• Title/Summary/Keyword: pKa

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Determination of the pKa for Histidine-51 Residue in the Ternary Compelx of Horse Liver Alcohol Dehydrogenase

  • Lee, Kang-Man;Son, Su-Yeon
    • Archives of Pharmacal Research
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    • v.15 no.3
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    • pp.229-233
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    • 1992
  • The pKa value of histidine-51 residue was determined by the pH dependency of contents of NADH bound to the active site in the orse liver alcohol dehydrogenase and % inactivation with diethyl pyrocarbonate treatment of the enzyme. The pKa for His-51 was -7.15 in the ternary complex and -6.7 in the enzyme itself.

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Acidities of Benzyltetrahydrothiophenium Halides in Water. A Simple Method of Estimation

  • 조봉래;김용관;한만소;오광진
    • Bulletin of the Korean Chemical Society
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    • v.16 no.12
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    • pp.1218-1222
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    • 1995
  • The pKa values of benzyltetrahydrothiophenium halides 1a-f in water have been estimated by measuring the absorbances of the solution in aqueous hydroxide ion solution. Assuming that the ratios of the activity coefficients remains close to unity, the absorbance of the solution can be expressed as A/[SH]o=(εSH+εS-K[OH-])/(1+K[OH-]), where A, [SH]o, K, εSH, and εS- are the absorbance of solution, the initial concentration of 1a-f, the equilibrium constant, and the extinction coefficients for SH and S-, respectively. The εS- and K values that best fit with this equation were calculated by a nonlinear regression analysis with a large number of absorbance data determined at different [OH-] and [SH]o. The pKa values of the SH were then calculated with the relationship Ka=-log K+14. The validity of this method has been demonstrated by the excellent agreements between the experimental and literature pKa values of three organic acids. The pKa values of 1a-f estimated by this method are in the range of 12.5-15.3 and correlate well with the Hammett equation. The large negative deviation for the pKa values of 1e and 1f from the Hammett plot has been attributed to the extra hydrogen bonding between the phenyl group and water molecules attracted by the hydrophilic substituents.

Apparent pKa and Partition Coefficient of Tranylcypromine (Tranylcypromine의 겉보기 해리항수(解離恒數) 및 분배계수(分配係數))

  • Kang, Gun-Il;Chung, Soon-Young
    • YAKHAK HOEJI
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    • v.28 no.5
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    • pp.293-297
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    • 1984
  • The pKa' of tranylcypromine was determined by potentiometric titration and ultraviolet spectrophotometric method and found to be 8.08 and 8.15, respectively. The Papp of tranylcypromine between n-heptane and aqueous buffer solution was measured to be 0.90 at pH 7.48 and 4.50 for Pm. The pKa' of tranylcypromine obtained by means of the partition method was 8.13.

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Effect of Kainic Acid on the Phosphorylation of Mitogen Activated Protein Kinases in Rat Hippocampus

  • Won, Je-Seong;Lee, Jin-Koo;Choi, Seong-Soo;Song, Dong-Keun;Huh, Sung-Oh;Kim, Yung-Hi;Suh, Hong-Won
    • The Korean Journal of Physiology and Pharmacology
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    • v.5 no.6
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    • pp.451-456
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    • 2001
  • In rat hippocampus, kainic acid (KA; 10 mg/kg; i.p.) increased the phosphorylated forms of ERK1/2 (p-ERK1/2) and Jun kinase1 (p-JNK1), but not p-JNK2 and p38 (p-p38). The preadministration with cycloheximide (CHX; 5 mg/kg; i.p.) inhibited KA-induced increase of p-JNK1, but not p-ERK1/2. Surprisingly, the phosphorylated upstream MAP kinase kinases (p-MKKs) were not correlated with their downstream MAP kinases. The basal p-MKK1/2 levels were completely abolished by KA, which were reversed by CHX. In addition, p-MKK4 and p-MKK3/6 levels were enhanced by CHX alone, but were attenuated by KA. Thus, our results showed that KA increased the p-ERK and p-JNK levels in rat hippocampus, which were not parallel with their classical upstreamal kinases.

