Biomedical subjects
Publications and source records attributed to SW Kim.
We investigate the nature of quantum localization exhibited by the center-of-mass motion of an ion in a Paul trap interacting with a standing laser field. Depending upon system parameters and the initial location of the ion, quantum suppression of chaotic diffusion is dominated by dynamical localization or localization due to partial barriers formed of broken separatrices and cantori.
Two different hydrophilic moieties, carboxyl derivatives of monosaccharidic (Glc, Gal, Man, Fuc) glycosides and methoxypolyethylene glycols of varying MW, were covalently attached to the insulin GlyA1, PheB1 and/or LysB29 amino groups (seven possible derivatives), and resulting insulin conjugates purified to homogeneity. In vivo bioactivity in rats of most derivatives was preserved while disubstituted PEG-insulins showed decreased potency. Only site-specific modification of PheB1 amino group with either moiety resulted in pronouncedly increased resistance of insulin to fibrillation, indicating that the B-chain N-terminus of the insulin molecule is mechanistically involved in the fibrillation process. Immunogenicity in vivo and in vitro of monoglycosylated insulins was comparable to that of insulin, diglycosylated insulins showed immunogenicity enhancement. Immunogenicity of PEG-insulins was significantly suppressed. PheB1-glycosylated insulins administered subcutaneously in dogs displayed extended action profiles, the most effective being PheB1-galactosylated insulin, resembling the pharmacodynamic response of intermediate-acting insulin preparations. The pharmacokinetic parameters of these insulin derivatives were not significantly different from that of insulin even though absorption and residence time and clearance were increased, providing some explanation for prolonged action profile. Lectin-specific binding as a retardation basis is not likely involved. In support of this, subcutaneously administered PheB1-PEG(600)-insulin showed an even more protracted action profile, suggesting that the basis of retardation is physical and nonspecific. This implies that by increasing PEG chain MW, further delay/prolongation of action can be achieved to yield new soluble basal insulin substitutes with potential clinical applications.
Methyl-methine linkages of Novolac, a commercially available t-butylphenol acetylene condensed (TBPA) resin, have been identified by recognition of pyrolysis pathways using pyrolysis-gas chromatography/mass spectrometry (Py-GC/mS) in vulcanized rubber. The diagnostic mass spectrum of t-butylphenol with methyl-methine linkages between phenolic rings was observed at m/z 192, corresponding to 4-t-butyl-2-ethyl-6-methylphenol. Other molecular ions were observed at m/z 178, 164, and 150 in the characteristic pyrolyzates. The ion at m/z 192 in the TBPA resin was observed to be characteristic for methyl-methine linkages between the phenolic groups, and the analytical pyrolysis-GC/mS method was thus able to identify the resin at low levels in vulcanized rubber. Copyright 1999 John Wiley & Sons, Ltd.
Two analytical methods, automatic thermal desorption gas chromatography/mass spectrometry (ATD-GC/MS) and pyrolysis gas chromatography/mass spectrometry (Py-GC/MS), were applied as direct methods for the analysis of oligomeric tackifying resins in a vulcanized rubber. The ATD-GC/MS method, based on discontinuous volatile extraction, was found to be an effective means for direct analysis of the oligomeric tackifying resins contained in a vulcanized rubber. The oligomeric tackifying resins, such as t-octylphenolformaldehyde (TOPF) resin, rosin-modified terpene resin, and cashew resin, could be directly analyzed in vulcanized rubber by ATD-GC/MS. Much simpler total ion chromatograms were obtained by ATD-GC/MS than by flash pyrolysis with a Curie-point pyrolyzer, permitting much easier interpretation. Ions at m/z 206, 135, and 107 were fingerprints in the characteristic mass spectra obtained by ATD-GC/MS for TOPF resin in the vulcanized rubber. 1H-Indene, styrene, and isolongifolene were observed as their characteristic mass spectra in the pyrolyzate of the rosin-modified terpene resin. From the cashew resin, phenol, 3-methylphenol, and 4-(1,1,3, 3-tetramethylbutyl)phenol were obtained as the characteristic pyrolyzates by discontinuous thermal extraction via ATD-GC/MS. Copyright 1999 John Wiley & Sons, Ltd.
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