Water-soluble Free Radical Research Articles

The Flavor Characteristics, Antioxidant Capability, and Storage Year Discrimination Based on Backpropagation Neural Network of Organic Green Tea (Camellia sinensis) during Long-Term Storage.

The storage period of tea is a major factor affecting tea quality. However, the effect of storage years on the non-volatile major functional components and quality of green tea remains largely unknown. In this study, a comparative analysis of organic green teas with varying storage years (1-16 years) was conducted by quantifying 47 functional components, using electronic tongue and chromatic aberration technology, alongside an evaluation of antioxidative capacity. The results indicated a significant negative correlation between the storage years and levels of tea polyphenols, total amino acids, soluble sugars, two phenolic acids, four flavonols, three tea pigments, umami amino acids, and sweet amino acids. The multivariate statistical analysis revealed that 10 functional components were identified as effective in distinguishing organic green teas with different storage years. Electronic tongue technology categorized organic green teas with different storage years into three classes. The backpropagation neural network (BPNN) analysis demonstrated that the classification predictive ability of the model based on the electronic tongue was superior to the one based on color difference values and 10 functional components. The combined analysis of antioxidative activity and functional components suggested that organic green teas with shorter storage periods exhibited stronger abilities to suppress superoxide anion radicals and hydroxyl radicals and reduce iron ions due to the higher content of eight components. Long-term-stored organic green teas, with a higher content of substances like L-serine and theabrownins, demonstrated stronger antioxidative capabilities in clearing both lipid-soluble and water-soluble free radicals. Therefore, this study provided a theoretical basis for the quality assessment of green tea and prediction of green tea storage periods.

Synthesis of biocompatible BSA-GMA and two-photon polymerization of 3D hydrogels with free radical type I photoinitiator.

Although the development of three-dimensional (3D) printing technology is growing rapidly in the biomedical field, it remains a challenge to achieve arbitrary 3D structures with high resolution and high efficiency. Protein hydrogels fabricated by two- photon polymerization (TPP) have excellent mechanical properties, high precision, and 3D architecture. However, a large number of the amino acid group in bovine serum albumin (BSA) would be consumed when the protein-based hydrogels use dyes of free radical type II photoinitiators. In this study, we use glycidyl methacrylate (GMA) to modify BSA molecules to obtain a series of BSA-GMA materials, allowing the protein material to be two-photon polymerized with a water-soluble free radical type I photoinitiator. The precisely controllable 3D structure of the BSA-GMA hydrogel was fabricated by adjusting the concentration of the precursor solution, the degree of methacrylation, and the processing parameters of the TPP technique. Importantly, BSA-GMA materials are free of acidic hazardous substances. Meanwhile, the water-soluble initiator lithium phenyl (2,4,6-trimethylbenzoyl) phosphite (LAP) allows TPP on the vinyl group of the GMA chain and thus without consuming its amino acid group. The as-prepared BSA-GMA hydrogel structure exhibits excellent autofluorescence imaging, pH responsiveness, and biocompatibility, which would provide new avenues for potential applications in tissue engineering and biomedical fields to meet specific biological requirements.

Anti-tumor and antioxidant activity of kaempferol-3-O-alpha-L-rhamnoside (Afzelin) isolated from Pithecellobium dulce leaves

BackgroundPithecellobium dulce (Roxb.), an evergreen medium-sized, spiny tree which have vast nutritional values and widely used in ayurvedic medicines and home remedies. The plant has also been a rich source of biologically active compounds. The present study was designed to isolate pure compound from ethyl acetate fraction of methanol extract of leaves and to know the efficacy as antioxidant as well as its anti-tumor activity on Ehrlich ascites carcinoma cell (EAC). MethodsThe leaves were extracted with methanol and fractionated with different solvents. The isolation of the compound was carried out by column chromatography from ethyl acetate fraction (EAF) and structure was revealed by 1H-NMR and 13C NMR. The antioxidant activity was investigated by the scavenging of 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radicals as well as the inhibition of oxidative damage of pUC19 plasmid DNA, hemolysis and lipid peroxidation induced by a water-soluble free radical initiator 2,2’-azo (2-asmidinopropane) dihydrochloride (AAPH) in human erythrocytes. In vivo anti-tumor activity of the compound was also evaluated by determining the viable tumor cell count, hematological profiles of experimental mice along with observing morphological changes of EAC cells by fluorescence microscope.ResultsThe isolated compound kaempferol-3-O-alpha-L-rhamnoside effectively inhibited AAPH induced oxidation in DNA and human erythrocyte model and lipid per oxidation as well as a stronger DPPH radical scavenging activity. In anti-tumor assay, at a dose of 50 mg/kg body weight exhibit about 70.89 ± 6.62% EAC cell growth inhibition, whereas standard anticancer drug vincristine showed 77.84 ± 6.69% growth inhibition.ConclusionThe compound may have a great importance as a therapeutic agent in preventing oxidative damage of biomolecules and therapeutic use in chemotherapy.

