• Bulletin of the Korean Chemical Society
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• v.34 no.6
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• pp.1684-1688
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• 2013

A rapid and sensitive method for determining usnic acid of Lethariella cladonioides in rat was established using high performance liquid chromatography (HPLC) quadrupole time-of-flight (QTOF) tandem mass (MS/MS). Rat plasma was pretreated by mixture of acetonitrile and chloroform to precipitate plasma proteins. Chromatographic separation was achieved on a column ($50{\times}2.1$ mm, $5{\mu}m$) with a mobile phase consisting of water (containing $5{\times}10^{-3}$ M ammonium formate, pH was adjusted to 3.0 with formic acid) and acetonitrile (20:80, v/v) at a flow rate of 0.3 mL/min. A tandem mass spectrometric detection with an electrospray ionization (ESI) interface was conducted via collision induced dissociation (CID) under negative ionization mode. The MS/MS transitions monitored were m/z 343.0448 ${\rightarrow}$ m/z 313.2017 for usnic acid and m/z 153.1024 ${\rightarrow}$ m/z 136.2136 for protocatechuic acid (internal standard). The linear range was calculated to be 2.0-160.0 ng/mL with a detection limit of 3.0 pg/mL. The inter- and intra-day accuracy and precision were within ${\pm}7.0%$. Pharmacokinetic study showed that the apartment of usnic acid in vivo confirmed to be a two compartment open model. The method was fully valid and will probably be an alternative for pharmacokinetic study of usnic acid.

• Journal of the Korean Chemical Society
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• v.54 no.5
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• pp.541-550
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• 2010

A new $N_4O_3$ heptadentate ligand, N,N'-Bis(2-hydroxybenzyl)-1,3-bis[(2-aminoethyl)amino]-2-propanol(H-BAP 4HCl)was synthesized. The hydrochloric acid salts of Br-BAP 4HCl, Cl-BAP 4HCl, $CH_3O$-BAP 4HCl and $CH_3$-BAP 4HCl containing Br-, Cl-, H-, $CH_3O-$ and $CH_{3^-}$ groups at the para-site of the phenol group of the H-BAP were synthesized. The structures of the ligands were confirmed by C. H. N. atomic analysis and $^1H$ NMR, $^{13}C$ NMR, UV-visible and mass spectra. The elemental stepwise protonation constants(${logK_n}^H$) of the synthesized $N_4O_3$ ligands showed six steps of the proton dissociation. The orders of the overall dissociation constants($log{\beta}_p$) of the ligands were Br-BAP < Cl-BAP < H-BAP < $CH_3O$-BAP < $CH_3$-BAP. The orders agreed well with that of Hammett substituent constants($\sigma_p$). The calculated stability constants($logK_{ML}$) between the ligands and transition metal ions agreed well with the order of the overall proton dissociation constants of the ligands but they showed a reverse order in Hammestt substituent constants($\sigma_p$). The order of the stability constants between the transition metal ions with the ligands were Co(II) < Ni(II) < Cu(II) > Zn(II) > Cd(II) > Pb(II).

• Mass Spectrometry Letters
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• v.6 no.1
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• pp.13-16
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• 2015

This study demonstrated the stabilizing role of a cyclodextrin on Keggin $[PW_{12}O_{40}]^{3-}$ via hydrogen bonding complexation unveiled by ESI-MS. The distinctive fragmentation pathways of the $\{PW_{12}\}/{\gamma}$-CD complexes from that of discrete $[PW_{12}O_{40}]^{3-}$ showed that the so-called "weak" non-covalent interactions can effectively change the dissociation chemistry of POM in the gas phase. The influence of different types of solvents and organic additives such as ${\gamma}$-CD on the stability of Keggin $[PW_{12}O_{40}]^{3-}$ was also addressed firstly by ESI-MS.

