Hydration structure around a non-electrolyte molecule as revealed by monte carlo calculation: have you seen the “iceberg”?

Monte Carlo calculations have been carried out for pure water and an infinitely dilute aqueous solution of methanol at 298.15 K at ordinary density by the Metropolis method in NTV ensemble. The hydration structure around methanol revealed by a graphic display technique indicates a structure-forming effect near the hydrophobic group.     

Synthesis of diazepinoquinoxalines and imidazolobenzopteridines

Diazepinoquinoxalines 3, 4 and imidazolobenzopteridines 5, 6a-d, 7a-d, 8, 9 were synthesized from 3-allylamino-6,7-dimethyl-2-quinoxalinecarboxamide ( 1 ) and 2-allylamino-6,7-dimethyl-3,4-dihydrobenzo[g]pteridin-4-one ( 2 ) by the intramolecular cyclization using phenylselenenyl chloride.     

RECENT PROGRESS OF NANO-MECHANICAL MAPPING

 Nano-mechanical mapping by atomic force microscopy has been developed as an useful application to measure mechanical properties of soft materials at nanometer scale. To date, the Hertzian theory was used for analyzing force-distance curves as the simplest model among several contact mechanics between elastic bodies. However, the preexisting methods based on this theory do not consider the adhesive interaction in principle, which cannot be neglected in the ambient condition. A new analytical method was introduced to estimate the elasticity and the adhesive energy simultaneously by means of the JKR theory, describing adhesive contact between elastic materials. Poly(dimethylsiloxane) (PDMS) and isobutylene-co-isoprene rubber (IIR) were analyzed to verify the applicable limit of the JKR analysis. For elastic samples such as PDMS, the force-deformation plots obtained experimentally were consistent with JKR theoretical curves. Meanwhile, for viscoelastic samples, especially for IIR, the experimental plots revealed large deviations from JKR curves depending on scanning velocity and maximum loading force. Some nano-rheological arguments were employed based on the difference between these specimens.     

Synthesis of porphyrin-introduced silica gels by sol-gel process

Using a hydroxyl group appended free base porphyrin derivative (HP), porphyrin-introduced silica gels were synthesized by a sol-gel process. The HP content in the materials linearly increased with increasing the HP concentration. Meanwhile, free base tetraphenylporphyrin (TPP) with no hydroxyl groups were almost not incorporated into the silica gels. These facts suggested that the interaction between hydroxyl groups of the HP molecules and silica network is considerably strong. The UV-vis characters of HP-introduced materials were almost the same as pure HP molecules. The Beer's plot indicated that the HP molecules in the materials are dispersed.     

Optical rotary dispersion of nitrobenzene derivatives—IV : Absolute conformation of twisted nitrobenzen derivatives and its control through conformational transmission

The origin of Cotton effect shown by o-nitrobenzoyl esters is discussed. The Cotton effect observed for 1-(?)-methyl ester of 3-nitrophalic acid and 4-nitrohemimellitic acid (6 and 12), indicated that the favoured twisting direction of the nitrobenzene moiety is determined by the asymmetric menthyl group through the intervening carboxyl groups. This provides a new concept in conformational analysis of aromatic compounds. Extending the concept of conformational transmission to 2,2′-dinitrobipenhyl derivatives with known ab twisted nitrobenzene was related to the sign of the Cotton effect at 330 nm in accordance with the result of X-ray crystal analysis 1-(?)-menthyl 4-bromo-2-nitrobenzoate (1)     

Water soluble cyclodextrin polymers: Their interaction with drugs

The complex forming ability of a water-soluble -cyclodextrin epichlorohydrin, polymer (CDPS) and its different molecular weight fractions was studied and compared with the complexing properties of -cyclodextrin (CD) and dimethyl-CD (DM-CD). CDPS was separated into two main fractions. CDPS and its fractions formed well soluble inclusion compounds with the studied drugs. The low molecular weight fraction formed rather stable complexes with small guest molecules, the high molecular weight fraction was found to be more efficient in binding larger substrates. Structural studies of furosemide-CD complexes were attempted by NMR spectroscopy.Presented at the Fourth International Symposium on Inclusion Phenomena and the Third International Symposium on Cyclodextrins, Lancaster, U.K., 20–25 July 1986.     

The inclusion complex of piromidic acid with dimethyl-β-cyclodextrin in aqueous solution and in the solid state

Inclusion complex formation of piromidic acid (PA) with dimethyl--cyclodextrin (DM--CD) in aqueous solution and in the solid state was confirmed by the solubility method, differential scanning calorimetry (DSC) and proton nuclear magnetic resonance (¹H-NMR) spectroscopy. The apparent stability constant,K _c , of the complex was estimated to be 244 M^–1. The stoichiometry of the complex was given as the ratio 1:2 of PA to DM--CD. The dissolution rate of the PA/DM--CD complex was much greater than that of intact PA.Presented at the Fourth International Symposium on Inclusion Phenomena and the Third International Symposium on Cyclodextrins, Lancaster, U.K., 20–25 July 1986.     

Photodestruction of fluorophores and optimum conditions for trace DNA detection by automated DNA sequencer.

Although automated DNA sequencers are becoming popular, their sensitivity in detecting DNA bands is still around 10(-17) mole/band. The sensitivity of a system depends on the laser power, labeling fluorophore, and the fluorescence-collecting yield. The emission and photodestruction cross-sections of the fluorophores are critical in optimizing the irradiated laser power and the migration speeds of DNA fragments to achieve high sensitivity. We investigated photodestruction cross-sections of various fluorophores to optimize the irradiation laser power. In addition, we used a cylindrical lens system to improve the fluorescence-collecting yield of a DNA sequencer using side entry laser irradiation. Fluoresceine isothiocyanate (FITC) commonly used in fluorescence studies, is very photo-destructive, the cross-section of the destruction being about 3.8 x 10(-20) cm2 in buffer solution while that of Texas Red is 1.5 x 10(-21) cm2. When the time for DNA fragments to transit through the irradiated region is 11 s, the optimum laser powers are 0.9 mW, with an Ar laser (488 nm) for FITC-DNA, and 18 mW, with an He-Ne laser (594 nm) for Texas Red DNA. We have developed a DNA sequencer, with a cylindrical lens system which improves the fluorescence-collecting efficiency by a factor of 4, and an He-Ne laser (5 mW). Although the sequencer uses a slab gel, an ultra-high sensitivity of 5 x 10(-20) mole/band (S/N-4) was achieved under optimized conditions.