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The hydration and molecular properties of ectoine (2-methyl-4-carboxy-3,4,56-tetrahydropyrimidine), an organic solute in halophilic and halotolerant microorganisms, were investigated for the first time using ab initio molecular orbital calculations. Two structures whose stability is the same were obtained at the MP2/6-31G* level of theory. One of the stable structures has a geometry in which the COO group is in axial position and the other in equatorial position.

Molecular dynamics experiments were performed to investigate the structure of one single tetramethylammonium (TMA) ion in water. The dynamical properties of the ion and its hydration shell molecules were examined. The TMA was analyzed as an ionic model in studying the hydrophobic behavior in water solutions. The orientation of the hydration shell molecules was nearly tangent to the ion. Lower self-diffusion coefficients were observed in the hydration shell molecules. However, TMA ions do not interfere with the low-frequency water power spectra.

This paper shows how the mechanics of elastic composite materials can be adapted to predict the basic creep of concrete with aging due to hydration. The prediction is made on the basis of the given composition of concrete, the elastic constants of the aggregate, and the aging viscoelastic properties of the portland cement mortar. The triaxial action of the composite is approximated by Dvorak's transformation field analysis. To convert the aging creep problem to an elastic problem of a composite material with inelastic strains, Granger and Bazant's approach is used. This approach relies on Bazant's age-adjusted effective modulus method that reduces the integral-type stress-strain relation for linear aging creep with nonconvolution kernel to a quasi-elastic incremental stress-strain relation with inelastic incremental strain. Explicit expressions for the aging creep properties of concrete as a composite are deduced. The model is calibrated and verified by Ward et al.'s and Counto's test data. The predictions obtained are almost as close as those recently obtained by Granger and Bazant's model. While the present model has the advantage of describing the triaxial composite action in a rational manner, it does not yet capture the effect of the deviation of the aggregate configuration from the case of a contiguous aggregate skeleton of maximum possible compactness. Further refinements in this respect are needed. Another refinement might be needed to take into account possible enhancement of creep in the interface layers between the mortar and the aggregate.

A study was conducted to characterize the partial molar values and adiabatic compressibilities for 14 monosaccharides in aqueous solutions. The hydration characteristics of the polar groups were also analyzed. Results indicated that each polar group in pentoses supported a stronger contraction of water than a polar group in 2-deoxyribose. Findings also showed similarities between the hydration of polar groups of pentoses and hexoses.

A study was conducted to analyze the chemical transfer energies of the -CH2- group and examine solvent effects on hydrophobic hydration and the three-dimensional structuredness of solvents. Constancy of absorbance was used as the criterion of the attainment of equilibrium. Results indicated that the chemical transfer energetics and entropies of -CH2- correlated with the solvent effect on HbH and the three-dimensional structuredness of aquo-organic cosolvents.

A study was conducted to investigate the molecular modeling of the tributyl phosphate complex of Europium nitrate in the clay hectorite. The energy minimization and molecular dynamics experiments were performed using computer software from Molecular Simulations Inc. Results indicated that optimized structures were sensitive to the number and kind of counterions found in the interlayer and to the level of hydration.

(Pt(CN-iso-C3H7)4)(M(CN)4) (M = Pt, Pd) were synthesized and their reversible hydration and sorption characteristics were investigated. Powder diffraction studies revealed that anhydrous (Pt(CN-iso-C3H7)4)(Pt(CN)4) and (Pt(CN-iso-C3H7)4)(Pd(CN)4) crystallize in a tetragonal space group with almost similar lattice constants. Gravimetric studies showed that variable guest-host stoichiometries are obtained when solid (Pt(CN-iso-C3H7)4)(Pt(CN)4) sorbs the guest at room temperature from the gas phase. Said sorption processes are reversible.

