Thermochemical study of processes of complex formation of Cu2+ ions with L-glutamine in aqueous solutions

Gorboletova, G. G.; Gridchin, S. N.; Lutsenko, A. A.

doi:10.1134/s0036024410110063

Cited by 6 publications

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“…In the interaction of aqua complexes of copper(II) with Asn -ion in the complex far less extensive destruction of hydration shells of the reacting species occurs than in the interaction of Cu 2+ ions with Glu -and Val -. The magnitude of the change in entropy in the case of complex formation CuAsn + [Δ r S 0 (CuAsn + ) 66.7 J mol -1 K -1 ] is less than Δ r S 0 (CuGlu + ) 86.0 J mol -1 K -1 [9] and Δ r S 0 (CuVal + ) 88.1 J mol -1 K -1 [10], which confirms the validity of the above assumptions. The endothermic contribution of the desolvation to the heat effect at the formation of asparaginate copper(II) complex is smaller than at the formation of glutaminate and valinate complexes.…”

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confidence: 83%

“…Evidently in the case of the formation of this complex the coordination of water molecules in the inner coordination sphere of the metal is impeded by the growing concentration of KNO 3 . A similar effect of potassium nitrate was noted in the study of the Cu 2+ complexing with L-glutamine and L-valine [9,10].…”

supporting

confidence: 59%

“…The standard heat effect of formation of monocoordinated asparaginate copper(II) complex corresponds to the greater exothermicity [Δ r H 0 (CuL + ) = -27450 J mol -1 ] than in the formation of glutamine, Δ r H 0 (CuGlu + ) = -21110 J mol -1 [9], and valine, Δ r H 0 (CuVal + ) = -22 350 J mol -1 [10] complexes, because the side chain of L-asparagine is more hydrophilic than the side chain of L-glutamine and L-valine. In the interaction of aqua complexes of copper(II) with Asn -ion in the complex far less extensive destruction of hydration shells of the reacting species occurs than in the interaction of Cu 2+ ions with Glu -and Val -.…”

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Effect of background electrolyte concentration on the heat effects in the processes of formation of L-asparagine complexes with Cu2+ ions in aqueous solution

2012

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A direct calorimetric method was used to measure the heat effects in the reactions of formation of Cu(II) complexes with L-asparagine in aqueous solutions at 298.15 K and ionic strength 0.5, 1.0, 1.5 (KNO 3 ). The standard thermodynamic characteristics (Δ r H 0 , Δ r G 0 , Δ r S 0 ) of the processes of complex formation in the system under study were calculated.Numerous publications concern the determination of the constants of reactions of the copper(II) asparaginate complexes in aqueous solution. We recalculated the stability constants of CuL + and CuL 2 , which were obtained by the different researchers in a variety of concentration conditions, to zero ionic strength according to Davis equation [1]. The most probable values of the thermodynamic stability constants of complexes of L-asparagine (L -) with the ion Cu 2+ were calculated as the mean values of those published in [2-5]: log β 0 (CuL + ) = 8.29 ± 0.01, log β 0 (CuL 2 ) = 15.09 ± 0.05. The recalculation of the constants to fixed values of ionic strength (I) was performed according to the equation proposed in [6]. Table 1 shows the thermodynamic characteristics of the formation of asparaginate Cu(II) complexes obtained by different researchers. It follows from Table 1 that the published data on the heat of complex formation in the system Cu 2+ -L-asparagine are contradictory. The difference in the determined heat effects of the CuL 2 species amounts to 14 kJ mol -1 . Effect of background electrolyte concentration on the thermodynamic characteristics of complex formation was not studied.The purpose of this paper is the determination by direct calorimetric method of the heat effects of the formation of copper(II) complexes with L-asparagine at 298.15 K and different values of ionic strength, as well as the calculation of standard thermodynamic characteristics of the complexation processes in the Cu 2+ -L-asparagine system.The heat effects of the interaction of solutions of copper(II) with solutions of L-asparagine accounting for all the processes occurring in the system can be calculated by formula (1).Δ mix H -Δ dil H = Δ r H(CuL + )α(CuL + ) + Δ r H(CuL 2 )α(CuL 2 ) + Δ dis H(HL ± )α(HL ± ) + Δ dis H(H 2 L + )α(H 2 L + ) + Δ r H(CuOH + )α(CuOH + ) + Δ r H w α(OH -).(1)Here Δ mix H is the heat effect of mixing the solutions of L-asparagine and Cu(NO 3 ) 2 ; Δ dil H is the heat effect of dilution of Cu(NO 3 ) 2 solution in the background electrolyte solution; Δ r H(CuL + ) and Δ r H(CuL 2 ) are heat effects of reactions of complexation of CuL + and CuL 2 respectively; Δ dis H(H 2 L + ), Δ dis H(HL ± ) are the enthalpies of the separate steps of L-asparagine dissociation [7]; Δ r H (CuOH + ) is the heat of formation of 1:1 hydroxo complex of Cu 2+ ; Δ r H w is the heat of formation of water in a solution of KNO 3 [8]; α(CuL + ), α(CuL 2 ), α(H 2 L + ), α(HL ± ), α(CuOH + ), and α(OH -) are the degrees of the occurrence of the corresponding reactions.The calculation of equilibrium composition of solutions before and after the calorimetric experiment

