scholarly journals Фемтосекундная абсорбционная спектроскопия восстановленной и окисленной форм цитохром c оксидазы: возбужденные состояния и релаксационные процессы в гемовых центрах a и a-=SUB=-3-=/SUB=-

2019 ◽  
Vol 127 (10) ◽  
pp. 697
Author(s):  
И.В. Шелаев ◽  
Ф.Е. Гостев ◽  
Т.В. Выгодина ◽  
С.В. Лепешкевич ◽  
Б.М. Джагаров
Keyword(s):  
Cytochrome C ◽  
Excitation Energy ◽  
Cytochrome C Oxidase ◽  
Ground State ◽  
Vibrational Relaxation ◽  
Vibrational Energy ◽  
Relaxation Processes ◽  
Electronic Relaxation ◽  
Electronic Excitation Energy ◽  
Reduced Forms

AbstractExcited electronic states and intraheme relaxation processes in the oxidized and reduced forms of mitochondrial cytochrome c oxidase extracted from a beef heart have been investigated by femtosecond absorption spectroscopy. The spectral and kinetic characteristics of short-lived intermediates have been measured from 80 fs to 20 ps after the photoexcitation. It is found that nonradiative electronic relaxation of the excitation energy in heme a , both in the oxidized (Fe(III) a ) and reduced (Fe(II) a ) forms, occurs successively as three processes, after the end of which heme a is in the ground state with a large store of vibrational energy. The subsequent vibrational relaxation (heme cooling) lasts for several picoseconds. It is found for reduced heme a _3 (Fe(II) a _3) that the electronic relaxation occurs as a result of two successive stages, which changes to vibrational relaxation in the ground state. The mechanism and dynamics of electronic excitation energy conversion in cytochrome c oxidase are analyzed.

A very rapid electronic relaxation process in a highly conjugated Zn(ii)porphyrin–[26]hexaphyrin–Zn(ii)porphyrin hybrid tape

2016 ◽  
Vol 18 (4) ◽  
pp. 3244-3249 ◽  
Author(s):  
Sangsu Lee ◽  
Hirotaka Mori ◽  
Taegon Lee ◽  
Manho Lim ◽  
Atsuhiro Osuka ◽  
...  
Keyword(s):  
Relaxation Process ◽  
Vibrational Relaxation ◽  
Energy Relaxation ◽  
Relaxation Processes ◽  
Electronic Relaxation ◽  
Vibronic State ◽  
Molecular Systems

We demonstrate that the electronic deactivation overtakes the vibrational relaxation processes in the energy relaxation processes from the initially excited vibronic state manifolds in highly conjugated molecular systems.

A BOXCARS investigation of vibrational relaxation in highly excited 1, 2-trans-dichloroethene

1993 ◽  
Vol 71 (11-12) ◽  
pp. 547-551 ◽  
Author(s):  
L. Wang ◽  
J. R. Xu ◽  
W. E. Jones
Keyword(s):  
Energy Transfer ◽  
Excitation Energy ◽  
Vibrational Relaxation ◽  
Vibrational Energy ◽  
Temporal Evolution ◽  
Maximum Energy ◽  
Vibrational Energy Transfer ◽  
Vibrational Energies

The BOXCARS technique has been used to study the collisional vibrational energy transfer from 1, 2-trans-dichloroethene excited into a quasicontinuum by a pulsed CO2 laser. The temporal evolution behaviour for vibrational energies in different modes was obtained. It has been shown that both the rate and maximum energy transferral to the ν4 mode are slightly larger than rates and energy transferral to the ν1 and ν2 modes and that this specificity declines with increase in excitation energy. The mechanism for this specificity is discussed.

The Master Equation for the Dissociation of a Dilute Diatomic Gas. XI. Vibrational Freezing in a Nozzle Flow

1974 ◽  
Vol 52 (6) ◽  
pp. 939-941 ◽  
Author(s):  
Nabil I. Labib ◽  
Huw O. Pritchard
Keyword(s):  
Relaxation Time ◽  
Energy Level ◽  
Master Equation ◽  
Rate Constant ◽  
Ground State ◽  
Vibrational Relaxation ◽  
Vibrational Energy ◽  
Nozzle Flow ◽  
Vibrational Energy Level ◽  
Diatomic Gas

A previously reported calculation on a model expansion in a nozzle flow is extended to the point where the whole vibrational energy "freezes" and the behavior of the vibrational relaxation time is examined. Starting with the high levels, each individual vibrational energy level becomes decoupled from the ground state in sequence, down to and including υ = 1; under these conditions, all measures of the vibrational relaxation time fail, but perhaps surprisingly the rate constant for recombination remains well defined.

scholarly journals A study of the magnetic properties of haem a3 in cytochrome c oxidase by using magnetic-circular-dichroism spectroscopy

1981 ◽  
Vol 193 (3) ◽  
pp. 687-697 ◽  
Author(s):  
A J Thomson ◽  
M K Johnson ◽  
C Greenwood ◽  
P E Gooding
Keyword(s):  
Circular Dichroism ◽  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Electronic State ◽  
Ground State ◽  
Magnetic Circular Dichroism ◽  
Circular Dichroism Spectroscopy ◽  
Magnetic Circular Dichroism Spectroscopy ◽  
Spin Singlet ◽  
Circular Dichroïsm

