• Title, Summary, Keyword: pH

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Prediction of optimum pH of hydrolases

  • Sung, Nak-Gyu;Yoo, Young-Je
    • 한국생물공학회:학술대회논문집
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    • pp.571-574
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    • 2000
  • Hydrolase is a group of the most widely used enzymes in industrial biological processes. Generally, their activities are easily changed with pH. With this characteristics, research for the optimal pH of hydrolases is required to obtain the optimization of process conditions. We selected xylanase, lysozyme, glucoamylase and barnase as model enzymes. To predict optimum pH of hydrolases, the calculation program based on Tanford-Kirkwood(TK) model was used. Results show that charge difference of catalytic residues is an important parameter deciding optimum pH and when charge difference of catalytic residues is maximum, optimum pH of the hydrolase establishes.

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The Parallel Measurements of Stomatal Apertures and Apoplastic pH on Guard Cells from Epidermal Strips and Intact Leaves of Commelina communis

  • Lee, Joon-Sang
    • Korean Journal of Environmental Biology
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    • v.20 no.1
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    • pp.78-84
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    • 2002
  • The effects of light and darkness on stomatal aperture and guard cell apoplastic pH in the intact leaf and in the isolated epidermal strips of Commelina communis have been investigated. Stomata in the intact leaf opened wide in the light. In contrast, stomata in the isolated epidermal strips did not respond clearly to light. To eucidate the relationship between the stomatal aperture and the guard cell apoplastic pH, apoplastic pH was measured. In the light the guard cell wall of intact leaf was acidified by pH 1.9 units, falling from pH 7.3 to pH 5.4 in the first 10 minutes. On the contrary, apoplastic pH of isolated epidermal strips changed slowly from pH 7.3 to pH 6.9 at 20 min. Stomata in the intact leaf closed rapidly in the dark. On the other hand, stomata in the isolated epidermal strips failed to close in dark. There was a slow increase in apoplastic pH on transfer to the dark after incubation for 1.5 h in the light and the level observed before the experiment was regained after around 40 min. When the isolated epidermal strips were transferred to the dark, apoplastic pH maintained a uniform level of around pH 7.2-7.4. These results indicate that the mechanism of stomatal opening and closing from isolated epidermal strips and intact leaves could be different.

Roles of Putative Sodium-Hydrogen Antiporter (SHA) Genes in S. coelicolor A3(2) Culture with pH Variation

  • Kim, Yoon-Jung;Moon, Myung-Hee;Lee, Jae-Sun;Hong, Soon-Kwang;Chang, Yong-Keun
    • Journal of Microbiology and Biotechnology
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    • v.21 no.9
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    • pp.979-987
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    • 2011
  • Culture pH change has some important roles in signal transduction and secondary metabolism. We have already reported that acidic pH shock enhanced actinorhodin production in Streptomyces coelicolor. Among many potential governing factors on pH variation, the putative $Na^+/H^+$ antiporter (sha) genes in S. coelicolor have been investigated in this study to elucidate the association of the sha on pH variation and secondary metabolism. Through the transcriptional analysis and overexpression experiments on 8 sha genes, we observed that most of the sha expressions were promoted by pH shock, and in the opposite way the pH changes and actinorhodin production were enhanced by the overexpression of each sha. We also confirmed that sha8 especially has a main role in maintaining cell viability and pH homeostasis through $Na^+$ extrusion, in salt effect experiment under the alkaline medium condition by deleting sha8. Moreover, this gene was observed to have a function of pH recovery after pH variation such as the pH shock, being able to cause the sporulation. However, actinorhodin production was not induced by the only pH recovery. The sha8 gene could confer on the host cell the ability to recover pH to the neutral level after pH variation like a pH drop. Sporulation was closely associated with this pH recovery caused by the action of sha8, whereas actinorhodin production was not due to such pH variation patterns alone.

