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Competitive Inhibition of Pepsin by Carboxylic Acids
신홍대,Hong Dae Shin Korean Chemical Society 1970 대한화학회지 Vol.14 No.2
In order to obtain the more effective evidence, supporting the hypothesis which have been previously described by former report that pepsin (EC 3.4. 4.1) forms a hydrophobic bond with the nonpolar side chain of its substrate, the inhibitory effect of carboxylic acids(from formic acid to iso-butyric acid) on the activity of pepsin to the synthetic dipeptide, N-Carbobenzoxy-L-glutamyl-L-tyrosine, was discussed. The kinetic study showed that the inhibition by carboxylic acids was competitive. The Kidecreased with increasing size of the inhibitor molecule. The $-{\Delta}F^{\circ}$increased linearly with increasing number of carbon atoms in the hydrocarbon chain of the inhibitor. It was confirmed that the hydrophobic bond between more than one side chain of amino acid residues(phenylalanine) in the binding region of the active center of pepsin and the side chain of amino acid residues in the substrate was formed as the first step of its enzymic mechanism. The inhibitory effect of carboxylic acids was due to the competition of the hydrocarbon group of the carboxylic acids with the side chain of the substrate for the hydrophobic binding site(the side chain of phenylalanine) of the pepsin.
신홍대,Hong Dae Shin Korean Chemical Society 1970 대한화학회지 Vol.14 No.2
The kinetics of the pepsin-catalyzed hydrolysis of N-carbobenzoxy-L-glutamyl-L-tyrosine at pH 3.5 and $37^{\circ}C$ were determined by a spectrophotometric technique. The pepsin used was further purified on a Sephadex G-75 column. The kinetics data were Km = l.7 ${\times}10^{-3}M,\;-{\Delta}F^{\circ}$ = 3.99Kcal/mole, and $k^3=\;2.1{\times}10^{-2}\;sec^{-1}$. An analysis of the above data and other investigators' data obtained from some dipeptides led to the following conclusions. (1) Phenylalanyl residues in a synthetic peptide are bound to pepsin more strongly than glutamyl or tyrosyl residues, supporting the theory that a part of the binding region of the active center is hydrophobic. (2) Dipeptides are bound to pepsin principally through their side chains and the binding involves both side-chain residues. (3) The nature of amino acids in dipeptides $R_2-R_1,\;affect\;the\;k_3$ values.
Sodium Alginate-$CaSO_4{\cdot}1/2H_2O$ 彈性體의 生成速度 및 彈性에 미치는 金屬酸化物의 影響
신홍대,허연,김은식,Shin, Hong-Dae,Huh, Yeonn,Kim, Uun-Sik 대한화학회 1965 대한화학회지 Vol.9 No.1
Sodium alginate-$CaSO_4{\cdot}$1/2 $H_2O$의 gel에 미치는 alkali鹽의 遲延효果를 Miyake date와 比較하고, Schwedoff法을 改良한 連續的 測定方法을 써서, 金屬酸化物의 添加에 依한 彈性 gel의 生成速度 및 彈性의 變化를 硏究하였다. 즉 (1) sample의 張力變化를 連續的으로 測定하여, sodium alginate와 $CaSO_4{\cdot}$1/2 $H_2O$ aqueous sol의 gel化 過程을 觀察하였다. (2) 彈性 gel의 生成速度에 미치는 $Na_3PO_4$의 遲延효果는 $Na_2CO_3$보다 크다는 點에서는 Miyake 報告와 一致하였으나, Miyake date처럼 兩者間에 그리 큰 差가 없었다. (3) 金屬酸化物이 彈性 gel生成速度에 미치는 影響에 어떤 規則性은 없었지마는 $SiO_2$와 MgO는 比較的 큰 速度增大효果를 나타내고 ZnO는 比較的 적었다. 그러나 $Al_2O_3$, $Sb_2O_3$와 $TiO_2$는 速度低下효果를 나타냈다. 