• Bulletin of the Korean Chemical Society
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• v.9 no.1
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• pp.40-44
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• 1988

The pH dependence studies of Raman spectra are reported for water-soluble free-base, Zn, Co and Cu tetrakis (4-sulfonatophenyl) porphine in pH 4, pH 7 and pH 13.9 aqueous solution. For free base porphine, the substantial differences are found in absorption and Raman spectra between pH 4 and pH 7 or pH 10 aqueous solutions due to the protonation at low pH. For Zn and Co porphyrins, the hydrolysis equilibrium constants are obtained by spectrophotometric titration experiments. The consistent shifts in Raman frequencies are found at high pH due to the hydrolysis. For Cu porphyrins, instead of hydrolysis the aggregation effect is detected at high pH through the absorption and Raman studies.

• Bulletin of the Korean Chemical Society
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• v.29 no.8
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• pp.1510-1518
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• 2008

Results of intrinsic and extrinsic fluorescence studies on choline oxidase revealed that the enzyme at high alkaline pH values has more accessible hydrophobic patches relative to acidic pH. Fluorescence quenching studies with acrylamide confirm these changes. The quenching constants were also determined at different pH(s) by using the Stern-Volmer equation. CD studies showed that at higher pH a transition from $\alpha$-helix to $\beta$- structure was appeared while at lower pH the content of $\alpha$-helix structure was increased. Furthermore, analysis of the spectral data using chemometric method gave evidence for existence of intermediate components at very high pH(s). Results of thermal denaturation evaluated that the enzyme has the most instability at higher pH(s). Altogether low and high pH values caused significant alteration on secondary and tertiary structures of choline oxidase via inducing of an intermediate.

• Journal of Korean Society of Water and Wastewater
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• v.27 no.6
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• pp.703-709
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• 2013

Among many microalgae cultivation types, heterotrophic culture with low cost carbon sources and energy saving culture method is crucial. A result of estimating the effects of pH on wastewater treatment using heterotrophic growing microalgae Chlorella sorokiniana shows that there was no difference in microalgae growth amount and nitrogen, phosphorus removal rate by wide range of pH(5 ~ 9). From pH 5 to 9, total nitrogen, phosphorous and glucose removal rates were 10.5 mg-N/L/d, 2 mg-P/L/d, 800 ~ 1000 mg/L respectively. This study reveals that C. sorokiniana cannot metabolite glycerol heterotrophically, however, glucose and acetate were proper carbon sources for growth and T-N, T-P and TOC removal. This research highlights the potential of heterotrophic microalgal growth with wastewater treatment plant with wide range of pH and carbon sources.

• Journal of Korean Society of Water and Wastewater
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• v.25 no.3
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• pp.343-348
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• 2011

Since 2005, food waste has been separately collected and recycled to animal feed or aerobic compost in South Korea. However, the conventional recycling methods discharge process wastewater, which contain pollutant equivalent to more than 50% of food waste. Therefore, anaerobic digestion is considered as an alternative recycling method of food waste to reduce pollutant and recover renewable energy. Recent studies showed that hydrogen can be produced at acidogenic stage in two-stage anaerobic digestion. In this study, the authors investigated the effects of pretreatment time and pH low set value on continuous mesophilic hydrogen fermentation of food waste. Food waste was successfully converted to $H_2$ when heat-treated at $70^{\circ}C$ for 60 min, which was milder than previous studies using pH 12 for 1 day or $90^{\circ}C$. Organic acid production dropped operational pH below 5.0 and caused a metabolic shift from $H_2/butyrate$ fermentation to lactate fermentation. Therefore, alkaline addition for operational pH at or over 5.0 was necessary. At pH 5.3, the result showed that the maximum hydrogen productivity and yield of 1.32 $m^3/m^3$.d and 0.71 mol/mol $carbohydrate_{added}$. Hydrogen production from food waste would be an effective technology for resource recovery as well as waste treatment.

