检索结果-内蒙古大学图书馆

MODIfICATION Of AffINITY LABELED ANTIBODIES

IMMUNOCHEMISTRY 1973年第7期10卷 455-460页

作者： HADLER, N METZGER, H NIAMDD ARTHRIT & RHEUMAT BRANCH BETHESDA MD 20014 USA

We previously showed that antibodies which had been affinity labeled at a tyrosyl residue with a diazonium labeling reagent could be further modified usefully. By reductively cleaving the azotyrosine bond, 3-aminotyrosine (3-NH 2 Tyr) was generated in situ , and this residue could then serve as an initiation point for further modifications - for example with the bifunctional reagent difluoro-dinitrobenzene (f 2 DNB). We now present the results of further experiments utilizing this approach. The affinity labeled nitrophenyl binding protein of the plasma cell tumor MOPC 315 was easily reduced with small amounts of dithionite (Na 2 S 2 O 4 ). When f 2 DNB was added it reacted initially at the 3-NH 2 Tyr at position 34 on the light chain and then subsequently with other amino acid residues leading to the formation of light-heavy and intra-light chain cross-links. Although under suitable conditions f 2 DNB also reacted with the native protein of MOPC 315, the reaction occurred largely on the heavy chain. These results testify to the high specificity obtainable using these procedures. Experiments involving the reaction of f 2 DNB with either labeled-unreduced protein, or labeled-reduced protein in the presence of the ligand dinitrophenyl-aminocaproate, suggests that the f 2 DNB may in part have functioned as an affinity labeling reagent. Parallel studies were performed with the phosphorylcholine binding protein of plasma cell tumor TEPC 15. This protein affinity labeled at two alternative tyrosines on the light chains. The azo bonds were much more difficult to reduce wwith dithionite. When they were cleaved some of the sites remained completely inactive whereas others bound normally. The stoichiometry suggests that those sites with a 3-NH 2 Tyr at position 92 were inactivated while those with 3-NH 2 Tyr at position 34 were unaffected. Native protein-15 reacted only minimally with f 2 DNB under the conditions used whereas the labeled-reduced protein became modified on the

关键词： BBS Borate-buffered saline DNP 2, 4-dinitrophenyl f 2 DNB = 1 5-diflioro-2, 4-dinitrobenzene

来源：评论

学校读者我要写书评

暂无评论

COMPARATIVE STUDIES ON PROPERTIES Of EUKARYOTIC PROTEIN-SYNTHESIS INITIATION fACTOR If-1 fROM SEVERAL SOURCES

引用

BIOCHIMICA ET BIOPHYSICA ACTA 1973年第3期324卷 410-419页

作者： CASHION, LM STANLEY, WM UNIV CALIF SCH BIOL SCIDEPT MOLEC BIOL & BIOCHEMIRVINECA 92664

Eukaryotic protein synthesis initiation factor If-I has been purified from a variety of cells and tissues, and some of the properties of these preparations are compared. If-I activity from all sources elutes close to the excluded volume of Sephadex G-200 columns, indicating similar, if not identical, molecular weights (350 000). There is little or no species or tissue specificity in the binding of the initiator tRNA from one source to If-I purified from another source. The ability of all If-I preparations to form a ternary complex with GTP and the initiator tRNA is inactivated by N- ethylmaleimide ; this sulfhydryl reagent also completely inactivates the rabbit reticulocyte If-I-mediated binding of the initiator tRNA (rabbit liver) to rabbit reticulocyte 40-S ribosomal subunits. Thus, it appears that If-I is an obligatory and ubiquitous protein synthesis initiation factor in the cytoplasm of all eukaryotes.

关键词： Met-tRNA i Met the aminoacylated form of the initiator tRNA in the cytoplasm of eukaryotes fMet-tRNA i Met the N- formylated form of Met-tRNA i Met If-I defined in ref. 2 Met-tRNA f Met ( Escherichia coli ) the aminoacylated (but non -N- formylated ) form of the initiator tRNA in E. coli fMet-tRNA f Met ( E. coli ) the N- formylated form of Met-tRNA f Met ( E. coli )

