共查询到20条相似文献,搜索用时 62 毫秒
1.
P Robertson K A Koehler R G Hiskey 《Biochemical and biophysical research communications》1979,86(2):265-270
The binding of magnesium ions to two tripeptides, -Arg--Gla--Gla-OMe and Z--Arg(NO2)--Gla--Gla-OMe, and to bovine prothrombin fragment 1 as a function of pH has been monitored by 25Mg NMR spectroscopy. Binding to the tripeptide was dependent on peptide ionizations occurring at pH 4.6 – 4.8. The pH dependence of magnesium ion binding to fragment 1 reveals two inflection points 4.2 may be attributed to the deprotonation of the third side chain carboxylic acid group of the double γ-carboxyglutamic acid sequence. The origin of the increased binding of magnesium ions to fragment 1 at pH values above 7 is unknown. 相似文献
2.
A De Flora A Morelli F Giuliano 《Biochemical and biophysical research communications》1974,59(1):406-413
A series of peptide analogs of luteinizing hormone releasing hormone (LH-RH), altered at position 6 and 10, was synthesized and evaluated for the ability to induce ovulation in the diestrous rat and for ability to release pituitary luteinizing hormone and follicle stimulating hormone. All the analogs with D-amino acid substitutions at position 6, even those with large bulky side chain, exhibited an amazingly high potency compared with the parent hormone, LH-RH. On the basis of the biological activities, structure-activity relationships in the central part of this molecule were discussed in detail. 相似文献
3.
Akira Yanai Keijiro Kato Teruhiko Beppu Kei Arima 《Biochemical and biophysical research communications》1976,68(4):1146-1152
The mode of action of bacteriophage-induced lytic enzyme “LE95” was investigated. The LE95 hydrolyzed peptide portion in peptidoglycan of and . The exposed amino terminal amino acid was identified as glutamic acid by analysis of terminal amino acid by dinitrophenylation. This result suggested the LE95 hydrolyzed the peptide bond between L-alanine and D-glutamic acid in the peptidoglycan of and . The enzyme did not hydrolyze various peptides prepared from bacterial cell wall. This experimental result suggested that the glycan chain of peptidoglycan would be essential for the enzymic activity. 相似文献
4.
The conformations of cyclo-(L-Thr-L-His) have been calculated by semi-empirical method without taking account on the solvent. The Thr side chain is folded above the DKP ring with ; this conformation seems to be due to a specific interaction of the hydroxylated side chain with the DKP ring. The His side chain can be folded in order to interact with the Thr side chain. In the open forms, the His side chain interacts with the peptide backbone. The most stable conformations are the folded forms in which the unprotonated imidazole ring is in the Nε-Hε tautomeric form. 相似文献
5.
A series of 12α-hydroxy steroids with varying side chains was prepared, and their 24-hour acetylation yields were compared, l2α-Hydroxy-5β-pregnan-20-one () was prepared from 3α, 12α-diacetoxy-5β~pregnan-20-one () and also by side chain degradation of 12α-acetoxy-5β-cholanoic acid (). 21-Benzyl-5β-pregnan-12α-ol () was synthesized by hydrogenation of the 21-benzylidine derivative of ketone . 23-Pheny1-5β-norcholan-12α-ol () was obtained by the Grignard reaction of 2-phenyl-ethylmagnesium bromide and ketone , dehydration, hydrogenation and hydride reduction; a similar sequence produced 20-methyl-5β-pregnan-12α-ol (). The acetylation results (Table 11) imply that branching at C-20 may be more significant for 12α-hydroxyl reactivity than side chain length or type. An additional compound with an unbranched side chain, 21-nor-5β-cholan-12α-ol (), was synthesized by a Grignard reaction on the 21-bromo intermediate . Acetylation rates determined by glc indicate (Table 111) That compounds with unbranched side chains have 12α-hydroxyl groups about ten times as reactive as their analogs with 20-methyl groups. 相似文献
6.
Patrick Argos 《Biochemical and biophysical research communications》1976,70(3):805-811
Five secondary structure prediction methods based on amino acid sequence have been used to predict the secondary structure of mouse nerve growth factor (NGF). The regions predicted helical correlate well with the proposal, based on the alignment of primary sequences, that the NGF peptide chain is structurally and evolutionarily related to proinsulin. 相似文献
7.