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confidence: 59%

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confidence: 99%

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Effect of background electrolyte concentration on the heat effects in the processes of formation of L-asparagine complexes with Cu2+ ions in aqueous solution

2012

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“…Стандартные теплоты комплексообразования Cu 2+ с L-глутамином получены путем экстраполяции к нулевой ионной силе. Получена полная термодинамическая характеристика (ΔrH о , Δr G о , Δr S o ) процессов комплексообразования в системе Cu 2+ -L-глутамин [4]. В [5] исследовании ученные описали новый метод синтеза теанина с использованием L-глутамина-Zn(II) комплекс (Zn(Gln) 2 ) вместо глутамина в качестве донора, который успешно уменьшил боковую аутотранспептидацию реакция и привела к более высокому выходу теанина.…”

Section: Introductionunclassified

Изучение DFT Анализа Различных Форм Глютамина

Ганиев,

Мардонов,

Ашуров

2023

bulchmedenu

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This paper presents the results of DFT analysis and electron-structural and coordination properties, boundary molecular orbitals and descriptors of global reactivity of various forms of glutamine, using quantum-chemical calculation. For glutamine, the MEP was calculated using the DFT/B3LYP program, the basis 6-311G++(d,p) and the surface of the molecular electrostatic potential was constructed

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“…The influence of the aqueous solution ionic strength on the heat effect of acid-base equilibrium involving dipeptides built of valine, alanine, glycine, serine, and asparagine have been analyzed earlier in [1][2][3][4][5][6][7][8][9][10], and standard thermodynamic parameters of the corresponding reactions (pK 0 , Δ r G 0 , Δ r H 0 , and Δ r S 0 ) have been determined.…”

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Thermodynamic parameters of protolytic equilibria of selected dipeptides in aqueous solutions

Gridchin

2015

Russ J Gen Chem

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Heat effects of stepwise dissociation of D,L-valyl-D,L-leucine, L-leucyl-L-leucine, D,Lleucylglycine, and glycyl-D,L-leucine (298.15 K; 0.1, 0.5, or 1.0 mol/L KNO 3 ) have been determined by direct calorimetry. Standard thermodynamic parameters of the studied equilibria have been calculated.The influence of the aqueous solution ionic strength on the heat effect of acid-base equilibrium involving dipeptides built of valine, alanine, glycine, serine, and asparagine have been analyzed earlier in [1-10], and standard thermodynamic parameters of the corresponding reactions (pK 0 , Δ r G 0 , Δ r H 0 , and Δ r S 0 ) have been determined.In this work we studied the dipeptides including leucine fragment: D,L-valyl-D,L-leucine, L-leucyl-Lleucine, D,L-leucylglycine, and glycyl-D,L-leucine. The constants of stepwise dissociation of their carboxylic and betaine groups were considerably different, thus allowing independent calorimetric determination of heat effects of reactions (1) and (2).The enthalpy of dissociation of H 2 L + and HL could be found as the difference between the mixing and the dilution enthalpies [Eq. (3)]:where Δ mix H being the enthalpy of mixing of HNO 3 solution with the dipeptide solution in the presence of the background electrolyte; Δ dil H being the enthalpy of dilution of the HNO 3 solution in the background electrolyte solution; α being the degree of protonation of HL and L -. Heat effects of dissociation of the studied dipeptides at 298.15 K in the presence of 0.1, 0.5, and 1.0 mol/L of KNO 3 are collected in Table 1.The values of Δ dis Н found for the set of ionic strengths allowed calculation of the standard thermodynamic parameters of the studied equilibria. In order to extrapolate the heat effects to zero ionic strength we used a one-parametric Eq. (4) [11]:where Δ dis Н and Δ dis Н 0 being the reaction enthalpies at the finite and zero ionic strength, respectively; b being an empirical coefficient; Δz 2 being a difference of charges of the reaction products and the starting reactants; and Ψ(I) being a theoretically derived function of ionic strength [11]. The corresponding thermodynamic parameters of the dipeptides dissociation constants were then calculated using the Vasilev equation (5) [11]: pK 0 = pK + AΔz 2 [I 1/2 /(1+1.6I 1/2 ) -0.05I] + 0.05I, (5) where K 0 and K being thermodynamic and concentration constants of dissociation, respectively, and A being a Debye-Huckel theory constant.Concentration constants of dissociation of D,Lvalyl-D,L-leucine, L-leucyl-L-leucine, D,L-leucylglycine, and glycyl-D,L-leucine have been earlier determined in [12][13][14][15]. Standard thermodynamic parameters of dissociation of the studied dipeptides are collected in Table 2 along with our results of similar calorimetry studies of a series of other dipeptides.The results of this work are in good agreement with the earlier suggestions on the dependence of thermo-

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Thermochemical study of processes of complex formation of Cu2+ ions with L-glutamine in aqueous solutions

Cited by 6 publications

References 5 publications

Effect of background electrolyte concentration on the heat effects in the processes of formation of L-asparagine complexes with Cu2+ ions in aqueous solution

Effect of background electrolyte concentration on the heat effects in the processes of formation of L-asparagine complexes with Cu2+ ions in aqueous solution

Изучение DFT Анализа Различных Форм Глютамина

Thermodynamic parameters of protolytic equilibria of selected dipeptides in aqueous solutions

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