• Polymer(Korea)
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• v.32 no.3
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• pp.263-269
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• 2008

To develop carriers of hydrophobic anticancer agents based on chitosan, chitosan oligosaccharide lactate (COS) was chemically modified with lithocholic acid (LA) which is one of the bile acids as a hydrophobic group. The physicochemical properties of the lithocholic acid conjugated chitosan nanoparticles (COS-LA) were investigated using $^1H$-NMR spectroscopy, dynamic light scattering (DLS) and spectrofluorophotometer. COS-LA-paclitaxel (CLs-Tx) nanoparticles loading paclitaxel as an anticancer agent were prepared by a dialysis method and its loading efficiency was measured through HPLC. On the basis of DLS results, the estimated particle sizes of CLs-Tx were around 300 nm. Also, the critical micelle concentration (CMC) was proven to be dependent on the degree of substitution of lithocholic acid. It showed that the CLs-Tx has the superior potential for the application as a paclitaxel carrier.

• Journal of Microbiology and Biotechnology
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• v.4 no.2
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• pp.113-118
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• 1994

A bacterial strain NS-83 isolated from soil was able to produce an extracellular thermostable protease. The strain was identified as Pseudomonas aeruginosa based on its morphological and physiological characteristics. A thermostable protease from this strain has been purified to homogeneity as judged by SDS-PAGE and isoelectric focusing. The purification procedures included hydrophobic interaction, ion exchange, and gel filtration chromatography. The $M_r$ and the pl of the enzyme were 32,000 and 5.9, respectively. The optimal pH at 55$^{\circ}C$ and the optimal temperature at pH 7.0 were 8.0 and 60$^{\circ}C$, respectively. The D-values of the enzyme at 60, 65, and 70$^{\circ}C$ were 22, 2.1, and 0.75 hrs, respectively. The enzyme activity was significantly inhibited in the presence of 1 mM o-phenanthroline or EDTA, suggesting that the enzyme is metalloprotease. The $K_m$, and $V_{max}$ for Hammarsten casein were found to be 3.2 mg/ml and 0.918 unit/ml, respectively. These enzymatic properties were similar to those of elastase produced from P. aeruginosa IFO 3455, but the enzyme was clearly different from the reported elastase, in respect to $Ca^{++}$ effects on enzyme-thermostability. This property, together with amino acid composition analysis, confirmed that the enzyme differs from the known P. aeruginosa elastase.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.4
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• pp.300-305
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• 2000

We have investigated the dielectric and electrical characteristics of palmitic acid(PA) stearic acid(SA) and arachidic acid(AA) Langmuir-Blodgett(LB) films because these fatty acid systems have a same hydrophilic group and a different hydrophobic one(methylene group or alkyl chain length). The fatty acid systems were used as LB films and the status of the deposited films was confirmed by evaluating the transfer ratio the UV absorption and the capacitance. The dielectric characteristics such as the frequency-capacitance characteristics and the dielectric dispersion and absorption characteristics of PA SA and AA through-plane were measured. The relative dielectric constants of PA, SA and AA LB films were about 3.0~4.6, 2.7~3.0 and 2.4~3.0 respectively. That is the relative dielectric constants were decreased in proportion to the chain length of methylene group. Also the dielectric dispersion and absorption of each fatty acid LB films have arisen from spontaneous polarization of dipole polarization in the range of 10$^4$~10$^{5}$ ［Hz］. The conductivity of PA, SA and AA LB films obtained from I-V characteristics were about 9$\times$10$^{-14}$ , 3$\times$10$^{-14}$ and 5$\times$10$^{-15}$ ［S/cm］. respectively. These results have shown the insulating materials and could control the conductivity y changing the length of methylene group. Also we have confirmed that the barrier height of fatty acid systems were almost the same ones obtained from dielectric characteristics.

