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The different effects of ionic liquid [bmim][P[F.sub.6]] on absorption spectra and reaction kinetics of the duroquinone triplet state in acetonitrile are discussed. An increase in the volume of the ionic liquid is shown to increase the self-aggregation of the monomeric cations.

Ethanol production from lignocellulose by recombinant yeast with high level expression of heterologous cellulase genes has been a major anticipation. The native secretion signal sequence of the cellulase endoglucanase I ( eg1) gene was replaced by Saccharomyces cerevisiae mating factor α prepro-leader sequence (MFα). The transformants containing native secretion signal ( Y1) and MFα secretion signal ( Y2) were characterized with respect to gene expression and growth on cellulose substrate. Increased enzyme activity and cellulose utilization were observed. The enzyme activity of Y2 was 0.084 U/ml, 61.5% higher than Y1 (0.052 U/ml). The sufficiency parameter ( S value) was raised from 0.6 to 0.84. MFα signal peptide was more efficient than the native signal peptide of eg1 gene, suggesting that signal peptide replacement is an efficient way to enhance the cellulase expression level in yeast, for cellulose-derived ethanol production. [ABSTRACT FROM AUTHOR]

The degradation kinetics of p-nitrophenol (p-NP) exposed to 254/185 nm UV light were studied in two modes, i.e., 254 nm UV light intensity enhanced mode and normal mode. It was observed that the extra 254 nm UV light source accelerated the degradation process both in the presence and the absence of oxygen. Considering that hydroxyl radical (OH) is the dominant factor that causes the degradation of p-NP, the enhanced degradation that occurred in the presence of the extra light source was attributed to the synergistic effect between OH attack and the primary reactions initiated by 254 nm UV light. The synergistic effect has been confirmed by 266 nm laser flash photolysis (LFP) experiments. It is demonstrated that the phenoxy radical generated from the photoionization of p-NP is capable of reacting with OH. On the basis of these results, it should be noted that UV light could cause more severe damage to p-NP attacked by OH in aqueous solution. [ABSTRACT FROM AUTHOR]

A wide range of pharmaceutical compounds have been identified in the environment, and their existence is a topic of growing concern, both for human and ecological health. The work described here has investigated the photolytic properties of L(+)-α-phenylglycine (L-α-PG-H) in aqueous solution as it can be degraded by photo-catalysis. In 266 nm laser flash photolysis of aqueous solution of L-α-PG-H saturated with nitrogen, two transient absorption bands are observed at 280–330 nm and 450–800 nm, respectively, due to L-α-PG-H radical cation and hydrated electrons (e). Then e reacts with L-α-PG-H to form the L-α-PG-H radical anion. Decaying rate constants of e observed at 720 nm is to be 8.9 × 108 dm3 mol−1 s−1. The rate constant for oxidation of L-α-PG-H by SO4 − is calculated as 4.5 × 108 and 4.3 × 108 s−1 mol−1 dm3, respectively. The dissociation constants (pKa) of L-α-PG-H is 3. Excited triplet of L-α-PG-H in solution is formed by laser flash photolysis. The quench rate constant of L-α-PG-H excited triplet ( ks) is determined to be 1.3 × 107 dm3 mol−1 s−1 and k0 is equal to 1.7 × 105 s−1. [ABSTRACT FROM AUTHOR]

Carboxyl‐functionalized magnetic nanogel was synthesized by facile “green” photochemical method. A possible mechanism of photochemical synthesis was proposed. Effects of irradiation time and volume of monomer dropped on the hydrodynamic diameter of the magnetic nanogel were investigated by photo correlation spectroscopy. The image of atomic force microscopy presented that the magnetic nanogel was with loosed structure. X‐ray diffraction analysis showed that UV irradiation did not induce phase change of Fe3O4. Superparamagnetic behaviors were retained for Fe3O4 while slightly reducing the value of saturation magnetization for surface coating. High magnetic content of (as high as 85%) and strong magnetization of Fe3O4 guaranteed that the magnetic nanogel was susceptive to external applied magnetic field. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 [ABSTRACT FROM AUTHOR]

Cationic polymer nanogels, positively-charged submicrometer polymeric particles that swell in water, have attracted an increasing research attentions in recent years because of their potential applications as gene carriers. In this paper, we report a novel method to synthesize polyethylenimine (PEI) nanogels with sizes ranging from 80 nm to 200 nm via UV irradiation at room temperature in aqueous solution without adding any kind of surfactants. The morphology of the nanoparticles is determined to be spherical. The nanogels are of high stability, high transfection efficiency, low toxicity and low immunogenicity, as having been confirmed by in vivo tests with mice as an animal model, and by in vitro tests with human lung and liver cancer cells as well. [ABSTRACT FROM AUTHOR]

Abstract  The antioxidant properties of hydroxycinnamic acid derivatives (HCA) were studied by laser flash photolysis. The transient species with maximum absorption at 360 nm were assigned to the phenoxyl radical of HCA. The SO4•− induced oxidation of HCA was also investigated. It was shown that the interaction of SO4•− with HCA resulted in the formation of HCA phenoxyl radicals with rate constants of 2.0–3.9×109 M−1 s−1. The reactions of HCA with triplet state of benzophenone were analyzed and quenching rate constants of 4.3–7.8×109 M−1 s−1 were determined. [ABSTRACT FROM AUTHOR]

