@article {5094,
	title = {Additive effect of 1-propanol and 2-propanol on molecular organization of H2O in the water-rich region: Excess chemical potential, partial molar enthalpy and volume of 1-propanol in 1-propanol-2-propanol-H2O at 25 degrees C},
	journal = {Bulletin of the Chemical Society of Japan},
	volume = {74},
	number = {5},
	year = {2001},
	note = {ISI Document Delivery No.: 443WKTimes Cited: 16Cited Reference Count: 25},
	month = {May},
	pages = {809-816},
	type = {Article},
	abstract = {Excess chemical potential, mu (E)(1P), partial molar enthalpy, H-1P(E) and volume of 1-propanol, V-1P(E), were determined as a function of mole fraction of l-propanol, rip, in mixed solvents of aqueous 2-propanol with various initial mole fraction of 2-propanol, x(2P)(0). The 1-propanol-1-propanol interaction functions, H-1P-1P(E) equivalent to N(partial derivativeH(1P)(E)/partial derivativen(1P)), and V-1P-1P(E) equivalent to N(partial derivativeV(1P)(E)/ partial derivativen(1P)), were evaluated by graphical differentiation. The rip-dependence of all these quantities indicates that l-propanol and 2-propanol modify the molecular organization of H2O in the same and additive manner in the water-rich region. The additive effect of 1-propanol and that of 2-propanol are in the ratio of (0.07/0.08).},
	keywords = {25-DEGREES-C, AQUEOUS 2-BUTOXYETHANOL, ENTROPIES, fluctuations, INTERMOLECULAR INTERACTIONS, LYSOZYME, MIXING SCHEMES, MIXTURES, TERT-BUTANOL},
	isbn = {0009-2673},
	url = {<Go to ISI>://000169365200004},
	author = {Hu, J. H. and Chiang, W. M. D. and Westh, P. and Chen, D. H. C. and Haynes, C. A. and Koga,Yoshikata}
}
@article {4613,
	title = {Excess partial molar enthalpy of 1-propanol in 1-propanol-NaCl-H2O at 25 degrees C: The effect of NaCl on molecular organization of H2O},
	journal = {Journal of Physical Chemistry B},
	volume = {103},
	number = {15},
	year = {1999},
	note = {ISI Document Delivery No.: 189YNTimes Cited: 23Cited Reference Count: 26},
	month = {Apr},
	pages = {2981-2983},
	type = {Article},
	abstract = {Excess partial molar enthalpies of l-propanol, H-1p(E), in 1-propanol-NaCl-H2O were measured directly, accurately, and in small increments in mole fraction of 1-propanol, x(1P), at 25 degrees C in the range x(NaCl) < 0.04 x(NaCl) is the mole fraction of NaCl. The enthalpic interaction function, H-1P-1P(E), between l-propanol molecules was then evaluated. H-1P-1P(E) is a convenient, model-free measure for the intermolecular interaction in terms of enthalpy. The behavior of these thermodynamic quantities was compared with that of the binary 1-propanol-H2O. Based on the knowledge accumulated in our laboratory on the binary aqueous l-propanol, the effect of NaCl on H2O became apparent. Our tentative conclusions are that (1) a NaCl molecule "binds" to seven or eight molecules of H2O on dissolving into H2O, and (2) the reminder of bulk H2O away from solute NaCl is not affected and stays almost the same as pure H2O.},
	keywords = {2-BUTOXYETHANOL, AQUEOUS SODIUM-CHLORIDE, CLUSTERS, EQUILIBRIUM, fluctuations, INTERMOLECULAR INTERACTIONS, LYSOZYME, SPECTROSCOPY, vibrational, VOLUMES, WATER},
	isbn = {1089-5647},
	url = {<Go to ISI>://000079934100023},
	author = {Matsuo, H. and To, E. C. H. and Wong, D. C. Y. and Sawamura, S. and Taniguchi, Y. and Koga,Yoshikata}
}
@article {3848,
	title = {Intermolecular interactions in 2-butoxyethanol-DMSO-H2O},
	journal = {Journal of Physical Chemistry},
	volume = {100},
	number = {1},
	year = {1996},
	note = {ISI Document Delivery No.: TN839Times Cited: 15Cited Reference Count: 23},
	month = {Jan},
	pages = {433-438},
	type = {Article},
	abstract = {Excess partial molar enthalpy, H-B(E), and chemical potential, mu(B)(E), of 2-butoxyethanol (B) were determined in ternary mixtures of B, dimethyl sulfoxide (D), and H2O. The data were obtained in small enough mole fraction increments to evaluate the so-called interaction functions, partial derivative H-B(E)/partial derivative x(B), partial derivative H-B(E)/partial derivative x(D), partial derivative mu(B)(E)/partial derivative x(B), and partial derivative mu(B)E/partial derivative x(D). These interaction functions previously proved useful in elucidating the {\textquoteright}{\textquoteright}mixing schemes{\textquoteright}{\textquoteright} in binary aqueous solutions of B and D. For the binary mixtures, it was found that both B and D influenced H2O in the