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Statistical Study For The prediction of pKa Values of Substituted Benzaldoxime Based on Quantum Chemicals Methods

  • Al-Hyali, Emad A.S.;Al-Azzawi, Nezar A.;Al-Abady, Faiz M.H.
    • Journal of the Korean Chemical Society
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    • v.55 no.5
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    • pp.733-740
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    • 2011
  • Multiple regression analysis was used for the calculation of pKa values of 15 substituted benzaldoximes by using various types of descriptors as parameters. These descriptors are based on quantum mechanical treatments. They were derived by employing semi-empirical calculation represented by the PM3 model and an Abinitio method expressed by Hartree-Fock(HF) model performed at the 6-311 G(d, p) level of theory. The parameters tested for their ability to represent the variations observed in the experimental pKa(s) are atomic and structural properties including Muliken charges on the atoms of hydroxyl group and C=N bond, the angle $C_6-C_1-C_7$, and length of O-H bond. Molecular properties are also used like energies of HOMO and LUMO, hardness(${\eta}$), chemical potential(${\mu}$), total energy(TE), dipole of molecule(DM), and electrophilicity index(W). The relation between pKa values and each of these parameters of the studied compounds is investigated. Depending on these relations, two sets of parameters were constructed for comparison between the PM3 and HF methods. The results obtained favor the Abinitio method for such applications although both models proved to have high predictive power and have sufficient reliability to describe the effect of substituents on pKa values of benzaldoxime compounds under consideration which is clear from the values of correlation coefficient $R^2$ obtained and the consistency between the experimental and the calculated values.

Very low protein diet plus ketoacid analogs of essential amino acids supplement to retard chronic kidney disease progression

  • Satirapoj, Bancha;Vongwattana, Peerapong;Supasyndh, Ouppatham
    • Kidney Research and Clinical Practice
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    • v.37 no.4
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    • pp.384-392
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    • 2018
  • Background: A very low protein diet (VLPD) with ketoacid analogs of essential amino acids (KA/EAA) administration can remarkably influence protein synthesis and metabolic disturbances of patients with advanced chronic kidney disease (CKD), and may also slow the decline in renal function. Methods: A retrospective cohort study was carried out to monitor renal progression and metabolic and nutritional status among 140 patients with CKD stage III or IV. One group (n = 70) was on a low protein diet (LPD) with 0.6 g of protein intake, and another group (n = 70) was on a VLPD with 0.3 g of protein and KA/EAA supplementation of 100 mg/kg/day for 12 months. Results: At 12-month follow-up, estimated glomerular filtration rate (GFR) significantly decreased from $41.6{\pm}10.2$ to $36.4{\pm}8.8mL/min/1.73m^2$ (P < 0.001) and urine protein increased from $0.6{\pm}0.5$ to $0.9{\pm}1.1g/day$ (P = 0.017) in the LPD group, but no significant changes in estimated GFR and urine protein were found in the VLPD plus KA/EAA group. A significant mean difference in rate of change in estimated GFR ($-5.2{\pm}3.6mL/min/1.73m^2$ per year; P < 0.001) was observed between the two groups. After Cox regression analysis, treatment with VLPD plus KA/EAA significantly protected against the incidence of declining GFR > 10% annually (adjusted hazard ratio, 0.42; 95% confidence interval, 0.23-0.79; P = 0.006) and significant correlations were found between using VLPD plus KA/EEA and increased GFR. Conclusion: VLPD supplementation with KA/EAA is associated with delayed renal progression while preserving the nutritional status in the patients with CKD. Co-administration of VLPD and KA/EAA may prove an effective alternative to conservative management of CKD.

Spectrophotometric Determination of Soil Chemical Properties Using Soiltek® KA-P Spectrophotometer (Soiltek KA-P 분광광도계률 사용한 토양 화학적 성질의 분광학적 분석)