• Mass Spectrometry Letters
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• v.10 no.2
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• pp.50-55
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• 2019

The fragmentation statistics of ion trap CID (Collision-Induced Dissociation) spectra using 87,661 tandem mass spectra of doubly charged tryptic peptides are analyzed here. In contrast to the usual method of using intensity information, the frequency of occurrence of fragment ions, with respect to the position of the cleavage site and the residues at these sites is studied in this paper. The analysis shows that the frequency of occurrence of fragment ion peaks is more towards the middle of the peptide than its ends. It was noted that amino acid with an aromatic and basic side chain at N- & C- terminal end of the peptide stimulates more peaks at the lower end of the spectrum. The residue pair effect was shown when the amide bond occurs between acidic and basic residues. The fragmentation at these sites (D/E-H/R/K) stimulates the generation of the y-ion peak. Also, the cleavage site H-H/R/K stimulates the generation of b-ions. K-P environment in the peptide sequence has more tendency to generate y-ions than b-ions. Statistical analysis helps in the visualization of the CID fragmentation pattern. Cleavage pattern along the length of the peptide and the residue pair effects, enhance the knowledge of fragmentation behavior, which is useful for the better interpretation of tandem mass spectra.

• IMMUNE NETWORK
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• v.12 no.5
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• pp.189-195
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• 2012

It has been reported that vitamin C plays an effective role in the treatment and prevention of cancer, but its specific mechanisms are still largely unknown. The incidence of colon cancer is now increasing in Korea. Therefore, we have examined here the effect of vitamin C on the induction of the apoptosis on colon cancer and its related mechanisms. We have found that remarkable increase of the apoptosis and the calcium influx in endoplasmic reticulum (ER) in human colon cancer cell line, HCT-8. However, vitamin C-induced apoptosis was effectively inhibited by the pre-treatment of BAPTA-AM (1,2-bis(o-aminophenoxy) ethane-N,N,N',N'-tetraacetic acid), which is well-known as a calcium specific chelator. During the apoptosis, we found the increase of the translocation of Bad to mitochondria from cytosol, after releasing from 14-3-$3{\beta}$. In this process, the expression of Bax, a well-known pro-apoptotic protein, was also increased. Taken together, vitamin C induces apoptosis of colon cancer cell line, HCT-8 through the increase of 1) the calcium influx in endoplasmic reticulum (ER), 2) the translocation of Bad to mitochondria, and 3) the expression of Bax.

• Nuclear Engineering and Technology
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• v.27 no.1
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• pp.18-24
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• 1995

Characteristics of poly(vinyl alcohol)-poly(methacrylic acid) system (PVA.-PMAA system) for fixation of radioactive contaminant on sand were studied. Dissociation of carboxyl group in PMAA was found to be suppressed by PVA Permeability of sand layer treated with PVA-PMAA solution is directly proportional to the PMAA concentration when the ［PMAA］ is below 0.082 M and the empirical proportional constant (k) is -8.95$\times$10￣$^4$cm$^{5}$ /mole. The change of permeability can be explained by the formation of an intermacromolecular complex between PVA and PMAA The polymer bridge formed on a sand surface combines sand yams more firmly. The PVA-PMAA system is more effective than the PVA system for the fixation of deposited condensational radionuclides.

• Journal of the Korean Chemical Society
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• v.53 no.2
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• pp.133-136
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• 2009

We present calculations for the 4-aminopyrimidine (4AP) – HCl and –HBr complexes. We predict that the charge separated (zwitterionic) form [4AP$H^+-Cl^-$] is not stable, but that [4AP$H^+-Br^-$] is stable enough for experimental detection in gas phase at low temperatures. The latter observation is attributed to smaller dissociation energy of HBr compared with HCl, and to “solvation” of HBr by the amino group in 4AP.

