Hydration Structure Around the Carboxyl Group Studied by Neutron Diffraction with 12C/13C and H/D Isotopic Substitution Methods

Time-of-Flight (TOF) neutron diffraction measurements have been carried out on aqueous 8 mol% sodium acetate solutions in D₂O. Scattering cross sections that were observed for sample solutions involving ¹²C/¹³C and H/D isotopically substituted acetate ions were used to derive the first-order difference functions, Δ_H(Q) and Δ_C(Q), and corresponding distribution functions, G _H(r;r) and G _C(r;r), which describe the environmental structure around the methyl and the carboxyl groups within the acetate ion, respectively. Structural parameters concerning the first hydration shell of the carboxyl group within the acetate ion were obtained through the least squares fit to the observed intermolecular difference function, Δ_C ^inter(Q). The nearest neighbor C _O...D _W1 (C_O: carboxyl carbon atom, D_W1: water deuterium atom) distance, r(C _O...D _W1 ), and the angle, ∠ C _O ...D _W1 -O _W (O _W : water oxygen atom), were determined to be 2.63(1) Å and 120(1)°, respectively. The coordination number, n(C _O ...D _W1 ), was obtained to be 4.0(1). These results are consistent with the hydration structure in which water molecules in the first hydration shell of the carboxyl group are hydrogen-bonded with oxygen atoms of the carboxyl group.     

Mass spectrometric studies of alkyl-, phenyl- and chloropyrimidines

The mass spectra of alkyl- and chloropyrimidines are recorded. A generalised fragmentation mechanism for the derivatives of pyrimidine is proposed. The principle of α-cleavage for heterocyclic compounds as proposed in the previous paper is shown to be valid for pyrimidine derivatives. Electronic structures of some molecular and intermediate ions are calculated by the openshell CNDO/2 and INDO methods.     

Evaluation of radioimmunoassay of the blood tobramycin level for the purpose of setting the dosage based on the clinical pharmacokinetic theory and a comparison of radioimmunoassay with other assay methods

With the purpose to use for therapeutic drug monitoring (TDM), blood concentrations of tobramycin (TOB) in each patient were measured by radioimmunoassay (RIA). A RIA kit of TOB (Clinical assay-Japan Travenol) was evaluated for precision and recovery, in that partial improvement of the method was made, in order to measure low level of TOB. The RIA was compared with high-performance-liquid-chromatography (HPLC), bioassay (BA) and 2 kinds of enzyme immunoassay (EIA) (EMIT and SLFIA). The RIA of TOB revealed high precision (1.8-2.4% in C.V.) and high reproducibility (5.0-6.9% in C.V.). It was found that this RIA kit can be used for measuring low level of serum TOB concentrations by a modification of the method. The total range of measurable blood level is from 0.1 to 16.0 micrograms/ml. The nearly one to one correspondence was observed between RIA and other 4 methods, when 154 samples obtained from 18 cases were measured. A representative case of TDM for TOB was demonstrated, in which predicted concentrations agreed fairly well with actual measured values at steady state. It was concluded that the RIA kit is useful for clinical application of TDM for the adequate dosage regimen of TOB. Modification of the method for rapid assay of a small number of samples will increase the clinical usefulness.     

VISUAL PIGMENTS—10. SPECTROSCOPY AND PHOTOPHYSICAL DYNAMICS OF RETINOL AND RETINYL ETHER

Abstract— The absorption and emission spectra, lifetimes and quantum yields of all-trans retinol have been examined as a function of solvent and temperature. In addition, the spectroscopy of retinyl ether and 2 other polyene alcohols have been determined. Based on the results obtained, we conclude that the singlet excited state of retinol and retinyl cther is of a forbidden character and of the type loosely called ¹A^-_g. Retinol forms a dimer in an alkane solvent when cooling from 298 to 77 K. A general structure for the dimer is proposed.     

Studies of heteroaromaticity—LXVI: Photochemical and thermal behaviours of heterocycles involving azido-ketone moiety

The photolyses and thermolyses of compounds 1 and 2 in a nucleophilic solvent such as alcohol and diethylamine have been studied and form 4,5-disubstituted amino and alkoxy or dialkylamino groups. The mechanism for the formation of the products are proposed and discussed.