  • Hyun, Hae-Nam;Oh, Sang-Sil;Koo, Bon-Jun;Kang, Ho-Jun
    • Korean Journal of Soil Science and Fertilizer
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    • v.33 no.2
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    • pp.127-138
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    • 2000
  • To enable rapid and convenient soil test, new soil analytical methods, which require only one instrument, UV/Vis spectrophotometer, were developed and named "Soiltek KA-P spectrophotometric methods". The Soiltek$^{(R)}$ KA-P spectrophotometric method was compared with standard method of RDA in analytical capability for soil chemical properties. Using the 78 soils collected from upland, paddy, orchard, and vinyl house soils, soil organic matter, exchangeable K, Ca, and Mg. CEC, available $SiO_2$, and nitrate were analyzed by the two methods. The color stability(ratio of the absorbance at elapsed time t to the absorbance at time t=0) of organic matter. Ca, Mg, and available $SiO_2$ decreased to about 2% within one hour. However, that of exchangeable K, CEC, and nitrate remained constant. The results obtained with Soiltek$^{(R)}$ KA-P spectrophotometric method showed highly significant correlation with those measured by the standard method of RDA($R^2$ >0.9501), in which the slopes were near unity of $1.0{\pm}0.05$. The standard deviation values of organic matter, exchangeable K, Ca, and Mg, CEC, available $SiO_2$, and nitrate were apparently lower than ${\pm}1.8gkg^{-1}$, ${\pm}0.05cmol^+kg^{-1}$, ${\pm}0.18cmol^+kg^{-1}$, and ${\pm}0.13cmol^+kg^{-1}$, ${\pm}1.0cmol^+kg^{-1}$, ${\pm}5.0mgkg^{-1}$, and ${\pm}10.0mgkg^{-1}$, respectively. All the measurements showed coefficients of variation of less than 7~17% and were within the confidence level of 95%, which means both the methods are precise. Considering the relative simplicity, low cost, precision and accuracy, the proposed Soiltek$^{(R)}$ KA-P spectrophotometric methods could be recommended as an alternative to standard method.

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RELIABILITY TESTING OF EATING ATTITUDE TEST FOR KOREAN ADOLESCENTS (한국판 청소년용 식이 태도 검사(EAT-26KA)의 신뢰도 조사)

  • Choi, Joon-Ho;Nam, Jung-Hyun;Cho, Yun-Gyoo;Choi, Bo-Yeul;Ahn, Dong-Hyun
    • Journal of the Korean Academy of Child and Adolescent Psychiatry
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    • v.9 no.1
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    • pp.91-97
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    • 1998
  • Objectives:This study was designed for testing of Eating Attitude Test for Korean adolescents (EAT-26KA) on internal reliability and test-retest reliability and evaluation of each items through factor analysis. Methods:Total 1,160 middle and high school students were surveyed on June 1996. The questionnaire had been delivered by school teachers two weeks earlier before survey started. Among the 1,160 students, 114 students were selected by random. And then they were retested with same questionnaire on July 1996, four weeks later Result:Internal consistency of EAT-26KA was relatively good(Cronbach’s ${\alpha}$ =.83). There was statistically significance on test-retest reliability(r=.63 p<.01). But two items showed negative correlations(item No. 9, 17). and 5 items had low level correlation(p>.05, item No. 2, 6, 12, 21, 24). We performed factor analysis on whole items except No. 25 item. Result of factor analysis showed that the factor structure of EAT-26KA were different from that of EAT-26. Conclusion:The EAT-26KA is useful for the survey of the eating behavior and problems in Korean adolescents.

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A Kinetic Study for the Reaction of 2,4-Dinitrophenyl Benzoate with Secondary Cyclic Amines

  • 엄익환;김명진;민지숙;권동숙
    • Bulletin of the Korean Chemical Society
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    • v.18 no.5
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    • pp.523-527
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    • 1997
  • Apparent second-order rate constants (kapp) have been measured spectrophotometrically for the reaction of 2,4-dinitrophenyl benzoate (DNPB) with 6 secondary cyclic amines in H2O containing 20 mole% DMSO at 25.0±0.1 ℃. The Bronsted-type plot (log kapp vs. pKa) shows a break at pKa near 9.1, e.g. two straight lines with βapp values of 0.67 and 0.44 for the low basic (pKa < 9.1) and the highly basic (pKa > 9.1) amines, respectively. Using an estimated k2 value of 3×109 sec-1, all the other microconstants (k1, k-1 and K) involved in the present aminolysis have been calculated. The k value decreases with increasing the basicity of amines while k1 and K values increase with increasing the amine basicity, as expected. Good linear Bronsted-type plots have been obtained for these microconstants of the present aminolysis of DNPB. The magnitudes of the slope of the Bronsted-type plots, k1 and k-1 have been calculated to be 0.43 and - 0.24, respectively, indicating the k-1 step is about two folds less sensitive than the k1 step to the amine basicity. The K value has been calculated to be 0.66, which appears to be much smaller than the one for other aminolyses showing general base catalysis. The small K value has been attributed to the absence of general base catalysis in the present aminolysis of DNPB.