Complexes of thallium(I) and cadmium(II) with dipeptides of L-phenylalanylglycine and Glycyl-L-phenylalanine

Abstract

As constantes de estabilidade dos complexos de íons tálio(I) e cádmio(II) com dipeptídeos de glicil-L-fenilalanina e L-fenilalanilglicina foram determinadas em solução aquosa a 25 °C e meio iônico 0,1 mol dm -3 usando uma combinação de técnicas potenciométricas e espectrofotométricas. Perclorato de sódio foi usado para manter a força iônica. A composição dos complexos formados foi determinada e observou-se que tálio (I) The stability constants of the complexes of thallium(I) and cadmium(II) ions with dipeptides of glycyl-L-phenylalanine and L-phenylalanylglycine were determined in aqueous solution at 25 °C and 0.1 mol dm -3 ionic medium using a combination of potentiometric and spectrophotometric techniques. Sodium perchlorate was used to maintain the ionic strength. The composition of the formed complexes was determined and it was shown that thallium(I) and cadmium (

Calculation of acidic dissociation constants of glycylglycine in water at different temperatures using ab initio methods

“…The acidic dissociation constants of glycylglycine have been determined using potentiometric technique. The method of determining acidic dissociation constant was previously described [2,10] and its values are used in this work. These values are compared together with the calculated values using the Tomasi's method at the B3LYP/6-31+G(d) level of theory.…”

“…This mesomeric effect can be expressed as a resonance between two canonical forms [1]. Different experimental procedures were frequently used for the determination of acidity constants [2][3][4][5][6][7][8][9][10], but during the last two decades there has been much interest in developing a methodology enabling theoretical prediction of pK a values, using various quantum theoretical techniques. As pK a equals DG/2.303 RT, where DG is a free energy change of the dissociation reaction either in a gas or solution, acidity of a compound can be determined by the DG value [11][12][13].…”

Determination of acidic dissociation constants of L-phenylalanyl-glycine and L-alanyl-L-alanine in water using ab initio methods

“…The data show that the water, exerting its hydrogen-bond-donor (HBD) capability, forms IHBs with the L-phenylalanyl-glycine and L-alanyl-L-alanine anions. These hydrogen bonds have been classified as strong, moderate and weak bonds, according to their lengths, angles and energies [61].…”

The Theoretical Calculations and Experimental Measurements of Acid Dissociation Constant and Thermodynamic Properties of Glycyl-Aspartic Acid in Aqueous Solution at Different Temperatures

“…The pKa is used for determining solubility and permeability of solutions in the environmental and pharmaceutical fields [7][8][9]. There are various experimental techniques to measure acidic dissociation constant such as HPLC, potentiometer, and spectrophotometry [10][11][12][13][14]. To determine the physiochemical properties of a substance, first it must be solved in a solvent.…”