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91.
The crystal structure of the title compound,C21H25N7O7,has been determined in the orthorhombic space group C222(1) with a=8.993(10),b=12.149(14),c=22.20(2) and Z=4.There exist intramolecular C-H…O and N-H…N hydrogen bonds in the title crystal structure.The intermolecular N-H…N and C-H…O hydrogen bonds together with π-π stacking interactions(face-to-face) link the molecules into an infinite three-dimensional supramolecular network. 相似文献
92.
93.
V. Sridhar D. Sudarshan Reddy N. Ravikumar Reddy S. Satyanarayana 《Journal of Chemical Sciences》2002,114(1):11-23
Equilibria and kinetics of the reaction of bromomethyl(aquo) cobaloxime with histamine, histidine, glycine and ethyl glycine
ester and iodomethyl(aquo) cobaloxime with cyanide, imidazole and substituted imidazoles were studied as a function ofpH at 25°C, 10 M ionic strength (KCl) by spectrophotometry technique. The rate of substitution of H2O varies with thepKa of the incoming ligand, thus establishing the existence of nucleophilic participation of the ligand in the transition state.
Dissociation kinetic reactions were also studied as a function ofpH. Binding and kinetic data were interpreted based on the basicity, steric crowd of the entering ligand and HSAB principle.
To compare the rate constants of the entering ligandspH independent second-order rate constants were calculated. 相似文献
94.
Danuta Witkowska Rossella Politano Dr. Magdalena Rowinska‐Zyrek Prof. Remo Guerrini Prof. Maurizio Remelli Prof. Henryk Kozlowski 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(35):11088-11099
Hpn, one of Helicobacter pylori′s nickel‐accessory proteins, is an amazingly peculiar protein: Almost half of its sequence consists of polyhistidyl (poly‐His) residues. Herein, we try to understand the origin of this naturally occurring sequence, thereby shedding some light on the bioinorganic chemistry of Hpn′s numerous poly‐His repeats. By using potentiometric, mass spectrometric, and various spectroscopic techniques, we studied the NiII‐ and CuII complexes of the wild‐type Ac‐THHHHYHGG‐NH2 fragment of Hpn and of its six analogues, in which consecutive residues (His or Tyr) were replaced by Ala (Ala‐substitution or Ala‐scan approaches), thereby resulting in Ac‐TAHHHYHGG‐NH2, Ac‐THAHHYHGG‐NH2, Ac‐THHAHYHGG‐NH2, Ac‐THHHAYHGG‐NH2, Ac‐THHHHAHGG‐NH2, and Ac‐THHHHYAGG‐NH2 peptides. We found that the His4 residue is critical for both NiII‐ and CuII‐ion binding and the effectiveness of binding varies even if the substituted amino acid does not take part in the direct binding interactions. 相似文献
95.
Cristina Gellini Giuseppina Sabatino Anna Maria Papini Maurizio Muniz‐Miranda 《Journal of Raman spectroscopy : JRS》2014,45(6):418-423
Surface‐enhanced Raman scattering has been employed to characterize the adsorption of an oligopeptide containing histidine residues on colloidal nanoparticles of metals as Ag and Cu obtained by laser ablation. The title molecule consists of two histidine and glycine residues alternating along the chain and terminating with an acetyl on one side and an amide group on the other. Histidine residues are found to act as docking sites of the molecule to the surface of the metal nanoparticles. Semiempirical parameterized model number 3 (PM3) calculations performed on molecule/metal model complexes suggest possible different adsorption geometries depending on the metallic substrate. This investigation could provide useful information to address the interaction of protein systems with metal ions, which is often related to fundamental biological process in living systems and can play an important role in different neuropathological diseases. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
96.
Guo Wei Fandian Meng Yuxiang Wang Yixiang Cheng Chengjian Zhu 《Macromolecular rapid communications》2014,35(24):2077-2081
A novel achiral polymer P‐1 is synthesized by the polymerization of (2,5‐bis(octyloxy)‐1,4‐phenylene)diboronic acid ( M‐1 ) with pyridine‐2,6‐diylbis(methanylylidene)bis(4‐iodoaniline) ( M‐2 ) via Pd‐catalyzed Suzuki coupling reaction. The tridentate ligand in the main chain backbone can further coordinate with Cu2+ to afford the corresponding achiral copper‐containing polymer complex P‐2 , which selectively responds to L‐/D‐histidine with significant fluorescence enhancement over other amino acids. Interestingly, P‐2 exhibits obvious CD response toward L‐ or D‐histidine compared with its model compound MC , indicating that this kind Cu(II)‐containing polymer complex sensor can be used as an effective chemosensor for enantioselective recognition of histidine enantiomers by means of CD spectroscopy.
