Free Carbonyl Groups Research Articles

Evaluation of a Series of 9,10-Anthraquinones as Antiplasmodial Agents

Background: A phytochemical study on medicinal plants used for the treatment of fever and malaria in Africa yielded metabolites with potential antiplasmodial activity, many of which are Anthraquinones (AQ). AQs have similar sub-structure as naphthoquinones and xanthones, which were previously reported as novel antiplasmodial agents. </P><P> Objective: The present study aimed to investigate the structural requirements of 9,10- anthraquinones with hydroxy, methoxy and methyl substituents to exert strong antiplasmodial activity and to investigate their possible mode of action. </P><P> Methods: Thirty-one AQs were synthesized through Friedel-Crafts reaction and assayed for antiplasmodial activity in vitro against Plasmodium falciparum (3D7). The selected compounds were tested for toxicity and probed for their mode of action against β-hematin dimerization through HRP2 and lipid catalyses. The most active compounds were subjected to a docking study using AutoDock 4.2. </P><P> Results: The active AQs have similar common structural characteristics. However, it is difficult to establish a structure-activity relationship as certain compounds are active despite the absence of the structural features exhibited by other active AQs. They have either ortho- or meta-arranged substituents and one free hydroxyl and/or carbonyl groups. When C-6 is substituted with a methyl group, the activity of AQs generally increased. 1,3-DihydroxyAQ (15) showed good antiplasmodial activity with an IC50 value of 1.08 µM, and when C-6 was substituted with a methyl group, 1,3- dihydroxy-6-methylAQ (24) showed stronger antiplasmodial activity with an IC50 value of 0.02 µM, with better selectivity index. Compounds 15 and 24 showed strong HRP2 activity and mild toxicity against hepatocyte cells. Molecular docking studies showed that the hydroxyl groups at the ortho (23) and meta (24) positions are able to form hydrogen bonds with heme, of 3.49 Å and 3.02 Å, respectively. </P><P> Conclusion: The activity of 1,3-dihydroxy-6-methylAQ (24) could be due to their inhibition against the free heme dimerization by inhibiting the HRP2 protein. It was further observed that the anthraquinone moiety of compound 24 bind in parallel to the heme ring through hydrophobic interactions, thus preventing crystallization of heme into hemozoin.

Novel "Turn-On" Fluorescent Probe for Highly Selectively Sensing Fluoride in Aqueous Solution Based on Tb3+-Functionalized Metal-Organic Frameworks.

A Zr-based metal–organic framework (Zr-MOF) which has free carbonyl groups is synthesized successfully through mix-ligand strategy. Subsequently, Tb3+ is encapsulated into a Zr-MOF by postcoordinated modification. The Tb3+@Zr-MOF exhibits the characteristic emission of Tb3+ because of efficient sensitization through antenna effects. The Tb3+@Zr-MOF is further developed as a novel “turn-on” fluorescent probe to detect fluoride ions in aqueous solution. The results show that Tb3+@Zr-MOF exhibits excellent selectivity, high stability, low detection limits, and good anti-interference for sensitizing fluoride ions. In addition, the possible sensing mechanism that the induced luminescence properties may be attributed to Lewis acid–base interactions is discussed.

Impact of wedelolactone in the anti‐glycation and anti‐diabetic activity in experimental diabetic animals

The glycation reaction is the addition of free carbonyl group of reducing sugar to the free amino groups of proteins, lipoproteins and nucleic acids which results in the formation of an Amadori product which may ultimately lead to the generation of advanced glycation products (AGEs). The impact of AGEs on proteins consequently generates free radicals, "a key player" for the pathogenesis of diabetes mellitus. Gel electrophoresis was carried out to see the visual changes taking place as a result of the glycation reaction. In this study, the anti-glycation and anti-diabetic effect of wedelolactone (WED) was seen both in vitro and in vivo. WED reverted various biochemical markers in streptozotocin-induced diabetic rats along-with the improvements in the oxidative stress markers. It also decreased the levels of the glycated serum protein and fasting blood glucose. Broadly, WED not only inhibited glycation in vitro but also proved to be an effective in vivo anti-glycating agent. © 2018 IUBMB Life, 70(6):547-552, 2018.