来源：评论

学校读者我要写书评

暂无评论

INTERSYSTEM EXCITON TRANSfER IN ISOLATED-CHLOROPLASTS

引用

BIOCHIMICA ET BIOPHYSICA ACTA 1973年第3期325卷 530-538页

作者： BRIANTAIS, JM VERNOTTE, C MOYA, I CNRS LAB PHOTOSYNTH 91190 GIF SUR YVETTE FRANCE

The following arguments in favor of exciton transfer between the two photosystems are presented: 1.(1) MgCl2 (1–10 mM range) decreases the intersystem transfer but does not modify the partition of absorbed photons between the photosystems. MgCl2 addition causes a simultaneous increase of excitation life time (τ) and of fluorescence intensity (f). The same linear relationship is obtained with or without added Mg2+. 2.(2) The deactivation of Photosystem II by the Photosystem II to Photosystem I transfer increases with the level of reduced Photosystem II traps. When all Photosystem II traps are closed, half of Photosystem II excitons are deactivated by transfer to Photosystem I. 3.(3) from the relative values of the 685-nm fluorescence yield and System II electron transport rate in limiting light, measured with and without MgCl2, the values of rate constants of Photosystem II deactivation were calculated. 4.(4) The intersystem transfer determines a 715-nm variable fluorescence, which is lowered by MgCl2 addition. When this transfer is decreased by MgCl2 the efficiency of the transfer between Photosystem II-connected units is enhanced, and a more sigmoidal fluorescence rise is obtained. A double-layer model of the thylakoid membrane where each photosystem is restricted to one leaflet is proposed to explain the decrease of the intersystem transfer after adding cations. It is suggested that MgCl2 decreases the thickness of the Photosystem I polar region, increasing the distance between the pigments of the two photosystems.

关键词： DCMU 3-(3 4-dichlorophenyl)-1 1-dimethylurea f fluorescence intensity τ excitation lifetime

来源：评论

学校读者我要写书评

暂无评论

CHRONOPOTENTIOMETRIC STUDY Of OXIDATION Of SOME DILUTED AMALGAMS IN PRESENCE Of TRACES Of OXYGEN DISSOLVED IN AQUEOUS-SOLUTION .2. STUDY Of INfLUENCE Of VARIOUS PARAMETERS ON REACTION-RATE

引用

JOURNAL Of ELECTROANALYTICAL CHEMISTRY 1973年第2期43卷 185-195页

作者： BUffLE, J PELLETIE.M MONNIER, D UNIV GENEVA DEPT CHIM MINERALE & ANALSECT CHIM SCIGENEVA 1211SWITZERLAND

The behaviour of dilute amalgams in the presence of trace amounts of dissolved oxygen in aqueous solution has been studied. The diffusion of oxygen in the solution and that of metal in the amalgam seem to be the factors which determine the rates of oxidation of Zn, Cd, Pb and Tl amalgams. The variation of metal concentration in a drop of amalgam with time of contact with traces of dissolved oxygen has been treated mathematically. The influence of different parameters was studied experimentally and these are in accordance with the proposed equation. A simple relation between the rate of oxidation and the amount of oxygen in the solution was found and this can be used for the determination of traces of oxygen in solution.

关键词： A area of the drop (cm 2 ) C O 2 ( r, t ) concentration of oxygen in the solution at a distance r from the centre of the electrode and time t (mol l −1 ) C O 2 sol concentration of oxygen in the bulk of the solution (mol l −1 ) C′ O 2 sol concentration of the added oxygen (mol l −1 ) C Ox ( r, t ) concentration of the oxidised form Me( m ), at the electrode (mol l −1 ) C R ( r, t ) concentration of metal in amalgam (mol l −1 ) at a distance r from the centre of the electrode and time t C R mean concentration of metal in the drop (mol l −1 ) C R 0 initial concentration of metal in the amalgam (mol l −1 ) D Ox diffusion coefficient of the oxidised form Me( m ) in solution (cm 2 s −1 ) D R diffusion coefficient of the metal in mercury (cm 2 s −1 ) D O 2 diffusion coefficient of oxygen in mercury (cm 2 s −1 ) D Pb diffusion coefficient of Pb in mercury (cm 2 s −1 ) D Pb 2+ diffusion coefficient of Pb 2+ in solution (cm 2 s −1 ) d thickness of the diffusion layer (cm) E potential (V) E 0 standard potential of the Me m + /Me(Hg) couple (V) f 0 flux of metal at the surface of the drop (mol cm −2 s −1 ) f faraday constant=96491C Me metal used for the preparation of amalgam Me( m ) metal ion with an oxidation state of + m Me(Hg) dissolved metal in the amalgam Me m + hydrated metal ion with an oxidation state of + m m oxidation state of oxidized metal n 2p/ m p oxidation state of reduced oxygen r distance from the centre of the drop (cm) r 0 radius of the drop (cm) R gas constant=8.3 J mol −1 K −1 t time (s) τ time up to the inflection point of the curve E = f ( t ) during the oxidation of the amalgam (s) γ i successive positive roots of the equation γ=tan γ, i =1,2,3,4…