Michael L. English Charles H. Stammer 《Biochemical and biophysical research communications》1978,83(4):1464-1467
A pentapeptide, Z-Gly-Gly-Phe-Phe-Ala · OH and the corresponding unsaturated pentapeptide, Z-Gly-Gly-Phe-ΔZPhe-Ala · OH , have been synthesized. The saturated compound was rapidly hydrolyzed by both chymotrypsin and thermolysin to the expected products, but the dehydropeptide was completely unhydrolyzed by either enzyme even after thirty hours. A new method of peptide stabilization to enzymolysis is made available. 相似文献
8.
An approach to the differentiation of leucine and isoleucine residues in EI mass spectra of peptides
Residues of leucine and isoleucine cannot generally be distinguished in the electron impact (EI) generated mass spectra of N-acylated peptide esters. We have obtained the mass spectra of model peptide esters containing leucine or isoleucine in various positions and trifluoroacetyl perdeutero leucine as the N-terminal blocking group. The mass spectra of the peptide derivatives show a pair of peaks as a result of the elimination from the M+ ion of neutral fragment of perdeuterated isobutene (M+-64) from the leucine side chain of the N-terminal blocking group and isobutene or butene (M+-56) from leucine or isoleucine residues of the peptide. The ratios of the intensities of the peaks show considerable variation with the position of leucine or isoleucine in the peptide chain and the length of the peptide, but for peptides which are identical except for the fact that one contains leucine and the other isoleucine in a given position the ratio is always smaller for the isoleucine containing peptide. The differences are sufficient to distinguish the isomeric residues if comparison spectra are available. 相似文献
9.
The antiinflammatory activity of a homologous series of α-alkyl substituted [4-(1-oxo-2-iso-indolinyl)-phenyl]-acetic acid has been assayed by some and tests.These compounds were shown to be particularly active in inhibiting prostaglandin biosynthesis from bovine seminal vesicles, and their potency was seen to increase as the size of the substituents in the side chain increased.The antiinflammatory activity is not correlated with inhibition of PG-synthetase. Discussion of the data takes into account the plasma protein binding and pharmacokinetics of these compounds. 相似文献
10.
Gianfranco Delle Fave Anna Kohn Laura de Magistris Marcello Mancuso Claudio Sparvoli 《Life sciences》1980,27(11):993-999
The effect of bombesin on gastrin release and gastric acid secretion was investigated in 10 healthy volunteers. Bombesin (0.6 μg · Kg?1 · hr?1) produced a significantly higher increase in plasma gastrin levels (86.7 11.1 pmo/1 than after a protein meal (39.6 ± 5.6 pmol1/1). The gastric acid secretory response to bombesin (12.1 ± 2.9 mEq · hr?1) was however significantly lower than the maximal response produced by pentagostrin (20.9 ± 3.5 mEq · hr?1) at the dose of 6 μg · Kg?1. Atropine did not modify gastrin release induced by bombesin but significantly reduced gastric acid secretion . From the data presented it may be hypothesized that less biologically active forms of gastrin and/or other peptides inhibiting the gastrin effect upon gastric acid secretion may be released by bombesin. 相似文献
11.
C M Deber P D Adawadkar J Tom-Kun 《Biochemical and biophysical research communications》1978,81(4):1357-1362
The synthesis of the cation-binding cyclic octapeptide, cyclo(Glu-Sar-Gly-(N-decyl)Gly)2 is reported. This peptide, containing two ionizable Glu carboxyl side chain protons per molecule, can form neutral cation complexes with divalent ions via protonmetal exchange. Solubilized in chloroform solution, the peptide has been found to extract calcium from an aqueous phase (pH 8.5, 100 mM Tris) generally on a molar basis. By contrast, under comparable conditions but with other metal chlorides, the peptide does not extract magnesium, sodium, or potassium. That the extraction proceeds via proton-metal exchange was demonstrated by the absence of (radioactive) chloride ion from the organic phase. Parallel sets of experiments performed with the naturally-occurring ionophore A23187 reaffirmed that the latter substance extracts calcium and magnesium with nearly equal propensity. 相似文献
12.