M.c.d. (magnetic-circular-dichroism) spectroscopy was used to study the magnetization properties of the haem centres in cytochrome c oxidase with magnetic fields of between 0 and 5.3 T over the temperature range 1.5–200 K. The oxidized, oxidized cyanide and partially reduced cyanide forms of the enzyme were studied. In the oxidized state only cytochrome a3+ is detectable by m.c.d. spectroscopy, and its magnetization characteristics show it to be a low-spin ferric haem. In the partially reduced cyanide form of the enzyme cytochrome a is in the diamagnetic low-spin ferrous form, whereas cytochrome a3–CN is e.p.r.-detectable and gives an m.c.d.-magnetization curve typical of a low-spin ferric haem. In the oxidized cyanide form of the enzyme both cytochrome a and cytochrome a3–CN are detectable by m.c.d. spectroscopy, although only cytochrome a gives an e.p.r. signal. The magnetization characteristics of haem a3–CN show clearly that its ground state is an electronic doublet and that another state, probably a spin singlet, lies greater than 10 cm-1 above this. These features are well accounted for by an electronic state of spin S = 1 with a predominantly axial distortion, which leaves the doublet, Ms = +/- 1, as the ground state and the component Ms = 0 as the excited state. This state would not give an e.p.r. signal. Such an electronic state could arise either from a ferromagnetic coupling between haem a3+(3)-CN and the cupric ion, Cua3, or form a haem in the Fe(IV) state.

scholarly journals Kinetic studies on the binding of cyanide to oxygenated cytochrome c oxidase

1976 ◽  
Vol 155 (2) ◽  
pp. 453-455 ◽  
Author(s):  
T Brittain ◽  
C Greenwood
Keyword(s):  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Kinetic Studies ◽  
Binding Properties ◽  
Cyanide Concentration ◽  
Cyanide Binding ◽  
Single Process ◽  
Reduced Forms

The reaction of cyanide with oxygenated cytochrome c oxidase was followed by means of flow-flash techniques. The oxygenated form, produced after photolysis of the partially reduced CO complex in the presence of cyanide and O2, shows cyanide-binding properties distinct from those of both the oxidized and the reduced forms of the protein. The binding is a single process (k = 22M-1-S-1) linearly dependent on cyanide concentration to as high as 75 mM. It is suggested that the oxygenated form is a conformational variant of the oxidized protein.

scholarly journals A re-examination of the reactions of cyanide with cytochrome c oxidase

1984 ◽  
Vol 220 (1) ◽  
pp. 57-66 ◽  
Author(s):  
M G Jones ◽  
D Bickar ◽  
M T Wilson ◽  
M Brunori ◽  
A Colosimo ◽  
...  
Keyword(s):  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Essential Feature ◽  
Tight Binding ◽  
Sodium Dithionite ◽  
Difference Spectra ◽  
Ferrocytochrome C ◽  
Cyanide Binding ◽  
Kinetic Predictions ◽  
Reduced Forms

Experiments were performed to examine the cyanide-binding properties of resting and pulsed cytochrome c oxidase in both their stable and transient turnover states. Inhibition of the oxidation of ferrocytochrome c was monitored as a function of cyanide concentration. Cyanide binding to partially reduced forms produced by mixing cytochrome c oxidase with sodium dithionite was also examined. A model is presented that accounts fully for cyanide inhibition of the enzyme, the essential feature of which is the rapid, tight, binding of cyanide to transient, partially reduced, forms of the enzyme populated during turnover. Computer fitting of the experimentally obtained data to the kinetic predictions given by this model indicate that the cyanide-sensitive form of the enzyme binds the ligand with combination constants in excess of 10(6) M-1 X s-1 and with KD values of 50 nM or less. Kinetic difference spectra indicate that cyanide binds to oxidized cytochrome a33+ and that this occurs rapidly only when cytochrome a and CuA are reduced.

Vibrationally excited nitric oxide produced in the flash photolysis of nitrosyl halides

1962 ◽  
Vol 268 (1334) ◽  
pp. 291-303 ◽  
Keyword(s):  
Nitric Oxide ◽  
Energy Transfer ◽  
Ground State ◽  
Vibrational Relaxation ◽  
Direct Evidence ◽  
Flash Photolysis ◽  
Vibrational Energy ◽  
Electronic States ◽  
Vibrationally Excited ◽  
Direct Production

The flash photolysis of nitrosyl chloride and nitrosyl bromide has been studied under isothermal conditions. Vibrationally excited nitric oxide molecules were produced and all levels from v " = 0 to v " = 11 were observed in absorption from the ground electronic states in the β, γ, δ and Є systems. Some of these bands have not previously been reported. The mechanism of the production is either directly NO R + hv → NO ( X 2 II , v ≤ 11) + R ( 2 P ), or by the sequence which includes the reactions NO R + hv → NO( 4 II ) + R , NO. 4 II + M → NO ( X 2 II , v > 0) + M In the latter case, the 4 II state of NO lies not more than 3·5 eV above the ground state. Other possible mechanisms and models accounting for the direct production of vibrationally excited NO in its ground electronic states are discussed. By flashing chlorine in the presence of NOCl it was shown that the reaction Cl + NOCl → Cl 2 + NO ( v > 0) does not occur, thus providing direct evidence that in reactions of the type A + BCD → AB + CD only the AB molecule containing the newly formed bond can be vibrationally excited. Vibrational relaxation is very rapid and probably occurs by step-wise degradation involving resonance vibrational energy transfer. NOCl and NOBr are very efficient and with NO itself the reaction NO ( v = n ) + NO ( v = 0) → NO ( v = n -1) + NO ( v = 1) can be followed.

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