• Journal of Photoscience
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• v.9 no.2
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• pp.178-181
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• 2002

Pyropheophorbide and pheophorbide-photosensitizers as chlorin analogues are promising new compounds for PDT because the chlorin analogues are activated with much longer red light at > 670nm and produce less long-term normal tissue phototoxicity than Photofrin. The various chlorin derivatives can be obtained by moditying peripheral substituted group among which meso-H, vinyl group and exocyclic ring are the most active positions. These characteristics prompted us to introduce various groups for constructing modified pyropheophorbide and pheophorbide a compounds. A stereospecific introduction of various double bonds at 3-position was performed to methylpheophorbide a to give a long hydrophobic moiety and cyclic derivatives. Chlorin-C$_{60}$ dyad and chlorin- $C_{60}$-porphyrin triad also were easily prepared by the reaction of terminal aldehyde of methyl pyropheophorbide a. For the reaction on meso $\delta$-position bromination and Vismeier formylation can occur. N,N-dimethylaminoacrolein also reacted on $\delta$-position and was cyclized to isobacteriochlorin, but other modification has not been succeeded. Exocyclic keto function was also modified to give purpurin derivatives, bicyclic and spiro compounds. In this presentation we report a series of modified pyropheophorbide and pheophorbide a derivatives.s.

• Bioinformatics and Biosystems
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• v.1 no.2
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• pp.115-122
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• 2006

A three-dimensional pharmacophore model was developed based on 24 currently available inhibitors, which were rationally selected from 472 compounds with diverse molecular structure and bioactivity, for generating pharmacophore of uPA (Urokinase Plasminogen Activator) inhibitors. The best hypothesis (Hypo1) comprised of five features, namely, one positive ionizable group, one hydrogen-bond acceptor group and three hydrophobic aromatic groups. The correlation coefficient, root mean square deviation and cost difference were 0.973, 0.695, and 94.291 respectively, suggesting that a highly predictive pharmacophore model was successfully obtained. The application of the model showed great success in predicting the activities of 251 known uPA inhibitors (test set) with a correlation coefficient of 0.837, and there was also none of the outcome hypotheses that had similar cost difference and RMS deviation (RMSD) with that of the initial hypothesis generated by Cat-Scramble validation test with 95% confidence level. Accordingly, our model should be reliable in identifying structurally diverse compounds with desired biological activity.

• Bulletin of the Korean Chemical Society
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• v.27 no.10
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• pp.1531-1536
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• 2006

Microsomal prostaglandin $E_2$ synthase (mPGES-1) is an enzyme that is associated with inflammation, pain, fever and cancer. Hologram quantitative structure activity relationship (HQSAR) was conducted on the series of MK-886 compounds acting as mPGES-1 inhibitors. A training set with 24 compounds was used to establish the HQSAR model. The best model was chosen based on the cross-validated correlation coefficient ($q^2$=0.884) and the correlation coefficient($r^2$=0.976). The model was utilized to predict the activity of the eight-test set of compounds giving the predictive $r^2$ value of 0.845. The descriptors of the model are based on fragment distinction (atoms, bond and connectivity) and fragment size (2-5 atoms). The atomic contribution maps generated from HQSAR were useful in identifying the important structural features responsible for the inhibitory activity of MK-886 inhibitors. Based on the generated model, the presence of hydrophobic biphenyl group seems to enhance inhibition of mPGES-1 that is in agreement with the previous experiments. In addition, it seems important for a halogen to be substituted to the biphenyl ring and for an acyl group to be attached to the indole moiety for enhanced activity.

• Molecules and Cells
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• v.27 no.6
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• pp.667-671
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• 2009

Visfatin (Nampt/PBEF) plays a pivotal role in the salvage pathway for $NAD^+$ biosynthesis. Its potent inhibitor, FK866, causes cellular $NAD^+$ levels to decline, thereby inducing apoptosis in tumor cells. In an effort to improve the solubility and binding interactions of FK866, we designed and synthesized IS001, in which a ribose group is attached to the FK866 pyridyl ring. Here, we report the crystal structure of rat visfatin in complex with IS001. Like FK866, IS001 is positioned at the dimer interface, and all of the residues that interact with IS001 are involved in hydrophobic or ${\pi}-{\pi}$-stacking interactions. However, we were unable to detect any strong interactions between the added ribose ring of IS001 and visfatin, which implies that a bulkier modifying group is necessary for a tight interaction. This study provides additional structure-based information needed to optimize the design of visfatin inhibitors.

