• Journal of Life Science
• /
• v.15 no.4 s.71
• /
• pp.633-640
• /
• 2005

The purified xylanase from Bacillus pumilus TX703 was modified with various chemical modifiers to determine the active sites of the enzyme. Treatment of the enzyme with group-specific reagents such as carbodiimide or N-bromosuccinimide resulted in complete loss of enzyme activity. These results assumed that these reagents reacted with glutamic acid or aspartic acid and tryptophan residues located at or near the active site. In each case, inactivation was performed by pseudo first-order kinetics. Inhibition of enzyme activity by carbodiimide and W-bromosuccinimide showed non-competitive and competitive inhibition type, respectively. Addition of xylan to the enzyme solution containing N-bromosuccinimide prevented the inactivation, indicating the presence of tryptophan at the substrate binding site. Analysis of kinetics for inactivation showed that the loss of enzyme activity was due to modification of two glutamic acid or aspartic acid residues and single tryptophan residue.

• Journal of the Korean Electrochemical Society
• /
• v.7 no.1
• /
• pp.26-31
• /
• 2004

The direct electrochemical studies of four laccases (plant and fungal laccases) have been investigated on a gold electrode functionalized with a new tether of 2.2'-dithiosalicylic aldehyde. Results from these studies indicate that the redox potential of the active site of plant laccase from Rhus vernificera is shifted to a more negative value(255 mV versus SCE) than that of fungal laccase from Pyricularia oryzae (480 mV versus SCE). Mechanistic studies indicate that the reduction of type-1 Cu precedes the reduction of type-2 and type-3 Cu ions when the electrode is poised initially at different potentials. Also a new tether, 2.2'-dithiosalicylic aldehyde, has been used to study the redox properties of two laccases (LCCI and Lccla) covalently attached to a gold electrode. An irreversible peak at 0.47V vs. SCE is observed in the cyclic voltammorams of LCCI. In contrast, the cyclic voltammograms of LCCIa contain a quasi-reversible peak at 0.18V vs. SCE and an irreversible peak at 0.50V vs. SCE. We find that the replacement of the eleven amino acids a the C-terminus with a single cysteine residue $(i.e., \;LCCI{\rightarrow}LCCIa)$ influences the rate of heterogeneous electron transfer between an electrode and the copper containing active sites $(K_{het}\;for\;LCCI=1.0\times10^{-2}\;s^{-1}\;and\;K_{het}\;for\;LCCI_a= 1.0\;times10^{-1}\;s^{-1}\'at\;0.18V\;versus\;SCE\;and\;4.0\times10^{-2}\;s^{-1}\;at\;0.50V\; versus\;SCE)$. These results show for the first time that the change of the primary structure of a protein via site-directed mutagenesis influences both the redox potentials of the copper ions in the active site and the rate of heterogeneous electron transfer.

• Journal of Environmental Science International
• /
• v.17 no.1
• /
• pp.119-128
• /
• 2008

Laboratory analytical results of 22 sets of hydrophobic adsorbent coils containing surface soil-vapor and two soil samples collected by conventional intrusive method from each boring location at two active dry cleaning facilities in the State of Illinois, U.S.A, were presented to evaluate the performance of soil-vapor survey. The most critical factor to determine the effectiveness of soil-vapor survey is the distance from the soil-vapor sampling device to the actual contamination, which is a function of soil porosity, permeability, primary lithology, and other geological and hydrogeological site-specific parameters. Also this factor can be affected by the history of contaminant-generating operations. The laboratory analytical results in this study showed longer dry cleaning operation history (i.e., 50 years) and presence of fine sand at the beneath Site B allow the contaminants to migrate farther and deeper over a fixed time compared to Site A(i.e., 35 years and silty clay) so that the soil-vapor survey is not likely the most effective environmental site investigation method alone for Site B. However, for Site A, the soil-vapor survey successfully screened the site to identify the location reporting the highest soil concentration of chlorinated solvents.

• BMB Reports
• /
• v.32 no.6
• /
• pp.599-604
• /
• 1999

A highly conserved amino acid, glutamic acid (Glu), present at position 152 in the catalytic domain of the human immunodeficiency virus type 1 (HIV-1) integrase (IN) protein has been known to be critical for enzymatic function since substitution of Glu 152 with other residues results in a complete loss of enzymatic activities. In order to better understand the role of Glu 152 as a conserved residue in enzymatic action, intragenic second site mutations have been introduced around residue 152 of a mutant IN (E152A), and their biochemical properties were analyzed in terms of enzymatic activities. Disintegration activities were found to be significantly restored in several second site mutant INs, while integration activities were only recovered weakly. However, endonucleolytic activities were not discovered in all the mutant INs. These findings indicate that the second site mutations can partially restore that catalytic structure of the active site disturbed by the E152A mutation and lead to the regaining of integration and disintegration activities. In addition, it is also suggested that endonucleolytic activity requires a more accurate structure of the catalytic site than that for the integration and disintegration activities.

