Changes In UV Spectra Research Articles

Photodegradation of dissolved organic matter of chicken manure: Property changes and effects on Zn2+/Cu2+ binding property

Untreated livestock manure contains high concentrations of dissolved organic matter (DOM), which can enter the environment through leaching and eluviation, showing an important impact on the environment. In this research, fresh chicken manure from a large-scale chicken farm was collected as the source of DOM. The infrared spectrum of the original DOM was characterized. TOC analysis, UV spectrum and 3D fluorescence spectrum were used to measure the properties of DOM before and after photodegradation. Infrared spectroscopy results show that chicken manure DOM may contain aliphatic and aromatic compounds, alcohols, phenols, polysaccharides and some protein substances; In three systems, the order of TOC removal rates of DOM was water + UV system (85%) > > water + simulated sunlight system (7.2%) > ice + simulated sunlight system (4.5%); Changes of UV spectra, fluorescence spectra, molecular weight distribution and pH value show that, in three systems, as the illumination time increased, photodegradation reduced pH value of the systems, aromaticity and humus contents of DOM, while increased the proportion of medium and/or small molecular weight components of DOM. The amounts of all these changes were proportional to DOM photodegradation rates in the system. The binding ability of DOM with Cu2+ and Zn2+ in water solution decreased significantly after the photodegradation.

Preparation of zinc porphyrin nanoparticles and application in monitoring the ethanol content during the solid-state fermentation of Zhenjiang Aromatic vinegar

This work presents a real-time ethanol content measurement method during the solid-state fermentation of “Zhenjiang” Aromatic vinegar. 5, 10, 15, 20-Tetraphenyl-21H, 23H-porphine zinc (ZnTPP) which was sensitive to ethanol was employed to capture VOC from semi-solid state vinegar during fermentation. Various self-assembled nanostructures of ZnTPP based was be synthesized, while the effect of aging time and the pH on the morphology of nanoporphyrin has been studied. The result of self-assembled was characrized by change of UV spectra. After self-assembled, the colorimetric signal of ethanol VOC was, significantly enhanced. Furthermore, colorimetric sensor array made up of four colorimetric dyes with porphyrin and nanostructure porphyrin were used for VOC detection during vinegar fermentation. Meanwhile, when it is combined with back-propagation artificial neural network (BP-ANN), volatile gas messages of vinegar substrate present an high relevance with alcoholic strength measured by Gas chromatography and mass spectrometry (GC–MS). Therefore, the colorimetric sensor array based on ZnTPP nanoparticles could be well used in monitoring the ethanol content during the solid-state fermentation.

Photo and thermal stress of linseed oil and stabilization strategies.

The thermal and light stability of linseed oil has been studied by monitoring the concentrations of fatty acids and lignans, as main nutraceutical components. Linseed oil was subjected to stressing light and temperature conditions, in accordance with the ICH international rules, and monitored by UV-vis spectroscopy and HPLC-DAD. The change of UV spectra along the photodegradation tests, setting the irradiation power at 350W/m2, confirmed a significant overall sensitivity of linseed oil to light. At the same time, the HPLC determination of the major fatty acids showed a marked variation in their concentration up to a residual concentration of 62.3 and 67.2% for α-linolenic and linoleic acid, respectively, after 18h. In contrast, thermal tests at 60°C showed some stability, with a concentration of residual fatty acids in the range 82-95% after 48h. The examined lignans showed significant stability when exposed to both light and heat. Several photoprotection approaches have been also studied to increase the photostability of linseed oil. A significant increase in the stability of fatty acids has been observed using amber glass containers or ascorbic acid or by combining the two protection factors.