Differential reactive oxygen species production of neutrophils and their oxidative damage in patients with active and inactive systemic lupus erythematosus

ObjectiveIncreasing interest is given to the involvement of the innate immunity and especially Polymorphonuclear neutrophils (PMN) in the physiopathological process of inflammatory diseases such as systemic lupus erythematosus (SLE). Here, we investigated the oxidative burst and damages in SLE patients neutrophils, considering the two phases of the disease, the active and the remission/inactive states. MethodsThis study was conducted on 30 SLE patients and 23 healthy controls. The oxidative burst in neutrophils of SLE patients and controls was triggered by fMLP and TPA, while reactive oxygen species (ROS) production was evaluated using a chemiluminescence assay. Oxidative damages in neutrophils were assessed by measuring Free thiol groups level and carbonyl groups, as protein oxidative markers. The malondialdehyde (MDA) level informed about the lipid peroxidation (LPO) and the catalase activity indicated the antioxidant enzymatic activity. ResultCompared to controls, SLE patients exhibited a significantly increased level of ROS production concomitantly to a decreased response time. Their Neutrophils were characterized by a decreased level of MDA and high levels of protein oxidation as evidenced by increased carbonyl groups and decreased SH levels. The catalase activity was higher in SLE patients' neutrophils compared to controls. When patients were clustered according to the disease activity, PMN of patients in active phase showed, paradoxically, a lower ROS production and exhibited higher oxidative damages than the inactive group. ConclusionOur results highlight an altered behavior of LES patients derived PMN particularly in the active phase of the disease. The evaluation of the redox status including the rate of ROS production could be a biological marker to follow the activity of the disease.

Immunoglobulin-G Glycation by Fructose Leads to Structural Perturbations and Drop Off in Free Lysine and Arginine Residues.

Non-enzymatic glycation is the addition of free carbonyl group of reducing sugar to the free amino groups of proteins and leads to the formation of early glycation products and further into advanced glycation end products (AGEs). Fructose reacts rapidly with the free amino groups of proteins to form AGEs. AGEs are believed to be involved in the pathogenesis of several diseases, particularly in diabetic complications. In this study, IgG was glycated with fructose monosaccharide at 10 mM concentration for varying time interval. The reaction mixture was kept at 37ºC. The early glycation of IgG was done by nitroblue tetrazolium assay (NBT), and the generation of AGEs was done by the extent of side chain modifications (lysine and arginine), Nε-carboxymethyl lysine, pentosidine and carbonyl content. The decrease in free lysine and arginine residues suggests that protein 'IgG' has undergone modification specifically on epsilon amino groups of lysine and arginine. Additionally, their fluorescence and absorbance characteristics were also systematically studied. The results suggest that the maximum Amadori product (ketoamine content) was formed on sixth day of the incubation. The conformational structural perturbation was observed within the glycated IgG protein as studied by using various physicochemical techniques. This study reports structural perturbation, formation of various intermediates and AGEs.

Physicochemical and functional properties of acid precipitated soy proteins-maltodextrin conjugates.

Physicochemical and functional properties of acid precipitated soy proteins-maltodextrin conjugates.

Effect of zinc oxide nanoparticles on the in vitro degradation of electrospun polycaprolactone membranes in simulated body fluid

ABSTRACTEven though the biodegradability of polycaprolactone (PCL) is well established, few studies have carried out on the effect of nanofillers on the in vitro degradability of electrospun PCL membranes. Thus, the authors incorporated common nanofiller zinc oxide (ZnO) nanoparticles in electrospun PCL membranes. From the study of morphological schanges as well as the changes in crystallinity, it is clear that the ZnO nanoparticles accelerated the degradation of PCL. The FTIR results ascertain that the hydrolysis of the PCL nanofibers generates free hydroxyl and carbonyl groups in the bulk of the polymer. The tensile property of the PCL/ZnO nanocomposite membranes decreased with an increase in filler loading during degradation.

