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11.
Field SJ Thornton NP Anderson LJ Gates AJ Reilly A Jepson BJ Richardson DJ George SJ Cheesman MR Butt JN 《Dalton transactions (Cambridge, England : 2003)》2005,(21):3580-3586
Protein film voltammetry of Paracoccus pantotrophus respiratory nitrate reductase (NarGH) and Synechococcus elongatus assimilatory nitrate reductase (NarB) shows that reductive activation of these enzymes may be required before steady state catalysis is observed. For NarGH complementary spectroscopic studies suggest a structural context for the activation. Catalytic protein film voltammetry at a range of temperatures has allowed quantitation of the activation energies for nitrate reduction. For NarGH with an operating potential of ca. 0.05 V the activation energy of ca. 35 kJ mol-1 is over twice that measured for NarB whose operating potential is ca. -0.35 V. 相似文献
12.
To investigate the molecular details of the phosphoryl-transfer mechanism catalyzed by cAMP-dependent protein kinase, we performed quantum mechanical (QM) calculations on a cluster model of the active site and molecular dynamics (MD) simulations of a ternary complex of the protein with Mg(2)ATP and a 20-residue peptide substrate. Overall, our theoretical results confirm the participation of the conserved aspartic acid, Asp(166), as an acid/base catalyst in the reaction mechanism catalyzed by protein kinases. The MD simulation shows that the contact between the nucleophilic serine side chain and the carboxylate group of Asp(166) is short and dynamically stable, whereas the QM study indicates that an Asp(166)-assisted pathway is structurally and energetically feasible and is in agreement with previous experimental results. 相似文献
13.
David A. Field 《Numerische Mathematik》1978,29(3):261-267
Summary A priori truncation error bounds are obtained for continued fractions of the formK(1/b
n),b
n complex. The error bounds are easily applied to the case whenb
n0 asn. A numerical example involving the complex error function is given. 相似文献
14.
Robert Y. Ning George F. Field Leo H. Sternbach 《Journal of heterocyclic chemistry》1970,7(3):475-478
The cyclic nitrones 7-chloro-1,3-dihydro-5-phenyl-2H-1,4-benzodiazepin-2-one 4-oxide ( 5a ) and 1,3-dihydro-7-methylthio-5-phenyl-2H-1,4-benzodiazepin-2-one 4-oxide ( 5b ) are photoisomerized to readily isolable oxaziridines, 7-chloro-4,5-epoxy-5-phenyl-1,3,4–5-tetrahydro-2H-1,4-benzodiazepin-2-one ( 6a ) and 4,5-epoxy-5-phenyl-1,3,4,5-tetrahydro-7-methylthio-2H-1,4-benzo-diazepin-2-one ( 6b ). Oxaziridine 6b upon further irradiation gave ring expansion and ring contraction products, 4,6-dihydro-2-phenyl-9-methylthio-5H-1,3,6-benzoxadiazocin-5-one ( 7b ) and 4-benzoyl-3,4-dihydro-6-methylthioquinoxalin-2(1H)-one ( 8b ) respectively. The ring contraction product, 4-benzoyl-6-chloro-3,4-dihydroquinoxalin-2(1H)-one ( 8a ), was obtained from irradiation of oxaziridine 6a . 相似文献
15.
Richard A. Gottscho J. Brooke Koffend Robert W. Field 《Journal of Molecular Spectroscopy》1980,82(2):310-338
Optical-optical double-resonance (OODR) induced photoluminescence into the lowest excited electronic states of BaO—a3Σ+, A1Σ+, b3Π, and —from C1Σ+ is described. These low-lying states are deperturbed to obtain spectroscopic constants and potential energy curves:
16 596(3) | 16 807.345(10) | 17 502.6(10) | 17 619.7(2) | |
469.0(7) | 499.620(19) | 447.62(8) | 447.95(22) | |
1.48(4) | 1.716(8) | 2.287(12) | 2.139(8) | |
2.14(9) | 1.02(3) | |||
0.2594(5) | 0.2583908(26) | 0.22426(16) | 0.22385(16) | |
1.44(5) | 1.111(3) | 1.18(4) | 1.15(4) | |
7.0(7) | ?4.0(21) | |||
2.1294(20) | 2.133512(11) | 2.2901(8) | 2.2922(8) |