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61.
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63.
Host 1 was designed and synthesized as a fluorescent sensor for 2,3-bisphosphoglycerate (BPG, 3). The design features a tris-functionalized triethylbenzene core to preorganize binding groups. The three cationic moieties, a tetra-N-oxide bipyridine-europium complex and two ammonium groups, were included to complement the three anionic functionalities on the guest. Beyond acting as a binding site, the europium complex was used to signal binding of the guest through modification of the charge transfer emission. A 1:1 complex with BPG was determined in 50 % methanol/acetonitrile with a K(a) of 6.7 x 10(5) mol(-1) by monitoring the reduction of the fluorescence signal upon guest addition. In the titration of related glycolytic intermediates lacking a second phosphate (4-6) into host 1, 2:1 host to guest binding was observed. Similarly, control compound 2, which lacks the ammonium groups, binds BPG and 4-6 in a 2:1 fashion. Also, phenylphosphate 7 binds to host 1 in a 1:1 stoichiometry with a K(a) over three times less than 3. 相似文献
64.
To study the importance of charge–charge and cation-π interactions for the binding of positively charged amine ligands to
their receptors, the energies of interaction between [(CH3)4–N]+, [(CH3)3–NH]+, and [(CH3)4–NH3]+ and acetate, as a model of Asp and Glu, and with benzene, as a model of aromatic side chains, were obtained at the MP2/aug-cc-pVDZ
level of theory. The free energies of solvation in water were also calculated for the different amines. It was found that,
although primary amines form stronger charge–charge interactions with acetate than tertiary or quaternary amines, the difference
is not large enough to compensate their higher solvation energy. Quaternary amines show the weakest interaction with acetate.
However, their alkyl groups can interact with various aromatic groups, enhancing ligand binding to the receptor. The analysis
was completed with MD calculations on amine binding to the G protein-coupled receptors β2AR and CCR5. The calculations on the model systems were found to be in good agreement with the simulations of the ligand-receptor
complexes.
Contribution to the Serafin Fraga Memorial Issue. 相似文献
65.
A facile seven-step sequence was developed from 4′-bromopropiophenone, utilizing a Suzuki-type coupling with an alkene, to give several novel 5-substituted pyrazole derivatives in overall yields of 11-31%. They are potent CB1 antagonists and have binding affinities similar to SR 141716A. Like SR 141716A, they may prove to be clinically useful for the treatment of obesity. 相似文献
66.
Neonatal exposure to synthetic estrogen endocrine disruptors or estrogen-receptor inhibitors induces developmental abnormalities in the male reproductive system. To investigate whether neonatal exposure affects spermatogenesis in juvenile and pubertal testis, Sprague-Dawley rat pups were given synthetic estrogen endocrine disruptors or estrogen-receptor inhibitors by a single injection on the day of birth at concentrations ranging between 2 to 40 mm, and sacrificed on day 21 (juvenile), 35 (prepuberty) or 50 (puberty). The testes were weighed and examined histologically at each stage. Further, the metabolites of steroidogenesis were analyzed using normal-phase high performance liquid chromatography. Neonatal exposure significantly reduced testis weights and steroidogenesis to one- fifth to one-half of that of the juvenile control, and further suppressed irreversible steroidogenesis and spermatogenesis during puberty. 相似文献
67.
Frontera A Saczewski F Gdaniec M Dziemidowicz-Borys E Kurland A Deyà PM Quiñonero D Garau C 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(22):6560-6567
Several structures of pi complexes of isocyanuric acid and of several thio derivatives with anions have been computed by using high level ab initio calculations. The nature of the complexes has been studied by means of the method of molecular interaction potential with polarization (MIPp) and Bader's theory of atoms-in-molecules. These molecules form favorable complexes with anions and can be used as binding units for building receptors for the molecular recognition of anions. In several cases, the anion-pi interaction has been demonstrated experimentally by means of X-ray crystallography. 相似文献
68.
D. L. Lipilin A. M. Churakov Yu. A. Strelenko V. A. Tartakovsky 《Russian Chemical Bulletin》2007,56(8):1566-1568
Treatment of 2-(tert-butyl-NNO-azoxy)anilines with phosgene at 20 °C was proposed as a novel route to 1,2,4-benzotriazin-3(4H )-one 1-oxides. This method involves a new reaction, viz., an intramolecular interaction of the tert-butyl-NNO-azoxy group with a C-electrophile (leading to the formation of the N(2)—C(3) bond of the triazine ring) followed by elimination
of the tert-butyl group. Complete assignment of the signals in the 1H and 13C NMR spectra of the compounds obtained was performed.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1507–1509, August, 2007. 相似文献
69.
Multigram quantities (2.5-10 g) of highly purified IgG were obtained within 4 h from serum by using Avid AL packed in a radial-flow column. Avid AL is an affinity gel containing a synthetic, low-mol-wt ligand capable of selectively binding IgG from serum of all animal species tested. By packing the gel in a radial-flow column up to 500 mL, a high flow rate of 50 mL/min can be achieved without adversely affecting the performance of the gel and the purity of the isolated antibody. 相似文献
70.
Total internal reflection fluorescence (TIRF) microscopy is used to measure the dissociation kinetic rate of fluorescein-labeled epidermal growth factor from its specific receptors on the surface of intact but mildly fixed A431 human epidermoid cells in culture. Prior applications of TIRF microscopy have been limited to nonreceptor binding or to model membrane systems. The evanescent field excites fluorescence selectively at the surface of the cell proximal to the coverslip. Prismless epiillumination TIR is employed to avoid space limitations and is achieved by passing the excitation laser beam through a high (1.4)-aperture objective so that the light is incident at the glass/water interface beyond the critical angle. Long-term focus is maintained by a special feedback system. Of the possible effects that can influence the time course of the postbleach fluorescence recoveries—the EGF/receptor dissociation ratek
2, the bulk solution diffusion rate of EGF, and the cell surface motion of the receptors—we infer that the dissociation ratek
2 dominates. Several fitting schemes are compared and indicate the presence of a multiplicity of values fork
2, ranging from about 0.05 to 0.004 s–1, with an average value of about 0.012 s–1. These results compare well with values previously obtained by radiolabel/washing techniques. The significance of the results in terms of kinetic models and the advantages of the TIRF technique for these sorts of measurements are discussed. 相似文献