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51.
As the relation of chirality and activities of drugs is researched deeply, people become to re-alize the clinic importance of chirality. The different enantiomers of a drug can have vastly differ-ent pharmacological activities, pharmacokinetic processes and toxicity[1,2]. The most well-docu- mented example is that of the drug substance thalidomide. Bitter lessons and scientific research promote the interest in single-enantiomer drugs, so the potential of the chiral drug market is enormous[3]. … 相似文献
52.
Rainer Telle Ai Momozawa Jochen M. Schneider 《Journal of solid state chemistry》2006,179(9):2850-2857
MAX-phases being usually composed of transition metals, group A elements and carbon/nitrogen are considered interesting materials for many applications because of their tremendous bulk modulus, “reversible” plasticity, and machinability. This is mainly due to their unique kind of bonding comprising covalent, ionic as well as metallic bonds providing “easy” planes of rupture and deformability due to the layered crystal structures.In transition metal boride systems, similar types of bonding are available. In particular the W2B5-structure type and its stacking variations allow the synthesis of strongly layered crystal structures exhibiting unique delamination phenomena.The paper presents ab initio calculations showing the similarities of bonding between the ternary carbides and the corresponding ternary or quaternary borides. Formation of boride-based nano-laminates from auxiliary liquid phases, from the melt as well as during sintering and precipitation from supersaturated solid solutions will be discussed by means of SEM and TEM studies. The role of impurities weakening the interlayer bonding will be addressed in particular. The pronounced cleavage parallel to the basal plane gives rise for crack deflection and pull-out mechanisms if the laminates are dispersed in brittle matrices such as boron carbide, silicon carbide or other transition metal borides. 相似文献
53.
Yoshimura T Chen ZN Itasaka A Abe M Sasaki Y Ishizaka S Kitamura N Yarovoi SS Solodovnikov SF Fedorov VE 《Inorganic chemistry》2003,42(16):4857-4863
Hexarhenium(III) complexes with terminal isothiocyanate ligands, [(n-C(4)H(9))(4)N](4)[Re(6)(mu(3)-S)(8)(NCS)(6)] (1) and (L)(4)[Re(6)(mu(3)-Se)(8)(NCS)(6)] (L(+) = PPN(+) (2a), (n-C(4)H(9))(4)N(+) (2b)), have been prepared by three different methods. Complex 1 was prepared by the reaction of [(n-C(4)H(9))(4)N](4)[Re(6)(mu(3)-S)(8)Cl(6)] with molten KSCN at 200 degrees C, while 2b was obtained by refluxing the chlorobenzene-DMF (2:1 v/v) solution of [Re(6)(mu(3)-Se)(8)(CH(3)CN)(6)](SbF(6))(2) and [(n-C(4)H(9))(4)N]SCN. The [Re(6)(mu(3)-Se)(8)(NCS)(6)](4)(-) anion was also obtained from a mixture of Cs(2)[Re(6)(mu(3)-Se)(8)Br(4)] and KSCN in C(2)H(5)OH by a mechanochemical activation at room temperature for 20 h and isolated as 2a. The X-ray structures of 1 and 2a.4DMF have been determined (1, C(70)H(144)N(10)S(14)Re(6), monoclinic, space group P2(1)/n (No. 14), a = 14.464(7) A, b = 22.059(6) A, c = 16.642(8) A, beta = 113.62(3) degrees, V = 4864(3) A(3), Z = 2; 2a.4DMF, C(162)H(144)N(14)O(4)P(8)S(6)Se(8)Re(6), triclinic, space group P1 (No. 2), a = 15.263(2) A, b = 16.429(2) A, c = 17.111(3) A, alpha = 84.07(1) degrees, beta = 84.95(1) degrees, gamma = 74.21(1) degrees, V = 4098.3(8) A(3), Z = 1). All the NCS(-) ligands in both complexes are coordinated to the metal center via nitrogen site with the Re-N distances in the range of 2.07-2.13 A. The redox potentials of the reversible Re(III)(6)/Re(III)(5)Re(IV) process in acetonitrile are +0.84 and +0.70 V vs. Ag/AgCl for [Re(6)(mu(3)-S)(8)(NCS)(6)](4)(-) and [Re(6)(mu(3)-Se)(8)(NCS)(6)](4)(-), respectively, which are the most positive among the known hexarhenium complexes with six terminal anionic ligands. The complexes show strong red luminescence with the emission maxima (lambda(max)/nm), lifetimes (tau(em)/micros), and quantum yields (phi(em)) being 745 and 715, 10.4 and 11.8, and 0.091 and 0.15 for 1 and 2b, respectively, in acetonitrile. The data reasonably well fit in the energy-gap plots of other hexarhenium(III) complexes. The temperature dependence of the emission spectra and tau(em) of 1 and [(n-C(4)H(9))(4)N](4)[Re(6)(mu(3)-S)(8)Cl(6)] are also reported. 相似文献
54.