Expression and purification to homogeneity of 2-oxo-hept-4-ene-1,7-dioate hydratase from Escherichia coli were conducted for kinetic, isotopic, labeling and stereochemical studies. Isotope labeling investigations revealed that the hydratase catalyzes the incorporation of a solvent deuteron at both C-3 and C-5 when the reaction is conducted in 2H2O. The enzymes also catalyzes the exchange of the C-3 proton of the alternate substrate 2-oxo-1,7-heptadioate with solvent deuterons.

A study was conducted to analyze the effects of hydrogen bonding and the hard core of water on hydrophobic hydration using Monte carlo simulation and the test particle technique. Cavities were produced at random locations for each configuration. Experimental results indicated that the free energy of cavity formation in water at a given density can be obtained by the hard-core effect. Findings also showed that the effect of hydrogen bonding correlated with the coordination-number dependence of the average energy of one molecule.

Nuclear magnetic relaxation dispersion (NMRD) of the water 2H and 17O resonances was used to examine the hydration of six B-DNA dodecamers with A-tracts of variable length and sequence. Its sensitivity was improved when the aqueous DNA solution was subdivided into microscopic emulsion droplets, allowing NMRD calculations to be conducted at -20 degrees C. NMRD data reveal that all six dodecamers possessed long-lived water molecules.

The hydrophobic hydration in a series of hydrocarbons is probed by using molecular dynamics simulations. The solutes considered range from methane to octane. Examination of the shapes of the hydration shell suggests that there is no single stable structure surrounding these solutes. The structure of the water molecules around the solute is not significantly perturbed, even for octane, and the hydrogen bond network is essentially preserved. The solutes are accommodated in the voids of the tetrahedral network of water in such a way as to leave the local environment almost intact. The hydrophobic hydration arises primarily because of the plasticity of the hydrogen bond network. Even for octane we find very little evidence for water-mediated interactions between nonbonded carbon atoms, leading us to suggest that the transition to globular conformations can only occur for very long, linear hydrocarbon chains.

X-ray diffraction, 29Si magic angle spinning nuclear magnetic resonance, and gravimetric adsorption methods were used to investigate the pore structure stability of MCM-41 materials during hydration/dehydration. Results revealed that the hydrolysis of the bare Si-O-Si(Al) bonds in the presence of water vapor causes the pore structure to collapse upon rehydration at room temperature. The whole MCM-41 structure collapses when MCM-41 is left in air for three months.

Characterization of the high hydration states of a layered protonic titanate provides insight into the osmotic swelling and exfoliation of the titanate into single sheets, which occurs upon the action of an aqueous solution with quarternary alkylammonium ions. X-ray diffraction patterns for the titanate displayed a broad diffraction halo in a 2 theta range of 20 to 25 degrees. The diffraction halo arises as a result of scattering from the nanosheets stacked irregularly as a result of centrifugation. Optical absorption spectra revealed characteristic features for semiconductors.

Ultrafast time-resolved fluorescence studies were performed to determine the solvation dynamics of water in lecithin/cyclohexane reverse micelles. Results showed that the reverse micellar samples are nonviscous when the hydration levels are greater than or equal to 4.8. However, a viscous gel is produced when small amounts of water are added to the samples. Moreover, the water in lecithin reverse micelles is more restricted than in Aerosol OT reverse micelles of similar hydration.

Research was conducted to examine fat estimation errors due to variation in soft tissue hydration. The objective of the study was to develop and validate a dual-energy X-ray absorptiometry (DXA) hydration physical model and to utilize it for the quantitative evaluation of several influences of fluid balance change on DXA soft tissue composition estimates. Results indicate a bias error in DXA soft tissue composition estimates as a function of tissue hydration.

The modelization of the OH stretching band by three Gaussian components was found to be the most efficient decomposition and as an adequate smoothing method. This was found in an application of two independent methods to interpret the shape and the intensity of the water OH stretching vibration band in a Fourier transform infrared study of water states in Aerosol-OT (AOT) reverse micelles as a function of the water content. A Langmuir adsorption isotherm model best satisfies the criteria for a model for determining the number of water molecules bound per AOT polar head. These are their ability to fit the experimental data, to reproduce the effect of the AOT concentration, and to examine the influence of the counterion forming the ion pair with AOT.

