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941.
Bernadó P Akerud T García de la Torre J Akke M Pons M 《Journal of the American Chemical Society》2003,125(4):916-923
We describe a novel method for determining weak association constants of oligomeric protein complexes formed transiently under equilibrium conditions. This type of equilibrium process is recognized as being biologically important, but generally hard to study. Heteronuclear spin relaxation rates measured at multiple protein concentrations are analyzed using relaxation rates predicted from hydrodynamic calculations, yielding equilibrium constants and structural characterization of the protein complexes. The method was used to study the oligomerization equilibrium of bovine low molecular weight protein tyrosine phosphatase. X-ray structures of monomeric and dimeric forms of the protein have been reported previously. Using longitudinal and transverse (15)N relaxation rates measured at four different protein concentrations, we detected the monomer, dimer, and a previously unknown tetramer and measured the dissociation constants of the equilibria involving these species. A comparison of experimental and predicted relaxation rates for individual backbone amide (15)N spins enabled delineation of the tetramerization interface. The results suggest a novel concept for substrate modulation of enzymatic activity based on a "supramolecular proenzyme". The fast and reversible switching of the "supramolecular proenzyme" would have obvious advantages for the regulation of enzymes involved in cell signaling pathways. 相似文献
942.
1 INTRODUCTION As is well known, some transition metal ions play an important role in controlling the behavior of many biological macromolecules and produce pro- found effects on their biological actions, medicine and people’s health[1~3]. Zinc is an essential com- ponent of many proteins. In the active sites of zinc enzymes, zinc is bound to the nitrogen of imidazole groups and oxygen of carboxylate groups of amino acids[4~6]. Additional interest in these proteins lies in the fact th… 相似文献
943.
de la Escosura-Muñiz A González-García MB Costa-García A 《Analytical and bioanalytical chemistry》2006,384(3):742-750
A new electroactive label has been used to monitor immunoassays in the determination of human serum albumin (HSA) using glassy-carbon
electrodes as supports for the immunological reactions. The label was a gold(I) complex, sodium aurothiomalate, which was
bound to rabbit IgG anti-human serum albumin (anti-HSA-Au). The HSA was adsorbed on the electrode surface and the immunological
reaction with gold-labelled anti-HSA was then performed for one hour by non-competitive or competitive procedures. The gold(I)
bound to the anti-HSA was electrodeposited in 0.1 mol L−1 HCl at −1.00 V for 5 min then oxidised in 0.1 mol L−1 H2SO4 solution at +1.40 V for 1 min. Silver electrodeposition at −0.14 V for 1 min followed by anodic stripping voltammetry were
then performed in aqueous 1.0 mol L−1 NH3–2.0×10−4 mol L−1 AgNO3. For both non-competitive and competitive formats, calibration plots in the ranges 5.0×10−10 to 1.0×10−8 mol L−1 and 1.0×10−10 to 1.0×10−9 mol L−1 HSA, respectively, with estimated detection limits of 1.5×10−10 mol L−1 (10 ng mL−1) and 1.0×10−10 mol L−1 (7 ng mL−1), respectively, were obtained. Levels of HSA in two healthy volunteer urine samples were also evaluated, using both immunoassay
formats. 相似文献
944.
Fanjul-Bolado P González-García MB Costa-García A 《Analytical and bioanalytical chemistry》2006,385(7):1202-1208
p-Nitrophenyl phosphate is one of the most widely used substrates for alkaline phosphatase in ELISAs because its yellow, water-soluble
product, p-nitrophenol, absorbs strongly at 405 nm. p-Nitrophenol is also electroactive; an oxidative peak at 0.97 V (vs. an Ag pseudoreference electrode) is obtained when a bare
screen-printed carbon electrode is used. When an amperometric detector was coupled to a flow-injection analysis system the
detection limit achieved for p-nitrophenol was 2×10−8 mol L−1, almost two orders of magnitude lower than that obtained by measuring the absorbance of the compound. By use of this electrochemical
detection method, measurement of 7×10−14 mol L−1 alkaline phosphatase was achieved after incubation for 20 min. The feasibility of coupling immunoassay to screen-printed
carbon electrode amperometric detection has been demonstrated by performing an ELISA for detection of pneumolysin, a toxin
produced by Streptococcus pneumoniae, which causes respiratory infections. The method is simple, reproducible, and much more sensitive than traditional spectrophotometry. 相似文献
945.
946.
ZHAO Zhen-Qiana b LIU Xia CHEN Wen-Tonga LI Yana WU A-Qinga ZENG Hui-Yia GUO Guo-Conga② HUANG Jin-Shuna a 《结构化学》2006,25(2):159-162
1 INTRODUCTION The alkali metal chalcogenide halides have at- tracted considerable interests since last decades due to their abundant interesting structures and good properties with potential applications[1~8]. The type of M3QX (M = alkali metal, Q = chalcogenide; X = halide) compounds has been well studied. The known structure types of these compounds are only ternary alkali metal oxide halides and can be classified as the following species: 1) cubic anti-perovskite type, such as K3O… 相似文献
947.
1 INTRODUCTION 5-Fluorouracil (5-FU) is an antimetabolite with good antimicrobial and antitumor activities but has toxic side effects[1~4]. In order to improve the topical delivery of 5-FU and reduce the side effects, many derivatives of 5-FU have been synthesized, some of which are of improved activity. 5-Fluorou- racil-1-acetic acid is a member of the family[5~8], which belongs to the pyrimidine base and is a cyto-toxic analogue of the natural base thymine, and has proven useful in th… 相似文献
948.
1 INTRODUCTION Isoquinoline and its derivatives have attracted much attention due to their physiological and phar- macological activities including antibacterial, antitu- mor, etc[1~3]. A lot of investigations in this field have been focused on the syntheses and applications in physiology and pharmacy of isoquinoline and its derivatives[4, 5]. Recently, a novel class of 1-subs- tituted isoquinolines or triazoloquinazolines deriva- tives have been identified as potential antagonists for the… 相似文献
949.
1 INTRODUCTION Due to their variability in binding modes, five- membered heterocyclic ligands such as pyrazole[1] and 1,2,4-triazole[2] have been drawn much attention. Consequently, there are numerous reports on their derivatives. Imidazoles resemble pyrazoles, and they are isomeric five-membered heterocyclic molecules containing two nitrogen atoms. Furthermore, imida- zole is also a ring component of adenine and purine, one of the most versatile binding sites in biological systems, so th… 相似文献
950.
YANG Honga ZHANG Zhi-Huia① GUO Jian-Huab LU Yan-Chuna a 《结构化学》2006,25(6):689-693
1 INTRODUCTIONThe design and synthesis of metal-organic coor- dinated polymer have attracted considerable atten- tion in recent years. The infinite networks construc- ted from transition metal complexes have intere- sting structures as well as potential applications as smart electronic, magnetic porous materials, cataly- sis, host-guest chemistry, and so on[1~4]. In the as- sembly and synthesis of polymer structures, the me- tal ions, bi- or multi-dentate ligand, solvent and the ratio of … 相似文献