Biomedical subjects

Sung Kuk Kim

Publications and source records attributed to Sung Kuk Kim.

13 recordsLinked to original sources

PubMed2007

A color version of the Hinsberg test: 1 degrees -3 degrees amine indicator.

The Hinsberg test to recognize the type of amine (1 degrees -3 degrees amines), which has been established for more than 100 years and well documented in textbooks, is not possible without conducting complicated organic reactions. We report for the first time unique chemosensors that are capable of showing selective color changes toward 1 degrees -3 degrees amines as a color version of the Hinsberg test. This simple and straightforward qualitative analysis, using the synthesized novel compounds herein, can be considered a new innovative tool for discriminating 1 degrees -3 degrees amines as an alternative to the historical Hinsberg test.

Amines↗

PubMed2006

Metal ion sensing novel calix[4]crown fluoroionophore with a two-photon absorption property.

1,3-Alternate calix[4]arene-based fluorescent chemosensors bearing two-photon absorbing chromophores have been synthesized, and their sensing behaviors toward metal ions were investigated via absorption band shifts as well as one- and two-photon fluorescence changes. Free ligands absorb the light at 461 nm and weakly emit their fluorescence at 600 nm when excited by UV-vis radiation at 461 nm, but no two-photon excited fluorescence is emitted by excitation at 780 nm. Addition of an Al(3+) or Pb(2+) ion to a solution of the ligand causes a blue-shifted absorption and enhanced fluorescence due to a declined resonance energy transfer (RET) upon excitation by one- and two-photon processes. Addition of a Pb(2+) ion to a solution of 1.K(+) results in a higher fluorescence intensity than the original 1.Pb(2+) complex regardless of one- or two-photon excitation, due to the allosteric effect induced by the complexation of K(+) with a crown loop.

Calixarenes↗

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

Pleckstrin homology domain of phospholipase C-gamma1 directly binds to 68-kDa neurofilament light chain.

Phosphoinositide-specific phospholipase C-gamma1 (PLC-gamma1) has two pleckstrin homology (PH) domains: an amino-terminal domain (PH1) and a split PH domain (PH2). Here, we show that overlay assay of bovine brain tubulin pool with glutathione-S-transferase (GST)-PLC-gamma1 PH domain fusion proteins, followed by matrix-assisted laser-desorption ionization-time of flight mass spectrometry (MALDI-TOF MS), identified 68-kDa neurofilament light chain (NF-L) as a binding protein of amino-terminal PH domain of PLC-gamma1. NF-L is known as a component of neuronal intermediate filaments, which are responsible for supporting the structure of myelinated axons in neuron. PLC-gamma1 and NF-L colocalized in the neurite in PC12 cells upon nerve growth factor stimulation. In vitro binding assay and immunoprecipitation analysis also showed a specific interaction of both proteins in differentiated PC12 cells. The phosphatidylinositol 4, 5-bisphosphate [PI(4,5)P(2)] hydrolyzing activity of PLC-gamma1 was slightly decreased in the presence of purified NF-L in vitro, suggesting that NF-L inhibits PLC-gamma1. Our results suggest that PLC-gamma1-associated NF-L sequesters the phospholipid from the PH domain of PLC-gamma1.

Amino Acid Sequence↗

PubMed2005

Fluorescence ratiometry of monomer/excimer emissions in a space-through PET system.

[Reaction: see text]. Fluorogenic calix[4]arenes (1 and 2) bearing a pendent ethyleneamine on their triazacrown rings, respectively, were synthesized in the cone conformation. Compared with 4, free 1 and 2 display a relatively weak emission, reflecting that a PET process from the pendent amine group (-CH2CH2NH2) to the fluorogenic pyrenes is mainly operated. Addition of various metal ions or anions to the solution of 1 or 2 reduces the PET because the pendent alkylamine takes part in the complexation, causing their fluorescence spectra to be changed. When Pb2+, a quenching metal ion, is added to 1 or 2, their pyrene monomer emission is enhanced with their excimer emission quenched, which is due to conformational changes of the facing carbonyl groups as well as to the participation of the ethyleneamine into the three-dimensional Pb2+ ion encapsulation. In contrast, upon addition of alkali metal ions to the 1 and 2, both monomer and excimer emissions are observed to increase, which is attributable to the CHEF effect and the retained conformations. For anion sensing, both 1 and 2 show a high selectivity for F- ions over other anions tested. When the F- ion is bound to 1 or 2 by hydrogen bonding between the amide NH of the triazacrown ring and F-, both their monomer and excimer emissions are weakened due to PET from the bound F- to the pyrene units.

Calixarenes↗

PubMed2005

Indium(III)-induced fluorescent excimer formation and extinction in calix[4]arene-fluoroionophores.