It has been possible to show a topography dependence for hydrophobic hydration of a molecular surface. This research involved making computer simulations of the interaction between the polypeptide melittin and water. These simulations show that the two different hydration structures also exist near a biomolecular surface. It is suggested that the temperature dependence of hydrophobic interaction connected with melittin hydration should be clearly different from that connected with small-molecule hydration even in the case of essentially complete enthalpy-entropy compensation at a specific temperature.

Experiments were performed to calculate the relative hydration free energy difference of a variety of pteridine, quinazoline, pyrimidine and purine analogues. Final relative hydration free energy difference was affected by gas-phase quantum mechanical energy and solvation free energy differences. The electronic and steric nature of the substituents located at the site of hydration influence the hydration reaction. Moreover, it was also observed that the type of aromatic ring and the ring positions also affect the heteroromatic compound hydration.

A study was conducted to analyze a reversible ordering-disordering transition of molecular arrangements occurring on the (010) face of a single crystal of potassium tetracyanoplatinate bromide during hydration and dehydration treatments. Atomic force microscopy experiments were performed using the SPA300 AFM instrument in a sealed chamber. Experimental results indicated that decreases in the conductivity of KCP(Br) single crystals during dehydration correlated with the molecular rearrangement process.

The structure of the protein-solvent interface is the subject of controversy in theoretical studies and requires direct experimental characterization. Three proteins with known atomic resolution crystal structure (lysozyme, Escherichia coli thioredoxin reductase, and protein R1 of E. coli ribonucleotide reductase) were investigated in parallel by x-ray and neutron scattering in [H.sub.2]O and [D.sub.2]O solutions. The analysis of the protein-solvent interface is based on the significantly different contrasts for the protein and for the hydration shell. The results point to the existence of a first hydration shell with an average density [approximately equal to]10% larger than that of the bulk solvent in the conditions studied. Comparisons with the results of other studies suggest that this may be a general property of aqueous interfaces.

Studies of ultramarathon athletes show no direct links between food and fluid intakes and performance levels. Subjects were monitored for carbohydrate and fluid amounts and ingestion rates and physical achievements during an ultramarathon. While nutrient intakes among the subjects averaged similar levels in carbohydrate, fat and protein, fluid intakes varied greatly. Results, however, revealed that intakes and performance are not significantly correlated.

Studies show that drinking a carbohydrate-NaCl beverage on a voluntary basis is sufficient to prevent dehydration in 10- to 12-year-old boys exercising in the heat. Physiological variables monitored during the test included body weight, stomach fullness perception, thirst, rectal temperature and heart rate. In 72 sessions, 67 demonstrated a positive fluid intake from voluntary ingestion of a carbohydrate-NaCl beverage.

Research shows that fluid intakes for teenage athletes may be inadequate to preserve sufficient hydration during exercise. Test subjects performing a run-ride-run duathlon were observed. No differences were noted in fluid intakes according to age or gender. All athletes lost body mass, but greater losses were noted for male athletes 15 years of age or older. Results indicate fluid intakes were not sufficient to prevent dehydration.

The coordination scheme of water in myoglobin and haemoglobin, the two oxygen carrier proteins in vertebrates, is still far from being fully understood. The TSDC (thermally stimulated depolarization currents) technique is a sensitive tool to study water molecules bound to biological macromolecules and characterized by mobility and order degree, quite different from those of bulk water. TSDC spectra for both proteins were recorded in the temperature range 100 to 300 K, at very low hydration levels (h = 0.01 to 0.62) obtained with different procedures. Different classes of water molecules were found: the preferred hydration sites and the water dipole activation energies are discussed. In particular, the existence of a critical hydration level which induces a partially irreversible structural transition was monitored in myoglobin. The technique allowed estimation of the average number of hydrogen bonds established by the water molecules in the inner cages of haemoglobin at different hydration levels.

