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Jin Yong Lee

Publications and source records attributed to Jin Yong Lee.

At least 19 recordsLinked to original sources
PubMed2006

Fluoride-sensing calix-luminophores based on regioselective binding.

Bifunctional (fluorescence and visible light absorption) anion-sensing compounds 1 and 2 based on calix[4]arene platform with 4-nitrophenylazo and pyrene moieties have been developed. The two NHs of the amide groups of 1 bind the fluoride anion through the H-bonding. This changes the characteristic excimer emission and forms a new emission peak from a static excimer. In 2, two OHs bind the fluoride anion, and this changes the characteristic absorption spectrum. The DFT calculation supports the regioselective binding of the fluoride anion, which is responsible for the different sensing property.

Calixarenes↗
PubMed2006

Conformational equilibrium of 1,2-dichloroethane in water: comparison of PCM and RISM-SCF methods.

The RISM-SCF and polarizable continuum model (PCM) approaches have been applied to study the conformational equilibrium of 1,2-dichloroethane (DCE) in water. Both the electron correlation effect and basis sets play an important role in the relative energies of the gauche and trans conformers in gas and solution phases. Both PCM and RISM-MP2 methods resulted in a consistent trend with the previous experimental and theoretical studies that the population of the gauche conformer increases in going from the gas phase to the aqueous solution. However, the PCM treatment could not describe the solvent effect completely in that the sign of the relative free energy of the gauche and trans forms is opposite to the most recent experimental and theoretical data, while the RISM-MP2 gives the right sign in the free energy difference. We found that the larger excess chemical potential gain (by ca. -4.1 kcal/mol) for the gauche conformer is large enough to result in the gauche preference of DCE in water, though it has to compensate for more solute reorganization energy (approximately 1.6 kcal/mol) and overcome the energy difference (approximately 1.6 kcal/mol) in the gas phase. The radial distribution functions between DCE and the nearest water shows that the electrostatic repulsion between chlorine and oxygen atoms is higher in the trans conformer than in the gauche one, while the attractive interaction between chlorine and hydrogen of water is higher in the gauche conformer.

Ethylene Dichlorides↗
PubMed2006

Conformations and electronic structures of axially coordinated fullerene-porphyrin-fullerene triad (C60CHCOO)2-Sn(IV) porphyrin.

The conformational (cis and trans) stability and electronic structures of (C(60)CHCOO)(2)-Sn(IV) porphyrin, recently synthesized as a novel fullerene-porphyrin-fullerene triad linked by metal axial coordination, have been studied by ab initio calculations. The cis conformer was found to be slightly more stable than the trans by 1.38 kcal/mol in the neutral compound. Upon the addition of an electron to the triad, the relative stability of the cis conformer was found to be higher (3.29 kcal/mol) than that in the neutral one. From the investigation of frontier molecular orbitals, for the cis conformer, it was found that the electrons are localized in HOMO of the porphyrin, while the electrons are localized in LUMO of the syn-fullerene. For the trans conformer, it was found that the electrons are localized in HOMO of the porphyrin, while the electrons are localized in LUMO of one of the two fullerene moieties, and the electrons are localized in LUMO2 of the other fullerene moiety, but the LUMO and LUMO2 have the same orbital energy. Thus, the PET may take place unidirectionally in the cis conformer from the porphyrin to the syn-fullerene, while it is bidirectional from the porphyrin to both of the fullerene moieties.

Electron Transport↗
PubMed2006

[Differences in medical care utilization rates of the disabled and the non-disabled with ambulatory care sensitive conditions].