J E Lever 《Biochemical and biophysical research communications》1977,79(4):1051-1058
Methods for predicting peptide chain conformation have been applied to amino acid sequences adjacant to the carbohydrate attachment sites of glycoproteins containing the -glycosylamine type of protein-carbohydrate linkage. Of 31 glycosylated residues examined 30 occur in sequences favouring turn or loop structures. Twentytwo of the glycosylated asparagine residues occur in tetrapeptides predicted to have the β-turn conformation. Carbohydrate attachment is therefore associated with peptide sequences which favour the formation of β-turn or other turn or loop structures. 相似文献
13.
G. Duvillier A. Nouvelot C. Richet T. Baltz P. Degand 《Biochemical and biophysical research communications》1983,114(1):119-125
The composition of the C-terminal end of a variant surface glycoprotein from (BoTat-1 VSG) has been examined. It has been reported for two VSGs (Holder, A.A., Biochem. J. (1983), , 261–262) that ethanolamine was involved in binding the C-terminal amino acid to an oligosaccharide side chain. Tryptic glycopeptides were prepared from BoTat-1 VSG and analyzed. One of them was found to contain ethanolamine and consequently was assumed to be C-terminal. It was shown that the glycopeptide also included phosphate, glycerol and fatty acids. The fatty acid composition was representative of that of glycerolipids. All the results suggest that the end of the molecule is a core of phosphatidylethanolamine. 相似文献
14.
Beverly A. Teicher Mikio Shikita Paul Talalay 《Biochemical and biophysical research communications》1978,83(4):1436-1441
A heat-stable protein activator from bovine adrenal cortex mitochondria stimulates the conversion of cholesterol to pregnenolone in crude extracts of adrenal mitochondria, and resembles in some of its properties, the sterol carrier protein of liver (Kan . . . . . , 423–429, 1972). We have shown that activator preparations also stimulate highly purified adrenal enzyme preparations comprising four components: cytochrome P-450 specific for side chain cleavage, adrenodoxin, adrenodoxin reductase, and an NADPH-generating system. Furthermore, this activator stimulates the conversion not only of cholesterol, but also of (20S)-20-hydroxycholesterol, (22)-22-hydroxycholesterol, and (20, 22)-20,22-dihydroxycholesterol to pregnenolone. Our findings provide additional evidence that the steroid-activator complexes are the substrates for the side chain cleavage enzyme and that the monohydroxy and dihydroxycholesterols are true intermediates in the conversion of cholesterol to pregnenolone by bovine adrenal cortex mitochondria. 相似文献
15.
The biosynthesis of 2-methylalkanes was studied in the crickets and . Labelled acetate, valine, and isobutyric acid were incorporated into the cuticular hydrocarbon of at levels of 6.0 ± 1, 6.5 ± 2, and 1.5 ± 0.7 percent respectively. The hydrocarbons of this insect are 20 percent 2-methylalkanes, primarily of even numbered carbon chain lengths, and 80% n-alkanes. Of the label incorporated into the hydrocarbon fraction, 28 ± 2 percent of sodium [1-14C] acetate, 98 ± 1 percent of L-[G-3H] valine, and 75 ± 10 percent of [1-14C] isobutyric acid were incorporated into the 2-methylalkanes. This suggests that valine is converted to isobutyric acid and is incorporated into the even numbered carbon chain length 2-methylalkanes during the initial stages of chain elongation. Similar data obtained in suggests that leucine is converted to isovaleric acid which is then incorporated into the odd numbered carbon chain length 2-methylalkanes. 相似文献
16.
The crystal and molecular structure of prostaglandin A1 (PGA1) has been determined by X-ray diffraction. (Space group P212121, , . Comparison of the structure of PGA1 with that of PGF1β (determined previously as the tribromobenzoate) indicates significant differences in the relative intramolecular side chain orientations. However, conformation and torsional angles within each side chain of PGA1 are retained with little or no change in comparison with PGF1β, indicating the presence of the C15-bromobenzoate groups in the latter have had little effect in altering internal side chain conformation in the solid state. The overall differences in relative side chain orientation in PGA1 are attributable to chemical and conformational changes in the substituted cyclopentane moiety (C8-C12). 相似文献
17.