A rapid rise in absorbance of around lambda = 250 nm to 300 nm results from flash photolysis of aqueous solutions of 2-diazocyclohexane-1,3-dione. This is followed by a much slower decay. There are strong similarities between these absorbance changes and those seen in the production of acetoacetic acid by flash photolysis of 2,2,6-trimethyl-4H-1,3-dioxin-4-one. In aqueous solution, 2-ketocyclopentyl-ideneketene is produced from flash photolysis of 2-diazocyclohexane-1,3-dione. This hydrates to the enol of 2-oxocyclopentanecarboxylic acid, with the enol then isomerizing to the keto form of the acid.

A water proton spin-lattice relaxation experiment is conducted by hydrating glass pores with 1 mM of tetramethyl-4-acetamido-piperidine-1-oxyl (TMAPO) solution. Results show that TMAPO concentration is constant in 127 nm thick samples during dehydration. However, this observation is not valid in 49.1 nm samples. The results of previous electron paramagnetic resonance research are thereby confirmed.

Changes in macromolecular hydration that accompany binding of the Escherichia coli cyclic AMP receptor protein (CAP) to its transcription-regulatory site in the lactose promoter were measured by the osmotic stress procedure. Results indicated that formation of a nonspecific complex is accompanied by the net release of two to 44 water molecules. The improved stabilities of CAP-DNA complexes with enhanced osmolality may affect the capacity fo E. coli cells to withstand dehydration and/or high external salt concentrations.

The functionally linked hydration changes in Escherichia coli aspartate transcarbamylase and its catalytic subunit was examined using enzymatic assays and non linear regression. Results revealed that both osmotic stress measurements and surface area calculations of aspartate transcarbamylase (ATCase) predict water release upon ligation of the trimer. Furthermore, osmotic stress data are an accurate reflection of the hydratton behavior of ATCase.

The quantitative nucleophilic reactivity and selectivity of biological nitrogen nucleophiles toward adduct formation with the quinone methide, 4-allylidene-2,5-cyclohexadien-1-one, were investigated. The results showed that the adduct formation was competitive with hydration at low nucleophilic concentration. Proteins, peptides and tyrosine exhibited enhanced reactivity toward quinone methides compared to simple amino acids.

The participation of complexed ions in the primary coordination sphere of nucleotide bases in the minor groove of B form DNA was proven through theoretical and computational studies. Findings revealed that the nature of the structures are closely related to temporal dynamic motions of the DNA. The concept of intrusion of ions into the spine of hydration was evaluated in the context of available empirical information.

Dehydration of Ca- and Mg-exchanged montmorillonite was studied along [H.sub.2]O isochores in the hydrothermal diamond-anvil cell by in situ X-ray diffraction using a synchrotron radiation source. At pressures between the [H.sub.2]O liquid-vapor (L-V) boundary and [approximately]10 kbar, the dehydration temperature for the conversion from the 19 A hydration state to the 15 [Angstrom] hydration state occurred over the temperature range 260-350 [degrees] C for Ca-exchanged montmorillonite and 200-250 [degrees] C for Mg-exchanged montmorillonite, with a slight increase with increasing pressure. For both materials, the rehydration from the 15 [Angstrom] to 19 [Angstrom] states occurred at the same temperature as dehydration at pressures along the [H.sub.2]O L-V boundary, thus showing no hysteresis. The rehydration hysteresis increased to nearly 75 [degrees] C at 6 kbar for Ca-exchanged montmorillonite and to the same amount at 2.5 kbar for Mg-exchanged montmorillonite. Dehydration experiments on Mg-exchanged montmorillonite along the isochores of 1.024 and 0.75 g/[cm.sup.3] showed conversion from the 15 [Angstrom] hydrate to the 12.5 [Angstrom] hydrate at 590-605 [degrees] C. The 12.5 [Angstrom] hydrate only partially rehydrated after cooling to room temperature along those two isochores. In an experiment started from the 15 [Angstrom] state, in which the pressure was below the [H.sub.2]O L-V curve, dehydration occurred at 400-500 [degrees] C and rehydration at 430-350 [degrees] C. When our previous results on Na-exchanged montmorillonite are combined with the current experimental data, systematic trends can be found in the effect of pressure and interlayer-cation species on the dehydration temperature and rehydration hysteresis.