OBJECTIVES: The purpose of this study was to determine whether the disabled have worse access to primary care than the non-disabled. METHODS: We used the National Disability Registry data and the National Health Insurance data for the calendar year 2003, and we analyzed 807,380 disabled persons who had been registered until December 2001 and we also analyzed 1,614,760 non-disabled persons for nine ambulatory care sensitive conditions (ACSCs). The rates of physician visits and hospitalizations for the patients with ACSCs were compared between the disabled and the non-disabled. Multiple logistic regression analysis was used to evaluate the association between medical care utilization and disability and to assess the association between hospitalization and the number of physician visits while controlling for potential confounders. RESULTS: The numbers of physician visits per 100 patients were 0.78-0.97 times lower for the disabled than that for the non-disabled with five of nine ACSCs. The numbers of hospitalizations per 100 patients were 1.16-1.77 times higher for the disabled than that for the non-disabled with all the ACSCs. While the ORs of a physician visit for the disabled were significantly lower than that for the non-disabled with all the ACSCs (OR: 0.44-0.70), and the ORs of hospitalization for the disabled were significantly higher (OR: 1.16-1.89). The lower physician visit group (number of physician visits < or =1) was more likely to be hospitalized than the higher physician visit group (number of physician visits > or =2) (OR: 1.69-19.77). The effect of the physician visit rate on hospitalization was larger than the effect of disability on hospitalization. CONCLUSIONS: The results suggest that the disabled were more likely to be hospitalized for ACSCs due to their lower access to primary care.

Adolescent↗
PubMed2005

Self-assembly of rectangles and prisms via a molecular "clip".

Aromatic molecular "clips" bearing two symmetrically bound platinum moieties have been prepared. The molecular "clip" 4 readily self-assembled with linear linkers such as 4,4'-bipyridyl, 1,4-bis[2-(4-isocyano-3,5-diisopropylphenyl)ethynyl]benzene, and nicotinic acid to form molecular rectangles. The overall dimensions of the rectangle 7 were 7.3 Angstroms x 15.3 Angstroms. The molecular "clip" also self-assembled with tritopic pyridyl and isocyanide ligands to form trigonal prismatic frameworks. The characterization of the supramolecules by multinuclear NMR, electrospray mass spectrometry, and X-ray crystal structures is also reported.

Journal Article↗
PubMed2005

A fluoride-selective PCT chemosensor based on formation of a static pyrene excimer.

[reaction: see text] Calixarene-based fluorescent chemosensor 1 with two fluorogenic pyrene units conjugated to amide groups as guest recognition sites is synthesized. Complexation of F(-) by 1 causes a red shift of its absorption band to 400 nm (Deltalambda = 54 nm) and a blue shift of the excimer emission to 470 nm (Deltalambda = 12 nm) together with enhanced fluorescence intensity. The blue-shifted excimer emission is attributed to a pyrene dimer formed in the ground state, a so-called static excimer.

Calixarenes↗
PubMed2005

Complexation of ferrocene derivatives by the cucurbit[7]uril host: a comparative study of the cucurbituril and cyclodextrin host families.

The formation of inclusion complexes between cucurbit[7]uril (CB[7]) and ferrocene and its derivatives has been investigated. The X-ray crystal structure of the 1:1 inclusion complex between ferrocene and CB[7] revealed that the guest molecule resides in the host cavity with two different orientations. Inclusion of a set of five water-soluble ferrocene derivatives in CB[7] was investigated by 1H NMR spectroscopy and calorimetric and voltammetric techniques. Our data indicate that all neutral and cationic guests form highly stable inclusion complexes with CB[7], with binding constants in the 10(9)-10(10) M(-)(1) and 10(12)-10(13) M(-1) ranges, respectively. However, the anionic ferrocenecarboxylate, the only negatively charged guest among those surveyed, was not bound by CB[7] at all. These results are in sharp contrast to the known binding behavior of the same guests to beta-cyclodextrin (beta-CD), since all the guests form stable inclusion complexes with beta-CD, with binding constants in the range 10(3)-10(4) M(-1). The electrostatic surface potentials of CB[6], CB[7], and CB[8] and their size-equivalent CDs were calculated and compared. The CD portals and cavities exhibit low surface potential values, whereas the regions around the carbonyl oxygens in CBs are significantly negative, which explains the strong affinity of CBs for positively charged guests and also provides a rationalization for the rejection of anionic guests. Taken together, our data suggest that cucurbiturils may form very stable complexes. However, the host-guest interactions are very sensitive to some structural features, such as a negatively charged carboxylate group attached to the ferrocene residue, which may completely disrupt the stability of the complexes.

