• Macromolecular Research
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• 제8권3호
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• pp.103-115
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• 2000

The structural changes viewed from the molecular level have been investigated for the isothermal crystallization phenomena of polyethylene (PE) and the solvent-induced crystallization phenomenon of syndiotactic polystyrene (sPS) glassy sample. The data, which were collected by the time-resolved measurements of Fourier-transform infrared spectra, Raman spectra, synchrotron-sourced small-angle X-ray scattering, wide-angle X-ray scattering, and so on, were combined together to extract the detailed structural information in these phase transition phenomena. In the case of PE, the isothermal crystallization from the melt to the orthorhombic form was found to occur via the conformationally-disordered trans chain form, followed by the formation of the lamellar stacking structure of regular orthorhombic-type crystals. In the case of sPS, the amorphous chains in the glassy sample were found to enhance the mobility through the interaction with the injected solvent molecules, which act as a trigger to cause the conformational ordering from the random coil to the regular T$_2$G$_2$-type helical form. The thus created short helical segments were found to grow into longer helices, which gathered together to form the crystallites, as revealed by the organized coupling of the infrared, Raman and X-ray scattering data.

• Journal of Microbiology and Biotechnology
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• 제30권5호
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• pp.633-641
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• 2020

Microbial rhodopsins are a superfamily of photoactive membrane proteins with the covalently bound retinal cofactor. Isomerization of the retinal chromophore upon absorption of a photon triggers conformational changes of the protein to function as ion pumps or sensors. After the discovery of proteorhodopsin in an uncultivated γ-proteobacterium, light-activated proton pumps have been widely detected among marine bacteria and, together with chlorophyll-based photosynthesis, are considered as an important axis responsible for primary production in the biosphere. Rhodopsins and related proteins show a high level of phylogenetic diversity; we focus on a specific class of bacterial rhodopsins containing the '3 omega motif.' This motif forms a stack of three non-consecutive aromatic amino acids that correlates with the B-C loop orientation and is shared among the phylogenetically close ion pumps such as the NDQ motif-containing sodium-pumping rhodopsin, the NTQ motif-containing chloride-pumping rhodopsin, and some proton-pumping rhodopsins including xanthorhodopsin. Here, we reviewed the recent research progress on these 'omega rhodopsins,' and speculated on their evolutionary origin of functional diversity.

• Applied Microscopy
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• 제19권2호
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• pp.43-58
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• 1989

To investigate the effects of hexavalent chromium on mitochondrial respiration of rat kidney, various hexavalent chromium concentrations were treated, then respiration and electron transfer enzyme activities were measured. Ultrastructural changes at state IV respiration of mitochondria were also observed. Then, to investigate protective role against hexavalent chromium in the body, low-molecular-weight, chromium-binding substances (LMCr) were purified from livers of rabbits 2hr after intravenously administrated with sodium dichromate at a dose of 74mg per kg body weight. And then, respiration rates of mitochondria treated with LMCr, hexavalent chromium containing 0.7mM chromium were measured. Hexavalent chromium decreased state IV respiration rates and electron transfer enzyme activities of mitochondria, and increased labile membrane and swelling. And partial inhibitions of condensed to orthodox conformational change were observed. Respiration rates of mitochondria treated with LMCr containing 0.7mM chromium did not differ from that of the non-treated mitochondria. But respiration rates of 0.7mM hexavalent chromium-treated mitochondria decreased by 42%, compared to non-treated mitochondria. These results suggest that LMCr may play an important role in detoxification of toxic hexavalent chromium.