55.
Metal-ion-assisted hydrolysis of dipeptides involving a serine residue in a neutral aqueous solution
Yashiro M Sonobe Y Yamamura A Takarada T Komiyama M Fujii Y 《Organic & biomolecular chemistry》2003,1(4):629-632
Dipeptides having a serine residue at the C-terminus, X-Ser, where X is an appropriate amino acid residue, were efficiently hydrolyzed in the presence of ZnCl2 at pH 7.0. The rapid hydrolysis of X-Ser is due to an autocatalysis of the hydroxy group in the serine residue, and is found to be accelerated by a metal ion, in particular by ZnCl2. Roles of the metal ion in the hydrolysis of peptides involving a serine residue, in relation to the recently reported protein cleavages, are discussed. 相似文献
56.
Nguyen Ai Viet 《Czechoslovak Journal of Physics》1981,31(3):269-274
In this paper the analytical expression is derived for the third-order optical harmonic coefficients x
abcd
v
(,,) of the atomic hydrogen at very low frequencies 0 in many level of the discrete energy spectrum.The author expresses his thank to Prof. Nguyen Van Hieu for suggesting the problem and fruitful discussions. 相似文献
57.
Stephen G. Davies Ai M. Fletcher Linlu Lv Paul M. Roberts James E. Thomson 《Tetrahedron: Asymmetry》2012,23(11-12):910-925
The conjugate addition of lithium (R)-N-benzyl-N-(α-methylbenzyl)amide to a range of β-fluoroaryl-α,β-unsaturated esters gave the corresponding β-amino esters with high diastereoselectivity and in good isolated yields. Sequential treatment of the resultant β-fluoroaryl-β-amino esters under optimised hydrogenolysis conditions, followed by ester hydrolysis with 2.0 M aq HCl, provided access to a range of β-fluoroaryl-β-amino acids in good yield. 相似文献
58.
Tzu‐Chuan Huang Shih‐Ming Chen Yi‐Chieh Li Jen‐Ai Lee 《Biomedical chromatography : BMC》2013,27(9):1100-1106
Urinary d ‐lactate is highly correlated to diabetic nephropathy – a progressive kidney disease in renal glomeruli. In this study, we used a C3H/3e mouse model to investigate the relationship between urinary d ‐lactate and aristolochic acid nephropathy where the glomerular structure is not affected. The nephropathy was induced using intravenous injections of aristolochic acid at a dosage of 10 mg/kg per day for 5 days and was characterized biochemically and histologically. The urinary excretions of proteins, N‐acetyl‐β‐d ‐glucosaminidase and serum creatinine were determined and connected to histological conventional findings. Urinary d ‐lactate was analyzed using column‐switching high‐performance liquid chromatography with fluorescence detection. The results showed a remarkable increase of urinary markers, including of urinary proteins and N‐acetyl‐β‐d ‐glucosaminidase, and the histological examination confirmed a diagnosis of acute tubule necrosis. The ratio of d ‐lactate to creatinine in the urine of aristolochic acid‐treated mice was approximately 36 times greater than that of the mice in the control group (p < 0.05). The ratios for the two groups of mice were 311.00 ± 71.70 and 8.60 ± 1.80 µmol/mmol creatinine, respectively. These data confirm in vivo that urinary d ‐lactate reflects renal injury conditions in aristolochic acid‐treated mice and may be a marker for the assessment of nephropathy. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
59.
Guomin Ai Jinxing Zhu Xiuzhu Dong Tong Sun 《Rapid communications in mass spectrometry : RCM》2013,27(17):1935-1944
60.