97.
《光谱学快报》2013,46(4-5):617-634
Abstract The complex formation between l‐histidine (HHis) and aluminum(III) ion in water solutions was studied by UV spectrophotometric and 27‐Al NMR measurements at 298 K. UV spectra were measured on solutions in which the total concentration of histidine was from 15.0 to 50.0 mmol/dm3 and the concentration ratio of histidine to aluminum was varied from 3∶1 to 10∶1 in the pH range between 4.2 and 6.0. The spectra were taken in the wavelength interval 240–340 nm. Nonlinear least‐squares treatment of the spectrophotometric data indicates the formation of the complexes Al(HHis)3+, Al(His)2+, Al(HHis)His2+, and Al2(OH)His4+ with the overall formation constants βp,q,r: log β1,1,1=11.90±0.04, log β1,1,0=7.25±0.08, log β1,2,1=20.1±0.1, and log β2,1,1=5.92±0.12 (p, q, r are stoichiometric indices for metal, ligand, and proton, respectively). 27Al‐NMR spectra were taken on solutions with the concentration of aluminum 50 mmol/dm3 and that of histidine 250 mmol/dm3. In the pH interval 5.0–6.1, two resonances at 9.5 ppm and 12.0 ppm were assigned to Al(HHis)2+ and Al(HHis)(His)2+ (or Al(OH)(HHis)2 2+), respectively. 相似文献
98.
The histidine-rich peptide H5WYG (GLFHAIAHFIHGGWHGLIHGWYG) was found to induce membrane fusion at physiologic pH in the presence of zinc chloride. In this study, we examined the ion selectivity of the interaction of Zn(2+) with H5WYG. This investigation was conducted by using adsorption at air/water interface and mass spectrometry. We found that a peptide-metal complex is formed with Zn(2+) ions. Electrospray ionisation-mass spectrometry (ESI-MS) reveals that the [H5WYG + Zn + 2H](4+), [H5WYG + Zn + H](3+) and [H5WYG + Zn](2+) ions, appearing by increasing the amount of Zn(2+) equivalent, correspond to a monomolecular H5WYG - Zn(2+) complex. Tandem mass spectrometry (MS/MS) provides evidence for the binding of the single Zn(2+) ion to the H(11) and H(19) and probably H(15) residues. 相似文献
99.
Histidine‐containing peptides are valuable therapeutic agents for a treatment of neurodegenerative diseases. However, the synthesis of histidine‐containing peptides is not trivial due to the potential of imidazole sidechain of histidine to act as a nucleophile if unprotected. A peptide ligation method utilizing the imidazole sidechain of histidine has been developed. The key imidazolate intermediate that acts as an internal acyl transfer catalyst during ligation is generated by deprotonation. Transesterification with amino acids or peptides tethered with C‐terminal thioester followed by N→N acyl shifts led to the final ligated products. A range of histidine‐containing dipeptides could be synthesized in moderate to good yields via this method without protecting the imidazole sidechain. The protocol was further extended to tripeptide synthesis via a long‐range N→N acyl transfer, and tetrapeptide synthesis. 相似文献
100.
建立了同时测定大鼠毛发中胱氨酸、酪氨酸和组氨酸的高效液相色谱(HPLC)检测方法。优化了色谱分离及检测条件,样品经酸解后进样分析。采用Titank C18色谱柱(4. 6 mm×250 mm,5μm),以10 mmol/L磷酸氢二铵缓冲液(含10 mmol/L 1-辛烷磺酸钠,用磷酸调至p H 2. 0)-乙腈为流动相,进行梯度洗脱,流速1. 0 m L/min,检测波长205 nm,进样体积为100μL,柱温为8℃。结果表明,在优化条件下,大鼠毛发中的胱氨酸、酪氨酸和组氨酸能实现有效分离。3种氨基酸的线性良好,相关系数(r)均大于0. 999;检出限(S/N=3)为49~442μg/L;定量下限(S/N=10)为148~884μg/L;样品的平均加标回收率为97. 8%~102%,相对标准偏差(RSD)为0. 1%~1. 6%。该方法操作简便、准确可靠、重现性好,可用于大鼠毛发中胱氨酸、酪氨酸和组氨酸的检测。 相似文献