Conformational dynamics of DNA affected by intercalation and minor groove binding: direct observation of large DNA.

Using fluorescence microscopy, we have observed moving DNA molecules in solution and analyzed the "higher-order" structure in a quantitative manner. It was found that EB (ethidium bromide), an intercalator, has the effect to increase the persistent length. In other words, EB expands DNA. Whereas, DAPI (4',6-diamidino-2-phenylindole), a minor groove binding drug, decreases the persistent length. It is demonstrated that the direct observation of DNA molecules with fluorescence microscopy is quite useful to study the interaction of various chemical compounds with DNA molecules.     

Network structures and thermal properties of polyurethane films prepared from liquefied wood

Polyurethane (PU) films were prepared by solution-casting after co-polymerization of liquefied woods (LWs) and polymeric methylene diphenylene diisocyanate (PMDI). The resulting PU films had various [NCO]/[OH] ratios ranging from 0.6 to 1.4 and contained 5.0-16.8% dissolved woody components at the [NCO]/[OH] ratio of 1.0. The crosslink densities of the films with [NCO]/[OH] ratios of 0.6-1.4 increased remarkably with increasing [NCO]/[OH] ratio. Similarly, there were large increases in glass transition temperatures (Tg). These characteristics could be attributed to effective incorporation of PMDI into the LW. The crosslink densities and Tg of the PU films prepared at the [NCO]/[OH] ratio of 1.0 increased because the amounts of dissolved woody components in the films increased. It is concluded that the dissolved woody components acted as crosslinking points in PU network formations. The thermal degradation of the PU films at an [NCO]/[OH] ratio of more than 0.8 or with more than 10.6% dissolved wood started above 262 degrees C under an N2 atmosphere. The thermostability was lost at low crosslink density or with large amount of co-polymerized glycerol structures in the PU networks.     

Direct observation of poly(3-hydroxybutyrate) depolymerase adsorbed on polyester thin film by atomic force microscopy

Poly[(R)-3-hydroxybutyrate] (PHB) depolymerases adsorbed on poly(L-lactide) (PLLA) thin film were directly observed by atomic force microscopy (AFM). A PLLA thin film of 100 nm thickness was prepared on a silicon wafer by spin-cast method. The PLLA thin film was treated at 220 degrees C and quenched to room temperature, resulting in the formation of a completely amorphous film with a smooth surface. Then, the PHB depolymerases from Pseudomonas stutzeri YM1006 and Ralstonia pickettii T1 were dispersed on the amorphous PLLA thin film. Direct AFM observation has revealed that the PHB depolymerases bind in an elliptic shape on the surface of the PLLA thin film and that a small ridge is created around each enzyme molecule. After removal of the enzymes with 40% ethanol aqueous solution, small hollows were found on the PLLA thin film. These results suggest that a PHB depolymerase interacts with polyester molecules during their adsorption to make a hollow on the substrate surface.     

Effects of fatty acids on calcium-stimulated adenosine triphosphatase in rat submandibular gland microsomes.

Effects of fatty acids on Ca²⁺-ATPase and Mg²⁺-ATPase in the microsomal fraction of rat submandibular gland have been investigated. Saturated fatty acids had almost no effect, but unsaturated fatty acids inhibited both ATPases. Modes of inhibition by linoleic acid were as follows: competitive for calcium and ATP with Ca²⁺-ATPase; non-competitive for magnesium and ATP with Mg²⁺-ATPase