Photooxidized Vespa orientalis venom Improves Memory and Learning Activities in Rats

The work was aimed to study the effect of photooxidized Vespa orientalis venom on memory and learning activity on rats in presence of scopolamine and ondansetron using T maze, Elevated plus maze and passive avoidance. UV radiation exposure of Vespa orientalis venom (VOV) for 15, 30, 45 and 60 min intervals in presence to methylene blue to detoxify venom and studied by change in UV spectrum. Antigenicity study and in in-vivo and in-vitro neutralization study of Photooxidized Vespa orientalis venom (PVOV) against immunoglobulin from hyperimmunized rabbit was performed. The memory and learning activity of PVOV in presence and absence of scopolamine and ondansetron was studied. Forty five minute UV Radiation exposed VOV showed shift in λmax and increase absorbance indicated alternations in venom protein concentration, this in supported when PVOV showed loss of toxicity and decrease in mortality time in neutralization study in mice. Administration of PVOV for 28 days produced a notable improvement in spatial and long memory in rats when subjected in several tasks. When PVOV administered with scopolamine and ondansetron, all the parameters of spatial and long term memory tasks were significantly reduced inferred that PVOV acted by modulating either muscarinic or serotonergic receptors. However, other possibility of low-molecular weight protein and peptides or enzymes, which might also act by serotonergic / cholinergic system that affect CNS action. We concluded that although there is a possibility of employing PVOV in the treatment of depressive and chronic degenerative illnesses as a nonherbal and nonsynthetic alternative for patients not responding to the available therapy.

The Ways of Factors Influencing High‐Solid Enzymatic Hydrolysis of Sugarcane Bagasse Treated by Liquid Hot Water

AbstractThe influence ways of structural feature, hydrolytic viscosity and monosaccharides′ concentrations on the enzymatic hydrolysis of high‐solid liquid hot water (LHW)‐treated lignocellulose were evaluated. The SEM observation showed that the residual lignin in the LHW‐treated sugarcane bagasse (SCB) played an important role in gluing fasciculate structures, and XRD detection indicated the decrease of crystalline index (CrI) of LHW‐treated SCB after lignin removal. The enzymatic hydrolysis of LHW‐treated SCB with and without lignin removal showed that the residual lignin might block the access of cellobiohydrolase to the crystalline cellulose. The fractal kinetic model indicated that the benefit of the low viscosity for high‐solid enzymatic hydrolysis of LHW‐treated SCB would appear with the time going. As the enzymatic hydrolysis proceeding, the accumulation of glucose imposed more and more intense inhibition on the cellulolytic hydrolysis, while the xylose showed a little inhibition. The changes of UV spectra indicated that the glucose accumulation hardly affected the side chains containing tyrosine (Try) and/or tryptophan (Trp) which should be not in the catalytic active center of cellulase.

Degradation and ecotoxicity of dye Reactive Black 5 after reductive-oxidative process : Environmental Science and Pollution Research.

This research paper describes the study of a reduction-oxidation system using commercial steel wool (Fe0) and H2O2 for degradation of the dye Reactive Black 5 and aromatic compounds in water. The reductive process alone allowed the almost complete removal of color (97 ± 1%) after 60min of reaction. The decrease in spectral area (λ = 599nm) associated with the chromophore group indicates breakage of the azo bonds. Moreover, the significant change in UV spectra can be associated with the formation of aromatic amines. Regarding the transformation products, a spectrophotometric method based on the diazotization reaction was employed to identify aromatic amines after reductive process, using sulfanilic acid as a model of aromatic amines. In addition, association with Fenton reagents improved the efficiency in the system with 93 ± 1% degradation of intermediates formed during the reductive process. Ecotoxicological analysis revealed that the dye solution, after the reductive and oxidative processes, was not toxic to Lactuca sativa seeds. For Daphnia magna, the EC50 (%) values observed revealed that dye solution has an EC50(%) = 74.1 and after reductive process, the toxicity increased (EC50(%) = 63.5), which might be related to the formation of aromatic amines. However, after the Fenton process, the EC50 (%) was >100. These results demonstrated that the Fenton reaction using steel wool as an iron source was very efficient to decrease color, aromatic transformation products, and the ecotoxicity of Reactive Black 5 in solution.

