• Bulletin of the Korean Chemical Society
• /
• v.26 no.12
• /
• pp.1981-1985
• /
• 2005

Kinetic studies have been performed for alkaline hydrolysis of a series of [(methoxy)(p-substituted styryl)carbene]pentacarbonyl chromium(0) complexes ($(CO)_5$Cr=$C(OCH_3)CH=CHC_6H_4X$, X = p-$OCH_3$, p-$CH_3$, H, p-Cl, p-$NO_2$). Second-order rate constants $(k_{{OH}^-})$ for the alkaline hydrolysis in 50% acetonitrile-water(v/v) were determined spectrophotometrically at various temperatures. At a low pH region (pH < 7.5), the observed rate constant $(k_{obs})$ remained constant with a small value, while in a high pH region (pH > 9.5), $k_{obs}$ increases linearly with increasing the pH of the medium. The second-order rate constants $(k_{{OH}^-})$ increase as the substituent X changes from a strong electron donating group to a strong electron withdrawing group. The Hammett plot obtained for the alkaline hydrolysis is consisted of two intersecting straight lines. The nonlinear Hammett plot might be interpreted as a change in the rate-determining step. However, the fact that the corresponding Yukawa-Tsuno plot is linear with $\rho$ and r values of 0.71 and 1.14, respectively indicates that the nonlinear Hammett plot is not due to a change in the rate-determing step but is due to ground-state stabilization through resonance interaction. The positive $\rho$ value suggests that nucleophilic attack by $OH^-$ to form a tetrahedral addition intermediate is the rate-determining step. The large negative ${\Delta}S^\neq$ value determined in the present system is consistent with the proposed mechanism.

• The Journal of Information Technology
• /
• v.10 no.2
• /
• pp.29-35
• /
• 2007

In this paper, we describe a study on the relationship between alkaline magenta emulsion manufacture and hardening test of films. The hardeners were prepared by condensation of equimolar amounts of trichlorotriazine with benzene-or naphthalene-based amino or oxy acids at 0 to $5^{\circ}C$ and at pH 7, and used as hardening agents for gelatin. The hardening test of alkaline magenta emulsion was studied at pH 8.5. For example I(R=ONa) had strong hardening properties, I substituted with an aminobenzosulfonate moiety (R=NHC6H4-p-SO3Me where Me = K, Na) was a much weaker gelatin hardener, and when substituted with amino- or oxynaphthalene derivative (II, III) did not harden gelatin at all. Compound with 2 dichlorotriazine groups as IV exhibited hardening properties. The hardener can be used in alkaline magenta emulsion layer of film and showed good hardening effect.

• Archives of Pharmacal Research
• /
• v.20 no.6
• /
• pp.643-646
• /
• 1997

Thermal stability of a red pigment, carthamin, frm Carthamus tinctorius was investigated to explore possible applications as natural color additives for foods, cosmetics, and nutraceuticals. Degree of degradation reactions of carthamin at acidic, neutral and alkaline conditions were determined with UV/V is spectral measurements. Decomposition half lives of carthamin at 25.deg. C were 4.0 h, 5.1 h, and 12.5 h at pH 5.0, pH 7.0, and pH 12.0, respectively, indicating that carthamin is much more stable at alkaline pH than acidic or neutral conditions. The activation energies of carthamin at pH 5.0, pH 7.0, and pH 12.0 were 15.6, 15.7 and 16.8 kcal/mol, respectively.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.32 no.3
• /
• pp.400-405
• /
• 2003

The surimi processing from jack mackerel and white croaker muscle using acidic and alkaline solubilization was evaluated. The optimum pH for solubilizing protein in acidic and alkaline range was around 2.5 and 10.5, respectively. The optimum pH value for recovery of protein was around 5. The protein solubility was decreased with increase of salt. The homogenized speed and time for maximum solubility were below 9,500 rpm and 30s, respectively The optimum ratio of water to minced muscle was 6 by evaluating breaking force, deformation and whiteness of cooked gel. The protein yield of alkaline processing is higher than that of conventional processing. In addition, the waste water of conventional processing had high solid, nitrogen content and chemical oxygen demand compare to those of acidic and alkaline processing.

• Applied Biological Chemistry
• /
• v.38 no.2
• /
• pp.106-110
• /
• 1995

An alkaline protease-producing bacterium was isolated from Korean hot pepper paste and identified as Alteromonas sp. CN301. A alkaline protease was purified and characterized. The optimal pH and temperature for the enzyme activity were pH 12.0 and $35^{\circ}C$, respectively. Molecular weight of the enzyme was determined as 31,000 dalton by the SDS-PAGE. The enzyme was stable in the range of $pH\;6.0{\sim}13.0$ showing the residual activity above 80% of the enzyme activity. The residual activity of the enzyme was 64% when the enzyme was incubated at $50^{\circ}C$ for 1 hr. The activity of the enzyme was not affected by most metal ions tested except $Hg^{2+}$, and activated by Triton X-100, Tween 20 and Tween 80. The enzyme activity was severely inhibited by PMSF and EDTA, suggesting that the enzyme is serine protease having metal ion in its structure.

