The photochemical formation rates of hydroxyl radicals (OH radicals) in river water and seawater were determined by a simple, rapid and sensitive benzene probe method, in which phenol formed by the reaction between benzene and photochemically-generated OH radicals was analyzed by on-line preconcentration HPLC. The OH radical formation rates from well-known OH radical sources, such as nitrate, nitrite and hydrogen peroxide, were in good agreement with those reported previously. River water samples containing high concentrations of nitrate and nitrite were found to show high OH radical formation rates. Ten to 80% of the OH radical formation in river water and seawater was due to the photolysis of nitrate and nitrite, but OH radical formation from hydrogen peroxide was negligible. The OH radical formation from unknown sources other than nitrate, nitrite and hydrogen peroxide was strongly correlated to the amount of fluorescent matter.

Transesterification of soybean oil catalyzed by combusted oyster shell, which is waste material from shellfish farms, was examined. Powdered oyster shell combusted at a temperature above 700 degrees C, at which point the calcium carbonate of oyster shell transformed to calcium oxide, acted as a catalyst in the transesterification of soybean oil. On the basis of factorial design, the reaction conditions of catalyst concentration and reaction time were optimized in terms of the fatty acid methyl ester concentration expressed as biodiesel purity. Under the optimized reaction conditions of a catalyst concentration and reaction time of 25wt.%. and 5h, respectively, the biodiesel yield, expressed relative to the amount of soybean oil poured into the reaction vial, was more than 70% with high biodiesel purity. These results indicate oyster shell waste combusted at high temperature can be reused in biodiesel production as a catalyst.

Upon the addition of small amounts of sodium dodecyl sulfate (SDS), the helicity of human serum albumin (HSA), lost in the urea denaturation, was mostly recovered. The profile of the recovery differed depending on the urea concentration. Then the urea concentrations were divided into three ranges: [1] a range below 3 M where the helicity only decreased as in the absence of urea (the helicity decreased down to 49% in the SDS solution); [2] a range between 4 and 8 M where the helicity initially increased up to 66% (this was the same as in the native state) and then sharply decreased; [3] a range above 9 M where the helicity only increased with an increase in added SDS concentration. When SDS was added prior to the urea denaturation, the same helicity was obtained at each surfactant concentration. Thus the SDS denaturation finally predominates over the urea denaturation. In the middle range, profiles of the structural change were rather complicated. The increase and decrease of helicity were accomplished below 3 mM SDS. It is worth noting that the helicity is recovered upon the addition of SDS less than 300 µM in the second range except for 8 M urea ([HSA] ) 10 µM). The helicity-recovery profile of HSA differs from that of a homologous protein, bovine serum albumin, the helicity of which recovers to some degree, but not completely. This difference might be attributed to the fact that the C-terminal helical-rod of HSA is amphiphilic, while that of bovine serum albumin is hydrophobic as a whole.

The measurement of photochemically generated nitric oxide radicals (NO) in natural waters has long been an arduous task because of a lack of simple analytical techniques, even though the environmental significance of this radical is paramount. We have developed a simple analytical method for the determination of photochemically generated NO in natural waters using 4,5-diaminofluorescein (DAF-2) as a probe compound. This method is based on the reaction of photoformed NO with DAF-2 in air-saturated solution to produce a highly fluorescent triazolofluorescein (DAF-2T) product. DAF-2T was determined by using reversed-phase HPLC with fluorescence detection, with excitation and emission wavelengths of 495 and 515 nm, respectively. Under optimum conditions, the calibration curve exhibited linearity in the range of 0.025-10 nM DAF-2T. The coefficients of variance for the measurements of the signal intensities of DAF-2T (from the photolysis of 0.5 microM and 5 microM NO(2)(-) with DAF-2) were less than 5% and 3%, respectively. For a total irradiation time of 30 min, the detection limit of the photoformation rate of NO was 1.65 x 10(-13) M s(-1), defined as 3sigma of the lowest measured DAF-2T concentration (0.025 nM). The proposed method is relatively unaffected by potential interferents in seawater. The method was employed to determine the photoformation rate of NO in the Seto Inland Sea and the Kurose River in Hiroshima Prefecture, Japan. The measured NO photoformation rates in seawater and river water samples ranged from (5.3-32) x 10(-12) M s(-1) and (9.4-300) x 10(-12) M s(-1), respectively.

The secondary structural change of horse heart myoglobin was examined in the thermal denaturation up to 130 degrees C. The original helicity of 82% gradually decreased to 67% with rise of temperature until 75 degrees C. Thereafter, it suddenly decreased to 24% at 90 degrees C and then slightly decreased to 14% at 130 degrees C. The helices of this protein were mostly destroyed between 75 and 100 degrees C. On the other hand, upon cooling to 25 degrees C from temperatures below 75 degrees C, the helicity completely recovered to the original value, but it did not after heating to temperatures above 80 degrees C. Thus, myoglobin maintains the reversibility of the structural change up to a temperature as high as 75 degrees C. This protein had another critical temperature around 90-100 degrees C in addition to 75 degrees C in the present thermal denaturation. Upon cooling to 25 degrees C after heating to temperatures above 80 degrees C, the extent of recovered helicity decreased with rise of temperature before cooling. The additive effect of sodium dodecyl sulfate (SDS) on the structural change of myoglobin differed below and above the critical temperature at 75 degrees C. In the temperature range below 75 degrees C where the structural change was reversible, the presence of SDS cooperated with the thermal denaturation to disrupt the structure. On the contrary, the presence of the surfactant more or less restrained the decrement of helicity at high temperatures above 85 degrees C. The helicity decreased and increased with an increase of SDS concentration upon cooling to 25 degrees C after heating to temperatures below 75 degrees C and after heating to temperatures above 85 degrees C, respectively. Then, upon cooling to 25 degrees C from any temperature, the helicity settled to a magnitude around 60% in the presence of the surfactant above 0.6 mM.

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