結果的으로 酸化物의 種類나 그 添加量에 따라 어떤 明確한 規則性을 觀察하지 못하였다. (4) 彈性率과 生成速度에 미치는 효果사이에 比例關係는 없없으나 金屬酸化物을 添加하면 一般的으로 彈性率이 增加하였다. 이들 酸化物 中에서 彈性率增大효果가 가장 큰 것은 MgO였다. The time-lag-effect of alkali salts on the gelation of sodium alginate-$CaSO_4{\cdot}$1/2 $H_2O$ is compared with Miyake's data, and then the formation rate of the elastics measured by the continuous method (an improved Schwedoff's method) and the change of rigidity with metallic oxides are studied as follows: (1) The gelation processes of sodium alginate and $CaSO_4{\cdot}$1/2 $H_2O$-aqueous sol are studied by measuring, continuously the increases of tensions ofsamples. (2) The time-lag-effect of $Na_3PO_4$ on the formation rate of the elastic gel is larger than that of $Na_2CO_3$, but the difference between the effects of the two alkali salts on the rate is found not so greater than predicted in Miyake's data. (3) Any regularities of the effect on the rate by metallic oxides are not observed. The increasing effects of the rates of $SiO_2$ and MgO are relatively large, and that of ZnO is relatively small. However, $Al_2O_3$, $Sb_2O_3$ and $TiO_2$show some decreasing effects. As a result it is noted that the regularities do not depend on the effect of oxide species and their amounts. (4) It is not found proportionality between the rigidity and the gelation rate. However, the increasing effect of the rigidity with the addition of metallic oxides can be observed. The rigidity increasing rate of MgO is the largest of them.
신홍대,윤주억,Hong Dae Shin,Joo Ok Yoon 대한화학회 1963 대한화학회지 Vol.7 No.1
Amino acid composition of Makjang was determined by combined usage of ion exchanged resin and paper chormatography in the following states. a. A fraction soluble in water b. Hydrolysate of the whole Makjang c. Same as a. (p.p.t. formed by tungstic acid or trichloroacetic acid being removed) d. Hydrolysate of c. (T and TCA) By comparing amino acid composition of Makjang with that of its raw material, we found that decomposition of essential amino acids during brewing is slight. From the amino acid composition of a,b,c,d, we discussed the ratio of amino acid liberation during brewing and assumed that Makjang contains peptide-like substances composing of glutamic acid and aspartic acid.
Sol-Gel 법을 응용한 가시광 감응 촉매 제조 및 유기물 분해 능에 관한 연구
신홍대,주현규,전일수,하진욱,이창하 한국화학공학회 2007 화학공학의이론과응용 Vol.10 No.1
본 연구에서는 sol-gel 법을 응용하여 가시광 감응 촉매를 제조 하였다. 열 처리 과정에서 나타나는 grain boundary상의 산소 결핍을 이용 하여, 결핍된 자리에 N을 도핑 하였고, 도핑 된 TiO2-xNx는 밝은 노란색과 50 nm 입자 특성을 나타내었다. 활용에 필요한 코팅성을 보완하기 위해, 볼 밀을 이용하여 고속 분쇄를 시도 하였다. 분쇄한 TiO2-xNx의 활성을 보완 하고자, H2PtCl6를 이용하여 UV-C lamp를 이용한 광 환원법과 NaBH4를 이용한 화학적 방법을 통해서 Pt가 담지된 회색의 Pt/ TiO2-xNx를 제조하였다. 제조한 촉매들은 Uv/Vis spectrometer, XRD, XPS, TEM, SEM, ICP, BET, DSC, EDS를 통해서 특성을 분석하였다. TiO2-xNx는 550nm 이하의 빛을 흡수하였고, pt를 담지한 TiO2-xNx는 전 파장의 빛을 흡수 하였다. XRD 분석의 2θ= 25.3의 피크를 통해서 두 촉매가 anatase 구조임을 확인 할 수 있었다. 가시광에서의 활성 테스트를 위해서 VOCs 물질 중 2-propanol을 분해 하였으며, 현재 상용 중에 있는 P25 (degussa)와 비교를 통해서 제조된 촉매들의 활성 능을 입증 하였다. 앞으로 상용화를 위해 더 많은 물질과 반응기에 대입 할 계획이다.