine derivatized peptide tetradentate ligand containing the PN2S donor atom set,

cysteinyl methyl ester, was synthesized in good yields by coupling a phosphine group to protected Gly- -Cys dipeptide. Complexation of the new ligand with rhenium proceeded in satisfactory yields by substitution reaction on ReVOCl3(PPh3)2 in a 1.2:1 molar ratio. The resulting rhenium complex was characterized by IR, FAB-MS, 1H and 31P NMR spectroscopy and was found to be neutral and diamagnetic. These studies revealed, that rhenium (V) in a trans-ReOCl2+ cor coordinates with the PN2S2− donor atom set formed by one neutral phosphine, one neutral thioether and two deprotonated amide groups of the ligand forming a neutral complex. High performance liquid chromatography tests verified the purity and high stability of the complex in solution for long periods of time. In alkaline organic media the complex transforms to an equally stable, more hydrophilic analogue, in which the methyl ester group of cysteine is hydrolyzed to the free carboxylate.  相似文献   

11.
Mass spectrometric quantification of the mu opioid receptor agonist Tyr-

The mu opioid receptor agonist Tyr-

-Arg-Phe-Lys-Amide (

-Arg2-Lys4-Dermorphin1-4amide=DALDA) was infused continuously for 2 h into sheep. The presence of DALDA in ovine plasma was determined by reversed-phase high-performance liquid chromatography (RP-HPLC) and mass spectrometry (MS) in plasma samples that were obtained at different times during and following that infusion. A stable isotope-incorporated internal standard, deuterated DALDA (d5-DALDA), was used for the MS quantification of DALDA via the protonated molecule ion, (M+H)+, of DALDA and of d5-DALDA. Time-course data (μg DALDA ml−1 plasma vs. time) were obtained. Tandem MS (MS–MS) provided the product-ion spectrum of the (M+H)+ ion of DALDA in one of the samples to confirm the amino acid sequence of DALDA.  相似文献   

12.
The effects of α,β-amyrin, a pentacyclic triterpene isolated from Protium heptaphylum was investigated on rat model of orofacial pain induced by formalin or capsaicin. Rats were pretreated with α,β-amyrin (10, 30, and 100 mg/kg, i.p.), morphine (5 mg/kg, s.c.) or vehicle (3% Tween 80), before formalin (20 μl, 1.5%) or capsaicin (20 μl, 1.5 μg) injection into the right vibrissa. In vehicle-treated controls, formalin induced a biphasic nociceptive face-rubbing behavioral response with an early first phase (0–5 min) and a late second phase (10–20 min) appearance, whereas capsaicin produced an immediate face-rubbing (grooming) behavior that was maximal at 10–20 min. Treatment with α,β-amyrin or morphine significantly inhibited the face-rubbing response in both test models. While morphine produced significant antinociception in both phases of formalin test, α,β-amyrin inhibited only the second phase response, more prominently at 30 mg/kg, in a naloxone-sensitive manner. In contrast, α,β-amyrin produced much greater antinociceptive effect at 100 mg/kg in the capsaicin test, which was also naloxone-sensitive. These results provide first time evidence to show that α,β-amyrin attenuates orofacial pain atleast, in part, through a peripheral opioid mechanism but warrants further detailed study for its utility in painful orofacial pathologies.  相似文献   

13.
α-Crystallins possess molecular chaperone properties and are one of the most abundant of the lenticular proteins. Posttranslational modifications of these proteins have been implicated as a possible etiology of human cataracts. This article will review current knowledge concerning the effects of known posttranslational modifications upon the molecular chaperone properties and aggregation behavior of α-A and α-B crystallin. Based upon these effects, experimental approaches will be discussed that may be useful in the development of reagents that may selectively inhibit the cataractogenic process in the aging human lens.  相似文献   

14.
Laminin-5 and α3β1 integrin promote keratinocyte survival; however, the downstream signaling pathways for laminin-5/α3β1 integrin-mediated cell survival had not been fully established. We report the unexpected finding of multiple interactions between 14-3-3 isoforms and proapoptotic proteins in the survival signaling pathway. Ln5-P4 motif within human laminin-5 α3 chain promotes cell survival and anti-apoptosis by inactivating Bad and YAP. This effect is achieved through the formation of 14-3-3ζ/p-Bad and 14-3-3σ/p-YAP complexes, which is initiated by α3β1 integrin and FAK/PI3K/Akt signaling. These complexes result in cytoplasmic sequestration of Bad and YAP and their subsequent inactivation. An increase in Akt1 activity in cells induces 14-3-3ζ and σ, p-Bad, and p-YAP, promoting cell survival, whereas decreasing Akt activity suppresses the same proteins and inhibits cell survival. Suppression of 14-3-3ζ with RNA-interference inhibits cell viability and promotes apoptosis. These results reveal a new mechanism of cell survival whereby the formation of 14-3-3ζ/p-Bad and 14-3-3σ/p-YAP complexes is initiated by laminin-5 stimulation via the α3β1 integrin and FAK/PI3K/Akt signaling pathways, thereby resulting in cell survival and anti-apoptosis.  相似文献   

15.
Reaction of FcCCo3(CO)9 with 2,3-bis(diphenylphosphino)maleic anhydride (bma). X-ray diffraction structure and redox properties of

The reaction between the tricobalt cluster FcCCo3(CO)9 (1) (where Fc = ferrocenyl) and the redox-active diphosphine ligand 2,3-bis(diphenylphosphino)maleic anhydride (bma) affords the new cluster

(3) in refluxing 1,2-dichloroethane or toluene. The cluster FcCCo3(CO)7(bma) (2), a logical precursor to 3, was observed in solution by IR spectroscopy when cluster 1 and bma were refluxed in the low boiling point solvent CH2Cl2; however, putative 2 could not be isolated due to its rapid conversion to the final product 3. Cluster 3 has been fully characterized in solution by IR and NMR (13C and 31P) spectroscopy and in the solid state by X-ray diffraction analysis.