• 한국응용약물학회:학술대회논문집
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• 한국응용약물학회 2008년도 Proceedings of the Convention
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• pp.89-99
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• 2008

GPCRs are large families of cell surface receptors that transmit signals through conformational changes upon ligand activation and an interaction with the heterotrimeric G-proteins. GPCRs regulate the cell-signaling pathways and participate in the regulation of physiological processes through the G-proteins defined by their ${\alpha}$ subunits. A family of 20 G protein-coupled receptors (GPCRs) that provide a large class of tractable drug targets for new anti-inflammatory drugs and, in certain instances, for the treatment of the inflammatory indications such as atherosclerosis, rhinitis, asthma, pulmonary disease and arthritis. In view of the important findings showing that $G{\alpha}_{12}/G{\alpha}_{13}$ regulate the various cellular processes such as actin-stress fiber formation, neurite retraction, platelet aggregation, gene induction, and apoptosis, we became interested in whether, after coupling to the activated GPCRs, the G-proteins and their downstream molecules might be involved in the pathologic processes of chronic inflammatory diseases (e.g., liver fibrosis). In this symposium, the possible link of the G-proteins with the pathophysiology will be discussed with the aim of finding potential new drug targets.

• Bulletin of the Korean Chemical Society
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• 제29권2호
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• pp.377-380
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• 2008

Ground state structures and ring flipping transition states of eight- and seven-membered silicon containing heterocyclic compounds such as dithienodisilacyclooctatriene and oxadithienodisilacycloheptadiene derivatives, respectively have theoretically been investigated. Although the bithienylene moiety of the derivatives does not change the ground state structures, they significantly increase the ring flipping barrier by 13-17 kcal/mol in the case of the eight-membered rings (2, 3, and 4) in comparison with that of silicon containing heterocyclic compound 6, chosen as a model. The same moiety increases the flipping barrier of seven-membered ring (5) is only slightly (3.3 kcal/mol) in comparison with that of model compound 7. Hence, it has been concluded that not only the existing ring strain of eight-membered ring but also the bithienylene moiety collectively increases the ring flipping barrier so as to prevent such conformational changes explaining anomalous NMR behaviour of dithienodisilacyclooctatriene derivatives (2-4). In contrast, the effect of substituents R1 and R2 at the olefinic carbons of the eight-membered ring on the flipping barrier turned out to be mild.

• Molecules and Cells
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• 제19권1호
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• pp.124-130
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• 2005

Protein kinase CKII is composed of two catalytic (${\alpha}$ or ${\alpha}^{\prime}$) subunits and two regulatory (${\beta}$) subunits. The ${\beta}$ subunit mediates tetramer formation through ${\beta}-{\beta}$ homodimerization and ${\alpha}-{\beta}$ heterodimerization. In a previous study R26 and R75, point mutants of $CKII{\beta}$ defective in ${\beta}-{\beta}$ dimerization, were isolated. In the present work we characterized these $CKII{\beta}$ mutants in vitro. Purified R26 and R75 bound to $CKII{\alpha}$ but were defective in binding to $CKII{\beta}$. R75 stimulated the catalytic activity of CKII whereas R26 gave little stimulation, and poly-L-lysine increased the stimulation of catalytic activity by R26 or R75. Circular dichroism and intrinsic fluorescence data pointed to different conformational changes in R26 and R75. Molecular modeling of these mutants provides an explanation of the difference in their ability to interact with $CKII{\beta}$ and to activate $CKII{\alpha}$.

• Molecules and Cells
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• 제43권8호
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• pp.705-717
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• 2020

While the growth factors like insulin initiate a signaling cascade to induce conformational changes in the mechanistic target of rapamycin complex 1 (mTORC1), amino acids cause the complex to localize to the site of activation, the lysosome. The precise mechanism of how mTORC1 moves in and out of the lysosome is yet to be elucidated in detail. Here we report that microtubules and the motor protein KIF11 are required for the proper dissociation of mTORC1 from the lysosome upon amino acid scarcity. When microtubules are disrupted or KIF11 is knocked down, we observe that mTORC1 localizes to the lysosome even in the amino acid-starved situation where it should be dispersed in the cytosol, causing an elevated mTORC1 activity. Moreover, in the mechanistic perspective, we discover that mTORC1 interacts with KIF11 on the motor domain of KIF11, enabling the complex to move out of the lysosome along microtubules. Our results suggest not only a novel way of the regulation regarding amino acid availability for mTORC1, but also a new role of KIF11 and microtubules in mTOR signaling.

