• Journal of Life Science
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• v.8 no.6
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• pp.681-686
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• 1998

IASL(iodo acetamide) and MSL(maleimide) disordered the orderly helix arrangement of myosin in the rest state of spin level. Especially the effect of IASL was great. Equatorial reflection(10,11) change inferred that myosin head was moved to the vicinity of actin filament by spin level. The intensity change of 143 $\AA$ and 72 $\AA$ could offer infor-mation of the mass projection of population of myosin heads along the filament axis. The slope of intensity profile of the mass projection of 143 $\AA$ and reflection of IASL is appeared and that of MSL is appeared sharply. The dec-rease of 215 $\AA$ reflection intensity the periodical characteristic of 143 $\AA$ reflection by spin label. The raise of MSL actin reflection at 51 $\AA$ and 59 $\AA$ in the actin reflection change refers that the shifted myosin head binds a certain actin or changes an actin structure by spin label effect. Because iodo acetamide has a tendency to decease the actin reflection, actin dose not bind myosin head. From this result, we could conclude that LASL and MSL are spin labeled on SH of myosin head and disordered the helix arrangement of actin.

• Journal of the Korean Applied Science and Technology
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• v.20 no.3
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• pp.268-273
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• 2003

IASL(iodo acetamide spin label) and MSL(maleimide spin label) disordered the orderly helix arrangement of myosin in the rest state of spin level. Especially the effect of IASL was great. The muscle was isometrically tetanized with three trains of 3ms pulses every 50ms between $5^{\circ}C$ with $25^{\circ}C$. Equatorial reflection change inferred that myosin head was moved to the vicinity of actin filament by spin level. The intensity change of $143{\AA}$ and $72{\AA}$ could offer information of the mass projection of population of myosin head along the filament axis. The slope of intensity profile of the mass projection of $143{\AA}$ and reflection of IASL is appeared and that of MSL is appeared sharply. The decrease of $215{\AA}$ reflection intensity the periodical character of $143{\AA}$ reflection by spin label. The raise of MSL actin reflection at $51{\AA}$ and $59{\AA}$ in the actin reflection change refers that the shifted myosin head binds a certain actin or changes an actin structure by spin label effect. Because iodo acetamide has a tendency to decease the actin reflection, actin dose not bind myosin head. From this result, we can conclude that IASL and MSL are spin labeled on SH of myosin head and disordered the helix arrangement of actin.

• BMB Reports
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• v.29 no.2
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• pp.169-174
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• 1996

Yeast cytochrome c (cyt c) was modified at cysteine-102 with a thiol-specific spin label and its interaction with liposomes containing acidic phospholipids was studied by electron paramagnetic resonance (EPR) spectroscopy. Association of cyt c with liposomes resulted in a significant reduction in the mobility of the spin label and a fraction of cyt c even seemed to be immobilized. Based on a large spectral change upon binding and the proximity of the spin-label to lysine-86 and -87, we propose these two residues to be the potential binding site at neutral pH. The interaction is electrostatic in nature because the spectral changes were reversed by addition of anions. Dissociation of the bound cyt c by anions, however, became less effective as the lipid/protein ratio increased. This suggests a repulsive lateral interaction among the bound cyt c. Unlabeled cyt c molecules added to preformed cyt c-liposome complex displaced the bound (spin labeled) cyt c and the process was competitive and reversible.

• Journal of the Korean Applied Science and Technology
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• v.22 no.1
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• pp.84-90
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• 2005

IASL(iodo acetamide) and MSL(maleimide) disordered the orderly helix arrangement of myosin in the rest state of spin level. Especially the effect of IASL was great. Equatorial refiection(10,11) change inferred that myosin head was moved to the vicinity of actin filament by spin level. The intensity change of 143${\AA}$ and 72${\AA}$ could offer information of the mass projection of population of myosin heads along the :filament axis. The slope of intensity profile of the mass projection of 143${\AA}$ and reflection of IASL is appeared and that of MSL is appeared sharply. The decrease of 215${\AA}$ reflection intensity is appeared the periodical characteristic of 143${\AA}$ reflection by spin label. The raise of MSL actin reflection at 51${\AA}$ and 59${\AA}$ in the actin reflection change refers that the shifted myosin head binds a certain actin or changes an actin structure by spin label effect. Because iodo acetamide has a tendency to decease the actin reflection, actin dose not bind myosin head. From this result, we could conclude that LASL and MSL are spin labeled on SH of myosin head and disordered the helix arrangement of actin.

• Bulletin of the Korean Chemical Society
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• v.17 no.3
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• pp.279-284
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• 1996

Decay of the spin label attached to cytochrome c or to stearic acid has been measured by electron paramagnetic resonance (EPR) spectroscopy to monitor membrane oxidation induced by cytochrome c-membrane interaction. Binding of cytochrome c sequestered the acidic phospholipids and membrane oxidation was efficient in the order linoleic oleic>stearic acid for a fatty acid chain in the acidic phospholipids. The spin label on cyt c was destroyed at pH 7 whereas that on stearic acid embedded in the membrane was destroyed at pH 4, presumably due to different modes of cyt c-membrane interaction depending on pH. Interestingly, cyt c also interacts with phosphatidylethanolamine, an electrically neutral phospholipid, to cause rapid membrane oxidation. Both EPR and fluorescence measurements indicated that electrostatic interaction is at least partially responsible for the process.

