Glycine solvation

Balabin, R. M. The first step in glycine solvation The glycine—water complex, J. Phys. Chem. B 2010,114,15075-15078. 

Quantum chemical modelling of the potential energy surface for the reaction between benzenesulfonyl chloride and glycine solvated with 1—4 water molecules showed that all of the reactions occurred via a complicated route, with varying attack by the nucleophile according to an S 2 mechanism. ... 

Balabin RM (2010) The first step m glycine solvation the glycine-water complex. J Phys ChemB 114 15075... 

Paleg, L.G., Stewart, G.R. Bradbeer, J.W. (1984). Proline and glycine betaine influence protein solvation. Plant Physiology, 75, 974-8. 

Fig. 2.6 Comparison of the calculated structures for glycine in the gas-phase and in water (COSMO solvation model). Note that the central bond angle in the zwitterionic form 1 is distorted by the hydrogen bond length of 1.96A computed for this structure in the gas phase. When solvation effects are included in the calculation using COSMO, the electrostatic interaction is reduced in magnitude due to charge screening by water, and the bond angle distortion is no longer present.

Alper, J. S., H. Dothe, and M. A. Lowe. 1992. Scaled Quantum Mechanical Calculation of the Vibrational Structure of the Solvated Glycine Zwitterion. Chem. Phys. 161, 199-209. 

Sukumar, N., and G. A. Segal. 1986. Effect of Aqueous Solvation upon the Electronic Excitation Spectrum of the Glycine Zwitterion A Theoretical Cl Study Using a Fractional Charge Model. J. Am. Chem. Soc. 108, 6880-6884. 

Alper, J. S., H. Dothe, and M. A. Lowe. 1992. Scaled Quantum Mechanical Calculation of the Vibrational Structure of the Solvated Glycine Zwitterion, Chem. Phys. 161, 199-209. Barron, L. D., A. R. Gargaro, L. Hecht, P. L. Polavarapu. 1991. Experimental and Ab Initio Theoretical Vibrational Roman Optical Activity of Alanine, Spectrochimica Acta 47A, 1001-1016. 

Water dissociation rate constant, 25°C. b Sum of rate constants for solvation and desolvation 25°C for polyethylene glycol, 4°C for glycine, diglycine, triglycine. 

Perhaps the most spectacular success of explanations based on solvation of ground states, published to date, is the dissection of activation parameters for solvolysis of t-butyl chloride in mixtures of ethanol and water, first discussed by Winstein and Fainberg (1957). The complex variation of AH and AS (Fig. 21) has been shown to be due almost entirely to ground state solvation effects, at least for the solvents ethanol—40% ethanol/water studied by Arnett et al. (1965). For 90%, 80%, 70%, 60%, 50% and 40% ethanol/water the parameter AH1 for solvation of the transition state (by transfer from the gas phase) was calculated to be linearly proportional to the corresponding value of AS, as expected from the behaviour of simple salts. The point for pure ethanol did not fall on the calculated line, and this was attributed to nucleophilic solvent assistance. The variation in AG, AH and AS (Fig. 21) can be reproduced remarkably well using ethane and the zwitterionic a-amino acid, glycine, as model compounds (Abraham et al., 1975 see also Abraham, 1974 Abraham and Abraham, 1974). 

In the previous papers, we applied QM/MM-ER to various systems to examine the efficiency of the method [19,63,64,38,65,66], Here, we present the results of a few applications. At first, we employ the QM/MM-ER approach to compute solvation free energy of a QM water molecule described by DFT in an MM water solvent [19]. Second, the method is utilized to compute free energy change associated with a proton transfer in glycine in aqueous solution [64], The results are compared with those obtained by experiments and the accuracy and efficiency of the QM/MM-ER approach is discussed. 

In Eq. (17-81), A/x (ZW) and A/x (NF) are, respectively, the solvation free energies of the ZW and the NF form of glycine. Since the free energy difference SGgas can be accurately computed by a sophisticated method based on the DFT or the molecular orbitals theory, the accuracies of the solvation free energies of the solute molecules dominate the reliability of the free energy difference SGaq. 

Table 17-4. Solvation free energies for the NF and the ZW form of glycine computed by the QM/MM-ER approach. Units are in kcal/mol...

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