• Analytical Science and Technology
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• v.10 no.4
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• pp.256-263
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• 1997

The new naphthol-containing hexadentate ligands, 1,12-bis (2-naphthol)- 2,5,8,11-tetraazadodecane 4HCl (nptr) and 1,14-bis(2-naphthol)- 2,6,9,13- tetraazatetradodecane .4HCl (npptr) were synthesized and characterized by elemental analysis, IR, NMR, and mass spectrometry. Acid dissociation constants and stability constants of Co(II), Ni(II). Cu(II), and Zn(II) complexes were determined at $25.0^{\circ}C$ and ionic strength ($\mu$)=0.10M($KNO_3$) by potentiometry. The relationship between basicity and stability constants of ligands containing aliphatic amines and 2-naphthol were studied.

• Proceedings of the Korean Society of Applied Pharmacology
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• 1996.04a
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• pp.175-175
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• 1996

The spinal dorsal horn is the area where primary afferent fibers terminate and cutaneous sensory information is Processed. A number of putative neurotransmitter substances, including excitatory and inhibitory amino acids and peptides, are present in this region and sites and cellular mechanisms of their actions have been a target of numerous studies. In this study, single neurons were acutely isolated and the properties of whole cell current and responses to excitatory and inhibitory neurotransmitters were studied by the patch clamp method. Young rats (7-14 days) were anesthetized with diethyl-ether, and the lumbar spinal cord was excised and cut transversely at a thickness of 30$\mu\textrm{m}$ by Vibroslicer. The treatment of spinal slices with low concentration of proteases (pronase and thermolysin 0.75 mg/$m\ell$) and mechanical dissociation yielded isolated neurons with near intact morphology. Multipolar, ellipsoidal and bipolar, and pyramidal cells were shown. By applying step voltage pulses to neurons held at -70 mV, two types of inward currents and one outward currents observed. The fast activating and inactivating inward current was the Na$\^$+/ current because of its fast kinetics and blocking by 0.5${\mu}$M TTX, a specific blocker of Na$\^$+/ channel. The second type of inward currents were sustained. Based on their kinetics and current-voltage relations, it was likely that the second type of inward current was the voltage-dependent Ca$\^$2+/ current. In the presence of TTX, the steady-state currents mainly represented outward K$\^$+/ current which looked like the delayed rectifier K$\^$+/ current. In addition, the membrane currents produced by agonist of excitatory amino acid (EAA) receptor and the endogenous transmitter candidate L-glutamate were recorded in isolated whole-cell voltage clamped neurons as well as responses to inhibitory amino acids (${\gamma}$-amino butyric acid, glycine). Drugs were applied by a method that allows complete exchange of the solution within 1 sec; an infinite number of solutions can be applied to a single cell.

• Journal of Life Science
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• v.24 no.12
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• pp.1378-1382
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• 2014

Phospholipase D (PLD) catalyzes the hydrolysis of phospholipid to phosphatidic acid (PA), a lipid secondary messenger. Two forms of PLD isozymes, phosphatidylcholine-specific PLD1 and PLD2, have been identified. PLD has emerged as a critical regulator of cell proliferation and survival signaling, and dysregulation of PLD occurs in a various illnesses, including cancer. PLD activity is essential for cell survival and protection from apoptosis. Overexpression of PLD isozymes or PLD-generated PA attenuates the expression of apoptotic genes and confers resistance to apoptosis. The apoptosis-related molecular mechanisms of PLD remain largely unknown. Recently, the dynamics of PLD turnover during apoptosis have been reported. The cleavage of PLD isozymes as specific substrates of caspase differentially regulates apoptosis. PLD1 is cleaved at one internal site, and PLD2 is cleaved two sites at the front of the N-terminus. The cleavage of PLD1 reduces its enzymatic activity, probably via the dissociation of two catalytic motifs, whereas the cleavage of PLD2 does not affect the catalytic motifs and its activity. Thus, PLD2 maintains antiapoptotic capacity, despite its cleavage. Therefore, the differential cleavage pattern of PLD isozymes by caspase affects its enzymatic activity and antiapoptotic function. Thus, PLD is considered a potential target for cancer therapy. We summarize recent studies regarding the functional role of PLD in apoptosis.