Solvation dynamics hydration

Schwartz, B. J. and Rossky, P. J. Aqueous solvation dynamics with a quantum mechanical solute computer simulation studies of the photoexcited hydrated electron, J.Chem.Phys., 101 (1994), 6902-6916... 

In order to study the influence of electron concentration on the observed dynamics, we performed experiments with different laser power densities. As an illustration, the transient absorption signals recorded at 715 nm in ethylene glycol upon photoionisation of the solvent at 263 nm with three different laser power densities are presented in Fig.3. As expected for a two-photon ionization process, the signal intensity increases roughly with the square of the power density. However, the recorded decay kinetics does not depend on the 263 nm laser power density since the normalised transient signals are identical (Cf. Fig.3 inset). That result indicates that the same phenomena occur whatever the power density and consequently that the solvation dynamics are independent of the electron concentration in our experimental conditions i.e. we are still within the independent pair approximation as opposed to our previous work on hydrated electron [8]. 

Sherman WV (1967b) Light-induced and radiation-induced reactions in methanol. I. y-Radiolysis of solutions containing nitrous oxide. J Phys Chem 71 4245-4255 Sherman WV (1967c) The y-radiolysis of liquid 2-propanol. III. Chain reactions in alkaline solutions containing nitrous oxide. J Phys Chem 71 1695-1702 Silva C, Walhout PK, Yokoyama K, Barbara PF (1998) Femtosecond solvation dynamics of the hydrated electron. Phys Rev Lett 80 1086-1089... 

Femtosecond spectroscopy has an ideal temporal resolution for the study of ultrafast water motions from femtosecond to picosecond time scales [33-36]. Femtosecond solvation dynamics is sensitive to both time and length scales and can be a good probe for protein hydration dynamics [16, 37-50]. Recent femtosecond studies by an extrinsic labeling of a protein with a dye molecule showed certain ultrafast water motions [37-42]. This kind of labeling usually relies on hydrophobic interactions, and the probe is typically located in the hydrophobic crevice. The resulting dynamics mostly reflects bound water behavior. The recent success of incorporating a synthetic fluorescent amino acid into the protein showed another way to probe protein electrostatic interactions [43, 48]. 

Figure 19 shows the typical fluorescence transients of TBE from more than 10 gated emission wavelengths from the blue to the red side. At the blue side of the emission maximum, all transients obtained from four Trp-probes in the cubic phase aqueous channels drastically slow down compared with that of tryptophan in bulk water. The transients show significant solvation dynamics that cover three orders of magnitude on time scales from sub-picosecond to a hundred picoseconds. These solvation dynamics can be represented by three distinct decay components The first component occurs in about one picosecond, the second decays in tens of picoseconds, and the third takes a hundred picoseconds. The constmcted hydration correlation functions are shown in Fig. 20a with anisotropy dynamics in Fig. 20b. Surprisingly, three similar time scales (0.56-1.431 ps, 9.2-15 ps, and 108-140 ps) are obtained for all four Trp-probes, but their relative amplitudes systematically change with the probe positions in the channel. Thus, for the four Trp-probes studied here, we observed a correlation between their local hydrophobicity and the relative contributions of the first and third components from Trp, melittin, TME to TBE, the first components have contributions of 40%, 35%, 26%, and 17%, and the third components vary from 32%, to 38%, 43%, and 53%, respectively. The...

EJ Hart and M Anbar have detailed the characteristics and the chemistry of the solvated electron in water, otherwise known as the hydrated electron and denoted by e] y or e. A number of reviews on the solvated electron are also available.In this article, we will recall briefly the main steps of the discovery and the principal properties of the solvated electron. We will then depict its reactivity and focus on recent results concerning the effect of metal cations pairing with the solvated electron. At last, we will present results on the solvation dynamics of electron. Due to the development of ultrashort laser pulses, great strides have been made towards the understanding of the solvation and short-time reactivity of the electron, mainly in water but also in polar solvents. However, due to the vast and still increasing literature on the solvated electron, we do not pretend for this review to be exhaustive. 