来源：评论

学校读者我要写书评

暂无评论

EffECT Of ADJUVANT DISEASE IN RATS ON CYCLOPHOSPHAMIDE AND ISOPHOSPHAMIDE METABOLISM

引用

BIOCHEMICAL PHARMACOLOGY 1973年第19期22卷 2453-2468页

作者： BECK, fJ WHITEHOUSE, MW UNIV CALIF SCH MED DEPT MED LOS ANGELES CA 90024 USA

After the injection of a variety of arthritogenic adjuvants into male Wistar rats, hepatic activation of cyclophosphamide and isophosphamide is rapidly and profoundly depressed. This selective injury is largely reversible with phenobarbital and principally restricted to the liver microsomal protein fraction, which demethylates aminopyrine and N,N dimethylaniline and generates 'alkylating metabolites' from cyclophosphamide in vitro. Evidence is presented, based upon both metabolite excretion studies and the duration of hexabarbital induced hypnosis, that this phenomenon is not an artifact in vitro and must be seriously considered in evaluating both the efficacy of potential antiarthritic drugs against the rat adjuvant arthritis and their toxicity in these arthritic animals. A quantitative separation of two pathological responses to the same adjuvant may be obtained: in Buffalo rats, whose liver metabolism may be profoundly impaired while they suffer minimal (or no) arthritis after being inoculated with adjuvants which are truly arthritogenic in other rat strains; with Mycobacterium tuberculosis dispersed in methyl oleate, which induces minimal arthritis in Wistar rats, but nevertheless impairs their liver metabolism over a prolonged period (14 days or more). Drug metabolism appeared to be normal in rats with two other immunologically mediated 'inflammatory diseases' (graft vs host disease and allergic encephalomyelitis) and in other rodents examined after adjuvant inoculations. A novel bioassay for cyclophosphamide and isophosphamide metabolites is described which utilizes their ability to prevent grafted rat lymphocytes from initiating a graft vs host reaction in tolerant recipient rats. At least four alkylating metabolites of cyclophosphamide were found in rat bile and tentatively identified by thin layer chromatography. The possible error in relying on changes in urinary excretion (rather than biliary excretion) of drug metabolites as a guide to changes in hepatic

关键词： CPA cyclophosphamide (Cytoxan 2-bis-β-chloroethyl-amino-tetrahydro-2H-1,3,2-oxazaphosphorine 2-oxide) IPA isophosphamide EAE experimental allergic encephalomyelitis TCE 2,2,2-trichloroethanol NBP 4- p -nitrobenzyl-pyridine DMA N , N -dimethylaniline GvHR graft vs host response f 1 first generation hybrid, tolerant to a lympho-cyte graft from either parent BCG Bacillus Calmette-Guerin( Mycobacterium bovis ) PB pheno-barbital P.I.U. plasma “inflammation units”

来源：评论

学校读者我要写书评

暂无评论

INHIBITION Of RETICULOCYTE PEPTIDE-CHAIN INITIATION BY PACTAMYCIN - ACCUMULATION Of INACTIVE RIBOSOMAL INITIATION COMPLEXES