Glycation of H1 Histone by 3-Deoxyglucosone: Effects on Protein Structure and Generation of Different Advanced Glycation End Products

Advanced glycation end products (AGEs) culminate from the non-enzymatic reaction between a free carbonyl group of a reducing sugar and free amino group of proteins. 3-deoxyglucosone (3-DG) is one of the dicarbonyl species that rapidly forms several protein-AGE complexes that are believed to be involved in the pathogenesis of several diseases, particularly diabetic complications. In this study, the generation of AGEs (Nε-carboxymethyl lysine and pentosidine) by 3-DG in H1 histone protein was characterized by evaluating extent of side chain modification (lysine and arginine) and formation of Amadori products as well as carbonyl contents using several physicochemical techniques. Results strongly suggested that 3-DG is a potent glycating agent that forms various intermediates and AGEs during glycation reactions and affects the secondary structure of the H1 protein. Structural changes and AGE formation may influence the function of H1 histone and compromise chromatin structures in cases of secondary diabetic complications.

Quercetin as a finer substitute to aminoguanidine in the inhibition of glycation products

Non-enzymatic glycation is the addition of a free carbonyl group of a reducing sugar to the free amino groups of proteins, which results in the formation of early and advanced glycation end-products (AGEs). Glycation reaction is profoundly associated with diabetes and its secondary complications, such as nephropathy and neuropathy. Glyoxal is a carbonyl species that reacts rapidly with the free amino groups of proteins to form AGEs. While the formation of AGEs with various glycating agents has previously been demonstrated, no extensive studies have been conducted to assess the role of quercetin in all three stages of glycation (early, intermediate and late). In this study, we report the glycation of HSA (human serum albumin) and its characterization by several spectroscopic techniques. Furthermore, inhibition of products at all stages of glycation was studied by various assays. Spectroscopic analysis suggests structural perturbations in the HSA macromolecule as a result of modification, which might be due to the generation of free radicals and the formation of AGEs. Inhibition in the formation of glycation has established that quercetin is a better and a more potent antiglycating agent than aminoguanidine at all stages of glycation.

Optimization of Cultural Conditions for Production of Exopolysaccaride by <i>Halomonas marina</i> HMA 103 under Batch-Culture

A moderately halophilic bacterium, Halomonas marina HMA 103 (MTCC 8968) accumulating intracellular polyesters also produced significant amount of exopolysaccharides (EPS) under batch-culture. Production of EPS by the bacterium was more or less parallel with the growth in modified basal synthetic medium. During growth, it produced 0.46 g/L of EPS after 50 h of incubation and was accompanied by the complete utilization of glucose from the medium. EPS production was maximum in 2% (w/v) glucose followed by sucrose and maltose and was positively influenced by yeast extract, beef extract and peptone. Optimum concentrations of sulfate and phosphate for EPS production were 2.4% (w/v) and 0.03% (w/v) respectively. High concentration (10% w/v) of NaCl stimulated both growth and EPS production by H. marina HMA 103. Characteristically, this EPS is a heteropolymer of glucose and mannose and the Fourier Transform Infrared (FTIR) spectrum showed distinct absorption peaks at 3424.2, 1638.7, 1122.9 and 622.3 cm-1 indicating the presence of free hydroxyl, phenyl or carbonyl groups of carbohydrate. Further, the detailed physico-chemical analysis will indicate the significance and potential importance of this EPS in biotechnology.

Chronic intermittent hypoxia increases rat sternohyoid muscle NADPH oxidase expression with attendant modest oxidative stress.

