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91.
Salem Faham Tadashi J. Mizoguchi Elinor T. Adman Harry B. Gray John H. Richards D. C. Rees 《Journal of biological inorganic chemistry》1997,2(4):464-469
Replacement of the cysteine at position 112 of Pseudomonas aeruginosa azurin with an aspartic acid residue results in a mutant (Cys112Asp) protein that retains a strong copper-binding site. CuII(Cys112Asp) azurin can be reduced by excess [RuII(NH3)6]2+, resulting in a CuI protein with an electronic absorption spectrum very similar to that of wild-type CuI azurin. Cys112Asp azurin exhibits reversible interprotein electron-transfer reactivity with P. aeruginosa cytochrome c 551 (μ?=?0.1?M sodium phosphate (pH?7.0);E°(CuII/I)?=?180 mV vs NHE); this redox activity indicates that electrons can still enter and exit the protein through the partially solvent-exposed imidazole ring of His117. The structure of CuII(Cys112Asp) azurin at 2.4-Å resolution shows that the active-site copper is five coordinate: the pseudo-square base of the distorted square-pyramidal structure is defined by the imidazole Nδ atoms of His46 and His117 and the oxygen atoms of an asymmetrically-bound bidentate carboxylate group of Asp112; the apical position is occupied by the oxygen atom of the backbone carbonyl group of Gly45. The CuII–Asp112 interaction is distinguished by an approximately 1.2-Å displacement of the metal center from the plane defined by the Asp112 carboxylate group. 相似文献
92.
Sato Yoji; Weil Max Harry; Tang Wanchun; Sun Shijie; Xie Jianlin; Bisera Joe; Hosaka Hidehiro 《Journal of applied physiology》1997,82(2):558-562
Sato, Yoji, Max Harry Weil, Wanchun Tang, Shijie Sun,Jianlin Xie, Joe Bisera, and Hidehiro Hosaka. EsophagealPCO2 as a monitor of perfusionfailure during hemorrhagic shock. J. Appl.Physiol. 82(2): 558-562, 1997.Measurement ofgastric wall PCO2(PgCO2) bytonometric method has emerged as an attractive option for estimatingvisceral perfusion during circulatory shock. However, gastric acidsecretion obfuscates the tonometric measurement. We, therefore,investigated the option of measuringPCO2 in the esophagus to minimizethese restraints. Hemorrhagic shock was induced in five Sprague-Dawleyrats, and five rats served as sham controls.PgCO2 wasmeasured with an ion-sensitive field effect transistor that wassurgically implanted into the gastric wall. Esophageal luminalPCO2(PeCO2) wasmeasured by a second ion-sensitive field effect transistor sensor.During hemorrhagic shock, mean aortic pressure declined from 150 to 50 mmHg. Gastric blood flow decreased from 58 to 12 ml · min1 · 100 g1 (21% of preshock) andesophageal blood flow from 44 to 7 ml · min1 · 100 g1 (16% of preshock).PgCO2simultaneously increased from 47 to 116 Torr andPeCO2 from 47 to 127 Torr. The increases inPgCO2 werehighly correlated with increases inPeCO2(r = 0.90). Esophageal tonometry may,therefore, serve as a practical alternative to gastric tonometry. 相似文献
93.
Ronald J. Ash Gary A. Flynn Rob M.J. Liskamp Harry C.J. Ottenheijm 《Biochemical and biophysical research communications》1984,125(2):784-789
Sparsomycin, ScRs configuration, was the most potent of the four possible stereoisomers as a competitive inhibitor of peptide bond formation. In addition, the configuration of the two chiral centers dictated whether the compound exhibited time- and temperature-dependent inhibition of peptidyl transferase when incubated with polysomes prior to enzyme assay. The data corroborate the thesis that a peptidyl transferase-mediated acylation of the pivotal sulfoxide moiety and subsequent Pummerer rearrangement play a significant role in the inhibitory properties of sparsomycin. 相似文献
94.
Buddy Setyono Harry Van Steeg Harry O. Voorma 《Biochimica et Biophysica Acta (BBA) - Gene Structure and Expression》1984,782(3):242-246
Eukaryotic initiation factors (eIF) associate readily with 32P-labeled Semliki Forest virus (SFV) mRNA in vitro, forming complexes which can be crosslinked by 254 nm ultraviolet irradiation. After ribonuclease digestion, the initiation factors were released and analysed by gel electrophoresis. Autoradiography revealed proteins by virtue of crosslinked 32P-labeled mRNA fragments. eIF-4A, -4B and -4C as well as three subunits of eIF-3 could be crosslinked with SFV mRNA. None of these proteins bound to ribosomal RNAs. 相似文献
95.
