Label-free molecular beacon system based on DNAs containing abasic sites and fluorescent ligands that bind abasic sites

A new class of label-free molecular beacon (MB) system based on DNA strands that contain abasic (AP) sites (AP-DNA) and adopt stem-loop structures, in combination with fluorescent ligands that bind these AP sites, has been developed. Unlike a conventional MB, which requires covalent labeling of the MB with a fluorophore and a quencher, the developed system (APMB) does not require covalent attachment of signal transduction units. Detailed sensing functions of a series of APMB systems were examined with the aid of the fluorescent ligand named ATMND to provide insight into the design strategy for APMB systems. The effects of the stem length and the position of the AP site in the stem moiety on the fluorescence response of the APMB system were examined. Genotyping of a G/C SNP of PCR amplification products was successfully demonstrated with the APMB system and blue-fluorescent ATMND as a ligand. The APMB system was further extended to a system that utilized green-fluorescent lumiflavin.     

STUDIES ON HUMAN LENS: I. ORIGIN AND DEVELOPMENT OF FLUORESCENT PIGMENTS

Abstract
Fluorescence spectra of normal mature human lenses have been measured and at least eight species with distinct emission characteristics identified. To determine the specific photochemical and photophysical processes responsible for the origin and development of these fluorophores, emission behavior of the products generated by successive irradiation of young human lenses (3–6 y old) as well as of L-tryptophan solution have been systematically monitored. Fluorescent products that resulted from this irradiation were comparable to many of the fluorophores detected in aged lenses, indicating that light plays a major role in the development of these pigments. In addition to photogenerated species, there are other compounds in human lenses, presumably advanced glycosylated end products, with marked fluorescence properties.
Several oxidation products of tryptophan including N -formylkynurenine or its derivatives, β-carboline or its derivatives, and anthranilic acid have been identified in the mature human lens. The development of several photoproducts also was attributed to endogenous ascorbate-mediated Maillard reaction products, which undergo photoconversion by the visible light. Although some of these chromophores could act as photosensitaizers, the sensitizing efficiency of many are low. Conversely, the near-UV filtering capability of these colored compounds conceivably could protect the vitreous and retina from development of any photochemical lesion.     

Heat-Resistant Polymer-Grafted Carbon Black: Grafting of Poly(Organophosphazenes) onto Carbon Black Surface

Abstract

The grafting of poly(organophosphazenes) onto carbon black surface by the reaction of poly(dichlorophosphazene) (PDCP) with carbon black having sodium phenoxide groups was investigated. PDCP was prepared by the ring-opening polymerization of hexachlorocyclotriphos-phazene in solution using sulfamic acid as a catalyst. The introduction of sodium phenoxide groups onto carbon black was achieved by treatment of phenolic hydroxyl groups on the surface with sodium hydroxide in methanol. Poly(diphenoxyphosphazene) (PDPP) was successfully grafted onto carbon black by the reaction of PDCP with sodium phenoxide groups introduced onto the surface followed by the replacement of chlorine atoms in PDCP with phenoxy groups. The percentage of grafting onto carbon black increased to 206% at 30°C after 12 h. It was found that only 1.4% of sodium phenoxide groups on carbon black surface was used for the grafting of PDCP because of the blocking of the surface by grafted polymer chains. Poly(diaminophenylphosphazene) and poly-(diethoxyphosphazene) were also grafted onto carbon black surface by the treatment of PDCP-grafted carbon black with aniline and sodium ethoxide, respectively. Poly(organophosphazenes)-grafted carbon blacks produced stable colloidal dispersions in good solvents for grafted polymers. Furthermore, thermogravimetric analysis indicated that poly-(organophosphazenes)-grafted carbon blacks were stable in air about 300°C.     

First Total Synthesis of Cleroindicin B,(±) Cleroindicin C and E

The isolation of cleroindicins B, C and cleroindicin E, together with three novel related compounds cleroindicins A, D and F, from chinese folk medicine Clerodendrum indicum Linn. was reported before1. Pharmaceutical studies showed that cleroindicin C has certain anticancer activity, so its total synthesis attracted our considerable interest.Cleroindicin B Cleroindicin C Cleroindicin EThe commercially available 2-(p-methoxyphenyl) ethanol 1 was selected as the starting material. Compound…     

Rhodium(I)-catalyzed asymmetric 1,4-addition of arylboronic acids to alpha,beta-unsaturated amides.