• Proceedings of the Korean Biophysical Society Conference
• /
• 2001.06a
• /
• pp.62-62
• /
• 2001

Serpins inhibit target proteases by forming tight acyl complex Via incorporation of the reactive center loop into ${\beta}$-sheet A. Metastability of the serpins control the translocation of the protease from the initial binding site to the opposite pole of the serpin. Recently the crystal structure of a serpin-protease complex revealed that the active site of the protease is distorted.(omitted)

• Proceeding of Spring/Autumn Annual Conference of KHA
• /
• 2008.11a
• /
• pp.222-225
• /
• 2008

In urban life, an interest in safety and demands for safety information about crimes and traffic are increasing. As well, communication on the internet is so active. In this study, we analyze web sites in US, UK, and JP, which have started safety map services, and then we provide basic material for the introduction of safety map into Korea. According to the analysis result, in US and UK, the safety map web sites are administered by the government and provided to the general public. The geographical area is provided around administrative districts and statistical data. In JP, The safety map web site provide not a one sided service but the service that user can directly take a part in, and also there is an web site for crimes against vulnerable people.

• Journal of the Korea Safety Management & Science
• /
• v.24 no.4
• /
• pp.71-83
• /
• 2022

This study is to investigate the degree of field awareness of how each provision of the Serious Disaster Punishment Act will affect accident prevention. As a result of conducting a survey of construction site workers, it was analyzed that construction site workers had a low sense of safety and did not voluntarily engage in safety activities. And it can be seen that they are taking a very passive position that it is efficient to implement safety under the supervision of the supervisor. Workers who need voluntary construction site safety activities are most aware of the situation at the site, but the problem was pointed out as "lack of procedures for listening to opinions and preparing improvement measures" for these problems. Future research is needed to see if this is a problem for individual workers or for those in charge of safety and health who do not correct it even though active opinions have been submitted.

• Proceedings of the Korean Nuclear Society Conference
• /
• 1996.11a
• /
• pp.230-235
• /
• 1996

The new concept of dry area formation based on Poisson distribution of active nucleation sites and the concept of the critical active site density is presented. A simple statistical model is developed to predict the change of slope of the boiling curve up to critical heat flux (CHF) quantitatively. The predictions by the present model are in good agreement with the experimental data. Also it turns out that the present model well explains the mechanism on how the surface wettability influences CHF.

• Proceedings of the Korean Society of Toxicology Conference
• /
• 2001.05a
• /
• pp.84-88
• /
• 2001

Human Thioredoxin (TRX) with with redox-active dithiol (C-C-Y-C-) in the active site has been cloned as adult T cell leukemia derived factor produced by HTLV-I transformed cells. Thioredoxin (TRX) is one of the major components of the thiol-reducing system and plays multiple roles in cellular processes such as proliferation, apoptosis and gene expression.(omitted)

• BMB Reports
• /
• v.31 no.4
• /
• pp.307-327
• /
• 1998

Cytochrome c peroxidase (CcP) is a yeast mitochondrial enzyme which catalyzes the reduction of hydrogen peroxide to water using two equivalents of ferrocytochrome c. The CcP/cytochrome c system has many features which make it a very useful model for detailed investigation of heme protein structure/function relationships including activation of hydrogen peroxide, protein-protein interactions, and long-range electron transfer. Both CcP and cytochrome c are single heme, single subunit proteins of modest size. High-resolution crystallographic structures of both proteins, of one-to-one complexes of the two proteins, and a number of active-site mutants are available. Site-directed mutagenesis studies indicate that the distal histidine in CcP is primarily responsible for rapid utilization of hydrogen peroxide implying significantly different properties of the distal histidine in the peroxidases compared to the globins. CcP and cytochrome c bind to form a dynamic one-to-one complex. The binding is largely electrostatic in nature with a small, unfavorable enthalpy of binding and a large positive entropy change upon complex formation. The cytochrome c-binding site on CcP has been mapped in solution by measuring the binding affinities between cytochrome c and a number of CcP surface mutations. The binding site for cytochrome c in solution is consistent with the crystallographic structure of the one-to-one complex. Evidence for the involvement of a second, low-affinity cytochrome c-binding site on CcP in long-range electron transfer between the two proteins is reviewed.