• 한국생물물리학회:학술대회논문집
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• 한국생물물리학회 2003년도 정기총회 및 학술발표회
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• pp.74-74
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• 2003

We report here the results on N-acetyl-N'-methylamide of oxazolidine (Ac-Oxa-NHMe) calculated using the ab initio molecular orbital method with the self-consistent reaction field (SCRF) theory at the HF level of theory with the 6-3l+G(d) basis set. The displacement of the $\square$-CH$_2$ group in proline ring by oxygen atom has affected the structure of proline, cis$\^$∼/ trans equilibrium, and rotational barrier. The up-puckered structure is found to be prevalent for the trans conformers of the Oxa amide. The higher cis populations of the Oxa amide can be interpreted due to the longer distance between the acetyl methyl group and the 5-methylene group of the ring for the trans conformer of the Oxa amide than that of the Pro amide. The changes in charge of the prolyl nitrogen and the decrease in electron overlap of the C$\^$∼/ N bond for TS structures seem to play a role in lowering rotational barriers of the Oxa amide compared to that of the Pro amide. The calculated preferences for cis conformers in the order of Oxa > Pro amides and for trans-to-cis rotational barriers in the order of Pro > Oxa amide in water are consistent with experimental results on Oxa-containing peptides. The pertinent distance between the prolyl nitrogen and the N$\^$∼/ H amide group to form a hydrogen bond might indicate that this intramolecular hydrogen bond could contribute in stabilizing the TS structures of Oxa and Pro amides and play a role in prolyl isomerization.

• Bulletin of the Korean Chemical Society
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• 제25권10호
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• pp.1465-1470
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• 2004

A short and efficient synthesis, solvent extraction and potentiometric measurements of new thiazole-containing naphtho-crown ethers are reported. The naphthalene moiety enhances the ammonium ion selectivity over potassium ion. The selectivity of ${NH_4}^+/K^+$ follows the trend $3\;{\approx}\;2\;>\;1$, indicating that the differences in conformational changes of 2 and 3 in forming ammonium complexes affect little on the resulting ammonium/potassium extraction selectivity ratio. The ammonium ion-selective electrodes were prepared with noctylphenyl ether plasticized poly(vinyl chloride) membranes containing 1-4 the effect of one naphthalene unit introduced on either right (2) or left (3) side of thiazolo-crown ether on their potentiometric properties (e.g., ammonium ion selectivity over other cations, response slopes, and detection limits) were not apparent. However, the ammonium ion selectivity of 1, 2 and 3 over other alkali metal and alkaline earth metal cations is 10-100 times higher than that of nonactin.

• 약학회지
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• 제41권6호
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• pp.773-781
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• 1997

The activity of $Ca^{2+}$calmodulin (CaM)-dependent protein kinase Ia (CaM kinase Ia) is shown to be regulated through direct phosphorylation by CaM kinase I kinase (CaMK IK). In the present study, three distinct CaMKIK peaks were separated from Q-Sepharose colunm chromatography of pig brain homogenate using a Waters 650 Protein Purification System. The purified CaMKIK from the major peak potently and rapidly enhanced CaM kinase Ia activity, reaching a maximal stimulation within 2min at the concentrations of 12-15nM. The activated state of CaM kinase Ia is characterized by a markedly enhanced $V_{max}4 as well as significantly decreased $K_m\;and\;K_a$ values toward peptide substrate and CaM, respectively. These observations suggest the activation process of CaM kinase Ia. The phosphorylation of CaM kinase Ia by CaMKIK may induce its conformational change responsible for the alterations in the kinetic properties, which ultimately leads to the rapid enzyme activation.