To show the effects of growth inhibitory factor (Cu4Zn3MT-III) involved in the scavenging of reactive oxygen species (ROS), a pulse radiolytic study was employed using N2O-saturated Cu4Zn3MT-III aqueous solutions. It was demonstrated that the oxidizing OH· radical efficiently reacted with Cu4Zn3MT-III by forming a thiyl radical RS· with a second-order constant of 1.46×1011 mol l−1s−1, which was determined by competition kinetics against KSCN. The thiyl radical RS· reacted rapidly and reversibly with a thiolate in Cu4Zn3MT-III to form radical anion RSSR· − with a constant of 1.65×109 mol lL−1s−1 per thiolate, while the constant of the decay of this radical anion was 2.72×105 s−1, and the equilibrium constant of the formation for RSSR· − was 6.08×103 mol−1 l. These values were close to those of Cd5Zn2MT-II. The SOD activity of Cu4Zn3MT-III to quench O2· − was assayed by the riboflavine-methionine-nitrobluetetrazolium (NBT) method which catalyzed the dismutation of superoxide (O2· −) at pH 7.8 with an IC50 value of 1.50×10−6 M for Cu4Zn3MT-III and 1.62×10−6 M for Cd5Zn2MT-II. Additionally, the down-regulation of GIF may be a main factor in the decrease of the scavenging ability for the free OH· and O2· − radicals, which is possibly associated with the pathogenesis of neurodegenerative disease. [ABSTRACT FROM AUTHOR]

Free radical reactions of Martynoside (MAR), a phenylpropanoid glycoside, with a variety of oxidants were studied in the aqueous solution by laser photolysis and pulse radiolysis techniques. The p K a value of MAR in aqueous solution was measured from the pH dependent changes of the UV absorption at 384 nm with value of p K a =9.2. The phenoxyl radical of MAR which exhibits maximum absorption at 360 nm was generated by one-electron transfer to N 3 • or Br 2 •- . Other important properties of phenoxyl radical such as extinction coefficient, formation and decay rate constants were also determined. The reaction rate constant of O 2 •- with MAR, k =8.5×10 4 dm 3 · mol -1 · s -1 , was measured by the method of competition kinetics. By measuring time-resolved luminescence emission at 1270 nm, the quenching rate constant of singlet oxygen by MAR was obtained to be 3.3×10 6 dm 3 · mol -1 · s -1 . Reduction potential of the MAR couple (MAR • /MAR), determined using rutin as reference compound, gave a value E =0.66 V vs. NHE. The antioxidative properties of MAR were compared with those of some well-known antioxidants. [ABSTRACT FROM AUTHOR]

The effects of quercetin and rutin on the repair of the radical cations of dCMP and poly C were studied using the technique of pulse radiolysis. The radical cations of dCMP and poly C were formed by the reaction of dCMP and poly C with SO4-. After pulse irradiation of nitrogen-saturated aqueous solutions containing dCMP, 20 mM K2S2O8, 200 mM t-BuOH and either rutin or quercetin, the initially formed radical cation of dCMP, detected spectrophotometrically, rapidly decayed with the concurrent formation of the phenoxyl radical of rutin or quercetin within 8-40 μs. The repair efficiencies of the tested compounds towards the poly C radical cation were also determined using the same procedure. The results indicate that dCMP and poly C radical cations can be rapidly repaired by quercetin and rutin. The rate constants of the repair reactions were determined to be 4.3-8.8 × 108 M/s and 1.5-3.6 × 108 M/s for dCMP and poly C radical cations, respectively. Together with findings from our previous studies, the present results demonstrate that non-enzymatic fast repair may be a universal form of repair involving phenolic antioxidants. [ABSTRACT FROM AUTHOR]

The repair activities and reaction mechanisms of phenylpropanoid glycosides (PPGs) and their analogues, isolated from Chinese folk medicinal herbs, towards oxidative DNA damage were studied with pulse radiolytic technique. On pulse irradiation of nitrogen-saturated 4 mM poly C aqueous solution containing one of the tested polyphenols, 40 mM K2S2O8 and 200 mM t-BuOH, the transient absorption spectrum of the oxidative radical of poly C decays with the concurrent formation of the phenoxyl radical of the tested polyphenols within several tens of microseconds after the electron pulse irradiation. The result indicated that there was a repair reaction between oxidative radical of poly C and the tested polyphenols. The repair activities also were observed for the tested polyphenols towards the radical cations of single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA). The rate constants were determined to be 3.7–6.4 × 109, 4.8–5.5 × 108 and 8.8–10.3 × 108 M−1·sec−1 for the repair reactions of oxidative radical of poly C and radical cations of ssDNA and dsDNA, respectively. The result of this study together with those of our previous studies demonstrates that PPGs and their analogues can fast repair not only the damage of deoxynucleoside and deoxynucleotide but also the damage of integral DNA, with the latter being closer to a cellular condition. [ABSTRACT FROM AUTHOR]

Ultrasmall superparamagnetic iron oxide (USPIO) with synthetic polymer, based on magnetite core, was synthesized viafacile photochemical in situpolymerization. A possible mechanism of photochemical in situpolymerization was proposed. The obtained polymer-enveloped UPSIO was characterized by transmission electron microscopy (TEM), photo-correlation spectroscopy (PCS), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric (TG) analysis and vibrating sampling magnetometer (VSM) measurement. Properties such as ultrasmall particle size, hydrophilicity, strong magnetization and surface characteristics, which are desirable for magnetic resonance imaging (MRI) contrast agents, were evaluated in detail. The resultant USPIO-based MRI contrast agent holds considerable promise in molecular MR tracking, MR immune imaging, cell tracking and targeted intracellular hyperthermia, etc. [ABSTRACT FROM AUTHOR]