Quinolone Antibacterials: Commentary and Considerations Regarding UV Spectra and Chemical Structure

Abstract Objective: Antibacterial quinolones represent an important class of pharmaceutical compounds that are widely used in therapy. Analytical methods that rely on their property to absorb light in the UV range are commonly used for their analysis. In the current study we present an interpretation of the relationship between chemical structure – UV spectra based on the comparative examination of UV spectral behavior of the eighteen quinolone derivatives and four model compounds. Methods: Eighteen quinolone derivatives and four model compounds were selected and their UV spectra were recorded in different solvents (methanol, 0.1M HCl, 0.1M NaOH). Results: The studied compounds show three absorption maximum values located around 210-230 nm, 270-300 nm and 315-330 nm values. A general characteristic was observed as the absorption bands exhibited both hypsochrome and bathochrome shifts, by comparison in different solvents. Most commonly we observed a slight hypsochrome shift at acidic pH (protonated form prevails) and basic pH (anionic form prevails). The structural differences are reflected in changes of UV spectra only when there are auxochrom substituents or different basic substituents are present in the quinolones structure. Conclusions: The correlations between the chemical structure of quinolone derivatives and their UV spectra using model compounds were established. This study provides useful information that can be used successfully in various UV spectrophotometric analysis methods or in more complex analytical methods using UV detection, and also in pharmacodynamic and kinetic studies.

Degradation of azo dye direct sky blue 5B by sonication combined with zero-valent iron

The degradation of azo dye direct sky blue 5B by sonication combined with zero-valent iron (US-Fe 0)was investigated and an evident synergistic effect was observed. The synergetic effect is mainly due to the increase of OH radical concentration from Fenton’s reaction. The OH radical concentrations in sole sonication and US-Fe 0 process were detected by using terephthalic acid as a fluorescent probe and found that OH radicals were generated continuously during sonication and the production of OH radicals in US-Fe 0 process was much higher than that in sole sonication. The degradation of direct sky blue 5B followed a pseudo-first-order kinetics and the degradation rate constants were found to be 0.0206 and 0.169 min −1 with sole sonication and US-Fe 0 process respectively. It was also found that the degradation ratio of direct sky blue 5B increased with the increase of zero-valent iron dosage and decrease of pH value of the dye aqueous solution. The degradation mechanism of direct sky blue 5B with US-Fe 0 process was discussed by the changes of UV–Vis spectrogram of the dye during degradation. The dramatic changes of UV spectra showed a disappearance of both azo and aromatic groups during the degradation.

Degradation of hyaluronic acid powder by electron beam irradiation, gamma ray irradiation, microwave irradiation and thermal treatment: A comparative study

In this study, high molecular weight hyaluronic acid in powder form (HMW-HA, with average molecular weight of 1042 kDa) was degraded to low molecular (LMW-HA, 200–230 kDa) by several methods, and the changes in molecular structure and antioxidative activities brought about by each degradation method were compared. The degradation methods used were electron beam irradiation (EB), gamma ray irradiation (GM), microwave irradiation (MW), and thermal treatment (TH). The FT-IR spectra showed no substantial changes of the spectral pattern between HMW and LMW-HAs. However, the UV absorbance of LMW-HA by MW was considerably greater at 265 nm indicating the formation of more double bonds. The antioxidative activities of all LMW-HA samples were found to have risen, but the MW-treated LMW-HA showed the most significant increase due to a newly formed double bond. EB- and GM-treated LMW-HA showed the lowest polydispersity and little change in UV spectra from those of HMW-HA.

A pH-Metric, UV, NMR, and X-ray Crystallographic Study on Arsenous Acid Reacting with Dithioerythritol