引用

PROCEEDINGS Of THE NATIONAL ACADEMY Of SCIENCES Of THE UNITED STATES Of AMERICA 1973年第1期70卷 22-26页

作者： KAPPEN, LS SUZUKI, H GOLDBERG, IH HARVARD UNIV MED SCHDEPT PHARMACOLBOSTONMA 02115

Pactamycin does not inhibit the overall initiation factor- and GTP-dependent binding of [(35)S]Met-tRNA(f) to rabbit reticulocyte ribosomes but does prevent the formation of Met-puromycin, provided that the antibiotic is present during the course of the binding reaction. These data indicate that pactamycin blocks the synthesis of a functional peptide-chain initiation complex. Sucrose density gradient centrifugation analysis of binding reactions shows that pactamycin causes the accumulation of an initiation complex on the smaller ribosomal subunit (smaller initiation complex), to which the 60S ribosomal subunit either cannot join or with which it forms a larger inactive 80S initiation complex that falls apart under the conditions used for isolation. The smaller initiation complex formed in the presence of pactamycin differs from the normal intermediate in peptide-chain initiation in being much more resistant to degradation by pancreatic RNase. In the presence of pactamycin, the inactive smaller complex can also form on mRNA to which an unaffected ribosomal couple is already attached, forming an oligoribosome lacking a larger ribosomal subunit or a "1.5 mer." These effects of pactamycin can be overcome to a considerable degree by elevation of the Mg(2+) concentration.

关键词： methionyl-puromycin methionyl-tRNA f initiation factors Mg 2+ concentration

来源：评论

学校读者我要写书评

暂无评论

Studies on the activation of purified mitochondrial ATPase by phospholipids

引用

BBA - Bioenergetics 1973年第3期305卷 519-533页

作者： Swanljung, Patrik frigeri, Luciano Ohlson, Kristina Ernster, Lars Department of Biochemistry University of Stockholm S-113 82 Stockholm Box 6409 Sweden

1. An ATPase which is activated by phospholipids and inhibited by oligomycin, has been purified from beef heart submitochondrial particles using affinity chromatography. Phospholipid and detergent are removed by washing the enzyme with a solution of serum albumin while it is attached to the biospecific adsorbent. 2. The ATPase is activated up to 18-fold by lysolecithin and to a smaller extent by cardiolipin, phosphatidylinositol and phosphatidylethanolamine. The amount required of each of these phospholipids to give half-maximal activation is apparently inversely related to the number of fatty acid chains in the lipid. Lecithin, which is a poor activator of the ATPase, competitively inhibits the activation by cardiolipin. 3. The activation of the ATPase consists of an increase in both the maximal velocity of the reaction and the affinity for substrate ATP. The pH optimum of the reaction is not influenced by the charge of the lipid. 4. Arrhenius plots of ATPase activated with lysolecithin show a transition to a higher activation energy at temperatures below 19 °C. The sensitivity of the lysolecithin-activated enzyme to oligomycin is markedly reduced below the same temperature. With cardiolipin the transition is observed at 13 °C. 5. ADP, Mg²⁺ and to a smaller extent ATP, Mg²⁺ enhance the activation of ATPase by suboptimal amounts of phospholipid. © 1973.

关键词： TES, N -tris(hydroxymethyl)methyl-2-aminoethanesulphonic acid f 1 , soluble ATPase or coupling factor 1 (ref. 8)

来源：评论

学校读者我要写书评

暂无评论

The ternary complex of initiation factor If-I, Met-tRNA^Met_f and GTP An aurintricarboxylate-sensitive intermediate in the initiation of eukaryotic protein synthesis

引用

BBA Section Nucleic Acids And Protein Synthesis 1973年第1期299卷 142-147页

作者： Dettman, Geraldine L. Stanley Jr., Wendell M. Department of Molecular Biology and Biochemistry School of Biological Sciences University of California Irvine CA 92664 United States

We have previously described an initiation factor, extensively purified from 0.5 M KCl extracts of rabbit reticulocyte polysomes, which forms a ternary 1:1 complex with the initiator tRNA [Met-tRNA^Met_f (rabbit liver)] and GTP. We now refer to this initiation factor as If-I. When the ternary complex was separated from GTP and [³⁵S]Met-tRNA^Met_f by Sephadex G-100 gel filtration and used as the only source of radioactive methionine in a rabbit reticulocyte in vitro amino acid incorporation system, the transfer of [³⁵S]methionine into acid-insoluble material, using A-U-G-(U)_x (x = 25 ± 5) as the messenger, was greatly stimulated as compared to the transfer of [³⁵S]methionine from free [³⁵S]Met-tRNA^Met_f. Kinetic experiments now confirm that the methionine residue in the ternary complex is a preferred precursor to the N-terminal position of newly initiated polypeptide chains. The formation of the complex is inhibited by low levels of aurintricarboxylate;however, the preformed ternary complex is stable and is not dissociated by the addition of aurintricarboxylate. When the preformed ternary complex is used in the in vitro amino acid incorporation system, aurintricarboxylate inhibits the formation of acid-insoluble material, but only at levels higher than those required for the prevention of ternary complex formation. Thus one reaction in protein biosynthesis which is very sensitive to the presence of aurintricarboxylate is the formation of the ternary complex. This phenomenon may partially explain the action of aurintricarboxylate upon eukaryotic protein synthesis initiation mediated by Met-tRNA^Met_f. © 1973.

