John J. Thomas

Use of 4-(nitrobenzyl)pyridine (4-nbp) to test mutagenic potential of slow-reacting epoxides, their corresponding olefins, and other alkylating agents

Olefins and their corresponding epoxide derivatives are extensively used in industrial processes. Many epoxides are used as intermediates in organic synthesis as well as in surfactants, fumigants, industrial sterilants, cosmetics, and pharmaceuticals. These compounds pose potential hazards for biological systems where 1,2-epoxides are able to cause adverse biological effects through genetic interactions Although there are some reports that aliphatic epoxides are mutagenic agents, sufficient evidence of carcinogenicity is still lacking. However, most of bacterial mutagenicity tests have shown that aliphatic epoxides are mutagenic. Trials showing possible carcinogenicity for ethylene oxide, propylene oxide, styrene oxide, 1,2-epoxybutane have been described Studies on the mutagenicity of styrene oxide and styrene have been controversial. However, the mutagenicity of styrene oxide was found to be positive in bacteria (Sugiura and Goto 1981). Epoxy butane was shown to be mutagenic (Hardin et al 1983; Voogd et al 1981), but there exists some disagreement concerning its carcinogenicity and mutagenicity. Eugene et al (1963) first used a 4-NBP (4-(4-Nitrobenzyl)pyridine) to determine the presence of alkylating agents. Later Hammock et al (1974) and Agarwal et al (1979) studied chemical reactivity of epoxide derivatives, demonstrating that the aliphatic epoxides showed strong reactivity to 4-NBP. Nelis et al (1982) have used a standard in vitro procedure for comparing alkylating agents of bionucleophUes based on their reaction with 4-NBP. An understanding of the biochemistry of genotoxins has led to the preliminary development of a modified NBP test system (Archer and Eng 1981). However, this test system depended on the use of gaseous oxygen which made it difficult and time consuming to employ. A modified chemical activation system (CAS) employing hydrogen peroxide in place of oxygen and designed to mimic the mammalian mixed oxidase enzymes, was developed and tested in this laboratory (Mauro 1982). A mixture of hydrogen peroxide, ascorbic acid, ferrous ion, EDTA, and hydrazine in phosphate buffer was found to activate Send reprint requests to John J. Thomas at the above address.

Km values of influenza virus neuraminidases for a new fluorogenic substrate, 4-methylumbelliferone N-acetyl neuraminic acid ketoside

Abstract A fluorogenic substrate of neuraminidase, 4-methylumbelliferone N -acetylneuraminic acid ketoside (MUN), was synthesized. K m values were obtained for Clostridium perfringens neuraminidase and strains of A- and B-type influenza neuraminidase from chicken red blood cell influenza virus eluates.

Photoelectrochemical conversion of hydrogen sulfide to hydrogen using artificial light and solar radiation

Abstract The CdS catalysed photoelectrochemical conversion of hydrogen sulfide to hydrogen was studied using a halogen lamp and sunlight as the illumination source. The process was optimized with respect to ruthenium dioxide loading, CdS concentration, and sulfide and sulfite ion concentrations. Solution volumes of 30 and 500 ml were investigated. The highest production rate from the 30 ml vessel was 12.9 of H 2 ml in 4 h, employing 5.0 mg/ml −1 CdS (0.25% RuO 2 ) and using the halogen lamp. On scaling-up to a 500 ml vessel, the highest production rate was 113.0 ml of H 2 in 4 h using solar radiation and 2.0 mg/ml −1 CdS (0.25% RuO 2 ).

4-(4-nitrobenzyl)pyridine tests for alkylating agents following chemical oxidative activation

A chemical activation system (CAS) designed to mimic the mammalian mixed-function oxidase enzymes was found to activate target compounds to reactive electrophiles. Activated compounds were assayed by reaction with 4-(4-nitrobenzyl)pyridine (NBP). A model nucleophile of 7-alkylguanine of nucleic acids, NBP produces a violet color following alkylation. Twenty compounds from several chemical classes were tested. The test generally gave positive and negative responses where expected. Two compounds, trichloroethylene and diethylnitrosamine, exhibited a linear Beers law relationship in the concentration range tested. A high degree of linear correlation (r>0.97) was obtained for these compounds. Other compounds showed varying degrees of linear correlation from high correlation (r=0.94) to weak correlation (r=0.44). The CAS-NBP assay results were compared to bacterial mutagenicity and animal carcinogenicity test results when information was available. A good correlation (r=0.80) existed between direct alkylating activity and direct mutagenicity. Similar correlations existed between NBP alkylation following activation and mutagenicity following microsomal activation (r=0.73). Also, different correlations were observed between carcinogenicity and NBP alkylation following activation (r=0.69) and without activation (r=0.38).

Hydrolysis of Phthalyl Amino Acid Esters of Fluoroscein in the Presence of Leucine Aminopeptidase

Summary Phthalyl amino acid esters of fluorescein were synthesized and characterized. They were tested (in vitro) for use as possible fluorogenic substrates for LAP. The rates of enzymatic hydrolysis of these compounds were compared with those of some commercially available fluorescein esters.