scholarly journals Photocycle Dynamics of the Archaerhodopsin 3 Based Fluorescent Voltage Sensor QuasAr1

2019 ◽  
Vol 21 (1) ◽  
pp. 160
Author(s):  
Alfons Penzkofer ◽  
Arita Silapetere ◽  
Peter Hegemann
Keyword(s):  
Schiff Base ◽  
Quantum Yield ◽  
Absorption Band ◽  
Absorption Spectra ◽  
Absorption Maximum ◽  
Light Exposure ◽  
Voltage Sensor ◽  
Proton Release ◽  
Protonation State ◽  
State Changes

The retinal photocycle dynamics of the fluorescent voltage sensor QuasAr1 (Archaerhodopsin 3 P60S-T80S-D95H-D106H-F161V mutant from Halorubrum sodomense) in pH 8 Tris buffer was studied. The samples were photoexcited to the first absorption band of the protonated retinal Schiff base (PRSB) Ret_580 (absorption maximum at λmax ≈ 580 nm), and the retinal Schiff base photoisomerization and protonation state changes were followed by absorption spectra recordings during light exposure and after light exposure. Ret_580 turned out to be composed of two protonated retinal Schiff base isomers, namely Ret_580I and Ret_580II. Photoexcitation of Ret_580I resulted in barrier-involved isomerization to Ret_540 (quantum yield ≈ 0.056) and subsequent retinal proton release leading to Ret_410 deprotonated retinal Schiff base (RSB). In the dark, Ret_410 partially recovered to Ret_580I and partially stabilized to irreversible Ret_400 due to apoprotein restructuring (Ret_410 lifetime ≈ 2 h). Photoexcitation of Ret_580II resulted in barrier-involved isomerization to Ret_640 (quantum yield ≈ 0.00135) and subsequent deprotonation to Ret_370 (RSB). In the dark, Ret_370 partially recovered to Ret_580II and partially stabilized to irreversible Ret_350 due to apoprotein restructuring (Ret_370 lifetime ≈ 10 h). Photocycle schemes and reaction coordinate diagrams for Ret_580I and Ret_580II were developed and photocyle parameters were determined.

Effect of salt on the tyrosine and protonated Schiff base deprotonation kinetics in bacteriorhodopsin

1985 ◽  
Vol 63 (7) ◽  
pp. 1699-1704 ◽  
Author(s):  
Paul Dupuis ◽  
M. A. El-Sayed
Keyword(s):  
Schiff Base ◽  
Quantum Yield ◽  
Salt Concentration ◽  
Slow Component ◽  
High Salt ◽  
Proton Release ◽  
High Ph ◽  
Bacteriorhodopsin Photocycle

It is observed that the number of protons pumped per M412 formed in the bacteriorhodopsin photocycle almost doubles at high salt concentrations. In this paper, we studied the rates of deprotonation of tyrosine and of the two components of the protonated Schiff base at high salt concentrations, and at different pHs and temperatures. It is found that at pH = 7, increasing the salt concentration decreases the rates of deprotonation of the protonated Schiff base and tyrosine. This strongly suggests that the observed gain in the quantum yield of proton release per M412 formed when the salt concentration is increased is not a result of an increase in these rates. However, at high pH, e.g. 9.6, increasing the salt concentration increases the rate of deprotonation of the Schiff base by about 50%. Under all conditions, the slow component of the Schiff base is found to lose its proton prior to tyrosine.

scholarly journals Absorption and Emission Spectroscopic Investigation of the Thermal Dynamics of the Archaerhodopsin 3 Based Fluorescent Voltage Sensor Archon2

2020 ◽  
Vol 21 (18) ◽  
pp. 6576
Author(s):  
Alfons Penzkofer ◽  
Arita Silapetere ◽  
Peter Hegemann
Keyword(s):  
Schiff Base ◽  
Melting Temperature ◽  
Absorption Maximum ◽  
Room Temperature ◽  
Voltage Sensor ◽  
Quantum Yields ◽  
Excitation Spectra ◽  
Thermal Dynamics ◽  
Absorption And Emission ◽  
Refrigerator Temperature