Effect of pH and zeta potential of Pickering stabilizing magnetite nanoparticles on the features of magnetized polystyrene microspheres

AbstractStyrene as a monomer was emulsified in water using several magnetite nanoparticles concentration and pH values. Emulsified styrene drops were used as templates for polymerization, in presence of water soluble free radical initiator, and formation of composite particles. Styrene template drops stabilization was verified by light as well as scanning electron microscopy imaging, which ensured the participation of the particles in building up a mechanical barrier to stop oil drops coalescence. Furthermore, the produced polystyrene composites were strongly attracted to an external magnet. The difference in particles size as a function of pH was elucidated using zeta potential measurements, which indicated dominance of pH on the hydrophilicity of the particles and consequently the extent of emulsification, which in turn affected the size of the obtained microspheres. Under some circumstances, capsules were formed instead of particles. Thereby, it can be concluded that the magnetic microspheres are optimally formed at pH 2.3 independently of the magnetite content used.

Ultrasound-induced synthesis of an imidazolium based poly(ionic liquid) in an aqueous media: A structural, thermal and morphological study

Here we describe an efficient and rapid way for the polymerization of the 3-Octyl-1-vinylimidazolium Bromide using ultrasonic irradiation. This way promoted high dispersion polymerization using a water-soluble free radical initiator namely 4,4′-Azobis (4-cyanopentanoic acid) and free of dispersant. The ionic liquid monomer was prepared via quaternization of 1-vinylimidazole with octyl bromide also promoted by ultrasound. The polymerization rates were compared with a conventional heating method and appeared to be higher in the case of the ultrasound method within a short reaction time. The structural/morphological features and thermal properties of the obtained products were determined by different analytical techniques such as (TGA), differential scanning calorimetry (DSC), X-ray diffraction (XRD), transmission electronic microscopy (SEM, TEM), Fourier transform infrared spectroscopy (FTIR) and NMR Spectroscopy (1H and 13C NMR). The morphology and the thermal behavior of the obtained poly(ionic liquid) were investigated and discussed. The results indicated that self-assembled nanospherical particles of 30–80 nm in diameter were obtained through the ultrasound method, while on the other hand; worm-like/cylindrical agglomerated nanoparticles with irregular sizes 50–300 nm in diameter were obtained via the classical heating method.

A Novel Nitrone-Trolox Conjugate Inhibits Membrane Lipid Oxidation Through Synergistic Antioxidant Effects

Polyunsaturated fatty acids are particularly sensitive to the deleterious effects of reactive oxygen species (ROS) as ROS can trigger their degradation through a chemical reaction called lipid peroxidation. Lipid oxidation has been reported to be involved in the early stages of several diseases as well as the deterioration of food supplies. To prevent the deleterious effects of ROS, water soluble free radical scavengers like α-phenyl-N-tert-butylnitrone (PBN) and 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox) have been widely used as protective agents in various biomimetic and biological models. In order to increase the hydrophobicity and the ability of these compounds to interact with membranes, three amphiphilic Trolox and PBN derivatives were recently designed by adding a perfluorinated chain to Trolox and PBN. A sugar moiety was added as well to ensure water solubility. In the present work, we studied the physical-chemical properties of the derivatives and related their antioxidant properties to their ability to interact with lipid membranes. We first investigated their ability to inhibit the AAPH-induced oxidation of 1,2-dilinoleoyl-sn-glycero-3-phosphocholine (DLPC) liposomes as well as their ability to interact with DLPC membranes. Results evidenced that the three derivatives are efficient to prevent lipid oxidation and that the location in the hydrophobic core of the membrane is a key parameter in the antioxidant efficiency. The derivative bearing both PBN and Trolox moieties on the same fluorinated carrier exhibited a synergistic antioxidant effect by delaying the oxidation process and by scavenging free radicals. Molecular dynamics simulations supported the understanding of the mechanism of action, highlighting various key physical-chemical descriptors.

