On-line screening methods for antioxidants scavenging superoxide anion radical and hydrogen peroxide by liquid chromatography with indirect chemiluminescence detection

The identification of radical species is possible by the electron spin resonance technique. However, the antioxidants in complex matrices such as biological and food samples are difficult to determine. Hence, we developed novel screening systems for antioxidants, which are mainly eliminating superoxide anion radical (O(2)(-)) and hydrogen peroxide (H(2)O(2)), by HPLC with luminol-based chemiluminescence (CL) detection. When the sample contains antioxidants, inhibited peaks corresponding to each antioxidant are observed on the chromatogram. The antioxidant activities of catechins and flavones were determined with flow injection analysis by the proposed indirect CL. The scavenging activity for H(2)O(2) and O(2)(-) were different from each catechin and flavone. Furthermore, the potential was dependent upon the number and the position of OH functional group in the structure. Some applications such as the screening of antioxidants in tea products were also investigated. In spite of many peaks appeared on the chromatogram at UV detection, only the peaks corresponding to the compounds having elimination effect to O(2)(-) and/or H(2)O(2) were detected as inhibited peaks. Consequently, the proposed HPLC-CL seems to provide new screening systems for antioxidants possessing inhibition activity of O(2)(-) and H(2)O(2).     

Determination of pindolol in human serum by HPLC

A method for determining pindolol from human serum by high-performance liquid chromatography (HPLC) is presented. Pindolol is extracted into methylene chloride from 1 mL of alkalinized serum with a recovery of 87%. The organic layer is evaporated and the residue is reconstituted in mobile phase for injection into the column. Samples are eluted from a 5-micron C18 column (250 x 4.6 mm) with acetonitrile-water containing 0.1% triethylamine, pH adjusted to 3.5 with phosphoric acid (20:80 v/v). Samples as low as 2 ng/mL have been detected.     

Dioxygen activation and substrate oxygenation by a p-nitrothiophenolatonickel complex: unique effects of an acetonitrile solvent and the p-nitro group of the ligand

The nickel(II) complex [Ni(Tp(Me2)) (SC(6)H(4)NO(2))] [1a; Tp(Me2) = hydrotris(3,5-dimethylpyrazol-1-yl)borate] reacts with O(2) to form the ligand oxygenation product ArSO(2)(-) in MeCN, and also 1a catalyzes the oxygenation of external substrates such as triphenylphosphine. The reactivity may correlate to the unique quinoid-like resonance structure of the thiophenolate ligand. The structure is stabilized by a p-nitro group and induced by coordination of MeCN.     

New pressure regulating system for constant mass flow supercritical-fluid chromatography and physico-chemical analysis of mass-flow reduction in pressure programming by analogous circuit model

Summary The newly developed regulating valve is based on high-speed flow switching, and is capable of controlling the column outlet pressure independent of the mass flow-rate of the fluid. The reproducibility of retention times in pressure-programming elution on a 4.6 mm i.d. ×250mm long silica gel column was better than 1% with supercritical carbon dioxide as the mobile phase. The outlet mass flow-rate decreased while the pressure was increasing, keeping the input flow to the system constant; this was due to the compressibility of the fluid. The amount of decrease in the outlet flow was calculated by introducing an analogous circuit model and new parameters, instrumental and column capacitances. The result agreed with the measured value within 30% error.     

AlanineESR Dosimetry system for routine use in radiation processing

A new alanine-polystyrene (PS) dosimeter prepared with simplified molding procedure and an automatic desk-top dose-reader of alanine dosimeter were developed for the purpose of routine use. Combination of these two allows us to apply a reliable alanine/ESR dosimetry system to routine dosimetric process control in industrial gamma radiation processing.     

Sequence-selective single-molecule alkylation with a pyrrole-imidazole polyamide visualized in a DNA nanoscaffold

We demonstrate a novel strategy for visualizing sequence-selective alkylation of target double-stranded DNA (dsDNA) using a synthetic pyrrole-imidazole (PI) polyamide in a designed DNA origami scaffold. Doubly functionalized PI polyamide was designed by introduction of an alkylating agent 1-(chloromethyl)-5-hydroxy-1,2-dihydro-3H-benz[e]indole (seco-CBI) and biotin for sequence-selective alkylation at the target sequence and subsequent streptavidin labeling, respectively. Selective alkylation of the target site in the substrate DNA was observed by analysis using sequencing gel electrophoresis. For the single-molecule observation of the alkylation by functionalized PI polyamide using atomic force microscopy (AFM), the target position in the dsDNA (～200 base pairs) was alkylated and then visualized by labeling with streptavidin. Newly designed DNA origami scaffold named "five-well DNA frame" carrying five different dsDNA sequences in its cavities was used for the detailed analysis of the sequence-selectivity and alkylation. The 64-mer dsDNAs were introduced to five individual wells, in which target sequence AGTXCCA/TGGYACT (XY = AT, TA, GC, CG) was employed as fully matched (X = G) and one-base mismatched (X = A, T, C) sequences. The fully matched sequence was alkylated with 88% selectivity over other mismatched sequences. In addition, the PI polyamide failed to attach to the target sequence lacking the alkylation site after washing and streptavidin treatment. Therefore, the PI polyamide discriminated the one mismatched nucleotide at the single-molecule level, and alkylation anchored the PI polyamide to the target dsDNA.     

Formation and Direct Repair of UV‐induced Dimeric DNA Pyrimidine Lesions

Direct repair of UV‐induced DNA lesions represents an elegant method for many organisms to deal with these highly mutagenic and cytotoxic compounds. Although the participating proteins are structurally well investigated, the exact repair mechanism of the photolyase enzymes remains a vivid subject of current research. In this review, we summarize and highlight the recent contributions to this exciting field.     

Antiproliferative effects of zerumbone-pendant derivatives on human T-cell lymphoid cell line Jurkat cells

Zerumbone is the major component of the essential oil of wild ginger, Zingiber zerumbet Smith. It is not only highly reactive but also has diverse bioactivities. Those effects derive from two conjugated double bonds of zerumbone and a carbonyl group in between, and we had already established a synthetic scheme for zerumbone-pendant derivatives without disturbing the conjugation system. Herein, twelve conjugates with salicylic acid or various benzoic acid derivatives were synthesized for evaluations of their antiproliferative effects on Jurkat cells as salicylic acid is bioactive and has a carboxylic group for coupling. Most of them resulted in IC₅₀ values as low as 1–10?μM, validating the utility of this activity-conserving strategy.