Gordon H. Purser

Non-enzymatic hydrolysis of creatine ethyl ester.

The rate of the non-enzymatic hydrolysis of creatine ethyl ester (CEE) was studied at 37 degrees C over the pH range of 1.6-7.0 using (1)H NMR. The ester can be present in solution in three forms: the unprotonated form (CEE), the monoprotonated form (HCEE(+)), and the diprotonated form (H(2)CEE(2+)). The values of pK(a1) and pK(a2) of H(2)CEE(2+) were found to be 2.30 and 5.25, respectively. The rate law is found to be Rate=-dCCEE/dt=k++[H2CEE2+][OH-]+k+[HCEE+][OH-]+k0[CEE][OH-] where the rate constants k(++), k(+), and k(0) are (3.9+/-0.2)x10(6)L mol(-1)s(-1), (3.3+/-0.5)x10(4)L mol(-1)s(-1), and (4.9+/-0.3)x10(4)L mol(-1)s(-1), respectively. Calculations performed at the density functional theory level support the hypothesis that the similarity in the values of k(+) and k(0) results from intramolecular hydrogen bonding that plays a crucial role. This study indicates that the half-life of CEE in blood is on the order of one minute, suggesting that CEE may hydrolyze too quickly to reach muscle cells in its ester form.

Altered UV absorbance and cytotoxicity of chlorinated sunscreen agents

Sunscreens are widely utilized due to the adverse effects of ultraviolet (UV) radiation on human health. The safety of their active ingredients as well as that of any modified versions generated during use is thus of concern. Chlorine is used as a chemical disinfectant in swimming pools. Its reactivity suggests sunscreen components might be chlorinated, altering their absorptive and/or cytotoxic properties. To test this hypothesis, the UV-filters oxybenzone, dioxybenzone, and sulisobenzone were reacted with chlorinating agents and their UV spectra analyzed. In all cases, a decrease in UV absorbance was observed. Given that chlorinated compounds can be cytotoxic, the effect of modified UV-filters on cell viability was examined. Chlorinated oxybenzone and dioxybenzone caused significantly more cell death than unchlorinated controls. In contrast, chlorination of sulisobenzone actually reduced cytotoxicity of the parent compound. Exposing a commercially available sunscreen product to chlorine also resulted in decreased UV absorbance, loss of UV protection, and enhanced cytotoxicity. These observations show chlorination of sunscreen active ingredients can dramatically decrease UV absorption and generate derivatives with altered biological properties.

Design and Development of a Portable Off-Grid Water Chlorination System

The design and fabrication of a portable water chlorination system is described. The backbone of the system is a custom-designed, efficient, and easily operated chlorine electrolysis cell. The cell produces concentrated hypochlorous acid (HOCl), a form of chlorine that readily kills harmful pathogens in untreated water. The cell is fabricated from durable yet inexpensive materials and requires only two inputs: (1) 12 volts of direct current, which can be supplied with standard car batteries that are commonplace worldwide, and (2) 800 milliliters of 0.43 molar sodium chloride solution, which can be substituted with seawater. The system was first tested in the laboratory under controlled conditions. The cell was powered for 70 minutes and samples of the solution were taken in 10-minute intervals. The hypochlorite ion (OCl− ) concentration was measured with a UV-visible light spectrophotometer. The results show that the cell produces enough hypochlorite in one hour to disinfect up to 1500 liters of clear surface water or 750 liters of turbid water. Successful laboratory test results led to field tests utilizing a solar photovoltaic power supply. Preliminary results of these tests are presented.Copyright