The transport of [14C]Gly-Pro was examined using a mutant of Salmonella typhimurium (strain TN87) deficient in an X-Pro dipeptidase and an X-Pro-Y iminopeptidase. The dipeptide was taken up by one saturable transport system having a of and a of 1.4 nmol/mg dry wt cell per min. The uptake of Gly-Pro was not inhibited by amino acids or tripeptides and the transport system exhibited a rather broad side chain specificity for dipeptides. Dipeptides containing hydrophobic residues were the most potent inhibitors of this dipeptide transport system exhibiting values between 10?8 and 10?7 M. In contrast, dipeptides containing glycine residues were particularly weak inhibitors. Finally, Gly-Pro was found to be in the intact form inside the cell and was concentrated more than 1000-fold. 相似文献
18.
The 0.5M KCl wash of rabbit reticulocyte ribosomes (I fraction) catalyzes the deacylation of Met-tRNAfMet. Upon DEAE-cellulose column chromatography, the deacylase activity elutes with the 0.1M KCl wash of the column (f1) and is well-resolved from the peptide chain initiation factors (1–3). The deacylase activity is specific for Met-tRNAfMet (retic., ). Other aminoacyl tRNAs tested including fMet-tRNAfMet (retic., ), Phe-tRNA (), Val-tRNA (retic.), and Arg-tRNA (retic.) are completely resistant to the action of the deacylase. In the presence of the peptide chain initiation factor (IF1) and GTP, retic. Met-tRNAfMet forms the initiation complex Met-tRNAfMet:IF1:GTP (2), and in this ternary complex Met-tRNAfMet is not degraded by the deacylase. Met-tRNAfMet binds to IF1 independent of GTP, and in this complex, this Met-tRNAfMet is degraded by the deacylase.Prior incubation of f1 with Met-tRNAfMet (retic.) strongly inhibited protein synthesis initiation, presumably due to deacylation of the initiator tRNA. This inhibition by f1 was completely prevented when Met-tRNAfMet (retic.) was pre-incubated with peptide chain initiation factors. 相似文献
19.
We have determined fluid translocation across the cellular layers lining the cornea by measuring changes in corneal transparency. The loss of 1.3 μ1/cm2 fluid from the stroma causes an increase of +1% in transparency. Amphotericin B () when added to the tear side (=mucosal side) of the epithelium causes a rapid increase in potential difference of ) followed by a slower increase of . The electrical resistance is reduced from . The resulting increase in calculated short circuit current is accompanied by a decrease in transparency at a rate of , corresponding to an uptake of fluid by the cornea of . Replacement of the fluid bathing the endothelial side of the cornea, in order to prevent water movement from the aqueous compartment into the stroma, did not significantly alter this uptake of fluid. Thus the epithelial fluid transport which is reported to be normally slightly secretory, becomes absorptive in the presence of amphotericin B. Serosal hypertonicity (20 mM mannitol) increases the water influx into the cornea induced by amphotericin B. These results indicate that amphotericin B induces sodium-selective channels in the epithelium leading to an accumulation of NaCl and water in the stromal layer of the cornea. Ouabain reduces the potential and calculated short circuit current in epithelia pretreated with amphotericin B. Following addition of ouabain, the NaCl and water accumulated in the stroma leak away resulting in a transient increase in transparency. Finally, a model is proposed that includes a stromal compartment involved in fluid transport and that agrees with the results presented here. 相似文献
20.
J C Mao 《Biochemical and biophysical research communications》1973,52(2):595-600
The substrate specificity of peptidyltransferase at the donor site was investigated by the “50S reaction”. Seventeen N-acetylated or unacetylated aminoacyl-tRNAs and dipeptidyl-tRNAs were used as the donor substrates and puromycin as the acceptor. Results indicated that the nature of amino acid side chain of the donor tRNA has a predominant effect on the reaction rate of peptidyltransferase. Amino acids or dipeptides with high hydrophobicity were transferred faster than those with low hydrophobicity. Amino acids with alkyl side chains are better donors than those with aromatic side chains. Substrates with C-terminal proline were transferred extremely slowly which can probably be attributed to its unusual α-imino structure in addition to its low hydrophobicity. 相似文献