Chronic intermittent hypoxia (CIH) causes upper airway muscle dysfunction. We hypothesized that the superoxide generating NADPH oxidase (NOX) is upregulated in CIH-exposed muscle causing oxidative stress. Adult male Wistar rats were exposed to intermittent hypoxia (5% O2 at the nadir for 90 s followed by 210 s of normoxia), for 8 h per day for 14 days. The effect of CIH exposure on the expression of NOX subunits, total myosin and 4-hydroxynonenal (4-HNE) protein adducts in sternohyoid muscle was determined by western blotting and densitometry. Sternohyoid protein free thiol and carbonyl group contents were determined by 1D electrophoresis using specific fluorophore probes. Aconitase and glutathione reductase activities were measured as indices of oxidative stress. HIF-1α content and key oxidative and glycolytic enzyme activities were determined. Contractile properties of sternohyoid muscle were determined ex vivo in the absence and presence of apocynin (putative NOX inhibitor). We observed an increase in NOX 2 and p47 phox expression in CIH-exposed sternohyoid muscle with decreased aconitase and glutathione reductase activities. There was no evidence, however, of increased lipid peroxidation or protein oxidation in CIH-exposed muscle. CIH exposure did not affect sternohyoid HIF-1α content or aldolase, lactate dehydrogenase, or glyceraldehyde-3-phosphate dehydrogenase activities. Citrate synthase activity was also unaffected by CIH exposure. Apocynin significantly increased sternohyoid force and power. We conclude that CIH exposure upregulates NOX expression in rat sternohyoid muscle with concomitant modest oxidative stress but it does not result in a HIF-1α-dependent increase in glycolytic enzyme activity. Constitutive NOX activity decreases sternohyoid force and power. Our results implicate NOX-dependent reactive oxygen species in CIH-induced upper airway muscle dysfunction which likely relates to redox modulation of key regulatory proteins in excitation-contraction coupling.

Chemical modification of chitosan in the absence of solvent for diclofenac sodium removal: pH and kinetics studies

Chitosan was modified with acetylacetone and ethylenediamine in the absence of solvent. The new biopolymer obtained from the modification was characterized by elemental analysis and NMR 13C and applied in the removal of diclofenac sodium aqueous solution varying the pH and time. Through elemental analysis was possible to verify a decreasing in C/N relation after reaction with acetylacetone and an increasing after modification with ethylenediamine. From NMR analysis was verified the appearance of peaks around 160-210 ppm in both materials due to free carbonyl groups in the first step of the modification, besides the formation of imine bonds. The adsorption tests showed that the highest value occurred at pH 4 and from the results of the kinetic study was found that maximum adsorption occurred within 45 minutes and experimental data adjusted better to linear adjustment, following pseudo second-order model. The results show a material efficient in the removal of emerging pollutants.