Silva C, Walhout PK, Yokoyama K, Barbara PF. (1998) Femtosecond solvation dynamics of the hydrated electron. Phys Rev Lett 80 1086-1089. 

Kambhampati P, Son DH, Kee TW, Barbara PF. (2002) Solvation dynamics of the hydrated electron depends on its initial degree of electron delocalization. JPhys ChemA 06 2374-2378. 

The slow component in the solvation TCF should have contributions both from the protein surface and from the hydration water. The DEM has been successful in quantifying the contribution of the hydration water to this slow dynamics. According to this model, dynamical equilibrium between the bound and free water introduces a slow timescale in the collective reorientational of the hydration water, which in turns slows down the solvation dynamics (Nandi and Bagchi, 1997 Pal et al., 2002 Bhattacharyya et al., 2003). 

Using fs resolution, two residence times of water at the surface of two proteins have been reported (Fig. 7.6) [21]. The natural probe tryptophan amino acid was used to follow the dynamics of water at the protein surface. For comparison, the behavior in bulk water was also studied. The experimental result together with the theoretical simulation-dynamical equilibrium in the hydration shell, show the direct relationship between the residence time of water molecules at the surface of proteins and the observed slow component in solvation dynamics. For the two biological systems studied, a bimodal decay for the hydration correlation function, with two primary relaxation times was observed an ultrafast time, typically 1 ps or less, and a longer one typically 15-40 ps (Fig. 7.7) [21]. Both times are related to the residence period of water at the protein surface, and their values depend on the binding energy. Measurement of the OH librational band corresponding to intermolecular motion in nanoscopic pools of water and methanol... 

E. Neria, A. Nitzan, R. N. Barnett, and U. Landman, Phys. Rev. Lett., 67, 1011 (1991). Quantum Dynamical Simulations of Nonadiabatic Processes—Solvation Dynamics of the Hydrated Electron. 

B. Bagchi, Water solvation dynamics in the bulk and in the hydration layer of proteins and self-assemblies. Anna. Rep. Prog. Chem., Sect. C, 99 (2003), 127-175. 

The solvation dynamics results of Zewail and co-workers are shown in Figure 8.5 for the protein Subtilisin Carlsberg (SC). The inset in the same figure shows faster solvation when the probe was dansyl-bonded and placed at a distance of 6-7 A from the protein surface. The 20-40 ps component was interpreted in terms of the bound free dynamic equilibrium proposed in a dynamic exchange model of the hydration layer. 

R. Pethig, Protein-water interactions determined by dielectric methods. Anna. Rev. Phys. Chem., 43 (1992), 177-205 E.H. Grant, Nature, 196 (1962), 1194 N. Nandi, K. Bhattacharyya, and B. Bagchi, Dielectric relaxation and solvation dynamics of water in complex chemical and biological systems. Chem. Rev., 100 (2000), 2013 B. Bagchi, Water dynamics in the hydration layer around proteins and micelles. Chem. Rev., 105 (2005), 3197. 

This chapter discusses recent developments in solvation dynamics and thermodynamics of f-element cations and the hydrol5ftic tendencies of these ions in aqueous media. Direct comparisons are made for the trivalent cations of the lanthanides and actinides while the data for the other oxidation states of the actinides are reviewed to assess the effects of charge density and structure on hydration and hydrolysis. Since the lanthanides were reviewed recently, major attention is given to the actinides and the similarities and differences in their behavior with that of the lanthanides. 

One of the most peculiar features of ILs is the distinct degree of mesoscopic order they possess. Importantly, the latter is taken into account to explain at least part of the unique properties of ILs, such as their complex solvation dynamics. Loading IL with water has a twofold effect (i) hydration of ions is hkely to disrupt the ion pairs and (ii) the hydrophobic effect pushes toward the self-assembly of the organic cations. 

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