关键词： Met-tRNA Met f the methionyl-tRNA species which functions as the initiator tRNA in the cytoplasm of eukaryotes P-site the ribosomal peptidyl-tRNA binding site A-U-G-(U) x x = 25 ± 5

来源：评论

学校读者我要写书评

暂无评论

Separation and characteristics of isoenzymes of wheat germ acid phosphatase

引用

Plant Science Letters 1973年第4期1卷 169-177页

作者： foster, Donald M Weber, Darrell J Department of Physiology School of Medicine Vanderbilt University Nashville TN 37232 United States Department of Botany Brigham Young University Provo Ut. 84601 United States

Isoenzymes of wheat germ acid phosphatase were separated into several fractions by DEAE-cellulose chromatography using a pH gradient. Disc electrophoresis indicated 7 separate isoenzymes. One DEAE-cellulose fraction, labeled as Group I, contained 4 of the 7 isoenzymes and another, labeled as Group II, contained the other 3. Sedimentation velocity analysis indicated that each group was monodisperse, as indicated by a single sedimenting peak. The 3rd and 7th isoenzymes (numbered on basis of electrophoretic migration) were isolated by further DEAE-cellulose chromatography. The absorption spectra of isoenzymes 3 and 7 were not alike but both indicate the presence of a metal. The isoenzymes 3 and 7 had similar pH optimum, but different substrate constants (K_m) for o-carboxyphenylphosphate. Inhibition studies indicated that both isoenzymes 3 and 7 had about 2 · 10³ times greater affinity for molybdate than for orthophosphate. Orthophosphate competitively inhibited the reaction of isoenzyme 3 with o-carboxyphenylphosphate. © 1973.

关键词： f fraction

来源：评论

学校读者我要写书评

暂无评论

On the specificity of Pseudomonas aeruginosa alkaline proteinase with synthetic peptides

引用

BBA - Enzymology 1973年第2期309卷 414-429页

作者： Morihara, Kazuyuki Tsuzuki, Hiroshige Oka, Tatsushi Shionogi Research Laboratory Shionogi and Co. Ltd Fukushima-ku Osaka 553 Japan

The specificity of Pseudomonas aeruginosa alkaline proteinase was studied using various synthetic peptides as substrates. Since it was found that the smallest peptide which is sensitive to the enzyme is a Z-tripeptide, in which an internal peptide bond is split, the primary specificity against the amino acid residue at either side of the splitting point was determined using various Z-tripeptides as substrates. The results indicated that the enzyme shows specificity against l-alanine at the imino side and l-phenylalanine at the carbonyl side of the splitting point, though its specificity is not as stringent as that seen with usual metal neutral proteinases. An experiment using l-alanine oligomers (from tetramer to hexamer) as substrates showed that the proteolytic activity increases drastically with increase in chain length, suggesting that the hydrolysis is markedly affected by amino acid residues more distant from the catalytic point in a peptide substrate ("secondary interaction"). The effect of secondary interaction was studied using various Z-tetra-or Z-pentapeptide substrates, which indicated that the specificity against peptides larger than Z-tripeptides was determined by secondary interaction, rather than by primary specificity, the presence of a hydrophobic or bulky residue being required at positions distant, rather than adjacent to the splitting point. © 1973.

关键词： iP 2 2 P- f diisopropyl phosphofluoridate p Cl-HgBzO − p- chloromercuribenzoic acids Tos-PheCH 2 Cl tosyl- l -phenylalanine chloromethyl ketone Tos-LysCH 2 Cl tosyl- l -lysine chloromethyl ketone Ac- acetyl -OMe methoxy- Bz benzoyl- -OEt ethoxy- Z- benzyloxycarbonyl- -OBz benzyloxy- -OBu t tert. -butoxy- -ONp p- nitrophenoxy -

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：