Effects of Acid Treatments on Chlorophyll, Carotenoid and Anthocyanin Contents in Arabidopsis (산성처리가 애기장대의 엽록소, 카로티노이드, 안토시아닌 등의 색소 함량에 미치는 영향)

  • Im, Kyung-Hoan
    • Research in Plant Disease
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    • v.16 no.1
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    • pp.81-85
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    • 2010
  • Arabidopsis seedlings subjected to low pH stress in the range of pH 5.6-4.0 did not show significant retardations in root and shoot growths. Treatment of pH 3.5-2.5 resulted in significant reductions in root and shoot length, especially in roots. Chlorophyll contents in seedlings increased during acid treatment of pH 5.6-4.0, but decreased by stronger acid treatment of pH 4.0 and lower pHs. Total carotenoid contents showed similar trend to chlorophyll contents by increasing during pH 5.6-3.5 treatments and decreasing by pH 3.0-2.5. Anthocyanin contents increased under acid stress of pH 5.6-3.0 and showed great reduction at pH 2.5. The ratios of carotenoids/chlorophylls and anthocyanins/chlorophylls increased by acid stress treatments. That indicates plants try to adjust physiologically to acid stress and protect chlorophylls by increasing carotenoid and anthocyanin contents. However, different responses of chlorophylls and anthocyanins to acid stress indicate both pigments play different roles in protecting plant from acid stress.

Effect of pH on the Green Tea Extraction (침출수의 pH가 녹차 침출액 성분에 미치는 영향)

  • Kim, Sang-Hee;Park, Jong-Dae;Lee, Lan-Sook;Han, Dae-Seok
    • Korean Journal of Food Science and Technology
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    • v.31 no.4
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    • pp.1024-1028
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    • 1999
  • Green tea infusions were prepared by extracting them with aqueous solution of different pHs and their physicochemical properties were analyzed. Yellowness, chroma and total color difference values were increased as pH increased. The content of total amino acids in the green tea infusion was not influenced by pH values. Total catechin contents of the green tea infusion extracted at pH 4.0, 5.0, 6.0 and 7.0 were 32.28, 31.84, 31.14 and 14.70 mg/g, respectively. Among the four catechins investigated, epigallocatechingallate and epigallocatechin are more unstable as the pH was changed from 6.0 to 7.0. As pH increased, the extraction of caffeine was also increased. In conclusion, extraction at low pH is preferred for the preparation of green tea infusion.

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The development of pH reading system based on vision system (영상 기반 pH 산도 측정 시스템 개발)

  • Moon, Ha-Jung;Lee, Dong-Hoon
    • Journal of IKEEE
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    • v.17 no.4
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    • pp.398-406
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    • 2013
  • Nuclear medicine imaging devices such as PET diagnose disease after injecting radiopharmaceuticals in human body for diagnosis. Radiopharmaceuticals should maintain the proper pH for human body safety. In general, pH paper is used to measure the pH of the radiopharmaceutical. pH of the sample compared with the standard color chart is used for measurement. However, the pH reading difference according to the experience of a rater can be generated. Also, a pH meter for measuring pH has a high sensitivity and contamination of the sensor must be avoided. In this paper, we developed the new hardware device for pH reading method and software was developed with vision algorithm to measure pH easily and simply.

Preparation of Positively and Negatively Charged Carbon Nanotube-Collagen Hydrogels with pH Sensitive Characteristic (양전하와 음전하를 띄며 pH 감응성인 카본나노튜브-콜라젠 Hydrogel의 합성)

  • Seo, Jae-Won;Shin, Ueon Sang
    • Journal of the Korean Chemical Society
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    • v.60 no.3
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    • pp.187-193
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    • 2016
  • In this study, preparation of positively and negatively charged carbon nanotube (CNT)-collagen (CG) hydrogels with pH sensitive characteristic was reported. The positive and negative characteristics of the prepared hydrogels were created by introduction of positively functionalized CNT-NH2 and negatively functionalized CNT-COOH, respectively, into the collagen hydrogel. The surface charge of CNTs (CNT-NH2 and CNT-COOH), CG and CNTs/CG hydrogels was measured by Zetasizer. The swelling ratios of CNT-NH2/CG and CNT-COOH/CG hydrogels in aqueous solution were checked by measuring of weight changes of the hydrogels in the range of pH 2~10. In detail, the positively charged CNT-NH2/CG hydrogel swelled up to 5% at pH 4 in comparison to the weight at pH 7, while the negatively charged CNT-COOH/CG hydrogel swelled up to 10% at pH 10. The prepared CNT-NH2/CG and CNT-COOH/CG hydrogels will be very useful as pH sensitive oral drug-delivering systems for gastrointestine (pH ~2) and small intestine (pH ~9), respectively.