Identification of a Rare Phytosteroid from Justicia gendarussa

Justicia gendarussa L. (Acanthaceae) is an evergreen, shade-loving, highly branched shrub. Traditionally, the plant is used in the treatment of rheumatism, dysuria, fever, carbuncles, jaundice, diarrhea, pains in the head, ear, paralysis, bruises, etc. [1, 2]. Previous reports on the pharmacological studies revealed the antioxidant, antiarthritic, antiinflammatory, analgesic, antinociceptive, antifertility, anticancer, hepatoprotective, and larvicidal properties of this plant [3–5]. Numerous chemical constituents such as sterols, flavonoids, alkaloids, reducing sugars, and O-methyl ethers of benzyl alcohol were reported from J. gendarussa leaf samples [6–8]. The present study led to the discovery of a new phytosteroid in the stem as well as callus sample of J. gendarussa. The stem samples of J. gendarussa were collected from natural forests of Dakshina Kannada District, Karnataka, India and the voucher specimen (MU/AB/BN-01) was deposited at the Herbarium of Department of Applied Botany. The callus was initiated on Murashige and Skoog medium supplemented with -naphthalene acetic acid and benzyl amino purine (1.0 + 0.1 mg/L) from the sterilized stem explants, cultured in liquid medium and harvested on the 35th day [9]. The sample was dried, extracted in ether using a Soxhlet apparatus for 8–10 h, and concentrated to dryness at 40 C. The dried extract was separated in TLC (silica gel G 60 F 254, Merck, India) using acetic acid:chloroform as solvent system. The clear spot obtained on the chromatogram was separated from the silica gel, redissolved in ether, and dried. The amorphous powder obtained was used for spectroscopic analysis using UV, FTIR, 1H NMR, and LC-MS/MS. The LC-MS analysis was performed in a Thermo Finnigan Surveyor-Thermo LCQ Deca XP MAX system with a BDS Hypersil C18 column (250 mm 4.6 mm), 100% MeOH as eluent, at ambient temperature, nebulization gas helium, and electron spray ionization method with UV and PDA as detectors. The data obtained from the LC-MS/MS spectrum were compared and predicted using NIST (National Institute of Standards and Technology, Gaithersburg, MD), version 2.0a, 2002 software. Based on all the spectral data obtained, the colorless amorphous compound was predicted as a phytosteroid: 1 -carboethoxy-1 -cyano-1,2-dihydro-[1,2]cyclopropcholest-3-one (1) with an elemental composition of C32H49NO3, m/z 496 [M + H] + by ESI-MS/MS. 1 -Carboethoxy-1 -cyano-1,2-dihydro-[1,2]cycloprop-cholest-3-one (1) was isolated as a amorphous powder. The UV spectrum of the compound in ether showed absorption maxima ( max) at 282 nm, and the FTIR spectrum of the compound in KBr exhibited absorption at ( ) 1743 and 1653 cm–1 for the ester and free carbonyl groups (C=O), 2370 cm–1 for the N C group, 3450 cm–1 for -OH or -NH stretch, and 2924 cm–1 for C-H stretching. In the 1H NMR (400 MHz, MeOD, , ppm) the ethyl protons of the carboethoxy moiety appeared as a triplet and a quartet centered at 2.30 and 4.16, integrating for three and two protons, respectively. The signal due to the protons attached to the cyclopropane ring appeared as doublets at 2.05 and 2.32, integrating for one proton each. The signal due to the two methyl and the methyl groups of the isopropyl moiety overlapped with each other and appeared in the region of 0.9–1.3, integrating for 12 protons. However, the signal due to other protons overlapped with each other and appeared as multiplets in the region of 0.875–4.5. The ESI-MS/MS spectrum (ESI, 4.5 kV) showed the molecular ion peak [M + H]+ at m/z 496, consistent with the proposed molecular formula of the phytosteroid C32H49NO3. Spectroscopy was used for the detection of phytosterols in the callus tissue of Cissus quadrangularis [10], ursane type triterpenes in Olea europaea [11] and azadirachtin in cell suspension cultures of Azadirachta indica [12], triterpenoid glycosides in Justicia betonica [13], flavonoids in Punica granatum [14], and triterpenes and sesquiterpenes in Pinus densata

Impact of chemical changes on the sensory characteristics of coffee beans during storage

Sensory changes during the storage of coffee beans occur mainly due to lipid oxidation and are responsible for the loss of commercial value. This work aimed to verify how sensory changes of natural coffee and pulped natural coffee are related to the oxidative processes during 15months of storage. During this period, changes in the content of free fatty acids (1.4–3.8mg/g oil), TBARS values (8.8–10.2nmolMDA/g), and carbonyl groups (2.6–3.5nmol/mg of protein) occurred. The intensity of “rested coffee flavour” in the coffee brew increased (2.1–6.7) and 5-caffeoylquinic acid concentration decreased (5.2–4.6g/100g). Losses were also observed in seed viability, colour of the beans and cellular structure. All the results of the chemical analyses are coherent with the oxidative process that occurred in the grains during storage. Therefore, oxidation would be also responsible for the loss of cellular structure, seed viability and sensory changes.