AIBA as Free Radical Initiator for Abrasive-Free Polishing of Hard Disk Substrate

In order to optimize the existing slurry for abrasive-free polishing (AFP) of a hard disk substrate, a water-soluble free radical initiator, 2,2′-azobis (2-methylpropionamidine) dihydrochloride (AIBA) was introduced into H2O2-based slurry in the present work. Polishing experiment results with AIBA in the H2O2 slurry indicate that the material removal rate (MRR) increases and the polished surface has a lower surface roughness. The mechanism of AIBA in AFP was investigated using electron spin-resonance spectroscopy and UV–Visible analysis, which showed that the concentration of hydroxyl radical (a stronger oxidizer than H2O2) in the slurry was enhanced in the present of AIBA. The structure of the film formed on the substrate surface was investigated by scanning electron microscopy, auger electron spectroscopy and electrochemical impedance spectroscopy technology, showing that a looser and porous oxide film was found on the hard disk substrate surface when treated with the H2O2-AIBA slurry. Furthermore, potentiodynamic polarization tests show that the H2O2-AIBA slurry has a higher corrosion current density, implying that a fast dissolution reaction can occur on the substrate surface. Therefore, we can conclude that the stronger oxidation ability, loose oxide film on the substrate surface, and the higher corrosion-wear rate of the H2O2-AIBA slurry lead to the higher MRR.

In vitro action of 2.2’-azobis-2 amidinopropan dihydrochloride,red wine polyphenols, resveratrol and catechin on anion permeability for chloride in human red blood cell

Introduction: The purpose of this study was to evaluate the ability of polyphenols (red wine polyphenols, resveratrol and catechin) on anion permeability for chloride and oxidative damage in human erythrocytes exposed to the water-soluble free radical initiator 2.2’-azobis-2 amidinopropan dihydrochloride (AAPH). Materials and Methods: The reducing agent treatment efficacy was observed by evaluation of anion permeability for chloride, lipid peroxidation and hemolysis in red blood cells (RBCs). Anion permeability for chloride is an indicator of membrane protein damage and is evaluated in RBCs by the specific absorption of methemoglobin (CM) at 590 and 635 nm after treatment of heparinized blood with NaNO2. The measurement of the membrane lipid degradation is obtained by the determination of malondialdehyde. The lipid peroxidation susceptibility is observed after the oxidative stress induced by AAPH. The hemolysis assays are conducted on blood samples in phosphate buffer saline and the morphological changes of erythrocytes are observed by optical microscopy as membrane damage verification parameter. Results: Polyphenol treatment is associated with a significant increase in anion permeability for chloride compared with control and AAPH affected cells. Treatment with polyphenols was associated with a significant reduction in mean ± standard error of the mean membrane lipid peroxidation compared with control and AAPH treatment. Hemolysis data are also obtained in the previously described conditions. RBCs morphology data indeed confirm previous observations. Conclusion: In this study, it is evident that after in vitro oxidative damage of the membrane, red wine polyphenol extracts are as effective reducing agents also on CM indicator of membrane protein damages. Consequently, both red wine and polyphenol extracts both alone and mixed among them efficiently relieve the effects of oxidative stress.

Purification and in vitro antioxidant activities of tellurium-containing phycobiliproteins from tellurium-enriched Spirulina platensis.

