Takaki Yamamura

Correlation between the concentrations of polynuclear aromatic hydrocarbons and those of particulates in an urban atmosphere.

The new technique for preparation of gases of a known concentration presented here makes it possible to prepare gases for environmental measurements and studies. The apparatus and operations of this technique are simple. The stability of the concentration of gas generated from the generator is excellent and the generation sustains for several hours a t least. The concentration varies to a smaller extent with changes in temperature and air flow rate than with the permeation tube technique. The prepared gas contains some water vapor which is preferred for experiments meant to simulate the real atmosphere. In this paper, SOz, NO, NOz, HCN, HzS, and NH3 gas generation was described, but other gases such as hydrogen fluoride and carbon dioxide can also be prepared by the same technique.

Copper complexes at N- and C-site of ovotransferrin: Quantitative determination and visible absorption spectrum of each complex

Copper complexes at the two sites of ovotransferrin (TF) differed markedly in the rate of Cu release by EDTA. During the reaction, lambda max of the remaining Cu-Tf complex shifted to red side, while the difference spectrum of FenCu2-nTf vs. FenTf in which the N-site had been preferentially occupied with Fe had lambda max at blue side from that of Cu2Tf, 440 nm. From these results, the intrinsic spectrum for Cu-complex at each site was assigned: lambda max 450 nm for N- and 430 nm for C-site. The differences in the release rate and the spectrum can be used for the identification of the two domains of Tf and for the analysis of metal-binding behavior of each site.

In situ emission levels of polynuclear aromatic hydrocarbons from gasoline and diesel engine vehicles on an expressway

Abstract Aerosol samples were collected in the Tsuburano Tunnel on Tomei Expressway during a week to evaluate the in‐situ emission levels of polynuclear aromatic hydrocarbons (PAHs) in the exhaust gas from a diesel engine car and a gasoline engine car. The atmospheric levels of PAHs indicated a significant variation with the traffic density of the passing vehicles in the tunnel. Particularly, the correlation coefficients between the traffic density and the PAHs levels were statistically higher for the gasoline car traffic than that for the diesel car traffic with confidence levels of 99 %. On the other hand, the contribution of PAH per vehicle to the tunnel atmosphere decreased with the increase of the ratio of the fraction of diesel car traffic relative to the total traffic. On the basis of these results, an experimental equation was derived with respect to a mass balance of PAH in the tunnel. As a result, it was estimated that on a mass basis, the average emission rates (μg/hr) of pyrene, chrysene, benz...

Binding of Cu (II), Tb (III) and Fe (III) to chicken ovotransferrin

The kinetics of binding of Cu (II), Tb (III) and Fe(III) to ovotransferrin have been investigated using the stopped-flow technique. Rate constants for the second-order reaction, k+, were determined by monitoring the absorbance change upon formation of the metal-transferrin complex in time range of milliseconds to seconds. The N and C sites appeared to bind a particular metal ion with the same rate; thus, average formation rate constants k+ (average) were 2.4 × 104 M−1 s−1 and 8.3 × 104 M−1 S −1 for Cu (II) and Tb (III) respectively. Site preference (N site for Cu (II) and C site for Tb (III)) is then mainly due to the difference in dissociation rate constant for the metals. Fe (III) binding from Fe-nitrilotriacetate complex to apo-ovotransferrin was found to be more rapid, giving an average formation rate constant k+ (average) of 5 × 105 M−1 s−1, which was followed by a slow increase in absorbance at 465 nm. This slow process has an apparent rate constant in the range 3 s−1 to 0.5 s−1, depending upon the degree of Fe (III) saturation. The variation in the rate of the second phase is thought to reflect the difference in the rate of a conformational change for monoferric and diferric ovotransferrins. Monoferric ovotransferrin changes its conformation more rapidly (3.4s−1) than diferric ovotransferrin (0.52 s−1). A further absorbance decrease was observed over a period of several minutes; this could be assigned to release of NTA from the complex, as suggested by Honda et al. (1980).

Kinetic study of the oxygenation process of hemerythrins from Lingula unguis and Siphonosoma cumanense

The kinetics of oxygen binding to hemerythrins from Lingula unguis and Siphonosoma cumanense were investigated by stopped-flow and temperature-jump methods. Results on the cooperative and non-cooperative forms of hemerythrin from L. unguis demonstrate that the two forms have large differences in behavior. At pH 6.8, when n = 1.11, kinetics characteristic of non-cooperative ligand binding are observed. The kon value was estimated as (6.3 ± 0.9) · 105 M−1 · s−1, which is much smaller than that observed for hemerythrin from a different species, S. cumanense (kon = (1.13 ± 0.08) · 107 M−1 · s−1), which is also non-cooperative. At pH 7.6 where n = 1.82, kinetics characteristic of non-cooperative ligand binding are not observed. Furthermore, rates of oxygen binding faster than those observed for pH 6.8 were found. Thus the change of oxygen affinity at pH 7.6 with increasing oxygen saturation observed in equilibrium binding studies is reflected in different kinetic behavior. The temperature-jump data were further analyzed according to a limiting case of the Monod-Wyman-Changeux model. Predictions from this analysis were qualitatively consistent with a factor of 2 difference in P12 between hemerythrin at pH 6.8 and at pH 7.6. Consequently, it can be postulated that the low-affinity form is similar to the structure held at pH 6.8, and the high-affinity form may be similar to the structure held at pH 7.6 koff values estimated from the data analysis of temperature-jump studies and those from the stopped-flow study of the reduction of hemerythrin with dithionite were different, which could be an indication that the reduction of hemerythrin with dithionite may include another rate-limiting step, such as a conformational change, apart from the O2-releasing step.

Kinetic study on oxygenation of Lingula unguis hemerythrin using the stopped-flow 02-jump method

AbstractO2-jump experiments with an improved stopped-flow apparatus have been used to study oxygenation and deoxygenation processes in Lingula unguis hemerythrin. With an O2 electrode set in the observation cell, O2 concentration conld be obtained directly. The reliability of this method has been compared with other conventional methods.O2-jump (up and down) experiments were carried out with L. unguis hemerythrin at pH 6.8 (non-cooperative pH) and at pH 7.6 (cooperative pH). At pH 6.8, both O2-jump (up) and O2-jump (down) experiments showed single exponential processes which were consistent with the following scheme:

In situ emission levels of carcinogenic and mutagenic compounds from diesel and gasoline engine vehicles on an expressway

{\text{Hr + O}}_{\text{2}} \mathop \rightleftharpoons \limits_{{\text{k}}_{{\text{off}}} }^{{\text{k}}_{{\text{on}}} } {\text{HrO}}_{\text{2}}

Binding of Cu(II), Tb(III) and Fe(III) to chicken ovotransferrin. A kinetic study.

. The value of kon was estimated to be (4.4 ± 0.5) × 105 M−1 s −1, and koff was (15 ± 5) s−1. These values are consistent with those obtained by the temperature-jump method (Zimmer et al. 1986). At pH 7.6, O2-jump (up) experiments showed two relaxation processes, whereas O2-jump (down) experiments showed a single exponential process. The faster process in the O2-jump (up) experiments could be attributed to the same process as that seen in the temperature-jump experiments (Zimmer et al. 1986). The slower process in the O2-jump (up) experiments corresponds to the process obtained in the O2-jump (down) experiments. The results are discussed in terms of a state with intermediate affinity in O2-binding and with the possible existence of a slow step in O2-binding.