Inhibitory Effect of Metformin and Pyridoxamine in the Formation of Early, Intermediate and Advanced Glycation End-Products

BackgroundNon-enzymatic glycation is the addition of free carbonyl group of reducing sugar to the free amino groups of proteins, resulting in the formation of a Schiff base and an Amadori product. Dihydroxyacetone (DHA) is one of the carbonyl species which reacts rapidly with the free amino groups of proteins to form advanced glycation end products (AGEs). The highly reactive dihydroxyacetone phosphate is a derivative of dihydroxyacetone (DHA), and a product of glycolysis, having potential glycating effects to form AGEs. The formation of AGEs results in the generation of free radicals which play an important role in the pathophysiology of aging and diabetic complications. While the formation of DHA-AGEs has been demonstrated previously, no extensive studies have been performed to assess the inhibition of AGE inhibitors at all the three stages of glycation (early, intermediate and late) using metformin (MF) and pyridoxamine (PM) as a novel inhibitor.Methodology/Principal FindingsIn this study we report glycation of human serum albumin (HSA) & its characterization by various spectroscopic techniques. Furthermore, inhibition of glycation products at all the stages of glycation was also studied. Spectroscopic analysis suggests structural perturbations in the HSA as a result of modification which might be due to generation of free radicals and formation of AGEs.ConclusionThe inhibition in the formation of glycation reaction reveals that Pyridoxamine is a better antiglycating agent than Metformin at all stages of the glycation (early, intermediate and late stages).

Molecular Dynamic Simulations and Vibrational Analysis of an Ionic Liquid Analogue

Deep eutectic solvents, considered ionic liquid (IL) analogues, show promise for many material science and engineering applications over typical ILs because they are readily available and relatively inexpensive. Atomistic molecular dynamics simulations have been performed over a range of temperatures on one eutectic mixture, 1:2 choline chloride/urea, using different force field modifications. Good agreement was achieved between simulated density, volume expansion coefficient, heat capacity, and diffusion coefficients and experimental values in order to validate the best performing force field. Atom-atom and center-of-mass radial distribution functions are discussed in order to understand the atomistic interactions involved in this eutectic mixture. Experimental infrared (IR) spectra are also reported for choline chloride-urea mixtures, and band assignments are discussed. The distribution of hydrogen-bond interactions from molecular simulations is correlated to curve-resolved bands from the IR spectra. This work suggests that there is a strong interaction between the NH2 of urea and the chlorine anion where the system wants to maximize the number of hydrogen bonds to the anion. Additionally, the disappearance of free carbonyl groups upon increasing concentrations of urea suggests that at low urea concentrations, urea will preferentially interact with the anion through the NH2 groups. As this concentration increases, the complex remains but with additional interactions that remove the free carbonyl band from the spectra. The results from both molecular simulations and experimental IR spectroscopy support the idea that key interactions between the moieties in the eutectic mixture interrupt the main interactions within the parent substances and are responsible for the decrease in freezing point.

Hydrolysis and Isomerization of Sugar Phosphates and Carbohydrate Phosphodiesters

Phosphoesters are abundant in carbohydrate structures, yet their chemical reactivity is less well known than that of nucleoside phosphoesters. Both classes of compounds contain sugar bound phosphoesters, but structural versatility of carbohydrates means that the reactivity range is wider, and reaction mechanisms not feasible in nucleic acid chemistry, are possible. Sugar phosphates, as well as their phosphodiester and phosphoanhydride derivatives with a phosphate group in glycosylic position, react like acetals under acidic conditions. Substrates with a phosphate group attached to an alcoholic OH react by intramolecular transesterification similar to that of RNA provided that there is a suitably positioned HO-group and a suitable leaving group. If there is a free carbonyl group allowing anomeric equilibria, base-catalyzed phosphate elimination through enediolate intermediates may compete with the cleavage, particularly under alkaline conditions. The few reports on phosphate migration show that the reaction is conceivable, but the competition between cleavage and phosphate migration possibly is different from reactions of nucleic acids and nucleotides.