• Journal of Life Science
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• v.9 no.6
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• pp.646-652
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• 1999

The effect of temperature on the structure change of the SH of myosin head have been investigated with improved resolution by x-ray diffraction using synchrotron radiation. The movement of myosin head and conformational change of contractile molecules were occurred in the muscle contraction. IASL (iodo acetamide) and MSL (maleimide) disordered the orderly helix arrangement of myosin in the rest state of spin level. The temperature effect on the structure change was great at the UL in the equatorial reflection. But those of IASL and MSL were minor. Equatorial reflection (10, 11) change inferred that myosin head was moved to the vicinity of actin filament by temperature change (from $25^{\circ}C$ to $0^{\circ}C$) at UL, but spin level was not changed. The intensity change of 143 $\AA$ and 72 $\AA$ could offer information of the mass profection of population of myosin heads along the filament axis. The slope of intensity profile of the mass profection of 143$\AA$ and reflection of MSL is appeared sharply and those of UL and IASL were not changed. The decrease of MSL actin reflection at 51 $\AA$ and 59 $\AA$ in the actin reflection change refers that the shifted myosin head binds a certain actin or changes an actin structure. From these results, we could conclude that IASL and MSL were spin labeled on SH of myosin head and disordered the helix arrangement of actin.

• BMB Reports
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• v.30 no.2
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• pp.138-143
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• 1997

In order to assess controversial' proposals concerning the fatty acid-induced uncoupling of mitochondrial oxidative phosphorylation, we investigated the interaction of stearic acid with key mitochondrial proteins and measured the effect of stearic acid on the respiration of cytochrome c oxidase vesicles. Electron paramagnetic resonance spectra of spin-labeled stearic acid clearly demonstrated that cytochrome c oxidase interacts strongly with stearic acid. However, the respiration of detergent-solubilized cytochrome c oxidase was not altered significantly by stearic acid. Surprisingly, adenine nucleotide carrier, which was assumed to bind and translocate fatty acid anions in the Skulachev model of uncoupling, did not bind stearic acid at all. The respiration rate of cytochrome c oxidase vesicles was increased by ~70% in the presence of $20{\mu}m$ stearic acid and this uncoupling was attributed to a simple protonophoric effect of stearic acid.

• BMB Reports
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• v.30 no.6
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• pp.397-402
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• 1997

A thiol-specific spin label was attached to cysteine-102 of yeast cytochrome c and electron paramagnetic resonance (EPR) spectra were measured as a function of added cytochrome c oxidase concentration. The intensity decreased due to line broadening as cytochrome c formed a complex with cytochrome c oxidase and reached a minimum when the ratio of cytochrome c to cytochrome c oxidase became one. Replacement of either Lys-72 or Lys-87 of cytochrome c by Glu did not result in a significant change in binding affinity. Interestingly the K72E mutant, unlike K87E, had a much lower rate of electron transfer than the wild type. These results indicate that many positively charged residues as a group participate in complex formation but Lys-72 might be important for cytochrome c to be locked in an orientation for an efficient electron transfer. A stoichiometry of 1 was also confirmed by optical absorption of the cytochrome c-cytochrome c oxidase complex which had been run through a gel chromatography cloumn to remove unbound cytochrome c. The EPR spectrum of this 1:1 complex, however, was a mixture of two components. This explains a biphasic kinetics for a single binding site on cytochrome c oxidase without invoking conformational transition.

• Applied Biological Chemistry
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• v.43 no.4
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• pp.236-240
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• 2000

Correlations between mitochondrial respiration, glycolysis activity and overall growth activity of rice (Oryza sativa: cv. Dasan) seedlings during low temperature exposure were studied in order to provide insights into the underlying mechanism for the primary phase of chilling injury in plants. Among cellular membranes involved in energy metabolism, only the mitochondrial inner membrane showed not only physical phase transition at ca. $13^{\circ}C$, as monitored by ESR spin label, but also functional phase transition at the same temperature, as assessed by cytochrome c oxidase activity. The main regulatory enzyme of glycolysis, phosphofructokinase, in situ did not suffer phase transition of its activity at least in the $4{\sim}27^{\circ}C$ range. Low temperature caused a significant accumulation of glucose 6-phosphate (G6P) and fructose 6-phosphate (F6P), which disappeared almost completely on rewarming of the seedlings. Temperature profiles of the steady state levels of G6P and F6P revealed the inflection point appearing at around phase transition temperature of the mitochondrial membrane. The results conform to our previous proposition on the mechanism for the early stage events of chilling injury that the accumulation of glycolytic metabolites in cells due to metabolic imbalance at low temperature gives rise to an excess supply of electrons during rewarming period, which, in turn, results in overproduction of active oxygen in mitochondria.