The aqueous solutions of arsenous acid with the meso and racemic forms of 1,4-dithiol-butane-2,3-diol, namely, dithioerythritol (dte) and dithiothreitol (dtt), respectively, were titrated pH-metrically in different molar ratios. The p K a values determined for As(OH) 3, and dtt were in good accordance with the literature data, and we determined for the first time the p K a value of dte. The deprotonation steps of both M (As(OH) 3 considered as a central metal ion) and H 2L components dte and dtt (considered as ligands) appeared at a higher pH in the titration curves of the ternary systems (M, H 2L, H (+)) than in the individual component. This unusual observation is explained by the condensation reactions between the reagents taking place in the pH < 8 range. In the solutions of c As(III) > 5.10 (-3) M, the precipitate formed upon mixing the arsenous acid and H 2L solutions in neutral medium, and the formation of the precipitate shifted toward acidic pH on the increase of the total concentrations. This indicated that pH-metry can follow the reactions only in an indirect way. Useful, but not satisfactory, information can be obtained by means of this method alone. Combined with NMR and UV spectroscopic measurements it is revealed that depending on the As(III)/H 2L molar ratio, different complexes form in the solutions. In the species with 1:2 composition, one of the ligands is strongly bound to the arsenic(III) probably via its two thiolate, while the second one is attached only weakly. The crystal structure of an As(III)-dte crystal of 1:1 composition, grown from ethanolic solution, shows that As(III) binds the ligand through its three p-orbitals in a manner similar to that expected in aqueous solution. While the uptake of the second ligand cannot be detected by pH-metry, the decomposition of thioether bonds above pH approximately 10 is confirmed by the change in UV spectra at approximately 265 nm to be a base-consuming process. In such alkaline solutions, most probably, rearrangement of the bonding scheme occurs, resulting in ligands being bound to the arsenic(III) through the oxygen donor atoms.

Charge Transfer Complex Role in the Formation of Chlorobenzene in the γ‐Irradiated Carbon Tetrachloride‐Benzene System

AbstractThe formation of carbon tetrachloride‐benzene charge transfer complex was confirmed by UV and NMR spectrometric studies. A change in UV spectrum of benzene is observed upon addition of carbon tetrachloride. Whereas the appearance of new bands supports the formation of charge transfer complex. NMR study shows that, chemical shift of benzene pmr signal depends on the CCl4‐C6H6 molar ratio. This observation is another criterion for the formation of benzene‐carbon tetrachloride charge transfer complex. Job's Continuous Variation method indicates that a 2:1 CCl4‐C6H6 charge transfer complex (2:1 CTC) is formed. The association constants (K2:1) of (2:1 CTC) was found to be 0.0197 M−2. The maximum concentration of (2:1 CTC) was found to be in samples with 2:1 CCl4‐C6H6 molar ratio (33% benzene mole). On the other hand the maximum yield of chlorobenzene was obtained, also, upon radiolysis of CCl4‐C6H6 samples at a 2:1 molar ratio (33% benzene mole). Therefore, it could be concluded that (2:1 CTC) participates in the formation of chlorobenzene upon radiolysis of the benzene‐carbon tetrachloride system. This conclusion was supported by the dependence of the chlorobenzene yield of a γ‐irradiated carbon tetrachloride‐benzene system (2:1 molar ratio) on irradiation time according to a third order kinetic equation with a very good linearity (R2 = 0.9977). Accordingly, the rate constant for the chlorobenzene formation under this condition was found to be ≈ 5.5 × 10−7 L2.mol−2.h−1. We propose a radiation chemical mechanism in which the 2:1 CTC plays a role in the formation of chlorobenzene.

Toxicity reduction of metal pyrithiones by near ultraviolet irradiation

Zinc pyrithione (ZnPT) or copper pyrithione (CuPT) have been effectively used as ship-antifouling agents, as an alternative to organotin compounds. Because of their instability in light and a lack of suitable analytical procedures, there is little data on their residue levels in environmental matrices. It is possible to investigate the fate of such compounds by toxicity alteration with certain treatments. The purpose of this study was to evaluate the degradation of pyrithiones through toxicity reduction by near ultraviolet (UV-A) irradiation. Metal pyrithiones dissolved in acetonitrile were irradiated with a UV-A lamp for 0, 0.5, 1, and 2 h, and were subjected to UV spectral measurement and toxicity evaluation using both sea urchin and freshwater rotifer bioassays. For the bioassays, photolyzed samples were dissolved in dimethyl sulfoxide after evaporation of the acetonitrile. The changes in UV spectra of photolyzed ZnPT or CuPT showed a time-dependent degradation, and the UV spectra at 2 h irradiation suggested substantial decomposition. Toxicities of ZnPT and CuPT were 12 and 5 microg/L as 24 h LC50 to the survival of rotifers and 10(-6) ng/L and 2.3 ng/L as 27 h EC50 to normal pluteus formation, respectively. By evaporation of the acetonitrile, the EC50 of ZnPT was 2.2 ng/L, which was the same as that of CuPT. The EC50s of ZnPT or CuPT for both species increased with longer irradiation times. Photolyzed ZnPT or CuPT demonstrated substantial degradation in the UV spectra, but possessed marked toxicity, which is probably due to toxic degradation products. One reason why photolyzed CuPT was toxic to rotifers was explained by the high toxicity of copper ions formed by UV-A irradiation.