Archon2 is a fluorescent voltage sensor derived from Archaerhodopsin 3 (Arch) of Halorubrum sodomense using robotic multidimensional directed evolution approach. Here we report absorption and emission spectroscopic studies of Archon2 in Tris buffer at pH 8. Absorption cross-section spectra, fluorescence quantum distributions, fluorescence quantum yields, and fluorescence excitation spectra were determined. The thermal stability of Archon2 was studied by long-time attenuation coefficient measurements at room temperature (21 ± 1 °C) and at refrigerator temperature (3 ± 1 °C). The apparent melting temperature was determined by stepwise sample heating up and cooling down (obtained apparent melting temperature: 63 ± 3 °C). In the protein melting process protonated retinal Schiff base (PRSB) with absorption maximum at 586 nm converted to de-protonated retinal Schiff base (RSB) with absorption maximum at 380 nm. Storage of Archon2 at room temperature and refrigerator temperature caused absorption coefficient decrease because of partial protein clustering to aggregates at condensation nuclei and sedimentation. At room temperature an onset of light scattering was observed after two days because of the beginning of protein unfolding. During the period of observation (18 days at 21 °C, 22 days at 3 °C) no change of retinal isomer composition was observed indicating a high potential energy barrier of S0 ground-state isomerization.

scholarly journals Absorption and Emission Spectroscopic Investigation of the Thermal Dynamics of the Archaerhodopsin 3 Based Fluorescent Voltage Sensor QuasAr1

2019 ◽  
Vol 20 (17) ◽  
pp. 4086 ◽  
Author(s):  
Penzkofer ◽  
Silapetere ◽  
Hegemann
Keyword(s):  
Schiff Base ◽  
Melting Temperature ◽  
Absorption Maximum ◽  
Voltage Sensor ◽  
Quantum Yields ◽  
Excitation Spectra ◽  
Thermal Dynamics ◽  
Absorption And Emission ◽  
Absorption Increase ◽  
Long Time

QuasAr1 is a fluorescent voltage sensor derived from Archaerhodopsin 3 (Arch) of Halorubrum sodomense by directed evolution. Here we report absorption and emission spectroscopic studies of QuasAr1 in Tris buffer at pH 8. Absorption cross-section spectra, fluorescence quantum distributions, fluorescence quantum yields, and fluorescence excitation spectra were determined. The thermal stability of QuasAr1 was studied by long-time attenuation coefficient measurements at room temperature (23 ± 2 °C) and at 2.5 ± 0.5 °C. The apparent melting temperature was determined by stepwise sample heating up and cooling down (obtained apparent melting temperature: 65 ± 3 °C). In the protein melting process the originally present protonated retinal Schiff base (PRSB) with absorption maximum at 580 nm converted to de-protonated retinal Schiff base (RSB) with absorption maximum at 380 nm. Long-time storage of QuasAr1 at temperatures around 2.5 °C and around 23 °C caused gradual protonated retinal Schiff base isomer changes to other isomer conformations, de-protonation to retinal Schiff base isomers, and apoprotein structure changes showing up in ultraviolet absorption increase. Reaction coordinate schemes are presented for the thermal protonated retinal Schiff base isomerizations and deprotonations in parallel with the dynamic apoprotein restructurings.

ULTRAVIOLET ABSORPTION SPECTRA AND ACIDITIES OF ISOMERIC THIATRIAZOLE AND TETRAZOLE DERIVATIVES

1959 ◽  
Vol 37 (3) ◽  
pp. 563-574 ◽  
Author(s):  
Eugene Lieber ◽  
J. Ramachandran ◽  
C. N. R. Rao ◽  
C. N. Pillai
Keyword(s):  
Absorption Spectra ◽  
Absorption Maximum ◽  
Dipole Moments ◽  
Ring System ◽  
Ultraviolet Absorption ◽  
Characteristic Absorption ◽  
Tetrazole Derivatives

The ultraviolet absorption spectra of 5-(substituted)amino-1,2,3,4-thiatriazoles and the corresponding isomeric 1-substituted-tetrazoline-5-thiones have been studied. The spectra and the dipole moments of the 5-(substituted)amino-1,2,3,4-thiatriazoles eliminate the possibility of meso-ionic structures for these compounds. The dipole moments of 5-amino-, 5-methylamino-, and 5-dimethylamino-1,2,3,4-thiatriazole were all high but approximately of the same value (5.77 to 5.84 D). This suggests that the amino thiatriazoles are best represented by conventional covalent structures with significant ionic resonance contributions. The thiatriazole ring system exhibits a characteristic absorption maximum at 250–255 mμ and an electron-withdrawing effect approximately equal to the tetrazolyl ring system. The tetrazolinethionolyl ring system is similarly electron-withdrawing. The relative acidities of the 1-substituted-tetrazoline-5-thiones and the 5-alkylmercaptotetrazoles have also been studied and the results support the observations made on the basis of their ultraviolet absorption spectra.