The retrogradation and swelling power of modified potato starches (변성 감자 전분의 노화와 팽윤력)

  • Kim, Ji-Tae;Noh, Wan-Seob
    • Applied Biological Chemistry
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    • v.35 no.5
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    • pp.404-409
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    • 1992
  • Hydroxypropylated starches and acetylated starches were prepared by reaction of potato starch with propylene oxide and acetic anhydride, respectively and then degree of retrogradation and swelling power were investigated in different pHs and temperature. The extent of retrogradation determined by glucoamylase method during freeze-thaw treatment and storage in low temperature $(0{\sim}5^{\circ}C)$ showed that modified potato starches were slowly retrograded as the increase of degree of substitution. The order of the retrogradation tendencies in different pHs were pH 4>pH 6>pH 8>pH 10. Retrogradation of hydroxypropylated potato starches were less than that of acetylated potato starches. Swelling power of starches were influenced more by the temperature than by the pH. The order of the swelling power tendencies in different pHs were pH 10>pH 2>pH 8>pH 4>pH 6.

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Effect of pH on Organic Acid Production by Anaerobiospirillum succiniciproducens (Anaerobiospirillum succiniciproducens에 의한 유기산 생성에 미치는 pH의 영향)

  • 강귀현;류화원장호남
    • KSBB Journal
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    • v.10 no.5
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    • pp.568-574
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    • 1995
  • To investigate the effect of pH on organic acid production by Anaerobiospirillum succiniciproducens, an anaerobic fermentation was carried out by maintaining the pH of the fermentation broth at 5.8, 6.0, 6.4, 6.8, and 7.2. At various pHs, the concentrations of cell were $1.0∼1.9g/\ell$ which were two to three times higher than those of the other worker's results, and the maximum was obtained at pH 5.8. Substrate consumption was increased by increasing the pH in the range of pH 6.0 to 6.8, while the sugar consumption rate at both pH 5.8 and 7.2 was very slow. The total amount of 2M $Na_2C0_3$ added for adjustment of pH change due to organic acid production was maximum at pH 6.8. Changes of conductivity of the fermentation broth was very simillar to those of 2M $Na_2C0_3$ added at various pHs. Therefore, it is suggested that determination of the amount of organic acid in a broth can be possible by measuring the conductivity. The maximum production yield of lactate based on glucose was 64% for pH 7.2 and 32% for pH 6.8, respectively.

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Effect of pH Stimulation on Acrosome Reaction of Bovine Spermatozoa (pH 자극이 소 정자의 첨모반응에 미치는 영향)

  • 박영식;임경순
    • Korean Journal of Animal Reproduction
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    • v.15 no.3
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    • pp.195-199
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    • 1991
  • This study was carried out ot investigate effect of pH stimulation on acrosome reaction of bovine spermatozoa. The results obtained were as follows : 1. When sperm was sequentially washed with SHP solution of pH 7.4, 7.7 and 7.4 and incubated in mTALP solution of pH 7.4 for 120min, 15, 30, 60 and 120min incubations showed significantly(p<0.05) higher sperm acrosome reaction rate than 0 min. 2. When sperm was sequentially washed with SHP solution of pH 7.4, 8.0 and 7.4 and incubated in mTALP solution of pH 7.4 for 15 minutes, sperm acrosome reaction rate was significantly(p<0.01) increased until 9 min. Incubation, but not increased thereafter. 3. When sperm were separately washed with SHP solutions of pH 7.0, 7.4 and 8.0 and incubated in mTALP solution of pH 7.4 for 9min, sperm acrosome reaction rate was 74.8, 71.8 and 93.4%. pH 8.0 showed signifciantly(p<0.01) higher sperm acrosome reaction rate than pH 7.0 and 7.4. The results suggest that stimulation of sperm with high pH induces sperm crosome reaction.

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