Charge solvation

Cation-TT interactions play a crucial role in molecular recognition. For example, Na /K cation interactions with aromatic rings of some amino acids are implicated in the biological functions of specific enzymes and in the selectivity of Na" /K channels. " The same factors are responsible of the relative stability of the charge-solvated vs. zwitterionic structure of amino acids. " ... 

The thermodynamic origins of the enhanced stabilities of macrocyclic ligands over their acyclic counterparts have been the subject of considerable debate since the term macrocyclic effect was first coined.83 Comparison of thermodynamic data for the several metal ion complexes of the [18]crown-6 and its acyclic counterpart are shown in Table 1. Enthalpy contributions to stabilization appear strongest for the K+ complex, while entropic contributions are stronger for the Na+ complex. Undoubtedly, the factors responsible for the thermodynamics will vary according to ion size, charge, solvation effects and structural preference. Hence, a single definable source of the macrocyclic effect is, in these systems at least, probably nonexistent. 

The results for phenolate and naphtholate show that internal transition may lead to solvated electron formation from aromatic anions. The fact that the products are the negatively charged solvated electron and a radical which is neutral (and not a positively charged one) may be partly responsible for the increased efficiency of anions over the undissociated molecules. Primary recombination may decrease in the absence of coulombic attraction. Moreover the ionization potential of the anion is lower. 

D. F. Calef and P. G. Wolynes, Smoluchowski-Vlasov theory of charge solvation dynamics, J. Chem. Phys., 78 (1983) 4145-53 P. G. Wolynes, Linearized microscopic theories of nonequihbrium solvation, J. Chem. Phys., 86 (1987) 5133-6. 

The relationship (15.29) was found for the case of charge solvation. Solvation of higher moments of a given charge distribution can be treated in the same way. For dipole solvation we will find a similar relationship, except that the electrostatic... 

Moult, James, Fidelis [126, 135] Rotamer library, complete search Electrostatic term, image-charge solvation term, van der Waals, hydrophobic term... 

Due to this heating and the energy gained from the charge solvation, cluster molecules are lost by evaporation ... 

Kapota, C. Lemaire, J. Maitre, P. Ohanessian, G. Vibrational signature of charge solvation vs salt bridge isomers of sodiated amino acids in the gas phase. J. Am. Chem. Soc. 2004,126, 1836-1842. 

Drays MK, Armentrout PB, Oomens J, Schafer M. IR spectroscopy of cationized aliphatic amino acids stability of charge-solvated structure increases with metal cation size. Int J Mass Spectrom. 2010 297 18-27. 

Cerda BA, Wesdemiotis C. Zwitterionic vs. charge-solvated structures in the binding arginine to alkali metal ions in the gas phase. Analyst. 2000 125 657-60. 

Scheme 1 Low-energy structures for the complex of and Trp. Structures can be classified as salt-bridge (SB interaction between the positive metal ion and the negative carboxylate of the zwitterionic amino acid) or charge solvation (CS interaction of the metal ion with Lewis-basic sites of the canonical amino acid). Nomenclature of the various structures further includes the main binding sites of the amino acid...

Fig. 2 Spectra of the trapped populations of Phe and Tip complexes of Ba (figure adapted from [11]). Comparison of the IRMPD spectra (upper trace in each panel) of the Ba complexes of Phe and Trp. The lower (red) trace in each panel shows the calculated spectrum of the SB conformation, and two expected diagnostic features for the Z[C02. Ring] (SB) conformation are designated by the (orange) bars labeled ZW. Two diagnostic features expected for the T[N,0,Ring] charge-solvated conformation are designated by the (purple) bars labeled CS, and are seen to be present in the observed spectra only in the Phe case...

Mino WK, Szczepanski J, Pearson WL, Powell DH, Dunbar RC, Eyler JR, Polfer NC (2010) Vibrational signatures of zwitterionic and charge-solvated structures for alkaline earth-tryptophan dimer complexes in the gas phase. Int J Mass Spectrom 297 131-138... 

In this expression, JCis the equilibrium constant for a given chemical equilibrium and the reaction volume A V is the difference between the volumes of the final and initial states in any particular process, for example, due to a change in molecule packing, electrostatic action of charges, solvation, and hydration effects. From Eq. (9.1), it is clear that the sign of the reaction volume A V imposes the direction of equilibrium shifts induced by pressure. If A V is negative, the equilibrium shifts... 

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