• Corrosion Science and Technology
• /
• v.8 no.3
• /
• pp.126-131
• /
• 2009

The interaction between wear and corrosion can significantly increase total material losses in water chemistry environment. The corrosive wear tests of a PWR steam generator tube material (Alloy 690) against the anti vibration bar material (409 SS) were performed at room temperature. The tests were performed in alkaline water chemistry conditions. NaOH solution was selected for test condition to investigate the corrosive wear effect of steam generator tube material in alkaline pH condition without other factors. The flow induced vibration can caused tube damage and the corrosion can be occurred by water chemistry. The test results showed that, in the alkaline solution at pH 13.9, the corrosion current density was increased about ten times than that in the distilled water. And wear rate at pH 13.9 was increased about ten times from that at neutral condition. However, the wear rate was decreased with time. The decrease would be attributed to the change in roughness of specimen or sub-layer of the worn surface with time. From microstructure observation, severe abrasive shape and several wear debris were found. From those results, it could infer that the oxide film on Alloy 690 changed to easily breakable one in the alkaline water, and then abrasion with corrosion became the main wear mechanism.

• Microbiology and Biotechnology Letters
• /
• v.44 no.3
• /
• pp.333-340
• /
• 2016

An alkaline protease was purified and characterized from an alkalophilic microorganism, Bacillus sp. DK1122, isolated from soil in central Korea. The optimum temperature and pH for the growth of the producer strain were 40℃ and pH 9.0, respectively. The protease was produced aerobically at 40℃ after 24 h incubation in modified Horikoshi I medium (pH 9.0) containing 0.5% (w/v) glucose, 0.8% (w/v) yeast extract, 0.5% (w/v) polypeptone, 0.1% (w/v) K₂HPO₄, 0.02% (w/v) MgSO₄·7H₂O, 1% (w/v) Na₂CO₃, and 3% (w/v) NaCl. The alkaline protease was purified by 70% ammonium sulfate precipitation of the culture supernatant of Bacillus sp. DK1122, followed by CM-Sepharose chromatography. The molecular weight of the enzyme was estimated to be 27 kDa on the basis of SDS-PAGE. The optimum temperature and pH for the protease activity were 60℃ and pH 9.0, respectively. Addition of CaCl₂ increased the thermal stability of the purified protease, where 90% of protease activity was retained at 60℃ for up to 3 h. Consequently, it is expected that the alkaline protease from this study, exhibiting stability at pH 7–9 and 60℃, may be promising for application in the food and detergent industries.

• Journal of Microbiology and Biotechnology
• /
• v.19 no.10
• /
• pp.1122-1126
• /
• 2009

The exogenously added cadaverine is effective in protecting Vibrio vulnificus from methyl viologen (MV)-induced superoxide stress at pH 8.5. Such a protective effect by cadaverine was not observed at pH 7.5. Consistently, the accumulated level of intracellular cadaverine at pH 8.5 is approximately four times as much as that of the control cell at pH 7.5. Cadaverine accumulation is not affected by MV. The protection of V. vulnificus by cadaverine from superoxide stress was abolished when cadB coding for the lysine-cadaverine antiporter was interrupted. However, the cadaverine-mediated protection was complemented with cadB DNA. Therefore, CadB of V. vulnificus not only acts as a lysine-cadaverine antiporter at acid pH to neutralize the external medium, but also mediates cadaverine uptake at alkaline pH to result in cell protection from superoxide stress.

• Nuclear Engineering and Technology
• /
• v.51 no.4
• /
• pp.1041-1046
• /
• 2019

In terms of long-term safety for radioactive waste disposal, the anionic iodide (I-129) with a long half-life ($1.6{\times}10^6yr$) is of a critical importance because this radionuclide migrates in geological media with limited interactions. Various studies have been performed to retard the iodide migration. Recently, some minerals that are likely generated from waste container corrosion, have been suggested to have a considerable chemical interaction with iodide. In this study, chalcocite and mackinawite were selected as candidate minerals for underground corrosion materials, and an iodide sorption experiment were carried out. The experiment was performed under anoxic and alkaline conditions and the pH effects on the iodide sorption were investigated in the range of pH 8 to 12. The results showed that both minerals demonstrated a noticeable sorption capacity on iodide, and the distribution coefficient ($K_d$) decreased as the pH increased in the experimental condition. In addition, when the alkalinity increased higher than a pH of 12, the sorption capacity of both minerals decreased dramatically, likely due to the competition of hydroxy ions with the iodide. This result confirmed that chalcocite was an especially good sorbing media for iodide under alkaline conditions with a pH value of less than 12.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.18 no.3
• /
• pp.348-355
• /
• 1989

This experiment was conducted to investigate the characteristics of alkaline protease from Aspergillus fumigatus which was isolated from soil as a superior strain for the production of the alkaline protease. The optimum temperature for enzyme activity was $50^{\circ}C$ and optimum pH was 9.0. The enzyme was stable at pH 8.0 to 10.0 and thermal inactivation was shown $30^{\circ}C$. The activity of the enzyme was increased by the addition of $Mn^{++},\;Cu^{++},\;Ba^{++},\;Mg^{++},\;$wheras it was inhibitied by $K^+,\;Fe^{+++},\;Ag^+,\;Pb^{++},\;Na^+,\;Ca^{++},\;Hg^+,\;Zn^{++}$. EDTA. 2, 4-DNP, ${\varepsilon}-amino$ caproic acid did not show inhibitory effect on the proteolytic activity of alkaline protease but P-chloromercuribenzoic acid inhibited the enzyme activity, indicating that reactive sulfhydryl group is required for the enzymatic activity. The reaction of this enzyme followed typical Michael-Menten Kinetics with the Km value of $8.33{\times}10^{-4}mole/{\ell}$ with the Vmax of $47.62{\mu}g/min$. This enzyme had stronger proteolytic activity than trypsin on substrate such as casin and hemoglibin.