Tellurium-containing phycocyanin (Te-PC) and allophycocyanin (Te-APC), two organic tellurium (Te) species, were purified from tellurium-enriched Spirulina platensis by a fast protein liquid chromatographic method. It was found that the incorporation of Te into the peptides enhanced the antioxidant activities of both phycobiliproteins. With fractionation by ammonium sulfate precipitation and hydroxylapatite chromatography, Te-PC and Te-APC could be effectively separated with high purity, and Te concentrations were 611.1 and 625.3 μg g−1 protein in Te-PC and Te-APC, respectively. The subunits in the proteins were identified by using MALDI-TOF-TOF mass spectrometry. Te incorporation enhanced the antioxidant activities of both phycobiliproteins, as examined by 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid assay. Moreover, Te-PC and Te-APC showed dose-dependent protection on erythrocytes against the water-soluble free radical initiator 2,2′-azo(2-asmidinopropane)dihydrochloride-induced hemolysis. In the hepatoprotective model, apoptotic cell death and nuclear condensation induced by tert-butyl hydroperoxide in HepG2 cells was significantly attenuated by Te-PC and Te-APC. Taken together, these results suggest that Te-PC and Te-APC are promising Te-containing proteins with application potential for treatment of diseases related to oxidative stress.

Inhibition of oxidative hemolysis in erythrocytes by mitochondria-targeted antioxidants of SkQ series.

In the present work we studied the effect of antioxidants of the SkQ1 family (10-(6'-plastoquinonyl)decyltriphenylphosphonium) on the oxidative hemolysis of erythrocytes induced by a lipophilic free radical initiator 2,2'-azobis(2,4-dimethylvaleronitrile) (AMVN) and a water-soluble free radical initiator 2,2'-azobis(2-methylpropionamidine) dihydrochloride (AAPH). SkQ1 was found to protect erythrocytes from hemolysis, 2 μM being the optimal concentration. Both the oxidized and reduced SkQ1 forms exhibited protective properties. Both forms of SkQ1 also inhibited lipid peroxidation in erythrocytes induced by the lipophilic free radical initiator AMVN as detected by accumulation of malondialdehyde. However, in the case of induction of erythrocyte oxidation by AAPH, the accumulation of malondialdehyde was not inhibited by SkQ1. In the case of AAPH-induced hemolysis, the rhodamine-containing analog SkQR1 exerted a comparable protective effect at the concentration of 0.2 μM. At higher SkQ1 and SkQR1 concentrations, the protective effect was smaller, which was attributed to the ability of these compounds to facilitate hemolysis in the absence of oxidative stress. We found that plastoquinone in the oxidized form of SkQ1 could be reduced by erythrocytes, which apparently accounted for its protective action. Thus, the protective effect of SkQ in erythrocytes, which lack mitochondria, proceeded at concentrations that are two to three orders of magnitude higher than those that were active in isolated mitochondria.

Tocotrienol prevents AAPH-induced neurite degeneration in neuro2a cells

ObjectivesReactive oxygen species induce neurite degeneration before inducing cell death. However, the degenerative mechanisms have not yet been elucidated. While tocotrienols have a known neuroprotective function, the underlying mechanism remains unclear and may or may not involve antioxidant action. In this study, we hypothesize that free radical-derived membrane injury is one possible mechanism for inducing neurite degeneration. Therefore, we examined the potential neuroprotective effect of tocotrienols mediated through its antioxidant activity.MethodsMouse neuroblastoma neuro2a cells were used to examine the effect of the water-soluble free radical generator 2,2′-azobis(2-methylpropionamide) dihydrochloride (AAPH) on neurite dynamics. After 24 hours of AAPH treatment, cell viability, neurite number, and the number of altered neurites were measured in the presence or absence of α-tocotrienol.ResultsTreatment of neuro2a cells with a low concentration of AAPH induces neurite degeneration, but not cell death. Treatment with 5 µM α-tocotrienol significantly inhibited neurite degeneration in AAPH-treated neuro2a cells. Furthermore, morphological changes in AAPH-treated neuro2a cells were similar to those observed with colchicine treatment.Conclusionsα-Tocotrienol may scavenge AAPH-derived free radicals and alkoxyl radicals that are generated from AAPH-derived peroxyl radicals on cell membranes. Therefore, α-tocotrienol may have a neuroprotective effect mediated by its antioxidant activity.

