Preparation,Isolation and Characterization of all of the Regioisomeric 61, 6N-Bis-O-(Monomethoxytrityl) and-(Dimethoxytrityl) Derivatives of Cyclomalto-Olgosaccharides

Abstract

Regioisomeric 6¹, 6ⁿ-bis-O-(monomethoxytrityl) or 6¹, 6ⁿ-bis-O-(dimethoxytrityl) cyclomaltohexaose, -cyclomaltoheptaose (n = 2-4), and -cyclomaltooctaose derivatives (n = 2-5) were prepared by the reaction of cyclomaltohexaose (1, cG₆, αCD), cyclomaltoheptaose (11, cG₇, βCD) or cyclomaltooctaose (21, cG₈, γCD) and 4-monomethoxytrityl chloride or 4,4′-dimethoxytrityl chloride in pyridine. Products were isolated by HPLC. The regiochemical determination of these positional isomers was done by converting these compounds to the respective 6¹, 6ⁿ-bis-O-(tert-butyldimethylsilyl) derivatives¹ whose structures have been already established.     

Simultaneous determination of methylene blue and new methylene blue by slab optical waveguide spectroscopy and artificial neural networks

A slab optical waveguide (SOWG) has been used for study of adsorption of both methylene blue (MB) and new methylene blue (NMB) in liquid-solid interface. Adsorption characteristics of MB and NMB on both bare SOWG and silanized SOWG by octadecyltrichlorosilane (ODS) were compared. The simultaneous determinations of both MB and NMB were explored by flow injection SOWG spectrophotometric analysis and artificial neural networks (ANNs) for the first time. Concentrations of MB and NMB were estimated simultaneously with the ANNs. Results obtained with SOWG were compared with those got by conventional UV-visible spectrophotometry.     

Polynomiality of primal-dual affine scaling algorithms for nonlinear complementarity problems

This paper provides an analysis of the polynomiality of primal-dual interior point algorithms for nonlinear complementarity problems using a wide neighborhood. A condition for the smoothness of the mapping is used, which is related to Zhu’s scaled Lipschitz condition, but is also applicable to mappings that are not monotone. We show that a family of primal-dual affine scaling algorithms generates an approximate solution (given a precision ε) of the nonlinear complementarity problem in a finite number of iterations whose order is a polynomial ofn, ln(1/ε) and a condition number. If the mapping is linear then the results in this paper coincide with the ones in Jansen et al., SIAM Journal on Optimization 7 (1997) 126–140. Research supported in part by Grant-in-Aids for Encouragement of Young Scientists (06750066) from the Ministry of Education, Science and Culture, Japan. Research supported by Dutch Organization for Scientific Research (NWO), grant 611-304-028     

Parallel Implementation of Successive Convex Relaxation Methods for Quadratic Optimization Problems

As computing resources continue to improve, global solutions for larger size quadrically constrained optimization problems become more achievable. In this paper, we focus on larger size problems and get accurate bounds for optimal values of such problems with the successive use of SDP relaxations on a parallel computing system called Ninf (Network-based Information Library for high performance computing).     

Versatile synthesis of epicatechin series procyanidin oligomers, and their antioxidant and DNA polymerase inhibitory activity

Proanthocyanidins, known as condensed tannins or oligomeric flavonoids, exist in many edible plants and show various interesting biological activities. We have developed a simple and versatile method of synthesizing procyanidin oligomers consisting of (−)-epicatechin and (+)-catechin. This method is applicable to the synthesis of various 3-O-substituted oligomers. We report here the stereoselective and length controlled synthesis of [4-8]-condensed (−)-epicatechin series procyanidin oligomers. We described the details of the synthesis of an two tetramers, (−)-epicatechin-(−)-epicatechin-(−)-epicatechin-(−)-epicatechin and (−)-epicatechin-(−)-epicatechin-(−)-epicatechin-(+)-catechin (arecatannin A1), (−)-epicatechin pentamer and two 3,3″,3?-tri-O-galloyl trimers, (−)-epicatechin-(−)-epicatechin-(−)-epicatechin-3,3″,3?-tri-O-gallate and (−)-epicatechin-(−)-epicatechin-(+)-catechin-3,3″,3?-tri-O-gallate with the condensation method using TMSOTf as a catalyst. The ability of DPPH radical scavenging activity and DNA polymerase inhibitory activity of these oligomeric compounds were investigated.     