Bridged-Ring Compounds↗
PubMed2005

Role of molecular orbitals of the benzene in electronic nanodevices.

In an effort to examine the intricacies of electronic nanodevices, we present an atomistic description of the electronic transport properties of an isolated benzene molecule. We have carried out ab initio calculations to understand the modulation of the molecular orbitals (MOs) and their energy spectra under the external electric field, and conducting behavior of the benzene molecule. Our study shows that with an increase in the applied electric field, the energy of the third lowest unoccupied molecular orbital (LUMO) of benzene decreases, while the first and second LUMO energies are not affected. Above a certain threshold of the external electric field, the third LUMO is lowered below the original LUMO and becomes the real LUMO. Since the transport through a molecule is to a large extent mediated by the molecular orbitals, the change in MOs can lead to a dramatic increase in the current passing through the benzene molecule. Thus, in the course of this study, we show that the modulation of the molecular orbitals in the presence of a tuning parameter(s) such as the external electric field can play important roles in the operation of molecular devices. We believe that this understanding would be helpful in the design of electronic nanodevices.

Journal Article↗
PubMed2005

Stacking effect of polyfluorene on the chemical shift and electron transport.

We investigate the structures, NMR chemical shifts, absorption spectra, frontier molecular orbitals, and transition density matrices of pi-stacked polyfluorenes by ab initio calculations. For F1-F4, we consider two different conformations, syn and anti. The simulated 1H NMR chemical shifts are in good agreement with the previous experiment, and the significantly upfielded chemical shifts explain that the fluorene moieties are stacked on each other. It is found that the relative stability for syn and anti conformers is almost equivalent in B3LYP calculations; however, the syn conformer becomes much more stable than the anti conformer in MP2 calculations, which is consistent with the experimental finding that only the syn conformers are relevant. The vertical detachment energy, which is linearly proportional to the ionization potential, shows the same size dependence as the previous experiment. The electron attachment energy decreases exponentially as the size increases, which implies that the electron transport would be possible even for long chains such as F3 and F4. This was evident from the frontier molecular orbitals (HOMO and LUMO). Also, it is found that the syn conformers are very favorable for electron transport through the pi-stacked fluorene moieties.

Biophysics↗
PubMed2005

[Estimating the burden of diseases due to high alcohol consumption in Korea].

OBJECTIVES: This study estimated the burden of disease due to high alcohol consumption using DALY, a composite indicator recently developed by the Global Burden of Disease study group. The results were analyzed by age and sex. METHODS: Firstly, high alcohol consumption-related diseases, and their relative risk (RR), were selected. Secondly, population attributable fractions (PAFs) were computed using formulae, including the relative risk (RR) and prevalence of exposure (Pe). Thirdly, the DALYs of high alcohol consumption-related diseases were estimated. Lastly, the attributable burdens of diseases due to high alcohol consumption wereconcluded as being the sum of the products that multiplied the DALYs of high alcohol consumption-related diseases by their population attributable fraction (PAF). RESULTS: The burden of high alcohol consumption in Korea was 2992.3 person years (PYs) per 100,000 persons in men, and 1426.6 in women. For men, the high alcohol consumption-induced diseases with the five biggest burdens were liver cirrhosis, hypertensive disease, liver cancer, cerebral infarction and intracerebral hemorrhage. For women, these were cerebral infarction, intracerebral hemorrhage, hypertensive disease, liver cirrhosis and liver cancer. CONCLUSION: This study highlighted the attributable fraction of diseases due to exposure to high alcohol consumption, by quantifying the results of exposure to risk factors. Therefore, it is now possible to assess interventions for risk factors in quantifiable terms in each population. Finally, measuring the risk factor burdens was expected to contribute to priority setting and effective resource allocation in public health policy.