Concentration and time dependent cytoprotective effects of anthocyanins against oxidative hemolysis induced by water and lipid soluble free radical initiators: an <i>in vitro</i> study

The non-enzymatic, free radical-mediated peroxidation of erythrocyte membranes is now correlated with a variety of pathological conditions, and considered as a primary event associated with hematotoxicity of variety of drugs and chemicals that induce erythrocyte hemolysis. The plant derived polyphenols including anthocyanins have been suggested to enhance red blood cell resistance to oxidative stress both in vitro and in vivo. The present study was designed to investigate the concentration and time dependent anti-hemolytic activity of anthocyanins using in vitro models of azo compounds-induced erythrocyte membrane peroxidative damage. Three different concentrations (1, 0.1 and 0.01 mg/ml) of anthocyanins solution were incubated with erythrocytes suspension 30 min before addition of either water soluble (AAPH) or lipid soluble (AMVN) free radical initiators. The level of hemoglobin released into the solution was determined spectrophotometrically, both in presence and absence of anthocyanins. Moreover, the most effective concentration was selected to be added at different time intervals (zero time, 2 and 3 hours) post challenge with either AAPH or AMVN and the extent of hemolysis was determined as mentioned before. The results showed that anthocyanins, concentration dependently attenuated hemolysis induced by azo compounds, and substantial cytoprotective effects of anthocyanins were observed when they added simultaneously with azo compounds, while delayed addition of anthocyanins for 2 and 3 h diminished but not abolished the protective effect of anthocyanins. In conclusion, anthocyanins can effectively display concentration and time dependent cytoprotective properties against azo compounds-induced peroxidative hemolytic damage.

Protective Effect of <i>Aloe vera (Aloe barbadensis</i> Miller) on Erythrocytes Anion Transporter and Oxidative Change

The purpose of this study was to evaluate the ability of aqueous extract of Aloe barbadensis Miller (Aloe vera) on oxidative damage and Anion Exchanger 1 (AE1, also known as Band 3) expression in human erythrocytes exposed to the water soluble free radical initiator 2.2’-azobis-2-amidinopropano dihydrochloride (AAPH). In addition, total phenolic compounds in the extracts were determined as catechin equivalent and the various antioxidant activities were compared to natural and synthetic standard antioxidants such as BHA and ascorbic acid. Since Aloe vera extract did not cause a consumption of the cytosolic antioxidant, glutathione (GSH) when it was direct incubated with GSH in basic aerated aqueous solution, this indicates that Aloe vera extract does not proceed auto oxidation at this experimental condition. Furthermore, Aloe vera extract prevent the consumption of GSH, in radical treated RBCs. It also inhibit consumption of GSH when it was direct incubated with AAPH. Aloe vera gel extract inhibits the generation of diphenyl-2-picrylhy-drazyl (DPPH) and the scavenging activity was increased in a dose dependent manner. Aloe vera extract was shown the similar reducing power than standards BHT and ascorbic acid. Biochemical analysis by SDS-PAGE and western blotting showed that AAPH-induced oxidative stress increased the susceptibility of AE1 to proteolytic degradation. Of note, our data evidenced that Aloe vera treatment was able to partially restore the normal RBC membrane protein profiles in a dose-dependent manner. These results clearly demonstrate the antioxidative activity of Aloe vera gel extract that might be ascribed to a synergistic action of the bioactive compounds contained therein.

Evidence of changes in hydrophilic/hydrophobic balance and in chemical activity of HSA induced by thermal treatments

Abstract Samples of human serum albumin (HSA) obtained as a result of heat denaturation followed by refolding controlled by a cooling of the protein solution were studied by several methods: chromatographic measurements, kinetic of the reaction with a water soluble free radical and by electron paramagnetic resonance (EPR) spectroscopy. In this context the interaction of this protein with β-cyclodextrin (β-CD) and sodium dodecyl sulfate (SDS) was also investigated. Reversed phase thin layer chromatography (RP-TLC) showed changes in lipophylicity of HSA, which are related with the existence of different ensembles of conformers. The UV-Vis absorption spectra had shown the broadening of absorption band of the protein and a hyperchrom effect in the presence of SDS; β-CD reduces the effect of SDS on protein UV-Vis spectra. Kinetic measurements related to the reaction of HSA with a water soluble DPPH type free radical provided evidence that reactivity of the HSA denaturated conformers is higher compared with the natural conformer. The affinity of SDS to the albumins surface and the effect of β-CD on the SDS/protein aggregates were also evident by changes in the EPR spectra of the spin probe CAT16.