New fluorogenic or/and chromogenic calix[4]arenes 1-3 with two facing amide groups linked to fluorescent pyrene units are synthesized. Orientations of the pyrene units are remote from each other in 1 and face-to-face pi-stacked in 2, which produces different photophysical properties. In the excited state, the two pyrene units of 2 form a strong intramolecular excimer displaying an emission at 472 nm with a relatively weak monomer emission at 395 nm. In contrast, 1 exhibits only a monomer emission at 398 nm because intramolecular hydrogen bonding between the phenolic OH oxygens and the amide hydrogens prevents pi-stacking of the two pyrene groups. Fluorescence changes upon addition of various metal ions show that 1 has a remarkably high selectivity for In(3+) over the other metal ions tested. Compound 1 forms 2:1 (metal:ligand), as well as 1:1 complexes, with In(3+), with fluorescence varying uniquely with the complex stoichiometry. Compound 3, which possess two pyrene units and two chromogenic azo groups, shows almost the same binding behavior toward metal ions as does 1, together with additional bathochromic shifts of the absorption maximum. Compared with 1, compound 3 emits a considerably weaker fluorescence, which is attributed to electron transfer from the pyrene units to the nitro groups of the phenylazo moieties.

Calixarenes↗

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

Two organometallic fragments inclusioned in a 1,3-alternate calix[4]arene tetraphosphane: evidence for transition metal-arene interaction through the cavity.

The preparation of an 1,3-alternate calix[4]arene tetraphosphane ligand, 25,26,27,28-tetrakis{2-(diphenylphosphino)ethoxy}calix[4]arene (4), is described. Ligand 4 is obtained in four steps in 17% overall yield. Reaction of 4 with AgBF4 produced the encapsulated two silver complex [Ag2{(P,P,P,P)-tetraphencalix[4]arene}](BF4)2. The solid-state structure shows that the encapsulated silver undergoes a substantial pi-interaction by two opposite arene rings. Rhodation of 4 employing [Rh(cot)2]BF4 yielded the encapsulated complex with a bent coordination mode. Two organometallic fragments inclusioned inside a 1,3-alternate calix[4]arene tetraphosphane was also achieved by the reaction of 4 with [PtH(PPh3)2 (thf)]+. Full characterization includes X-ray structural studies of compounds 4-6.

Journal Article↗

PubMed2005

Bifunctional fluorescent calix[4]arene chemosensor for both a cation and an anion.

[reaction: see text] A new fluorogenic cone calix[4]triazacrown-5 (1) bearing two pyrene amide groups and its structural analogue 2 have been prepared. Excited at 343 nm, 1 and 2 reveal excimer emissions at 448 and 472 nm, respectively. When heavy metal ions such as Pb(2+) and Co(2+) are bound to 1, the fluorescence intensities of both monomer and excimer are quenched whereas H bonding-assisted F(-) binding to 1 gives rise to a quenched monomer emission with little excimer emission change.

Journal Article↗

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

Silver ion shuttling in the trimer-mimic thiacalix[4]crown tube.

Novel 1,3-alternate calix-thiacalix[4]crown trimers bearing crown-5 and crown-6 were prepared. As proven by X-ray diffraction, in a 1:2 mole ratio of ligand to metal ion, the Cs(+) and K(+) ions prefer to be encapsulated in the trimeric thiacalix[4]crown-6 and crown-5, respectively. On the contrary, the Ag(+) ion was found to be entrapped in the central thiacalix spacer as a 1:1 complex confirmed by (1)H NMR spectrosocpy. Variable-temperature (1)H NMR studies for the trimeric thiacalix[4]crown-6 encapsulating the silver ion revealed that the Ag(+) ion oscillates through the central thiacalix spacer with the aid of cation-pi interactions.

Journal Article↗

PubMed2003

Rapid metal ions shuttling through 1,3-alternate Thiacalix[4]crown tubes.

Several new thiacalix[4]monocrown and thiacalix[4]biscrown compounds were synthesized. Their metal ion extractabilities are found to be lower than those of conventional calix[4]crowns. By use of X-ray crystal structures and (1)H NMR spectroscopy, this result is explained by weaker electrostatic interactions of the polyether ring oxygen atoms with the metal ions and diminished pi-metal ion interactions between the metal ions and the aromatic rings of the thiacalix[4]crowns. Temperature-dependent (1)H NMR spectroscopic measurements reveal coalescence temperatures T(c)(intra) and T(c)(inter) for metal ion exchange. In one case, this exchange was rationalized as metal ion shuttling through a thiacalix[4]biscrown tube. Since the metal ions are less tightly complexed by the polyether units in thiacalix[4]biscrowns than in conventional calix[4]biscrowns, more facile metal ion exchange between the two polyether units takes place in the former.

Journal Article↗

PubMed2003

Molecular taekwondo. 2. A new calix[4]azacrown bearing two different binding sites as a new fluorescent ionophore.

Synthesis and binding studies of a new calixarene-based fluoroionophore were made. Calix[4]azacrown having an anthracenyl unit displayed large chelation-enhanced fluorescence effects with Cs(+), Rb(+), and K(+) over other metal ion tested. Interesting "molecular taekwondo" processes between Cs(+)-Cu(2+) and Cs(+)-Ag(+) pairs were monitored via fluorescent changes.

Journal Article↗