HPLC for Separation and Quantification of Deoxyribonucleic Acid Fragments and Measurement of Deoxyribonucleic Acid Degradation

DNA quantification has made its mark in pharmaceutical analysis and the life sciences. In particular, in the quality control of nucleic acid drugs and the detection and quantification of genetically modified organisms, evaluation of the DNA degradation rate has become imperative. In this study, by using high-performance liquid chromatography with an anion-exchange column, we established a method for the separation and quantification of DNA fragments in mixed DNA samples. By using a NaCl concentration gradient, DNA fragments in mixed DNA sample were separated well. A calibration curve from 0.05 to 12.4 ng μL^?1 was obtained with high linearity and the correlation coefficient was 0.9999. The limit of detection was 0.02 ng μL^?1 and the limit of quantification was 0.06 ng μL^?1 for S/N = 3 or S/N = 10, respectively. The relative standard deviation was less than 2 % in the measurement of peak area repeatability. The recovery of approximately 1 ng μL^?1 of a specific DNA spiked in a mixed DNA sample was 99.9 ± 3.6 %. The method was able to measure the degradation rate of 600 bp DNA with a variation of approximately 1 %.     

Facile synthesis of platinum nanoparticle-containing porous carbons,and their application to amperometric glucose biosensing

This study describes the facile synthesis of platinum nanoparticle-containing porous carbons (Pt/C) by carbonization of freeze-dried agarose gels containing potassium tetrachloroplatinate under a nitrogen atmosphere at 800 °C. By adjusting the ratio between agarose and platinate in the freeze-dried gels, the Pt content in the final Pt/C products could be systematically varied from 0–10 wt.%. Transmission electron microscopy, inductively coupled plasma atomic emission spectrometry, X-ray photoelectron spectroscopy, Raman spectroscopy, and nitrogen physisorption measurements revealed that the Pt/C materials obtained by this method possess high surface areas (350–500 m² g⁻¹), narrow Pt nanoparticle size distributions (6 ± 3 nm) and nanocrystalline graphite –like carbon character. By immobilization of glucose oxidase on the surface of a 4 wt.% Pt/C electrocatalyst prepared by this route, a very sensitive amperometric glucose biosensor was obtained (response time <2 min, sensitivity 1.9 mA M⁻¹; and a linear response with glucose concentration up to 10 mM). The simplicity and versatility of the described synthetic method suggests its application to the preparation of carbon supported noble metal catalysts including palladium/C and gold/C.

This study describes the facile synthesis of platinum nanoparticle-containing porous carbons (Pt/C) by carbonization of freeze-dried agarose gels containing potassium tetrachloroplatinate. The Pt/C materials exhibited excellent electrocatalytic activities, as demonstrated by their successful integration into amperometric glucose biosensor

     

Cobalt oxide supported gold nanoparticles as a stable and readily-prepared precursor for the in situ generation of cobalt carbonyl like species

A treatment of cobalt oxide supported gold nanoparticles (Au/Co₃O₄) under syngas atmosphere effectively generated a cobalt carbonyl-like active species in the reaction vessel. The preparation of Au/Co₃O₄ was quite simple and the in situ generated cobalt species could be used as a stable and easy handling alternative for dicobalt octacarbonyl without bothersome purification prior to use. The reactions, which are sensitive to the purity of the dicobalt octacarbonyl, such as the alkoxycarbonylation of epoxides and the Pauson-Khand reaction, smoothly progressed with Au/Co₃O₄.     

Prolongation of the active lifetime of a biomolecular motor for in vitro motility assay by using an inert atmosphere

Over the last few decades, the in vitro motility assay has been performed to probe the biophysical and chemo-mechanical properties as well as the self-organization process of biomolecular motor systems such as actin-myosin and microtubule-kinesin. However, aggression of the reactive oxygen species (ROS) and concomitant termination of the activity of biomolecular motors during investigation remains a drawback of this assay. Despite enzymatic protection that makes use of a combination of glucose, glucose oxidase, and catalase, the active lifetime of biomolecular motors is found to be only a few hours and this short lifetime restricts further study on those systems. We have solved this problem by using a newly developed system of the in vitro motility assay that is conducted in an inert nitrogen gas atmosphere free of ROS. Using microtubule-kinesin as a model system we have shown that our system has prolonged the active lifetime of the biomolecular motor until several days and even a week by protecting it from oxidative damage.