USING IMPEDANCE-SENSING SYSTEM TO EVALUATE THE EFFECT OF WOUND HEALING BEHAVIOR ON CELLS TREATED BY VITAMIN C

Burn injuries could be local or systemic problems, so multiple disciplines should be considered, including nutrition. Vitamin C is a cofactor of prolyl and lysyl hydroxylation for collagen maturation and ceramide synthesis and an important water-soluble free radical scavenger. Clinically, supplement of vitamin C is part of burn care for improving the healing process and decreasing further damage. With modified interdigitated microelectrode plate (IMP), electrical burn of MDCK cells was produced with constant current for few seconds. Healing process of cells damaged by different duration of direct constant current and damaged cells treated with 100 μM vitamin C were recorded by modified IMP and impedance-sensing system. The rate of change of conductivity is fast in the group of shorter exposure time and vitamin C-treated cells. Compared with the result of MTT test, we concluded that vitamin C decreased the duration of healing through increase cell proliferation.

Peptide Fractionation and Free Radical Scavenging Activity of Zein Hydrolysate

Alcalase-treated zein hydrolysate (ZH) was separated by gel filtration, ultrafiltration, and reversed-phase HPLC, and the scavenging activities for 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS*+), 1,1-diphenyl-2-picrylhydrazyl (DPPH*), and superoxide anion (O2*-) radicals of different peptide fractions were measured to establish the antioxidant efficacy. Results showed that the ability to stabilize water-soluble free radicals (ABTS*+) by ZH components was insensitive to the peptide size, whereas that against ethanol-soluble free radicals (DPPH*) and O2*- was molecular weight dependent. Antioxidative peptides of <1 kDa were further separated by HPLC into 30 components, of which those with great hydrophobicity exhibited strong DPPH* and O2*- scavenging ability and those with intermediate hydrophobicity displayed the maximum ABTS*+ scavenging activity. Two dominant components (fractions 8 and 17) were further purified and identified by LC-PDA-ESI-MS to be Tyr-Ala and Leu-Met-Cys-His, respectively. The results demonstrated that the free radical scavenging activity of ZH depended on the radical species and was strongly related to the molecular weight and hydrophobicity of the constituting peptides.

Protection of wheat bran feruloyl oligosaccharides against free radical-induced oxidative damage in normal human erythrocytes

The present work assessed the protective effect of water-soluble feruloyl oligosaccharides (FSH), ferulic acid ester of oligosaccharides from wheat bran, against in vitro oxidative damage of normal human erythrocytes induced by a water-soluble free radical initiator, 2,2′-azobis-2-amidinopropane dihydrochloride (AAPH). In the whole process of AAPH-initiated oxidation, hemolysis occurred quickly after the lag time. The rate of hemolysis is correlated dose-dependently with AAPH concentration. Significant decrease in reduced glutathione (GSH) levels of erythrocyte with concomitant enhancement in oxidized gluthione (GSSG) levels was noticed. It was also observed that lipid and protein peroxidation of erythrocytes induced by AAPH was significantly increased, and scanning electron microscopy observations showed that AAPH induced obvious morphological alteration in the erythrocytes from a smooth discoid to an echinocytic form. FSH suppressed depletion of GSH, lipid peroxidation, and methaemoglobin and protein carbonyl group formation of erythrocytes in concentration- and time-dependent manners, remarkably delayed AAPH-induced hemolysis. Morphological changes to erythrocyte caused by AAPH were effectively protected by FSH. It was also observed that FSH could work synergistically with endogenous antioxidants in erythrocytes. These results indicated that FSH efficiently protected normal human erythrocytes against oxidative stress, and they could be used as a potential source of natural antioxidants.