The conjugate addition of arylboronic acids to alpha,beta-unsaturated amides was carried out in the presence of a chiral rhodium catalyst and an aqueous base. The catalyst prepared in situ from Rh(acac)(CH(2)=CH(2))(2) and (S)-binap provided (R)-N-benzyl-3-phenylbutanamide with 93% ee in the addition of phenylboronic acid to N-benzyl crotonamide. The reaction suffered from incomplete conversion resulting in moderate yields, but addition of an aqueous base, such as K(2)CO(3) (10-50 mol%) was found to be highly effective to improve the chemical yields. The role of the base giving a RhOH species active for transmetalation with arylboronic acids was discussed.     

Cationic ring-opening transfer polymerization of spiro ortho esters initiated by carbon black

The ring-opening transfer polymerization of spiro ortho esters (SOE) initiated by carbon black was investigated. In the absence of carbon black, no polymerization occurred at all. In the presence of channel black containing carboxyl group, the ring-opening transfer polymerization of SOE was initiated at 50-70°C. to give polyether ester, namely alternating copolymer of epoxide and lactone. The rate of polymerization of 1,4,6-trioxaspiro[4.4]nonane and 1,4,6-trioxaspiro[4.5]decane was considerably small compared with that of 1,4,6-trioxaspiro[4.6]undecane. The activation energy of the polymerization of 2-chloromethyl-1,4,6-trioxaspiro[4.6]undecane was estimated to be 6.0 kcal/mol. The initiating activity of carbon black increased with an increase in carboxyl group content of carbon black. Furnace black that contained no carboxyl group was unable to initiate the polymerization. Furthermore, the carbon black lost the initiating ability of the polymerization upon the blocking of carboxyl group on the surface by the treatment with potassium hydroxide or diazomethane. Based on these results, it was concluded that carboxyl group on carbon black plays an important role in the initiation. During the polymerization, a part of the polymer formed was grafted onto carbon black: the grafting ratio was 10–30%. The mechanisms of initiation and grafting were discussed.     

Cu-mediated chemoselective trifluoromethylation of benzyl bromides using shelf-stable electrophilic trifluoromethylating reagents

Copper-mediated chemoselective trifluoromethylation at the benzylic position by the use of shelf-stable electrophilic trifluoromethylating reagents 3 in good to high yields under mild conditions is described for the first time. The generality of this trifluoromethylation for a wide variety of benzyl bromides facilitates the rapid creation of structural diversity of medicinal candidates in drug discovery.     

Protein adsorption on polymer-modified silica particle surface

Silicon substrate surface and silica particle surface were modified with five kinds of polymers, poly(2-methoxyethyl methacrylate) (pMEMA), poly(2-hydroxyethyl methacrylate) (pHEMA), poly(acrylamide) (pAAm), poly(methyl methacrylate) (pMMA), and poly(styrene) (pSt), using a combined polymerization of surface-initiated polymerization that gives dense polymer chain layers and atom transfer radical polymerization (ATRP) that yields polymers with a narrow molecular weight distribution. Measurements of water contact angle and polymer chain amount on the modified silicon substrate surface and adsorption amounts of proteins (albumin and fibrinogen) on the modified silica particle surface revealed that the amount of polymer on the modified surface greatly affects the suppression of protein adsorption on the surface.     

FLUORESCENCE LIFETIME OF ACRIDINE ORANGE IN SODIUM DODECYL SULFATE PREMICELLAR SOLUTIONS

Abstract— The absorption and fluorescence spectra, and the fluorescence lifetime of acridine orange (AO) were measured in a wide range of the sodium dodecyl sulfate (SDS) concentration below and above the critical micelle concentration (cmc). The fluorescence consisted of two components with different lifetimes; short (<3 ns) and long (>3 ns). The short and long lifetime components are attributed to the AO monomer and dimer associated with detergent, respectively. The lifetime of the dimer increased with increasing the SDS concentration just below the cmc. It decreased suddenly to a constant value just above the cmc. The lifetime of the monomer showed only a slight increase in the concentration range of SDS employed.