• KSBB Journal
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• 제7권3호
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• pp.201-208
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• 1992

Cell surface binding of epidermal growth factor(EGF) to EGF receptors was studied for a series of site-directed receptor mutants transfected into B82 mouse fibroblasts. Scatchard plots for truncation mutant receptors significantly lost nonlinearity for truncations below residue 1022. Transient plots of dissociation kinetics exhibited biphasic behavior for all receptor types, but the fraction of receptor in slow-dissociating form was reduced by an order of magnitude for the truncation mutants below residue 1022. Comparison of dissociation kinetics between control cells and cells treated with Triton X-100 revealed no significant variation for the slow-dissociating receptor form, but a noticeable variation was observed for the fast-dissociating receptor form when EGF receptors were truncated below residue 991. These results suggest that high affinity of EGF binding at cell surface depend on the EGF receptor cytoplasmic region.

• Journal of Pharmaceutical Investigation
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• 제31권1호
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• pp.19-25
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• 2001

The purpose of this study was to use a ternary polymeric matrix system for high drug loading of a highly soluble drug for controlled release delivery. The controlled drug delivery of diltiazem HCl (solubility > 50% in water at $25^{\circ}C$) with high loading dose (the final loading dose of drug was 34%) from a ternary polymeric matrix (gelatin, pectin, HPMC) was successfully accomplished. This simple monolithic system with 240 mg drug loading provided near zero-order release over a 24 hour-period by which time the system was completely dissolved. The release kinetics of diltiazem HCl tablet with high loading dose from the designed ternary polymeric system was dependent on the ratios of HPMC : pectin binary mixture. The release rate increased as pectin : HPMC ratio were increased. Swelling behavior of the ternary system and the ionic interaction of formulation components with cationic diltiazem molecule appear to control drug diffusion and the release kinetics. Comparable release profiles between commercial product and the designed system were obtained. The binding study between gelatin with diltiazem HCl showed the presence of two binding sites for drug interaction with subsequent controlled diffusion upon swelling. This designed delivery system is easy to manufacture and drug release behavior is highly reproducible and offers advantages over the existing commercial product.

• Journal of the Korean Chemical Society
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• 제25권2호
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• pp.124-126
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• 1981

• Journal of Microbiology and Biotechnology
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• 제16권12호
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• pp.1897-1903
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• 2006

In order to investigate the functions of the C-terminal region of chitinase ChiCW of Bacillus cereus 28-9, a C-terminal truncated enzyme, ChiCW$\Delta$FC, was expressed in Escherichia coli and purified to homogeneity for biochemical characterization. Compared with ChiCW, ChiCW$\Delta$FC exhibited higher chitinase activity at high temperature and pH, but expressed lower hydrolytic and binding activities toward insoluble substrates. In addition, kinetic properties indicated that ChiCW$\Delta$MC hydrolyzed oligomeric and polymeric substrates less efficiently than ChiCW. These results suggest that the C-terminal region of ChiCW plays important roles in substrate binding and hydrolysis of chitin. In addition, the biological meaning of C-terminal proteolytic modification of ChiCW is discussed.

• KSBB Journal
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• 제11권2호
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• pp.225-237
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• 1996

Intrinsic binding kinetics of of 125I-bovine serum albumin (125I-BSA) and immobilized monoclonal anti-BSA (MAb 9.1) were studied. Small non-porous polystyrene beads (0.5${\mu}$m diameter) were used as a solid support to minimize the mass transfer interference on rate measurements. We demonstrated both theoretically and experimentally that the binding reaction is kinetically controlled. Rate measurements show that the association reaction is of second order and the dissociation reaction is of first order. Between 4 and $37^{\circ}C$ the measured equilibrium constant agrees well with the equilibrium constant calculated from the rate measurements. The temperature effects on association are much greater than on dissociation; the activation energy for association is about 9Kca1/mole, as compared to 2Kca1/mole for dissociation. The use of small non-porous beads as a solid support in binding studies essentially avoids mass transfer limitations; such a system makes it possible to determine the intrinsic binding characteristics of any immobilized antibody on a solid surface.