The catalytic activity of cross-linked subtilisin crystals in acetonitrile showed pronounced hysteresis. In a comparison of drying techniques, the highest rates of reaction were attained with crystals dried by washing with organic solvent. In all cases, full activity could be recovered in aqueous buffer. Crystals rinsed with anhydrous solvent were found to retain about 70 waters per enzyme molecule more than those dried over molecular sieves. When different solvents were utilized to dry the enzyme crystals, the catalytic rate in anhydrous acetonitrile was seen to vary substantially.

Ab ion-source reaction chamber was developed and used to obtain the ion-solvent equilibria of the hydration of diprotonated alpha,omega-alkyldiammonium ions H3N(CH2)pNH3(sup 2+) where p = 5,6,7,8,9,10,12 and (CH3)3N(CH2)pN(CH3)3(sup 2+) methylammonium ions where p = 2,3,4,6. The results showed that water molecules alternately occupy the alpha and omega charge sites during hydratio of the diprotonated diamines.

The competition between Na+ and K+ for coordination by G quartets was examined, utilizing the oligonucleotide d(G3T4G3) as a model system. d(G3T4G3) forms a dimeric foldback structure containing three G quartets in the presence of either NaCl or KCl. Findings revealed that the conversion of (d(G3T4G3))2 from the sodium to the potassium form is associated with a net free energy change. The preferred coordination of K+ over Na+ has been found to be caused by the greater energetic cost of Na+ dehydration with respect to K+ dehydration.

Anti-sesquinorbornene has approximately three times greater reactivity toward H3O+-catalyzed hydration than does ethyl vinyl ether. However, the two have similar general reaction characteristics. This was concluded from a study of the addition of water in H2O and D2O in the presence of H3O+ and some general acids. A mechanism for acid-catalyzed hydration of anti-sesquinorbornene which is similar to that generally accepted for alkenes, where the rate-limiting step involves proton transfer from H3O+ to the double bond, is presented.

The water proton spin-lattice relaxation rate was determined in Fe contaminated water filled porous glasses with pore diameters of 548 and 2917 angstroms and 0.65T at room temperature as a function of pore hydration. Findings revealed that in full to about quarter full contaminated porous glass, a volume-independent relaxation improvement of water proton spins is present. This rate could be bigger than the bulk water relaxation rate.

Fourier transform infrared spectroscopy of the L and unphotolyzed states of the chromophores of the D85T and D85N mutants of bacteriorhodopsin revealed a purple spectra that is characteristic of the wild-type protein instead of a blue spectra. Replacing chloride by bromide near the protonated Schiff base altered the charge of the Schiff base counterion. Replacing Asp85 with a neutral residue reduced the H-bonding strength of the Schiff base, indicating that a water molecule is coordinated to the bound halide in these mutants.

Hydrated aluminum cluster cations Al+(H2O)n, where n = 3-50 were subjected to fragmentation reaction with the inducing effect of black body radiation under ambient temperature and then investigated using modified FT-ICR mass spectrometer. It is observed that when n = 12-24, oxidation of the Al+ ion in the center and release of an H2 molecule occur simultaneously with the evaporation of water. The resulting product is a solvated Al(OH)2+(H2O)n-2 hydroxide ion cluster which is analogous to the existing Al(OH)2+(H2O)4 ions in solutions.