Detoxification of Corn Stover and Corn Starch Pyrolysis Liquors by Pseudomonas putida and Streptomyces setonii Suspended Cells and Plastic Compost Support Biofilms

Plant biomass can be liquefied into fermentable sugars (levoglucosan then to glucose) for the production of ethanol, lactic acid, enzymes, and more by a process called pyrolysis. During the process microbial inhibitors are also generated. Pseudomonas putida (ATCC 17484) and Streptomyces setonii75Vi2 (ATCC 39116) were employed to degrade microbial inhibitors in diluted corn stover (Dcs) and diluted corn starch (Dst) pyrolysis liquors. The detoxification process evaluation included measuring total phenols and changes in UV spectra, a GC-MS analysis, and a bioassay, which employed Lactobacillus casei subsp. rhamosus (ATCC 11443) growth as an indicator of detoxification. Suspended-cell cultures illustrated limited detoxification ability of Dcs and Dst. P. putida and S. setoniiplastic compost support (PCS) biofilm continuous-stirred-tank-reactor pure cultures detoxified 10 and 25% (v/v) Dcs and Dst, whereas PCS biofilm mixed culture also partially detoxified 50% (v/v) Dcs and Dst in repeated batch culture. Therefore, PCS biofilm mixed culture is the process of choice to detoxify diluted pyrolysis liquors.

Calculation of the visible-UV absorption spectra of hydrogen sulfide, bisulfide, polysulfides, and As and Sb sulfides, in aqueous solution.

Recently we showed that visible-UV spectra in aqueous solution can be accurately calculated for arsenic (III) bisulfides, such as As(SH)3, As(SH)2S- and their oligomers. The calculated lowest energy transitions for these species were diagnostic of their protonation and oligomerization state. We here extend these studies to As and Sb oxidation state III and v sulfides and to polysulfides Sn2-, n = 2–6, the bisulfide anion, SH-, hydrogen sulfide, H2S and the sulfanes, SnH2, n = 2–5. Many of these calculations are more difficult than those performed for the As(iii) bisulfides, since the As and Sb(v) species are more acidic and therefore exist as highly charged anions in neutral and basic solutions. In general, small and/or highly charged anions are more difficult to describe computationally than larger, monovalent anions or neutral molecules. We have used both Hartree-Fock based (CI Singles and Time-Dependent HF) and density functional based (TD B3LYP) techniques for the calculations of absorption energy and intensity and have used both explicit water molecules and a polarizable continuum to describe the effects of hydration. We correctly reproduce the general trends observed experimentally, with absorption energies increasing from polysulfides to As, Sb sulfides to SH- to H2S. As and Sb(v) species, both monomers and dimers, also absorb at characteristically higher energies than do the analogous As and Sb(III)species. There is also a small reduction in absorption energy from monomeric to dimeric species, for both As and Sb III and v. The polysufides, on the other hand, show no simple systematic changes in UV spectra with chain length, n, or with protonation state. Our results indicate that for the As and Sb sulfides, the oxidation state, degree of protonation and degree of oligomerization can all be determined from the visible-UV absorption spectrum. We have also calculated the aqueous phase energetics for the reaction of S8 with SH- to produce the polysulfides, SnH-, n = 2–6. Our results are in excellent agreement with available experimental data, and support the existence of a S6 species.