Adult↗
PubMed2004

An excimer-based, binuclear, on-off switchable calix[4]crown chemosensor.

A new fluorescent chemosensor with two different types of cation binding sites on the lower rims of a 1,3-alternate calix[4]arene (1) is synthesized. Two pyrene moieties linked to a cation recognition unit composed of two amide groups form a strong excimer in solution. For 1, the excimer fluorescence is quenched by Pb2+, but revived by addition of K+ to the Pb2+ ligand complex. Thus, metal ion exchange produces an on-off switchable, fluorescent chemosensor. Computational results show that the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbitals (LUMO) of the two pyrene moieties interact under UV irradiation of 1 and its K+ complex, while such HOMO-LUMO interactions are absent in the Pb2+ complex.

Calixarenes↗
PubMed2004

Experimental and theoretical study on the olefin metathesis of alkenyl Baylis-Hillman adducts using second-generation Grubbs catalyst.

[reaction: see text] We have investigated the olefin metathesis from alkenyl Baylis-Hillman adducts using second-generation Grubbs catalyst. In the experiment, the ring-closing metathesis (RCM) product could not be found, while the cross-metathesis (CM) products were found. The computational studies provided consistent explanations for the experimental result. The most limiting factor for the RCM process using second-generation Grubbs catalyst is caused by the high strain and steric effect in the metallacyclobutane intermediates.

Journal Article↗
PubMed2004

Hydrogen bonding patterns of calix[4]arenes with thiourea functionalities in solution and in the solid state.

[structure: see text] We have synthesized a number of calix[4]arene derivatives presenting thiourea functional groups at their upper rims by the condensation of a 1,3-di(p-amino)calix[4]arene with alkyl isothiocyanates. Mono- and dithiourea-substituted calix[4]arenes were prepared selectively in good yields, and homocoupling of the former led to calix[4]arene dimers with a thiourea linker. X-ray crystallography revealed interesting intra- and intermolecular hydrogen bonding patterns. (1)H NMR data and computational studies also provided some insight into the hydrogen bonding patterns.

Calixarenes↗
PubMed2004

Efficient fluoride-selective fluorescent host: experiment and theory.

A new naphthalene derivative containing a urea group at the 1,8-position of naphthalene was synthesized and showed a unique absorption and fluorescence peak with fluoride ion. Calculations suggested that a new peak was attributed to the increased anionic character of urea nitrogen due to the strongly charged hydrogen bonding between fluoride and amide protons of the urea. The fluoride selectivity among halides (F(-), Cl(-), Br(-)) comes from the fact that the fluoride approaches much closer to the amide protons than other halides and resides in the cavity with fast dynamics. The nature of electronic transitions that were analyzed from the calculations by the collective electronic oscillator method also supports the anionic nature of the complex between host and fluoride.

Journal Article↗
PubMed2004

Early and late hormonal responses to the microdose gonadotropin-releasing hormone agonist in normal menstruating women.