• Journal of Sericultural and Entomological Science
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• v.39 no.2
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• pp.169-173
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• 1997

The behavior of tyrosine(Tyr.) residue of Bombyx mori silk fiber from yellow fluorescent cocoon has been examined for the dependence of pH in aqueous silk solution under the presence of orange II salt. Through the peak separation of angular dependence of spectral pattern of 15N-Tyr. and [1-13C]-Tyr. between the fiber axis and the molecular bond direction, N-H bond in fiber as well as the orientation distribution around the fiber axis were analyzed. Also, and sericin component was obtained from these angular dependence of oriented spectral pattern. The pH dependence of the 13C NMR chemical shift of B. mori silk fibroin was examined in aqueous solution in the presince of orange II are broad at pH$\geq$7.0. However, these become sharper at pH$\geq$8.0 and remain sharp at higher pH. In these higher pH range, a chemical shift change occurs due to the deprotonation of the Tyr. side group of fibroin. At higher pH. such a hydrophobic cluster is destroyed because of the electrostatic interaction according to the deprotonation of the Tyr-OH group.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.1
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• pp.13-18
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• 2000

We have fabricated LB ultra-thin films of maleate system by LB technique and evaluated the deposited status of LB ultra-thin films by I-V characteristics such as capacitance. It was found that the thickness of LB ultra-thin per layer is $27~30[{\AA}]$ by XRD. And, we have known that the conductivity along the horizontal direction of LB ultra-thin films was about $10^{-8}[S/cm]$, it corresponds to the semiconducting materials. Also, the I-V characteristics along the vertical direction of LB ultra-thin films was dominated by Schottky type current, the activation energy obtained by current-temperature characteristics was about 0.84[eV] and the conductivity was about $10^{-14}[S/cm]$, it corresponds to the insulator. And, the anisotropic conduction mechanism of the LB ultra-thin films in vertical direction and horizontal direction is determined by the hydrophilic group and the hydrophobic group in LB ultra-thin films. The above results are applicable to the semiconductor devices such as switching device, which function at the molecular level.

• BMB Reports
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• v.36 no.2
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• pp.149-153
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• 2003

The dibucaine number (DN) was determined for serum cholinesterase (EC 3.1.1.8, SChE) in plasma samples. The ones with a DN of 79-82 were used, because they had the "usual" SChE variant. The enzyme was assayed colorimetrically by the reaction of 5,5'-dithiobis-[2-nitrobenzoic acid] (DTNB) with the free sulfhydryl groups of thiocholine that were produced by the enzyme reaction with butrylthiocholine (BuTch) or acetylthiocholine (AcTch) substrates, and measured at 412 nm. Dibucaine, a quaternary ammonium compound, inhibited SChE to a minimum within 2 min in a reversible manner. The inhibition was very potent. It had an $IC_{50}$ of $5.3\;{\mu}M$ with BuTch or $3.8\;{\mu}M$ with AcTch. The inhibition was competitive with respect to BuTch with a $K_i$ of $1.3\;{\mu}M$ and a linear-mixed type (competitive/noncompetitive) with respect to AcTch with inhibition constants, $K_i$ and $K_I$ of 0.66 and $2.5\;{\mu}M$, respectively. Dibucaine possesses a butoxy side chain that is similar to the butryl group of BuTch and longer by an ethylene group from AcTch. This may account for the difference in inhibition behavior. It may also suggest the existence of an additional binding site, other than the anionic binding site, and of a hydrophobic nature.