• Title/Summary/Keyword: Biophysics

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The effect of surface charge balance on thermodynamic stability and kinetics of refolding of firefly luciferase

  • Khalifeh, Khosrow;Ranjbar, Bijan;Alipour, Bagher Said;Hosseinkhani, Saman
    • BMB Reports
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    • v.44 no.2
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    • pp.102-106
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    • 2011
  • Thermodynamic stability and refolding kinetics of firefly luciferase and three representative mutants with depletion of negative charge on a flexible loop via substitution of Glu by Arg (ER mutant) or Lys (EK mutant) as well as insertion of another Arg in ER mutants (ERR mutant) was investigated. According to thermodynamic studies, structural stability of ERR and ER mutants are enhanced compared to WT protein, whereas, these mutants become prone to aggregation at higher temperatures. Accordingly, it was concluded that enhanced structural stability of mutants depends on more compactness of folded state, whereas aggregation at higher temperatures in mutants is due to weakening of intermolecular repulsive electrostatic interactions and increase of intermolecular hydrophobic interactions. Kinetic results indicate that early events of protein folding are accelerated in mutants.

The $GABA_c$ Receptor Is Present in Isolated Cone-Horizontal Cell Axon Terminals From Catfish Retina

  • Jung, Chang-Sub;Lee, Sung-Jong;Paik, Sun-Sook;Bai, Sun-Ho
    • Proceedings of the Korean Biophysical Society Conference
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    • 1998.06a
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    • pp.35-35
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    • 1998
  • Catfish retina contains cone- and rod-horizontal cells. Only the cone-horizontal cell (cone-HC) has an axon and axon terminal. We compared the distribution of excitatory and inhibitory receptors in axon terminals and somata to begin to learn about the distinct functions of these two structures.(omitted)

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Thermal Dissociation and Conformational Lock of Superoxide Dismutase

  • Hong, J.;Moosavi-Movahedi, A.A.;Ghourchian, H.;Amani, M.;Amanlou, M.;Chilaka, F.C.
    • BMB Reports
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    • v.38 no.5
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    • pp.533-538
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    • 2005
  • The kinetics of thermal dissociation of superoxide dismutase (SOD) was studied in 0.05 M Tris-HCl buffer at pH 7.4 containing $10^{-4}\;M$ EDTA. The number of conformational locks and contact areas and amino acid residues of dimers of SOD were obtained by kinetic analysis and biochemical calculation. The cleavage bonds between dimers of SOD during thermal dissociation and type of interactions between specific amino acid residues were also simulated. Two identical contact areas between two subunits were identified. Cleavage of these contact areas resulted in dissociation of the subunits, with destruction of the active centers, and thus, lost of activity. It is suggested that the contact areas interact with active centers by conformational changes involving secondary structural elements.

Sulfhydryl Oxidation Regulates Cloned Mechanosensitive Two-Pore $K^+$ Channel Expressed in Mammalian Cell Lines

  • Kim, Yangmi;Park, Kyoung-Sun;Earm, Yung-E;Ho, Won-Kyung
    • Proceedings of the Korean Biophysical Society Conference
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    • 2002.06b
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    • pp.34-34
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    • 2002
  • Oxidative stress has been considered as a major cause of inducing cell damage, but it is recently recognized that mild oxidative stress or receptor-mediated production of ROS contributes to the regulation of various cellular functions. Several ion channels, such as L-type $Ca^{2+}$ channels and $Ca^{2+}$-activated $K^{+}$ channels, have been shown to be regulated by oxidation of thiol group in their structure, and are suggested to be involved in ROS-sensitive cellular signaling.(omitted)

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Glucose Transporters and Insulin Action : Some Insights into Diabetes Management

  • Jung, Chan-Y.;Lee, Wan
    • Archives of Pharmacal Research
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    • v.22 no.4
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    • pp.329-334
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    • 1999
  • Insulin stimulates glucose uptake in muscle and adipose cells primarily by recruiting GLUT4 from an intracellular storage pool to the plasma membrane. Dysfunction of this process known as insulin resistance causes hyperglycemia, a hallmark of diabetes and obesity. Thus the understanding of the mechanisms underlying this process at the molecular level may give an insight into the prevention and treatment of these health problems. GLUT4 in rat adipocytes, for example, constantly recycles between the cells surface and an intracellular pool by endocytosis and exocytosis, each of which is regulated by an insulin-sensitive and GLUT4-selective sorting mechanism. Our working hypothesis has been that this sorting mechanism includes a specific interaction of a cytosolic protein with the GLUT4 cytoplasmic domain. Indeed, a synthetic peptide of the C-terminal cytoplasmic domain of GLUT4 induces an insulin-like GLUT4 recruitment when introduced in rat adipocytes. Relevance of these observations to a novel euglycemic drug design is discussed.

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Thermodynamic Studies on the Interaction of Copper Ions with Carbonic Anhydrase

  • Sarraf, N.S.;Mamaghani-Rad, S.;Karbassi, F.;Saboury, A. A.
    • Bulletin of the Korean Chemical Society
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    • v.26 no.7
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    • pp.1051-1056
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    • 2005
  • The interaction of bovine carbonic anhydrase II with copper ions was studied by isothermal titration microcalorimetry, circular dichroism, UV spectrophotometry and temperature scanning spectrophotometry methods at 27 ${^{\circ}C}$ in Tris buffer solution at pH = 7.5. It was indicated that there are three non-identical different binding sites on carbonic anhydrase for $Cu^{2+}$. The binding of copper ions is exothermic and can induce some minor changes in the secondary and tertiary structure of the enzyme, which does not unfold it, but can result in a decrease in both activity and stability of the enzyme.

Protein Kinase Modulates the $GABA_c$ Currents in Cone-horizontal Cell Axon-terminals Isolated from Catfish Retina

  • Paik, Sun-Sook;Lee, Sung-Jong;Jung, Chang-Sub;Bai, Sun-Ho
    • Proceedings of the Korean Biophysical Society Conference
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    • 1999.06a
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    • pp.54-54
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    • 1999
  • Protein kinase modulation of gamma-aminobutyric acid C (GABA$_{c}$) currents in freshly dissociated catfish retinal cone-horizontal cell axon-terminals was studied under voltage clamp with the use of the whole cell patch-clamp technique. Responses to pulses of GABA were monitored in intracellular application of adenosin 3',5'-cycle monophophate (cAMP)-dependent protein kinase (PKA) and protein kinase C (PKC) activators, and their inhibitors or inactive analogues.(omitted)d)

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