Calculation of the visible-UV absorption spectra of hydrogen sulfide, bisulfide, polysulfides, and As and Sb sulfides, in aqueous solution

Recently we showed that visible-UV spectra in aqueous solution can be accurately calculated for arsenic (III) bisulfides, such as As(SH)3, As(SH)2S- and their oligomers. The calculated lowest energy transitions for these species were diagnostic of their protonation and oligomerization state. We here extend these studies to As and Sb oxidation state III and v sulfides and to polysulfides S n 2-, n = 2–6, the bisulfide anion, SH-, hydrogen sulfide, H2S and the sulfanes, S n H2, n = 2–5. Many of these calculations are more difficult than those performed for the As(iii) bisulfides, since the As and Sb(v) species are more acidic and therefore exist as highly charged anions in neutral and basic solutions. In general, small and/or highly charged anions are more difficult to describe computationally than larger, monovalent anions or neutral molecules. We have used both Hartree-Fock based (CI Singles and Time-Dependent HF) and density functional based (TD B3LYP) techniques for the calculations of absorption energy and intensity and have used both explicit water molecules and a polarizable continuum to describe the effects of hydration. We correctly reproduce the general trends observed experimentally, with absorption energies increasing from polysulfides to As, Sb sulfides to SH- to H2S. As and Sb(v) species, both monomers and dimers, also absorb at characteristically higher energies than do the analogous As and Sb(III)species. There is also a small reduction in absorption energy from monomeric to dimeric species, for both As and Sb III and v. The polysufides, on the other hand, show no simple systematic changes in UV spectra with chain length, n, or with protonation state. Our results indicate that for the As and Sb sulfides, the oxidation state, degree of protonation and degree of oligomerization can all be determined from the visible-UV absorption spectrum. We have also calculated the aqueous phase energetics for the reaction of S8 with SH- to produce the polysulfides, S n H-, n = 2–6. Our results are in excellent agreement with available experimental data, and support the existence of a S6 species.

First derivative UV spectra of surface water as a monitor of chlorination in drinking water treatment.

Many countries require the presence of free chlorine at about 0.1 mg/l in their drinking water supplies. For various reasons, such as cast-iron pipes or long residence times in the distribution system, free chlorine may decrease below detection limits. In such cases it is important to know whether or not the water was chlorinated or if nonchlorinated water entered the system by accident. Changes in UV spectra of natural organic matter in lakewater were used to assess qualitatively the degree of chlorination in the treatment to produce drinking water. The changes were more obvious in the first derivative spectra. In lakewater, the derivative spectra have a maximum at about 280 nm. This maximum shifts to longer wavelengths by up to 10 nm, decreases, and eventually disappears with an increasing dose of chlorine. The water treatment system was monitored by this technique for over 1 year and changes in the UV spectra of water samples were compared with experimental samples treated with known amounts of chlorine. The changes of the UV spectra with the concentration of added chlorine are presented. On several occasions, water, which received very little or no chlorination, may have entered the drinking water system. The results show that first derivative spectra are potentially a tool to determine, in the absence of residual chlorine, whether or not surface water was chlorinated during the treatment to produce potable water.

Improvement of Antitermitic Activities of Catechin by Combination with Heavy Metals

SummaryAntitermitic activities of catechin-metal complexes were investigated for further utilization of catechin as a termite control agent. Catechin (CA), heavy metal salts (NiCl2, CuCl2, ZnCl2) and CA/metal mixtures with Ni(II), Cu(II) and Zn(II) were subjected to bioassays using a subterranean termite,Coptotermes formosanusShiraki. The astringent properties of each system were assessed by measuring the weight of precipitate with bovine serum albumin (BSA). Changes in UV spectra of the CA/metal mixtures were also measured. CA caused less than 30% mortality after the 21-day test period, and had no BSA-precipitating capacity. The effects of heavy metals on CA activities varied with metal. CA/Ni(II) showed the highest termiticidal activity among tested materials, but exhibited no BSA-precipitating capacity and little change in UV spectrum. On the other hand, both CA/Cu(II) and CA/Zn(II) increased the BSA-precipitating capacity and UV absorption with time after preparing the CA/metal solutions, but their termiticidal activity was almost equal to CA. Termiticidal activity of CA was improved by the addition of Ni(II) but hardly changed by Cu(II) or Zn(II), while astringent properties of CA were hardly changed by addition of Ni(II) but improved by Cu(II) or Zn(II). Termiticidal activity was negatively correlated with astringent property.

