GC-MS analysis of off-odor volatiles from irradiated pork

The main compounds of off-odor volatiles from irradiated refrigerated vacuum-packaged pork were ana- lyzed by gas chromatograph/mass spectrometer (GC-MS).The analytical results showed that the main compounds of off-odor volatiles were dimethyl disulfide,dimethyl sulfide,dimethyl trisulfide,S-methyl thioacetate,and methanethiol.It was proved that the off-odor volatile came from irradiated S-containing amino acid and thiamin.

254/185 nm photolysis of p-nitrophenol

Degradation of low-concentration p-nitrophenol(p-NP)aqueous solution was carried out in 254/185 nm photolysis.The effects of Mn^(2+),pH value,O_2 and O_3 on the degradation efficiency have been investigated.It was observed that the singlet oxygen scavenger Mn^(2+)did not affect the degradation of p-NP.In acidic and alkaline solutions,the degradation efficiency was enhanced in comparison to that in neutral solution.The presence of O_2 dramatically promoted the degradation of p-NP,while that of O_3 impeded it.

Laser photolysis of ionic liquid [bmim][PF_6]

Photoinduced chemical reactions of 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF_6]) were studied by laser photolysis at a wavelength of 266 nm.Excited triplet state ~3[bmim]^+ was observed,radical cation [bmim]^(2+) and neutral [bmim] radical via photoionization were also formed.Energy transfer from ~3[bmim]^+ toβ-carotene was confirmed.Oxidation via one electron transfer from TMPD to ~3[bmim]^+ was also observed and the rate constant was determined to be 1.2×10.5 L.mol^(-1).s^(-1).The reaction of [bmim][PF_6] with hydrated electron (e_(aq)) was confirmed by laser photolysis in aqueous solution.

Primary study on solvent effect of COCA4 by laser photolysis

Reaction of p-tert-oxocalix[4]arene in acetonitrile (CH3CN) by 308nm laser pulses was investigated to understand its mechanism as polymer stabilizer. Four main absorption bands were observed at 300nm, 400nm, 460nm and 540nm. The 300nm absorption was assigned to the absorption of phenoxy radical, and the 460nm and 540nm were triple state absorption. It was concluded that the relative stable phenoxy radical mediate was formed through intramolecular energy transition of carbonyl triplet after laser excitation in CH3CN. The formation mechanism of phenoxyl radical was quite different from that in cyclohexane (C6H12), which was cooperation of two-photon process and one-photon process.

Photochemical properties of a new kind of anti-cancer drug: N-glycoside compound

Due to the nontoxicity and efficient anti-cancer activity, more and more attention has been paid to N-glycoside compounds. Laser photolysis of N-(α-D-glucopyranoside) salicyloyl hydrazine (NGSH) has been performed for the first time. The research results show that NGSH has high photosensitivity and is vulnerable to be photo-ionized via a monophotonic process with a quantum yield of 0.02, generating NGSH+· and hydrated electrons. Under the aerobic condition of cells, the hydrated electrons are very easy to combine with oxygen to generate 1O2 and O2-, both of which are powerful oxidants that can kill the cancer cells. In addition, NGSH+· can be changed into neutral radicals by deprotonation with a pKa value of 4.02 and its decay constant was determined to be 2.55×109dm3·mol-1·s-1. NGSH also can be oxidized by SO4-. with a rate constant of 1.76×109 dm3·mol-1.s-1, which further confirms the results of photoionization. All of these results suggest that this new N-glycoside compound might be useful for cancer treatment.

In-situ synthesis of PHEMA magnetic nanogels via photochemical method

One-pot synthesis of magnetic nanogels via photochemical method is reported in this paper. Poly(2-hydroxyethyl methacrylate)(PHEMA) magnetic nanogels are synthesized by in-situ polymeriza-tion of 2-hydroxyethyl methacrylate(HEMA) and N,N'-methylene-bis-(acrylamide)(MBA) in Fe3O4 aqueous suspension under UV irradiation. The structure and compositions of magnetic nanogels are characterized by FTIR,TGA,SEM,TEM and PCS. TGA measurement indicates that magnetic nanogels contain 90% magnetite. Both naked Fe3O4 and magnetic nanogels are superparamagnatic at room temperature according to magnetization curves. The swollen capability of the hydrogel shell is proved by contrasting the particles sizes obtained by SEM,TEM and PCS. Particle diameters can be manipu-lated by changing monomer concentration and irradiation time. A mechanism of the coating process is proposed.

SDS-PAGE study on photooxidation damage of lysozyme induced by riboflavin

The photooxidation damage of lysozyme under 315-375 nm irradiation in the presence of riboflavin was studied by using sodium dodecyl sulfate-polyacrylamide gel electrophoresis(SDS-PAGE).Indica- tions showed that the mechanisms and products of oxidative damage were relative to the concentra- tion of riboflavin,the time of irradiation and the ambience.The type I process was examined in a nitrogen saturated solution,whereas both type I and type II were observed in an aerobic atmosphere and type II was the dominant process.The study also suggested that antioxidants,such as melatonin, can reduce the damage of lysozyme effectively.