OBJECTIVE: To assess the effect of a microdose gonadotropin-releasing hormone (GnRH) agonist on the LH, FSH, and E2 secretion in normal menstruating women. DESIGN: Prospective study. SETTING: Tertiary teaching hospital. PATIENT(S): Five normal menstruating women. INTERVENTION(S): Five microg of triptorelin was injected daily in 5 women for 7 days beginning from the cycle day 3. In the next cycle, the same amount of triptorelin was injected into the same women daily for 3 days. MAIN OUTCOME MEASURE(S): Serial serum FSH, LH, and E2 levels. RESULT(S): The FSH levels peaked (27.53 +/- 6.34 IU/L) after 5 hours, and the LH levels peaked (34.35 +/- 7.81 IU/L) by 4 hours. The increased gonadotropin levels persisted even after the second and third day of the GnRH-agonist injections, although the peak levels were not as high as observed with the first injection (19.56 IU/L in the second day, 9.15 IU/L in the third day for FSH; 32.18 IU/L in the second day, 13.59 IU/L in the third day for LH). The down-regulation of gonadotropins was established in 4 days. When the GnRH-agonist was administered for 7 days, the E2 level began to increase 6 days after the last injection. When the GnRH-agonist was administered for 3 days, the E2 level began to increase 3 days after the last injection. CONCLUSION(S): Pituitary down-regulation could be achieved even with a microdose of GnRH agonist. The increased level of gonadotropins persisted for 3 days at this dose. The duration of the down-regulation was influenced by the duration of GnRH-agonist administration.

Adult↗
PubMed2003

The clinical efficacy and efficiency of a 100-IU starting dose of recombinant follicle stimulating hormone (Puregon) in Korean women undergoing in vitro fertilization and embryo transfer.

AIM: A prospective, non-comparative study was conducted to evaluate the efficacy and efficiency of a starting dose of 100 IU recombinant follicle stimulating hormone (rhFSH, Puregon) in women undergoing ovarian stimulation prior to in vitro fertilization (IVF). METHODS: A total of 40 women were down-regulated with gonadotropin releasing hormone agonist (long protocol), then treated with a fixed dose of 100 IU rhFSH for the first 4 days, and the dose of gonadotropin administration was adjusted according to patient's response thereafter. A maximum number of 3 embryos were transferred in 32 patients. RESULTS: Nine patients were treated with intracytoplasmic sperm injection, and 24 with conventional IVF. The duration of stimulation was 10.8 +/- 1.8 days, serum estradiol concentration on human chorionic gonadotropin day was 1693.0 +/- 1651.2 pg/mL, and 1480 +/- 450 IU rhFSH was used. A mean number of 8.4 +/- 5.7 oocytes were retrieved, 4.9 +/- 4.3 embryos obtained, 2.4 +/- 0.9 embryos transferred, and 3.5 +/- 3.2 embryos cryopreserved. The proportion of mature oocytes was 71.6%, and the fertilization rate was 86.4%. Clinical pregnancy was achieved in 8 patients (25.0%), and all of these pregnancies are ongoing or delivered. There were 3 cases of twin gestations (37.5%). The implantation rate was 13.1% (11/84). There was one case of moderate ovarian hyperstimulation syndrome, however, the patient recovered within 7 days without any complications. CONCLUSION: The starting dose of 100 IU rhFSH has a good safety profile, and is adequate in controlled ovarian hyperstimulation for IVF with a small amount of gonadotropin administered.

Adult↗
PubMed2003

Association between vitamin D receptor gene haplotypes and bone mass in postmenopausal Korean women.

OBJECTIVES: The objective of the study was to evaluate the effect of vitamin D receptor (VDR) gene haplotypes on bone mineral density (BMD). STUDY DESIGN: The VDR Bsm I, Apa I, Taq I, and poly(A) polymorphisms were analyzed in 417 postmenopausal Korean women. Serum 1,25(OH)(2) vitamin D(3), osteocalcin, bone alkaline phosphatase, and CrossLaps were measured by immunoradiometric assay and enzyme-linked immunosorbent assay. BMD at the lumbar spine and proximal femur was determined by dual-energy x-ray absorptiometry. RESULTS: At all skeletal sites, genotypes not carrying the baTL haplotype allele (uppercase letters signifying the absence, lowercase letters the presence, of the restriction site, and L a repeat length of more than 17) had significantly lower BMD than baTL homozygotes. The former genotypes were more prevalent in women with low bone mass than in healthy women. No significant differences in vitamin D(3) or bone markers levels were noted among the baTL haplotype genotypes. CONCLUSION: The VDR baTL haplotype allele is related to bone mass in Korean women.

Aged↗