Leilo Zolla Harry A. Kuiper Alessandro Finazzi Agrò Maurizio Brunori 《Journal of inorganic biochemistry》1984,22(3):143-153
Addition of KCN to Helix pomatia β-hemocyanin fully saturated with either O2 or CO results in a decrease of the spectroscopic properties of the protein (absorbance at 340 nm and luminescence at 550 nm) due to the displacement of the gaseous ligands (O2 or CO) from the active site. The anionic form of cyanide (CN?) is supposed to bind to the active site; its intrinsic affinity for the protein, as calculated from independent O2 and CO displacement experiments, is between 2 and 6 × 106M?1. The replacement of O2 or CO shows some differences which may be correlated with the different modes of binding at the active site. Thus, while displacement of oxygen by cyanide is hyperbolic, addition of cyanide to carbonylated hemocyanin shows a lag phase. This finding suggests the formation of a mixed liganded complex at the active site. The simultaneous presence of CO and CN? at the active site of hemocyanin is also supported by the experiment in which addition of small amounts of KCN to hemocyanin partially saturated with O2 and CO gives rise to an increase of emission intensity and a concomitant decrease of the O2 absorption band. The mixed-liganded species displays luminescence properties similar to those of CO-saturated hemocyanin, and the formation of the complex is reversible on dialysis or oxygenation. 相似文献
96.
Saroja Narasimhan Stephen Allen R Colin Hughes Harry Schachter 《Glycoconjugate journal》1984,1(1):51-61
The ricin-resistant mutant baby hamster kidney (BHK) cell line RICR21 is unable to make the sialylated bi- or triantennary complexN-glycans found in wild type cells and accumulates instead non-bisected hybrid structures containing three Man residues and one or two sialylated antennae (Hugheset al 1983, Carbohydr Res 120215-34). Specific assays forN-acetylglucosaminyltransferases I, II, III and IV were applied to Triton X-100 extracts of wild type BHK, RICR14 and RICR21 cells. It was shown that RICR21 cell extracts had a decreasedN-acetylglucosaminyltransferase II specific activity (17 to 27% of wild type values). It is suggested that in wild type cellsN-acetylglucosaminyltransferase II action proceeds quickly, leading to complexN-glycan synthesis, while in RICR21 cells potential substrates forN-acetylglucosaminyltransferase II move into the trans-Golgi compartment before the transferase can act, thereby leading to hybrid structures. 相似文献
97.
Nuclear protein kinases 总被引:8,自引:0,他引:8
98.
An "artificial tongue" is described which can be used to calibratethe stimulus delivery characteristics of flow systems for liquidtaste stimuli. The calibrator, which functions on the basisof conductance measurements, is used to ascertain the behaviourof certain test solutions in the flow system. The test solutionsare so prepared that they mimic the hydraulic properties ofthe stimulus solutions to be used. The special apparatus requiredis neither complex nor costly, and the procedures involved arestraightforward. 相似文献
99.
Shen K. Yang Harry V. Gelboin John D. Weber V. Sankaran Daniel L. Fischer James F. Engel 《Analytical biochemistry》1977
The optical isomers of (±)r-7,t-8-dihydroxy-7,8-dihydrobenzo[a]pyrene and its synthetic precursor (±)r-7,t-8-dihydroxy-7,8,9,10-tetrahydrobenzo[a]pyrene were resolved as their di-(−)menthoxyacetates using high-pressure liquid chromatography. Saponification of the resolved diesters yielded the corresponding enantiomers. The specific rotation, CD spectra, and ORD curves are reported. The resolution of these optical isomers permits detailed studies on the enzymatic intermediates and the mechanism of benzo[a]pyrene activation to its carcinogenic form. The method is of general usefulness for the resolution of optical isomers. 相似文献
100.
Harry J. McArdle Ian A. Johnston 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1980,135(2):157-164
Summary Sarcoplasmic reticulum has been isolated from the white muscle of 15 species of teleost fish adapted to diverse thermal environments. Evidence has been obtained that the Ca2+-dependent ATPase of fish sarcoplasmic reticulum has undergone evolutionary modification for function at different temperatures. Compared with tropical fish, cold adapted species have higher rates of Ca2+ transport and Ca2+-ATPase activities at low temperatures. Most species have linear Arrhenius plots over the temperature range 0–30°C. Activation enthalpies (H
) of the ATPase ranged from 53–190 kJ mol–1 and were positively correlated with environment temperature. Activation entropy (S
) varied from negative values in cold adapted species to positive values in tropical fish.In contrast to the Ca2+-ATPase, the basal ATPase of fish sarcoplasmic reticulum showed no relationship between either ATPase activity or thermodynamic activation parameters and environmental temperature.Only the Ca2+-dependent ATPase is coupled to Ca2+ transport. The percentage of total ATPase activity which is Ca2+ activated is higher at low temperatures in cold than in warm adapted species. For example, ratios of Ca2+-dependent/total ATPase at 2°C varied from 80–98% in Arctic, Antarctic and North Sea species to only 2–50% in various tropical fish. Above 20°C, similar ratios in the range 80–98% were obtained for all species. The nature of the basal ATPase and mechanisms of temperature adaptation of fish sarcoplasmic reticulum are discussed.Abbreviations
ET
environmental temperature
-
EGTA
ethylene glycol-bis (-aminolethyl ether)-N, N-tetraacetic acid
-
HEPES
N-2-hydroxylpiperazine-N-2-ethanesulfonic acid
-
SR
sarcoplasmic reticulum 相似文献