Poly(PEGMA) magnetic nanogels:Preparation via photochemical method,characterization and application as drug carrier

One-pot synthesis of magnetic nanogels with excellent biocompatibility via the photochemical method is reported in this paper.Poly(PEGMA) modified superparamagnetic nanogels(poly(PEGMA) magnetic nanogels) were synthesized by in-situ polymerization using poly(ethylene glycol) methacrylate(PEGMA) as the monomer and N,N'-methylene-bis-(acrylamide)(MBA) as the cross-linking agent in magnetite aqueous suspension under UV irradiation.The surface functional groups and components of magnetic nanogels were analyzed by Fourier transform infrared spectroscopy(FTIR) and a thermogra-vimetric analyzer(TGA).The results indicated that the poly(PEGMA) magnetic nanogels were synthe-sized successfully by coating poly(PEGMA) on the Fe3O4 nanoparticles under UV irradiation,and the Fe3O4 nanoparticles content in this nanogels was above 50 wt%.The morphology,size,zeta-potential and magnetic property were also characterized.The magnetic nanogels had a nearly spherical shape and core-shell structure,the average size in aqueous system measured by photon correlation spec-troscopy(PCS) was 68.4 nm,which was much bigger than that in the dry state,the nanogels behaved superparamagnetically with saturated magnetization of 58.6 emu/g,and the zeta-potential was-16.3-_17.3 mV at physiological pH(6.8-7.4) which could help to maintain stability in blood.The preliminary application as drug carrier was made and the doxorubicin-loaded magnetic nanogels had an excellent property in slow-release.The experiment indicated that the magnetic nanogel was an ideal candidate carrier in target drug delivery systems and other biomedical application.

Pulse radiolysis study on gatifloxacin——A fluoroquinolone antibiotic

The reactions between gatifloxacin(GFX) and various one-electron oxidants,such as ˙OH,N3˙,Br2˙ˉ,and SO4˙ˉ,have been studied by pulse radiolysis techniques.The GFX radical anion formed in the reaction of GFX with eaqˉ could either be protonated or deprotonated,and the absorption of GFX radical anion was located at 390 nm.The transient species produced by the reaction of GFX with ˙OH radical shows a broad band in the 380?600 nm region with a shoulder,while the oxidation by N3˙,SO4˙ˉ,and Br2˙ˉ results in an absorption band with λmax = 370 nm.At neutral condition(pH 7),the rate constants of GFX reacting with ˙OH,N3˙,Br2˙ˉ,SO4˙ˉ and eaqˉ are estimated to be 1.0 × 1010,3.1 × 109,2.8 × 109,3.0 × 109,and 1.8 × 1010 dm3 mol?1 s?1,respectively.From the pH dependence on the formation of electron adducts and on the rate constant of GFX with eaqˉ,the pKa of GFX radical anion is estimated to be 5.5 and 9.3.

Effects of pH and polarity on the excited states of norfloxacin and its 4′-N-acetyl derivative:a steady-state and time-resolved study

The properties of norfloxacin(NFX)and its 4?-N-acetyl derivative(ANFX)are investigated in different pH aqueous solutions and H2O-CH3CN mixed solutions,to determine the effects of pH and polarity on their ground and excited states.The triplet states of NFX and ANFX are affected more by pH than by polarity.The pH dependence of the NFX and ANFX triplet states is likely due to the different quantum yields of different protonated forms.Steady-state fluorescence,time-resolved fluorescence,and laser flash photolysis experiments at different pH values provide clear evidence of the involvement of different intramolecular charge-transfer pathways in the singlet states of NFX and ANFX.The different electron-donating capacities of 1-N,1?-N,and 4?-N under different conditions determine the major pathway.

Effects of high-energy-pulse-electron beam radiation on biomacromolecules

To study the molecular mechanism of high mutation frequency induced by high-energy-pulse-electron (HEPE) beam radiation, the effects of HEPE radiation on yeast cells, plasma membrane, plasmid DNA, and protein activity were investigated by means of cell counting, gel electrophoresis, AO/EB double fluorescent staining, etc. The results showed that the viability of yeast cells declined statistically with increase of absorbed doses. The half lethal dose (LD50) was 134 Gy. HEPE beam radiation had little influence on the function of plasma membrane and protein, while it could induce much DNA damage of single strand breaks (SSB) and double strand breaks (DSB) that were required for gene mutation. The G-value for DSB formation of HEPE beam radiation in aqueous solution was 5.7 times higher than that caused by 60Co gamma rays. HEPE can be a new effective method for induced mutation breeding and deserves further research in the future.

Studies on kinetics of reactions between phycobiliproteins and hydroxyl radicals by a pulse radiolytic technique

Scavenging of hydroxyl radical (·OH) by phycobiliproteins (C-phycocyanin, Allophyco- cyanin and R-phycoerythrin) was studied by competitive kinetics methods. Hydroxyl radicals were generated from pulse radiolysis of aqueous systems saturated with nitrous oxide (N2O). The experimental results indicated that the three types of phycobiliproteins are all strong scavengers of· OH, the rate constants are around (2.8-5.6)×109 L·2 mol1 · s 1.