The influence of small monovalent metal ions on hydrogen bonds of aquo-protein complexes is studied on Li/HCONH2-OH2 as an example. Using results obtained from ab initio calculations with minimal GLO basis sets, the remarkable changes in the hydrogen bond energy and charge distribution, due to metal ion complex formation, are discussed. The metal ion seems to enhance strongly the donor-acceptor...

The acidity constants of some amino acids (Am) were determined by potentiometric pH titration. The stability constants of the 1:1 complexes formed between M2+: Ca2+, Mg2+, Mn2+, Co2+, Ni2+, Cu2+ or Zn2+ and Am2-, were determined by potentiometric pH titration in aqueous solution (I = 0.1 M, NaNO3, 25°C). The order of the stability constants was reported. It is shown that the stability of the bi...

The use of substrate analogues as inhibitors provides a way to understand and manipulate enzyme function. Here we report two 1 A resolution crystal structures of liver alcohol dehydrogenase in complex with NADH and two inhibitors: dimethyl sulfoxide and isobutyramide. Both structures present a dynamic state of inhibition. In the dimethyl sulfoxide complex structure, the inhibitor is caught in t...

Five rare earth complexeslanthanum(III),praseodymium(III),neodymium(III), samarium(III) and europium(III) have been synthesized from Schiff base ligand (N,N-bis (2-hydroxy-1-naphthylidene) acetylhydrazone). The complexes were characterized based on elemental analysis, molar conductance, ultraviolet, infrared, mass, thermogravimetric and powder X-ray diffraction studies. Infrared spectra sug...

A conductance study of the interaction between Cs+, Rb+, NH4+, K+, T1+ and Ag+ ions and18-crown-6 (18C6), benzo-18-crown-6 (B18C6), dicyclohexyl-18-crown-6 (DC18C6),dicyclohexyl-24-crown-8 (DC24C8), dibenzo-24-crown-8 (DB24C8) in different binarymixtures of acetonitrile (AN) with dimethylsulfoxide (DMSO) and dimethylformamide (DMF)at 25 °C has been carried out. Formation constants of the result...

The catalytic reaction mediated by DNA polymerases is known to require two Mg(II) ions, one associated with dNTP binding and the other involved in metal ion catalysis of the chemical step. Here we report a functional intermediate structure of a DNA polymerase with only one metal ion bound, the DNA polymerase beta-DNA template-primer-chromium(III).2'-deoxythymidine 5'-beta,gamma-methylenetriphos...

The hammerhead ribozyme is generally accepted as a well characterized metalloenzyme. However, the precise nature of the interactions of the RNA with metal ions remains to be fully defined. Examination of metal ion-catalyzed hammerhead reactions at limited concentrations of metal ions is useful for evaluation of the role of metal ions, as demonstrated in this study. At concentrations of Mn2+ ion...

in this study a sensitive, simple and accurate spectrophotometric method was suggested for determination of tamsulosin in bulk powder and pharmaceutical dosage form based on the formation of an ion-pair complex between the drug and bromocresol green in a buffer solution at ph 3.5. the formed yellow color complex was extracted with chloroform and measured at 415 nm. the optimum reaction conditio...

H-N-H is a motif found in the nuclease domain of a subfamily of bacteria toxins, including colicin E7, that are capable of cleaving DNA nonspecifically. This H-N-H motif has also been identified in a subfamily of homing endonucleases, which cleave DNA site specifically. To better understand the role of metal ions in the H-N-H motif during DNA hydrolysis, we crystallized the nuclease domain of c...