Protonated water clusters, H + (H 2 O) n (n ) 5-8), from a supersonic expansion have been investigated by vibrational predissociation spectroscopy and ab initio calculations. The experimental spectra were obtained at an estimated cluster temperature of 170 ( 20 K. Recorded absorption bands at the frequency range of 2700-3900 cm -1 are attributed to the free-and hydrogen-bonded-OH stretches of the ion core and the surrounding solvent molecules. Ab initio calculations, performed at the B3LYP/6-31+G* level, indicate that geometries of the H + (H 2 O) 5-8 isomers are close in energy, with the excess proton either localized on a single water molecule, yieldingSystematic comparison of the experimental and computed spectra provides compelling evidence for both cases. The unique proton-transfer intermediate H 5 O 2 + (H 2 O) 4 was identified, for the first time, by its characteristic bonded-OH stretching absorptions at 3178 cm -1 . The existence of five-membered-ring isomers at n ) 7 is also evidenced by the distinct bonded-OH stretches at 3500-3600 cm -1 and by the free-OH stretch of threecoordinated H 2 O at 3679 cm -1 . Among these H + (H 2 O) 7 isomers is a newly discovered H 5 O 2 + -containing pentagonal ring, which is computed to be lowest in Gibbs free energy at 170 K. Its spectroscopic signature is the splitting of two equivalent bonded OH stretches into a doublet (3544 and 3555 cm -1 ) by vibrational coupling through ring closure. No profound spectral evidence, however, was found for the formation of four-membered rings although it is predicted to be favorable in terms of total interaction energy for H + (H 2 O) 7 . Six-membered ring and three-dimensional cagelike structures are also stable isomers but they are less strongly bound. The preference of five-membered-ring formation at n ) 7 appears to be the result of a delicate balance between entropy and enthalpy effects at the presently investigated cluster temperature. The correlation of this investigation with other studies of neutral water clusters and of the hydration of biological macromolecules is emphasized.

The effect of alcohol on rabbit bone marrow and on the differentiation of mouse bone marrow stromal cells was investigated. Alcohol was administered intragastrically at a dose of 10 mL/kg/day for 1 to 6 months. Alcohol induced a significant increase in serum lipid peroxides, triglyceride, and cholesterol, and a reduction in superoxide dismutase activity. Fatty infiltration in the liver and adipogenesis in bone marrow were found histologically after alcohol administration. Fat cell hypertrophy and proliferation and diminished hematopoiesis in the subchondral area of the femoral head were observed. Triglycerides were deposited in osteocytes, which became pyknotic, and the percentage of empty osteocyte lacunae increased. None of these abnormal changes were detectable in the control group. In the in vitro study, the marrow stromal cells were treated with increasing (0.03, 0.09, and 0.15 mol/L) concentrations of ethanol for 4 to 21 days. Alcohol induced the differentiation of the cells into adipocytes. The number of adipocytes increased with longer durations of exposure to ethanol and with higher concentrations. Cells treated with ethanol also showed diminished alkaline phosphatase activity and expression of osteocalcin. These novel findings indicate that alcohol can directly induce adipogenesis, decrease osteogenesis in bone marrow stroma, and produce intracellular lipid deposits resulting in the death of osteocytes, which may be associated with the development of osteonecrosis, especially in patients with long-term and excessive use of alcohol.

Vibrational predissociation spectra of protonated water clusters H+(H2O)n, n = 9-11, are presented. Examination of the spectra in the free-OH stretching region revealed predominance of a single absorption band at approximately 3690 cm(-1) for three-coordinate H2O acting as a double-proton-acceptor/single-proton-donor in the n = 11 cluster. In contrast, the intensity of the absorption band of two-coordinate H2O acting as a single-proton-acceptor/single-proton-donor at approximately 3715 cm(-1) decreases with cluster size, and that of one-coordinate H2O acting as a single-proton-acceptor at approximately 3740 and approximately 3650 cm(-1) diminishes nearly entirely at n > 10 in the spectrum. To deduce the information about cluster temperature, we measured the spontaneous dissociation rates of the cluster ions inside an octopole ion trap and fitted the measured rate constants to an empirical Arrhenius equation. Temperatures in the range of 150 K were estimated for all H+ (H2O)9-11, suggesting that the thermal effect may populate the structures other than the true ground state. The results, combined with previously acquired spectra for H+ (H2O)5-8 (J.-C. Jiang, Y.-S. Wang, H.-C. Chang, S. H. Lin, Y. T. Lee, G. Niedner-Schatteburg and H.-C. Chang, J. Am. Chem. Soc., 2000, 122, 1398) and Monte Carlo simulations with the OSS2 model potential (L. Ojamlie, I. Shavitt and S. J. Singer, J. Chem. Phys., 1998, 109, 5547), show a systematic change in hydrogen-bond topology from tree-like, single-ring, multiple-ring to cage-like isomers (and their mixtures) as the cluster size increases from n = 5 to n = 11.