, as the CH2Cl2 solvate, crystallized in the triclinic space group

for 3602 observed reflections with 13σ(I). Cyclic voltammetric investigations of 3 in CH2Cl2 reveal the presence of three reversible redox responses assigned to the 0/1+, 0/1−1, and 1/2 redox couples. The nature of the HOMO and the two lowest unoccupied molecular orbitals (LUMO and SUMO) in 3 has been determined by carrying out extended Hückel calculations on the model compound

, the results of which are discussed relative to the observed electrochemistry of 3 and related cluster compounds.  相似文献   

16.
Sequences of 40 very diverse representatives of the α-crystallin–small heat-shock protein (α-Hsp) superfamily are compared. Their characteristic C-terminal ‘α-crystallin domain' of 80–100 residues contains short consensus sequences that are highly conserved from prokaryotes to eukaryotes. There are, in addition, some positions that clearly distinguish animal from non-animal α-Hsps. The α-crystallin domain is predicted to consist of two hydrophobic β-sheet motifs, separated by a hydrophilic region which is variable in length. Combination of a conserved α-crystallin domain with a variable N-terminal domain and C-terminal extension probably modulates the properties of the various α-Hsps as stress-protective and structural oligomeric proteins. Phylogeny reconstruction indicates that multiple α-Hsps were already present in the last common ancestor of pro- and eukaryotes. It is suggested that during eukaryote evolution, animal and non-animal α-Hsps originated from different ancestral gene copies. Repeated gene duplications gave rise to the multiple α-Hsps present in most organisms.  相似文献   

17.
The peptides, phalloidin and α-amanitin, contain two unusual indole-derived chromophores, whose absorption, fluorescence and phosphorescence in aqueous solutions are described. Fluorescence is very weak, but phosphorescence at 77 K is intense. Phalloidin seems to undergo adiabatic photodissociation in alkaline solutions and to fluorescence from the indole anion form. In contrast, neither the phenolic nor the indolic protons of α-amanitin undergo photodissociation. The pKa value of the phenolic hydroxy group of α-amanitin is 9.71 at 23°C.  相似文献   

18.
α-Crystallin is renown for resisting crystallization and electron microscopic image analysis. The spatial conformation thus remaining elusive, the authors explored the structure and chaperone functioning by analyzing the effects of site-directed mutagenesis, the properties of naturally occurring aberrant forms of α-crystallin and the influence of chemical modifications. The authors observed that the globular multimeric structure, as well as the chaperoning capacity are remarkably tolerant towards changes and modifications in the primary structure. The essential features of the quaternary structure—globular shape, flexibility, highly polar exterior and accessible hydrophobic surface pockets—support a ‘pitted-flexiball’ model, which combines tetrameric subunit building blocks in an open micelle-like arrangement.  相似文献   

19.
α-Crystallin is a multimeric lenticular protein that has recently been shown to be expressed in several non-lenticular tissues as well. It is shown to prevent aggregation of non-native proteins as a molecular chaperone. By using a non-thermal aggregation model, we could show that this process is temperature-dependent. We investigated the chaperone-like activity of α-crystallin towards photo-induced aggregation of γ-crystallin, aggregation of insulin and on the refolding induced aggregation of β- and γ-crystallins. We observed that α-crystallin could prevent photo-aggregation of γ-crystallin and this chaperone-like activity of α-crystallin is enhanced several fold at temperatures above 30°C. This enhancement parallels the exposure of its hydrophobic surfaces as a function of temperature, probed using hydrophobic fluorescent probes such as pyrene and 8-anilinonaphthalene-1-sulfonate. We, therefore, concluded that α-crystallin prevents the aggregation of other proteins by providing appropriately placed hydrophobic surfaces; a structural transition above 30°C involving enhanced or re-organized hydrophobic surfaces of α-crystallin is important for its chaperone-like activity. We also addressed the issue of conformational aspects of target proteins and found that their aggregation prone molten globule states bind to α-crystallin. We trace these developments and discuss some new lines that suggest the role of tertiary structural aspects in the chaperone process.  相似文献   

20.
A trial was performed to examine the effects of levels of barley substitution and supplementation with β-glucanase in a corn–soybean diet on growth performance and intestinal characteristics of broiler chickens. The experiment involved five levels of barley substituted for corn (0, 125, 250, 500, and 1000 g/kg) and two levels of β-glucanase supplement (with 0.5 g/kg and without) in a factorial arrangement with two replicates. Four hundred day-old commercial strain Harber broiler chickens were randomly allocated into twenty groups of ten dietary treatments for a six-week feeding trial, growing (0–3 week) and finishing period (4–6 week). Unless supplemented with β-glucanase, broilers receiving the diet with more than 250 g/kg of the barley substitute gained slower during the growth period. Conversely, supplementing β-glucanase did not improve total weight gain (0–6 weeks) with a diet of 500 g/kg barley substitution. As the level of barley substitution increased, feed intake in the growing period decreased significantly and viscosity of the intestinal contents increased. However, such an increase did not significantly influence feed conversion (P>0.05). Supplementation with β-glucanase on diet up to 250 g/kg of barley substitute not only enhanced body weight gains of growing broilers, but also improved the live-weight of six-week-old broilers (P<0.05).  相似文献   

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