The hydration effects on substituting Na+ for Cs+ or Mg2+ ions in the ionic atmosphere of poly(rA)*2poly(rU) and poly(rA)*poly(rU) are examined using a combination of ultrasonic velocity and density techniques. Minimal effects were observed in the titration of the Na+ salt of each helix with Cs+, suggesting that both Na+ and Cs+ form outer-sphere counterion RNA complexes. Positive compressibility values and volume effects as well as a small dehydration of the whole Mg2+-RNA complexes resulted from the substitution of Na+ for Mg2+.

Molecular dynamics (MD) simulation of an Antennapedia homeodomain-DNA complex reveals an intermediary role for hydration water molecules in intermolecular contacts for specific DNA recognition. The results complement NMR data and provide information on the lifetimes of the hydration water molecules. MD simulations describe the pathways of hydration water molecules that exchange in and out of the protein-DNA interface. The results are discussed with regard to NMR structure and biochemical and genetic data.

The hydration of ditipyl ketene (tipyl = 2,4,6-triisopropylphenyl) generates a 98% pure solution of 2,2-ditipylethene-1,1-diol. The diol has a symmetric arrangement of the C=C-O-H moieties containing solvated OH groups. 1H and 13C NMR spectroscopic study of the carboxylic enol confirms the structure and indicates the identicalness of the two OH groups. The synthesis involves the preparation of ditipyl ketene, ditipylacetic acid, and 2,2-ditipyl bis-(trimethylsilyl) acetal as intermediates.

Muller's two-state model of bulk and hydrated water produces nearly compensating enthalpy and entropy changes with very small changes in the parameter values. Hydration-related heat capacity changes and temperature-related proton NMR chemical shifts support Muller's hydrated water model. According to the model, hydrogen bonds are enthalpically stronger but fewer in number in hydrated water. The application of the model to propane shows the sensitivity of entropy to small changes in parameter values.

The hydration of phenylacetylene involves the scission of its C-C triple bond in the presence of a ruthenium (II) metal complex acting as a catalyst. The ruthenium (II) metal complex consists of mer,trans-(PNP)RuCl2(PPh3), with PNP comprised of CH3CH2CH2N(CH2CH2PPh2)2. The products of hydration for phenylacetylene are toluene and carbon monoxide. Different intermediate species are separated to assist in determining the reaction mechanism involved in the hydration of phenylacetylene, using a ruthenium (II) metal complex as catalyst.

Food packaging with nylon-6 polyamide membrane gives a safe rehydration system using nonpurified water. The membrane allows rehydration of freeze-dried food by an inward passage of water from a source of nonpurified water. The membrane does not allow microorganisms to pass through for a time sufficient for the food to get rehydrated. The performance of the system depends on the temperature, and composition of food and rehydrating water.

Short-range repulsions exhibited between the colloidal particles and biological surfaces of water are caused by the entropic repulsion from the confinement of thermally mobile surface groups. This is the reason why water is always a good solvent or suspending medium for colloidal and biological structures such as deoxyribonucleic acid, viruses, proteins and cells. The attractive van der Waals and the repulsive electric double-layer forces are considered to be the major forces that operate between two macromolecules or surfaces in liquids.

A study has been conducted to describe the mechanisms involved in the hydration of the orthophosphate anion in the gas phase and its conversion to the metaphosphate ion using the Electrospray method. Mass spectrometry was also used to measure the ion concentration. Calculations suggest that conversion did not occur because the metaphosphate ion and its hydrates were not observed. The kinetic energy thresholds for collision-induced decomposition revealed a high activation energy barrier.

The free energy values, delta-G(degree sign)(sub n-1, n) obtained for 16 carboxylic anions, RCO2(super -) and 17 monoanions of the oxo acid of N, P, Cl,I and S shows a nearly linear relationship with their gas phase acidities, corresponding to the dissociation of AH into A(super -) and H(super +). The hydration exoergicities of dicarboxylates is less than those of RCO2(super -) anions due to intramolecular hydrogen bonding which stabilizes these anions. The hydration free energies of doubly charged anions and oxo anions are discussed.