Novel bioreactor for resolution of (R,S)‐1‐phenylethanol using the functional conducting polymer and ionic liquid with excellent catalytic activity and stability

AbstractBackgroundBioreactors are widely used in the chemical, food and medical industries. However, enzyme immobilization in the bioreactor often results in the loss of activity and stability to varying degrees. To resolve the problem, a new functional conducting polymer monomer, 2,5‐di(2‐thienyl)‐1H‐pyrrole‐1‐(p‐phenylacetic acid) (DPP), was designed, synthesized and electrodeposited on copper net to form ultrathin poly(DPP) film containing free carbonyl groups. Then, pseudomonas cepacia lipase was covalently coated on the film with 1‐ethyl‐3‐(3‐dimethyl‐aminopropyl)‐carbodiimide /N‐hydroxy‐succinimide as activator, and 1,3‐di(isobutyl)‐imidazolium hexafluorophosphate ionic liquid was finally coated on the surface of the film. In this study, an as‐prepared bioreactor was employed for the resolution of (R,S)‐1‐phenylethanol to investigate catalytic characterization of the enzyme immoblized on the bioreactor.ResultsThe enzyme immobilized on the bioreactor offers high activity, reactivity and stability. Under optimal conditions, initial reaction rate, the conversion of (R,S)‐1‐phenylethanol and enantiomeric excess of (R)‐1‐phenylethyl acetate was 1.76 U mg‐1, 47.4% and 99%, respectively. Also, the stability of the lipase immobilized on the bioreactor was 5.1‐fold that of the native lipase in hexane. The lipase immobilized on the bioreactor was recycled 10 times without substantial diminution in activity.ConclusionThe functional conducting polymer combined with the ionic liquid for the enzyme immoblization provided good enzyme activity and stability. It is also promising for both the construction of bioreactors and industrialized continuous production. © 2013 Society of Chemical Industry

Effects of bleaching on characteristics and gelling property of gelatin from splendid squid (Loligo formosana) skin

Gelatins obtained from splendid squid (Loligo formosana) skin subjected to bleaching using hydrogen peroxide (H2O2) at various concentrations were characterised. Yield of gelatin increased with increasing H2O2 concentration used. Gelatin from skin bleached with higher H2O2 concentrations had the lower free amino group and carbonyl group contents than the control gelatin (without bleaching). Gelatins had α-chains with MW of 123–129 kDa as the major components. FTIR spectra of all gelatins revealed the significant loss of triple-helix. Gel strength of gelatin generally decreased as H2O2 concentrations increased. Varying pHs rendering net charge of zero (5.18–6.34) were found among samples, as determined by ζ-potential titration. Gelatin prepared from skin bleached with 2% H2O2 showed the highest L*, but lowest ΔE*-values, compared with others. H2O2 at higher concentrations yielded gelatin with increasing b*-value. Thus, the properties of gelatin were governed by bleaching process, particularly H2O2 concentration.

Surface characterization and radical decay studies of oxygen plasma‐treated PMMA films

Polymethylmethacrylate (PMMA) films were modified by RF oxygen plasma with various powers applied for different periods, and the effects of these parameters on the surface properties such as hydrophilicity, surface free energy (SFE), chemistry, and topography were investigated by water contact angle, goniometer, X‐ray photoelectron spectroscopy (XPS), and atomic force microscopy, and the types of the created free radicals and their decay were detected by electron spin resonance spectroscopy (ESR). SFE and contact angle results varied depending on the plasma parameters. Oxygen plasma treatment (100 W–30 min) enhanced the hydrophilicity of PMMA surface as shown by decreasing the water contact angle from 70° to 26°. XPS analysis showed the change in the amounts of the present functionalities as well as formation of new groups as free carbonyl and carbonate groups. The roughness of the surface increased considerably from ~2 nm to ~75 nm after 100 W–30 min oxygen plasma treatment. ESR analysis indicated the introduction of peroxy radicals by oxygen plasma treatment, and the intensity of the radicals increased with increasing the applied power. Significant decrease in radical concentration was observed especially for the samples treated with higher powers when the samples were kept under the atmospheric conditions. As a conclusion, RF plasma, causes changes in the chemical and physical properties of the materials depending on the applied parameters, and can be used for the creation of specific groups or radicals to link or immobilize active molecules onto the surface of a material. Copyright © 2012 John Wiley & Sons, Ltd.