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Superoxide radical anion has been demonstrated to be a mediator of many disease states, including inflammatory, autoimmune, and cancerous diseases. As a consequence, we have developed a program to design, synthesize, and test synthetic low-molecular weight superoxide dismutase (SOD) mimics as potential pharmaceutical agents. A critical feature of the design of metal-based drugs is not only high activity as an enzyme mimic but also chemical stability. In this report we describe the synthesis and characterization of a series of C-substituted 1,4,7,10,13-pentaazacyclopentadecane, [15]aneN5, ligands, 1, and their corresponding Mn(II) complexes, 2 and 3, as their dichloro complexes, [Mn([15]aneN5)Cl2]. The purpose of the work is to probe the role that substituent (methyl and fused cycloalkyl) groups exert on the catalytic activity and stability of the complexes. All of the 18 new complexes described here are catalysts for the dismutation of superoxide, and substantial substituent effects are observed with kcat...

The rate of neutralization of sulfuric acid aerosol by ammonia gas has been measured in a laboratory flow reactor for particle diameters between 0.3 and 1.4 micrometers and for relative humidities between 8 and 80%. The rates were between 21 and 70% of the rates expected if diffusion of NH/sub 3/ to the aerosol droplets was the rate-determining factor, and the reaction coefficient, which is the fraction of gas-particle collisions resulting in a chemical reaction, increased with increasing particle size. A simple model of H/sub 2/SO/sub 4/ aerosol generation and neutralization in the atmosphere showed that sulfate aerosol more acidic than NH/sub 4/HSO/sub 4/ should only be present during periods of rapid oxidation of the precursor SO/sub 2/ and high ratios of (SO/sub 2/) to (NH/sub 3/) or when the equilibrium vapor pressure of NH/sub 3/ over the partially neutralized H/sub 2/SO/sub 4/ droplet exceeds the ambient NH/sub 3/ partial pressure.

A sulfur-specific flame photometer has been used for the real time measurement of sulfur-containing aerosols. Specificity for the aerosols was achieved with a diffusion tube stripper which removed sulfur-containing gases from the air stream by diffusion to an adsorbing wall but transmitted particles to the flame photometer. The sensitivity of the flame photometer to (NH4)2SO4 and NH4HSO4 aerosols was identical, but a reduced response was found for H2SO4 aerosol. This occurred because of the high temperature (145°C) of the flame photometer burner block which caused the evaporation and loss of H2SO4 to the wall before reaching the flame. The addition of NH3 to the sample air just upstream of the burner converted H2SO4 to (NH4)2SO4 or NH4HSO4 and produced the expected increase in the flame photometer response. Heating the aerosol upstream of the diffusion stripper converted the sulfates to sulfur-containing gases over a temperature range characteristic of the aerosol being sampled. These gases were removed in the stripper, thereby decreasing the flame photometer output. The normalized response to aqueous H2SO4 aerosol decreased from unity at 50°C to 0.04 at 110°C and for (NH4)2SO4 and NH4HSO4 aerosols from unity at 115°C to zero at 190°C. When the aerosol contained both H2SO4 and (NH4)2SO4, the resultant thermogram was a function of both the (NH4)2SO4/H2SO4 ratio and the manner in which the two components were mixed in the particles comprising the aerosol (i.e. homogeneously with constant (NH4)2SO4/H2SO4 ratios or heterogeneously with varying ratios).

A personal monitoring method for SO/sub 2/ and NO/sub 2/ in the 1 to 10 ppM range, using triethanolamine (TEA) impregnated molecular sieve 13X as solid sorbent for sample collection was developed. Known concentration standards of SO/sub 2/ and NO/sub 2/ were generated by using liquid permeation tubes in a Kin-Tek three-channel gas calibration system. SO/sub 2/ and NO/sub 2/ were stripped from the sorbent with a standard eluant mixture (0.003 M NaHCO/sub 3//0.0024 M Na/sub 2/CO/sub 3/) and determined by ion chromatography as nitrite and/or nitrate and sulfate after oxidation of the sulfite with H/sub 2/O/sub 2/. Preparation and conditioning procedures for TEA-molecular sieve 13X, sample stability on the sorbent during storage, interferences of other species, effect of humidity on the recovery, and specific advantages of the proposed procedure over the existing methods are discussed.