Identification of dimehtyl tellurenyl sulfide and methanetellurol in the headspace gases above tellurium-amended bacterial cultures using gas chromatography with fluorine-induced chemiluminescence detection and mass spectrometric detection
~ Jerry W. Swearingen Jr. 1 , Manuel A. Araya 2 , Mary F. Plishker 1 , Claudia P. Saavedra 2 , Claudio C. Vasquez 2 and Thomas G. Chasteen 1 . (1) Sam Houston State University , Huntsville , TX , (2) Universidad de Santiago de Chile
Escherichia coli JM109 cells were modified to express genes from a DNA fragment from Geobacillus stearothermophilus V that is believed to encode proteins for methyltransferase activity and tellurium resistance. Later experimentation shows the modified E. coli cells also have selenium resistance. The modified bacterium was inoculated methanetellurol (CH 3 TeH), dimethyl telluride (CH 3 TeCH 3 ), dimethyl ditelluride (CH 3 TeTeCH 3 ), and dimethyl tellurenyl sulfide (CH 3 TeSCH 3 ) were detected in the headspace using gas chromatography- sulfur chemiluminescence detection or mass spectrometric detection. CH 3 TeH and CH 3 TeSCH 3 have never been previously detected in the headspace gases above tellurium-amended bacterial cultures. No standards were available for CH 3 TeH and CH 3 TeSCH 3 , therefore a method was developed in order to synthesize these organo-tellurium compounds for retention time correlation, boiling point determination, and structural studies using GC-MS. Diluted sulfuric or hydrochloric acid was added to zinc along with small amounts of CH 3 TeTeCH 3 and dimethyl diselenide (CH 3 SeSeCH 3 ). The headspace gases of this reaction yielded both CH 3 TeH and CH 3 TeSCH 3 along with traces of the reactants CH 3 SeSeCH 3 and CH 3 TeTeCH 3 . DL- dithiothreitol was also tested as a reducing agent. Manual headspace extraction and solid phase microextraction (SPME) was separately used in the detection of headspace gases. The question about whether the mixed species tellurium compound (CH 3 TeSCH 3 ) is a product of bacterial metabolism or a product of either an exchange or disproportionation reaction between different tellurium and sulfur organic species will be covered. The synthesis of dimethyl tellurenyl selenide (CH 3 TeSeCH 3 ) will also be discussed along with a description of future experiments involving the detection of this compound in the headspace gases above bacterial cultures amended with both toxic selenium and tellurium salts.
Inhibition of Mushroom Tyrosinase by Phthalic Acid
~ Shauna R. Anderson and Mary F. Plishker
The enzyme tyrosinase, which catalyzes the production of melanin pigments from tyrosine, is involved in the browning of fruit and hyperpigmentation in skin. The activity of mushroom tyrosinase can be assayed using L-DOPA as the substrate. In this study, tyrosinase activity has been found to be affected by low levels of phthalic acid. The presence of 5.0 mM phthalic acid reduces the activity of tyrosinase to approximately 10% of the control sample. In the presence of phthalic acid and dimethylsulfoniopropionic acid, DMSP, the enzyme displays a slightly different pattern of inhibition. Kinetic analyses of these inhibitors will be presented.
The Effect of Ibuprofen and Caffeine on the Activity of Mushroom Tyrosinase
~ Sara E. Spikes and Mary F. Plishker
The activity of the enzyme tyrosinase from mushrooms can be assayed using L-DOPA as the substrate. This activity is inhibited by the common analgesic ibuprofen. In the presence of the sodium salt of ibuprofen at a concentration of 60mM, the tyrosinase activity is reduced by approximately 30% when compared to control samples. At 150mM of ibuprofen, enzyme activity is reduced by 80%, but at higher concentrations activity increases. In the presence of caffeine at a concentration of 50mM, the tyrosinase activity is increased by 37%. Kinetic analyses of these activities suggest that ibuprofen is acting as a mixed inhibitor, while caffeine appears to be an activator for the enzyme.
Extracellular Enzymes of White Rot Fungi
~ Hudson P. Pace , Kenneth Wunch, Jerry L. Cook and Mary F. Plishker
White rot fungi, including Marasmiellus troyanus and Phanerochaete chrysosporium , have been shown to release several extracellular enzymes under conditions of nitrogen and/or carbon deprivation. Included in the extracellular enzymes are those involved in the oxidation and depolymerization of lignin. Incubation of growing colonies of these two fungi in water results in the appearance of dye decolorization activity in the water using Poly R-478 dye. Filtered extracts of these aqueous cultures of M. troyanus and P. chrysosporium have been examined for protein content and enzymatic activity. SDS-PAGE banding patterns indicate the presence of several bands corresponding to molecular masses in the range of 50,000 to 90,000 daltons. Comparisons of the banding patterns of the two fungi will be presented.
Photochemistry of 1,4-Dimethyl-1,4-dihydro-1,4-epoxynaphthalene
~ Gydeon A. Gilzow , Benny E. Arney and Rick C. White
Irradiation of 1,4-Dimethyl-1,4-dihydro-1,4-epoxynaphthalene is acetonitrile leads to formation of the delocalized 1,3- diradical corresponding to cleavage of a benzylic C-O bond. Two pathways from the diradical are a phenyl migration leading to series of mono- and dimethylindenes and an “oxygen walk” leading to the tentatively identified 1,4-Dimethyl-1,4-dihydro-1,4-epoxynaphthalene. A full picture of this rich system and supporting results will be presented.
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