Photocontrol of lactate dehydrogenase-spiropyran collagen membrane

Collagen fibrils were modified with β-l-[3,3-dimethyl-6′-nitrospiro-(indoline-2,2′-2H-benzopyran)] propionic anhydride. The spiropyran collagen membrane showed reverse photochromism. Lactate dehydrogenase (LDH, E.C. 1.1.1.27) was entrapped in the spiropyran collagen membrane. The activity of the LDH-spiropyran collagen membrane decreased under visible-light irradiation, and then increased again after incubation in the dark. The optimum pH of the LDH-spiropyran collagen membrane was displaced toward lower pH values under visible-light irradiation. The activity change of the LDH-spiropyran collagen membrane under visible-light irradiation depended on the LDH content.     

Light absorption due to higher harmonics of molecular vibrations in transparent amorphous polymers for plastic optical fibers

We have studied simple empirical equations to estimate light absorption loss α_v due to harmonics of molecular vibrations of transparent amorphous polymers used in plastic optical fibers (POFs). In the visible region, absorption involves two losses. One is α_v, and the other is the electronic transition absorption loss, α_e. Of the two, α_v is considerably larger than α_e in the wavelength region used for optical communication with POFs. We have clarified relationships between chemical structure of repeat units of polymers and α_v. We find that α_v is proportional to the concentration of specific chemical bonds (C? H, N? H, and Obond;H bonds) in the polymer solid, and we propose empirical equations to estimate α_v from the polymer density and the chemical structure of the repeat unit. These equations are used to estimate α_v of several polymers [i.e., poly(methyl methacrylate), polystyrene, and polycarbonate]. The estimated values are nearly equal to the experimental or reference values. Furthermore, to minimize the attenuation in the POF, we conclude that the POF core polymer should have no N? H, O? H, or aliphatic C? H bonds in its repeat unit.     

Triplet state formation of aromatic hydrocarbons quenched with silver ion in ethanol

Fluorescence quenching rate constants of aromatic hydrocarbons by silver ions are determined. The values obtained are not well interpreted with thermodynamical considerations based on an electron transfer mechanism, but related to the intersystem crossing rate constant of the fluorescer. Triplet state formation in the course of quenching has been confirmed by laser photolysis studies.     

Quantitative analysis by nuclear magnetic resonance using precision coaxial tubing

Quantitative analysis by n.m.r. using precision coaxial tubing is described. A solution of the intensity standard is placed in the central capillary and the sample of interest in the surrounding annulus. By this method the contamination of the sample by the standard compound can be avoided and an accurate determination can be carried out by using solutions of correct concentrations of the intensity standard. Applications to several types of quantitative problems are given. In order to get a higher accuracy and precision the experimental conditions were also studied.