• Journal of Microbiology and Biotechnology
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• v.32 no.4
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• pp.514-521
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• 2022

We report the effect of pH on the supramolecular complexation of two biothiols, viz., homocysteine (Hcy) and cysteine (Cys), with cucurbit[7]uril (CB[7]). Under basic pH conditions, Cys did not complex with CB[7], whereas Hcy efficiently complexed with CB[7], as confirmed by ¹H NMR spectroscopy and Ellman's reagent (5,5'-dithio-bis(2-nitrobenzoic acid), DTNB) assay. ¹H NMR and Raman spectroscopic studies revealed that, in the absence of CB[7], Hcy auto-oxidized slowly (~36 h) to homocystine (HSSH) under basic pH conditions. However, the rate of Hcy oxidation increased by up to 150 fold in the presence of CB[7], as suggested by the DTNB assay. Thus, supramolecular complexation under basic pH conditions led to the formation of a HSSH-CB[7] complex, and not Hcy-CB[7]. The results indicate that Hcy is rapidly oxidized to HSSH under the catalysis of CB[7], which acts as a reaction chamber, in basic pH conditions. Our studies suggest that Hcy concentration, a risk factor for cardiovascular disease, can be selectively and more easily quantified by supramolecular complexation with CB [7].

• Molecules and Cells
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• v.25 no.2
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• pp.158-162
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• 2008

Recent molecular genetics studies have revealed that cyclic electron transport around photosystem I is essential for normal photosynthesis and growth of plants. Chloroplastic NAD(P)H dehydorgenase (NDH) complex, a homologue of the complex I in respiratory electron transport, is involved in one of two cyclic pathways. Recent studies on the function and structure of the NDH complex are reviewed.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.11a
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• pp.105-106
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• 2017

Previous studies have confirmed the performance of pH reduction agents using liquid sodium phosphate based ammonium chloride as a pH reduction agent. In this study, the pH reduction performance considering economical and applicability as a practical stage and the property change analysis for the identification of the reaction mechanism of the pH reduction agent were carried out. As a result, the pH reduction performance at a low rate of the pH reducing agent was confirmed. The specific gravity of CaO decreased significantly after XRF analysis. It is also believed that this reduces the amount of Ca(OH)₂ produced and contributes to pH reduction.

• Journal of Pharmaceutical Investigation
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• v.4 no.1_2
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• pp.25-30
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• 1974

The adsorption of nalidixic acid on human erythrocytes was found to expressed by Freundlich's isotherm. The amount of adsorption of nalidixic acid on erythrocytes increased with an increase of pH. The adsorption of nalidixic acid on human plasma was found to expressed at Scatchard's equation by the equilibrium dialysis method. An influence of pH on adsorption of nalidixic acid to human plasma proteins was studies at pH 4-10. It was found that the degree of adsorption increase with the increase of pH from 4-6, but descreased above pH 9.

• Journal of Oral Medicine and Pain
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• v.8 no.1
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• pp.127-142
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• 1983

This thesis was to investigate sex defferencd by employing the methodes of Bernadskij's and it's modification by means of the evaluation of pH of dentin in 162 extracted teeth. The obtained were as follows: 1. In 72% of all experinments, pH of human dentin substance was higher in female than in male. Mean pH was 13.175±0.031 in male and 13.245±0.030 in female. 2. After comparative studies on each pH in anatomical region of tooth arrangement, the sex difference of pH was most obviously showed in molars. 3. In pH change according to ages, the 30's was the highest in male and the 20's in female, also pH showed decresing tendency by the increasing of age in both male and female. 4. There was no pH difference in anatomical regions of tooth arrangment. 5. Mean pH was 13.282±0.013 in under 50 years of age and 13.282±0.022 over 50. It proved that pH was higher in under 50 years of age than in over 50.

• BMB Reports
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• v.28 no.3
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• pp.204-209
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• 1995

The pH dependence of kinetic parameters in the amination direction of the aspartase from Hafnia alvei has been determined. The V/K for fumarate is bell shaped with pK values of 6.4 and 8.7. The maximum velocity for fumarate is also bell shaped with pK values of 7.2 and 9.1. The pH dependence of 1/K, for potassium (competitive inhibitor of ammonia) decreases at low pH with pK 7.6. Together with data [Yoon and Cook (1994) Korean J. Biochem. 27, 1-5] on the deamination direction of the aspartase, these results are consistent with two enzyme groups which are necessary for catalysis. An enzymatic group that must be deprotonated has been identified. Another enzyme group must be protonated for substrate binding. Both the general base and general acid group are in a protonation state opposite that in which they started when aspartate was bound. A proton is abstracted from C-3 of the monoanionic form of L-aspartate by an enzyme general base with, a pK of 6.3~6.6 in the absence and presence of $Mg^{2+}$ Ammonia is then expelled with the assistance of a general acid group giving $NH_{4+}$ as the product.