Gene expression profiling reveals new protective roles for vitamin C in human skin cells

The skin is a protective barrier against external insults and any lesion must be rapidly and efficiently repaired. Dermal fibroblasts are the major source of extracellular connective tissue matrix and play an important role in wound healing. Vitamin C is an important water-soluble free radical scavenger and an essential cofactor for collagen synthesis by dermal fibroblasts and, consequently, may contribute to the maintenance of healthy skin. Using microarray analysis, we investigated the effects of long-term exposure to a stable vitamin C derivative, ascorbic acid 2-phosphate (AA2P), in contact-inhibited populations of primary human dermal fibroblasts. Compared with “scorbutic” cells, cells exposed to AA2P increased the expression of genes associated with DNA replication and repair and with the G 2/M phase of the cell cycle. Consistent with the gene expression changes, AA2P increased the mitogenic stimulation of quiescent fibroblasts by serum factors and cell motility in the context of wound healing. Furthermore, AA2P-treated fibroblasts showed faster repair of oxidatively damaged DNA bases. We propose that vitamin C may protect the skin by promoting fibroblast proliferation, migration, and replication-associated base excision repair of potentially mutagenic DNA lesions, and we discuss the putative involvement of hypoxia-inducible transcription factor-1 and collagen receptor-related signaling pathways.

Phospholipid−Protein Adducts of Lipid Peroxidation: Synthesis and Study of New Biotinylated Phosphatidylcholines

Oxidative stress gives rise to a number of electrophilic aldehydes from membrane phospholipids, and these compounds have been linked to pathophysiologic events associated with the progression of cardiovascular disease. A headgroup biotinylated phosphatidylcholine (PC) has been prepared, and its oxidation chemistry has been studied. Biotin or biotin-sulfoxide groups were attached to PC at the ammonium headgroup via a di-ethylene glycol link. The modified phospholipids have calorimetric and colloidal properties similar to those of the parent. The oxidation of PLPBSO (the biotin-sulfoxide analogue of 1-palmitoyl-2-linoleoylglycerylphosphatidylcholine, PLPC) was studied under a variety of conditions. PLPBSO, like PLPC, undergoes oxidation to give electrophiles that adduct to small model peptides as well as to isolated proteins such as human serum albumin. PLPBSO incorporates into human blood plasma, and treatment of the plasma with water soluble free radical initiators gives rise to a number of biotinylated plasma proteins that can be isolated via (strept)avidin affinity. Isolated peptide or protein-lipid adducts can be identified by proteomics analyses, and studies on model peptides show that phospholipid-protein adduction sites can be identified by known algorithms. Biotinylated lipids such as PLPBSO and modern proteomics tools would appear to provide a new approach to exploring the chemistry and biology of membrane peroxidation associated with oxidative stress.

New water-soluble benzophenone derivatives as initiators of free radical polymerization of acrylates

Triplet state quenching of benzophenone derivatives in the presence of amino-acids undergoes via photoinduced intermolecular electron transfer mechanism (PET), which is followed by the transformations yielding free radicals able to initiate polymerization. This paper describes a series of water soluble free radical photoinitiating systems consisting of sodium 4-benzoylbenzenesulfonate (BBS) and sodium 4,4'-dibenzoylbenzenesulfonate (DBBS) as the light absorbing chromophores and amino acids or sulfur-containing amino acids acting as the electron donors. Photoinitiated polymerization were carried out for the mixture composed of poly(ethylene glycol)diacrylate (PEGDA) - 1 % NH 4 OH (3:1). The mechanistic aspect of photoinitiating processes was investigated by the measurement of polymerization kinetics and by the nanosecond laser flash photolysis. The photoreduction of benzophenone derivatives in the presence of the electron donors was studied in acetonitryle and water solutions. Nanosecond laser flash photolysis indicated a weak efficiency of ketyl radical formation (λ max = 550 nm), which is due to the hydrogen atom abstraction by the excited triplet state of the sulfobenzophenone chromophore. It is also documented that in the presence of amino acids or sulfur containing amino acids PET process leads to formation of α-aminoradicals that can initiate PEGDA polymerization. Based on photochemistry of tested benzophenone derivatives, photochemistry of sulfur-containing amino acids and obtained results the mechanism describing primary and secondary processes occurring during photoinitiated polymerization via PET process is proposed.