Synthesis of photo-functional polymers with both pendant phenacyl ester and spiro ortho ester groups and photochemical properties of the resulting polymers

Photo-functional polymers with both pendant phenacyl ester and spiro ortho ester groups were synthesized by the one-pot method for the reaction of poly(methacrylic acid) with 2-bromomethyl-1,4,6-trioxaspiro-[4.4]-nonan followed by the reaction with phenacyl bromides using 1,8-diazabicyclo-[5.4.0]-7-undecene. These condensation reactions proceeded smoothly and quantitatively. Photochemical properties of the obtained polymers were evaluated by UV and IR spectroscopy. The photo-cleavage of pendant phenacyl ester groups was monitored by the change of UV spectra, and the ring-opening reaction of pendant spiro ortho ester groups was monitored by IR spectrscopy. From these results, it was found that the photo-cleavage of pendant phenacyl ester groups proceeded smoothly to give the corresponding carboxylic acid groups and radicals, and then the produced pendant carboxylic acid groups reacted with pendant spiro ortho ester groups by the baking process.

The ultraviolet studies on protein-lipid interaction of a protein kinase C-gamma phorbol-binding domain.

Family of protein kinase C (PKC) isozymes play a key role in transducing a vast number of signals into the cells. The members of classical PKC family are activated by binding of various lipid ligands to one of the several cysteine-rich domains of the enzyme. Second cysteine-rich (Cys2) domain of PKC-gamma was expressed in Escherichia coli as a fusion protein with glutathione-S-transferase (GST) using the cDNA sequence from rat brain. The Cys2 protein after cleavage from GST was purified to homogeneity using glutathione-agarose and Mono-S cation exchanger column. In order to investigate the interaction of lipids and calcium with Cys2 protein we used UW spectroscopy. The UV spectrum of Cys2 protein exhibited a maximum at 205 nm. Exposition of Cys2 protein to phosphatidylserine (PS) vesicles resulted in significant decrease in the absorbance in the 210 nm region. Changes in UW spectrum of Cys2 protein induced by phorbol 12,13-dibutyrate (PDB) were smaller than those induced by PS, and addition of PDB with PS had no effect on the PS induced changes in UV spectrum of Cys2. Neither phosphatidylcholine (PC) nor phosphatidylethanolamine (PE) affected UV spectrum of Cys2 but in the presence of phosphatidylinositol 4,5 bisphosphate (PIP2) or phosphatidyliinositol 4-phosphate (PIP) vesicles some changes were observed. Calcium ions alone or in the presence of PS had no effect on the UV spectrum of Cys2 protein. These data indicate that PS comparing to PDB, interacts with a larger area of Cys2 protein, and that the binding sites for these two molecules are at least overlapping. The site of PIP and PIP2 interaction with PKC-gamma is distinct from that of phorbol ester binding site.

Electrochemical and optical properties of poly[(disilanylene)oligophenylenes], peculiar behavior in the solid state

Electrochemical properties of poly[(disilanylene)oligophenylenes], [(SiR 1R 2SiR 1R 2)(C 6H 4) m ] n (R 1=R 2=Me, R 1=R 2=Et, and R 1=Ph, R 2=Me; m=1–4) were investigated. The cyclic voltammograms (CVs) of the polymer films on indium–tin oxide (ITO) display irreversible oxidation peaks. Disilanylene–phenylene polymers ( m=1) were oxidized in one step, while polymers with longer oligophenylene groups ( m=2–4) underwent multi-step oxidation and the oxidation peaks shifted to lower potentials with the increase of the number of phenylene groups ( m) between disilanylene units. Poly[(dimethyldiphenyldisilanylene)phenylene] (R 1=Ph, R 2=Me; m=1) exhibited changes in UV spectrum and CV profile, presumably due to the conformation changes in the polymer chain, on annealing the film at 210°C. We also measured CVs of poly[(dimethylsilylene)biphenylene] and poly[(tetraethyldisiloxanylene)biphenylene] for comparison and found that the Si–Si orbital plays an important role in the first oxidation step of disilanylene–oligophenylene polymer films.