following manner: in the water-rich composition range (region I) within a certain threshold (x(B) < 0.0175 and x(D) < 0.28 at 25 degrees C), both solutes enhance the hydrogen-bonded network of water in their vicinity, and the mixtures retain the percolated nature of the network. At higher B or D concentrations (region II) a qualitatively different mixing scheme becomes operative. The results from this work suggest that, in the ternary mixtures, solute B and D influences the percolated hydrogen bond network of water competitively or cooperatively. The observed effects are in accordance with those characteristic of mixing scheme I in the binary mixtures, as long as the concentration of both solutes is within the threshold values. When either one of the solutes is concentrated beyond its threshold, mixing scheme II seems to set in. It was found that D diminished the positive (unfavorable) enthalpy of B-B interactions and that this effect was almost completely compensated by changes in interaction entropy. Hence, D had little net effect on the Gibbs energy of mutual B interactions, or in other words, D did not weaken the hydrophobic attraction between B molecules. Evaluation of {\textquoteright}{\textquoteright}heterogeneous{\textquoteright}{\textquoteright} B-D interactions in region I suggested that they were weaker than B-B interactions and governed by reorganization of water-water hydrogen bonding rather than interactions between specific groups in B and D. Some implications of these findings on cosolvent effects in aqueous solutions of biopolymers are discussed.},
	keywords = {AQUEOUS 2-BUTOXYETHANOL, denaturation, DIMETHYL-SULFOXIDE, LYSOZYME, MIXING SCHEME, MIXTURES, NEUTRON-DIFFRACTION, PARTIAL MOLAR ENTHALPIES, VOLUMES, WATER-RICH REGION},
	isbn = {0022-3654},
	url = {<Go to ISI>://A1996TN83900065},
	author = {Westh, P. and Koga,Yoshikata}
}
@article {3762,
	title = {The pK(a) of the general acid/base carboxyl group of a glycosidase cycles during catalysis: A C-13-NMR study of Bacillus circuluns xylanase},
	journal = {Biochemistry},
	volume = {35},
	number = {31},
	year = {1996},
	note = {ISI Document Delivery No.: VB211Times Cited: 149Cited Reference Count: 43},
	month = {Aug},
	pages = {9958-9966},
	type = {Article},
	abstract = {The 20 kDa xylanase from Bacillus circulans carries out hydrolysis of xylan via a two-step mechanism involving a covalent glycosyl-enzyme intermediate. In this double-displacement reaction, Glu78 functions as a nucleophile to form the intermediate, while Glu172 acts as a general acid catalyst during glycosylation, protonating the departing aglycone, and then as a general base during deglycosylation, deprotonating the attacking water, The dual role of Glu172 places specific demands upon its ionization states and hence pK(a) values. C-13-NMR titrations of xylanase, labeled with [delta-C-13]glutamic acid, have revealed pK(a) values of 4.6 and 6.7 for Glu78 and Glu172, respectively. These agree well with the apparent pK(a) values obtained from a study of the pH dependence of k(cat)/K-m and demonstrate that, at the enzyme{\textquoteright}s pH optimum of 5.7, the nucleophile Glu78 is deprotonated and the general acid Glu172 initially protonated. Remarkably, the pK(a) for Glu172 drops to 4.2 in a trapped covalent glycosyl-enzyme intermediate, formed by reaction with 2{\textquoteright},4{\textquoteright}-dinitrophenyl 2-deoxy-2-fluoro-beta-xylobioside [Miao et al. (1994) Biochemistry 33, 7027-7032], A similar pK(a) is measured for Glu172 when a glutamine is present at position 78. This large decrease in pK(a) of similar to 2.5 units is consistent with the role of Glu172 as a general base catalyst in the deglycosylation step and appears to be a consequence of both reduced electrostatic repulsion due to neutralization of Glu78 and a conformational change in the protein. Such {\textquoteright}{\textquoteright}pK(a) cycling{\textquoteright}{\textquoteright} during catalysis is likely to be a common phenomenon in glycosidases.},
	keywords = {ACTIVE-SITE RESIDUES, AMINO-ACIDS, beta-glucosidase, ELECTROSTATIC INTERACTIONS, ESCHERICHIA-COLI, IDENTIFICATION, LYSOZYME, MECHANISMS, NUCLEAR-MAGNETIC-RESONANCE, PROTEINS},
	isbn = {0006-2960},
	url = {<Go to ISI>://A1996VB21100003},
	author = {McIntosh, L. P. and Hand, G. and Johnson, P. E. and Joshi, M. D. and Korner, M. and Plesniak, L. A. and Ziser, L. and Wakarchuk, W. W. and Withers, S. G.}
}