• Toxicological Research
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• 제15권1호
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• pp.95-101
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• 1999

Cytochrome P450 (CYP) 3A4 metabolizes aflatoxin B1 (AFB1) to AFB1-exo-8,9-epoxide (8,9-epoxidation) and aflatoxin Q1 (AFQ1; 3$\alpha$-hydroxylation) simultaneously. We investigated whether each metabolite was formed via its own binding site of CAP3A4 active site. Kinetics of the formation of the two metabolites were sigmoidal and consistent with the kinetics of substrate activation. The HIll model predicted that two substrate binding wites are involved in the oxidationof AFB1 by CYP3A4. Dehydronifedipine, a metabolite of nifedipine generated by CYP3A4, inhibited the formation of AFQ1 without any inhibition in the formation of AFB1-exo-8,9-epoxidation. Dehydronifedipine was found to act as a reversible competitive inhibitor against 3$\alpha$-hydroxylation of AFB1. Vmax and S0.5 of the 8,9-epoxidation were not changed in the presence of 0, 50, or 100 $\mu\textrm{M}$ dehydronifedipine. S0.5 of 3$\alpha$-hydroxylation was increased from 58$\pm$4 $\mu\textrm{M}$ to 111$\pm$8 $\mu\textrm{M}$ in the presence of 100 $\mu\textrm{M}$ nifedipine whereas Vmax was not changed. These results suggest that there exist two independent binding sites in the active site of CAP3A4 . One binding site is responsible for AFB1-exo-8,9-epoxidation and the other is involved in 3$\alpha$-hydroxylation of AFB1. Dehydronifedipine might selectively bind to the site which is responsible for the formation of AFQ1 in the active site of CYP3A4.

• Proceedings of the Korean Biophysical Society Conference
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• 한국생물물리학회 1996년도 정기총회 및 학술발표회
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• pp.25-25
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• 1996

A mature mutant ribose binding protein (RBP) of Escherichia coli was obtained by site-directed mutagenesis, replacing Thr-3 in the N-domain of wild-type mature RBP (WT -mRBP) with a Trp residue (N- Trp-mRBP). The equilibrium unfolding properties and the refolding kinetics of this protein were monitored by fluorescence and circular dichroism (CD). (omitted)

• Molecules and Cells
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• 제24권1호
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• pp.119-124
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• 2007

TLR4 together with CD14 and MD-2 forms a pattern recognition receptor that plays an initiating role in the innate immune response to Gram-negative bacteria. Here, we employed the surface plasmon resonance technique to investigate the kinetics of binding of LPS to recombinant CD14, MD-2 and TLR4 proteins produced in insect cells. The dissociation constants ($K_D$) of LPS for immobilized CD14 and MD-2 were $8.7{\mu}m$, and $2.3{\mu}m$, respectively. The association rate constant ($K_{on}$) of LPS for MD-2 was $5.61{\times}10^3M^{-1}S^{-1}$, and the dissociation rate constant ($K_{off}$) was $1.28{\times}10^2S^{-1}$, revealing slow association and fast dissociation with an affinity constant $K_D$ of $2.33{\times}10^6M$ at $25^{\circ}C$. These affinities are consistent with the current view that CD14 conveys LPS to the TLR4/MD-2 complex.

• Bulletin of the Korean Chemical Society
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• 제34권4호
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• pp.1145-1152
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• 2013

The rate constant of alkaline fading of methyl green ($ME^{2+}$) was measured in the presence of non ionic (TX-100), cationic (DTAB) and anionic (SDS) surfactants. $ME^{2+}$ hydrolyses and fades in neutral water and in this work we search the effects of surfactants on its fading rate. The rate of reaction showed remarkable dependence on the electrical charge of the used surfactants. It was observed that the reaction rate constant decreased in the presence of DTAB and SDS and increased in the presence of TX-100. Binding constants of $ME^{2+}$ to TX-100, DTAB and SDS and the related thermodynamic parameters were obtained by classical (or stoichiometric) model. The results show that binding of $ME^{2+}$ to TX-100 and DTAB are two-region and that of SDS is three-region. Also, the binding constants of $ME^{2+}$ to surfactant molecules in DTAB/TX-100 and SDS/TX-100 mixed solutions and their stoichiometric ratios were obtained.

• Journal of Microbiology and Biotechnology
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• 제11권1호
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• pp.35-39
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• 2001

A simple method for studying the lectin-like interactions between Helicobacter pylori and cultured human epithelial cell lines was developed using an enzyme-linked, biotin-streptavidin bacterial-adhesion assay. The present study suggests that this method is suitable for evaluating the participation of lectin interactions in the adhesion of H. pylori to cultured HeLa S3 and Kato III cells, both fixed and glycosidase-treated cells, as well as assessing glycoconjugated binding inhibition studies. The time-course and dose-dependent kinetics of the biotin-labeled H. pylori adhesion th the formaldehyde-fixed Hela S3 and Kato III cell lines exhibited saturation. In addition, the binding of the biotin-labeled H. pylori to the formaldehyde-fixed cultured cells was partially blocked by pre-incubation with glycoconjugates and polyclonal antibodies against a heparan sulfate binding protein from H. pylori.