The 3 and 4 vibrational transitions of methane trapped in solid parahydrogen have been observed by using Fourier transform infrared and high resolution laser spectroscopy. The observed spectrum is interpreted in terms of rovibrational states of the spherical rotor which are subjected to the crystal field splitting. The 4 band shows extremely sharp lines of a width of ϳ0.003 cm Ϫ1 , while the 3 band exhibits broader lines of a width of 1 cm Ϫ1. The infrared selection rules derived from an extended group theory to take into account the field effect are consistent with the observed spectra. The intermolecular interaction and the field effect in solid parahydrogen are analyzed quantitatively.

Click triazole-based oligopeptides 1-3 were found to self-dimerize (K(dim) ≈ 10-680 M(-1)) in a head-to-tail fashion based on (1)H variable concentration, 2D, and H/D exchange NMR, VPO, CD, FT-IR studies and Gaussian 03 simulations. The dimerization constant K(dim) was shown to increase with increasing number of the amino acid units. Within the same oligomeric series, the K(dim) value is strongly affected by the size of the C-terminal end group. The tripeptides 2 are also excellent organogelators of aromatic solvents.

Reported here are the first rotationally assigned near-infrared spectra of the ethylene dimer. The vibrational bands observed in this study correlate with ν9 and ν11 of the ethylene monomer, corresponding to C–H stretching motion. The spectral patterns have been identified as due to the vibrational transitions of a symmetric top molecule with D2d symmetry. This structure of the dimer has been predicted by ab initio calculations as the most stable geometry due to the fact that it enables the formation of four equivalent hydrogen bonds. Both vibrational bands show considerable homogeneous broadening corresponding to vibrational predissociation lifetimes of 0.37 and 0.18 ns for ν9 and ν11 excitation, respectively.

We have compared diazepam pharmacokinetics in 16 Chinese and 18 white Caucasian healthy male volunteers, resident in Hong Kong and have correlated them with physical attributes. Serum concentrations of diazepam and desmethyldiazepam were measured in venous blood by an enzyme-linked immunoassay (0-3 h samples) and HPLC (3-72 h samples). Pharmacokinetic parameters were derived assuming a two compartment model, distribution phase less than 6 h, and 100% oral systemic availability. Compared with the Chinese the white Caucasians were older, heavier, taller, and fatter, as judged by skin fold thickness (SFT) and total body weight to 'Ideal' body weight (TBW/IBW) ratio; respective mean differences being 16%, 27%, 4%, 26%, and 15% (p less than 0.05). Mean diazepam apparent volume of distribution (V) and V/IBW were larger in the white Caucasians (52% & 39% respectively, p = 0.002). SFT and TBW/IBW ratio yielded the best correlations with V, V/TBW and V/IBW (0.50-0.75, p less than 0.05). Obesity indices contributed most to the overall regressions (R2 up to 0.52), and for V there was a further small effect (2%, partial F test) due to ethnic group, possibly reflecting stature. Mean peak diazepam concentration (Cmax) was similar in both ethnic groups. Time to Cmax (tmax) was more often prolonged in the Chinese (chi 2 test, p = 0.01). Body fat and stature may thus account for these inter-ethnic differences in the apparent volume of distribution of diazepam, a highly lipid-soluble drug.