INFLUENCE OF THE THICKNESS OF THE n-Si SUBSTRATE AND ITS DOPING LEVEL ON THE ABSORBING PROPERTIES OF SILICON PLASMON STRUCTURES IN THE INFRARED RANGE

2021 ◽  
Vol 88 (6) ◽  
pp. 887-894
Author(s):  
A. I. Mukhammad ◽  
P. I. Gaiduk
Keyword(s):  
Surface Layer ◽  
Absorption Band ◽  
Absorption Spectra ◽  
Doping Level ◽  
Phase Synchronization ◽  
Dispersion Relations ◽  
Infrared Range ◽  
Si Substrate ◽  
Significant Difference ◽  
Dielectric Interfaces

The absorption spectra of Si/SiO2/Si3N4/Si+ and Si/SiO2/Si+ structures with an island surface layer are calculated using the finite difference time domain method. The absorption spectra were modeled depending on the thickness of the substrate and its doping level. It was found that the thickness of the i-Si substrate does not affect the overall absorption of the structure. At the same time, an increase in the thickness of the n-Si substrate leads to an expansion of the absorption band with an intensity of more than 70%. It is established that the doping level of the substrate affects the absorption value of the structures and bandwidth with an absorption value above 80%. It is shown that a wide absorption band with intensity of more than 80% occurs at the doping level of the substrate in the range of 2 . 1019—5 . 1019 cm–3. Dispersion relations in the Si+/SiO2/Si+ structure with an unstructured surface layer are obtained. These dispersion relations may indicate the existence of plasmon oscillations in the system. It is established that a violation of the phase synchronization of the modes at both Si/dielectric interfaces at a significant difference between the doping levels of the substrate and the surface layer can lead to a decrease in the absorption.

scholarly journals Локализованные экситоны в спектре оптического поглощения оксида цинка, легированного марганцем

2019 ◽  
Vol 61 (5) ◽  
pp. 817
Author(s):  
В.И. Соколов ◽  
Н.Б. Груздев ◽  
В.А. Важенин ◽  
А.В. Фокин ◽  
А.В. Дружинин
Keyword(s):  
Zinc Oxide ◽  
Charge Transfer ◽  
Absorption Band ◽  
Optical Absorption ◽  
Absorption Spectra ◽  
Polarized Light ◽  
Threshold Energy ◽  
Impurity Absorption ◽  
Charge Transfer Transitions ◽  
Long Time

AbstractThe results of the study of optical absorption and EPR signals of single crystals of zinc oxide doped with manganese are presented. A broad impurity absorption band with the threshold energy about 2.1 eV, which was treated as a result of charge transfer transitions, has been observed for a long time in ZnO : Mn absorption spectra. In absorption spectra of a polarized light at 4.2 and 77.3 K, we first detected several lines of different intensity in a 1.877–1.936 eV range of energies of the light quanta. The observed lines are attributed to a donor exciton [( d ^5 + h ) e ] that emerges as a result of the Coulomb binding a free s electron and a hole, which is localized on p – d hybridized states. The EPR spectra of Mn^2+ ion signals, when corresponding to the impurity absorption band exposed to light, are found to be not photosensitive. The obtained results indicate that the ZnO : Mn impurity absorption is due to transitions from antibonding p – d hybridized DBH states to the conduction band.

scholarly journals On the influence of their state in solution on the absorption spectra of dissolved dyes

1909 ◽  
Vol 82 (554) ◽  
pp. 256-270 ◽  
Keyword(s):  
Refractive Index ◽  
Absorption Spectra ◽  
Organic Solvents ◽  
Absorption Maximum ◽  
Previous Investigation ◽  
Cyanine Dyes ◽  
Water Band ◽  
The One

In a previous investigation of the absorption spectra and sensitising properties of some iso cyanine dyes,* the influence of the solvent was examined and it was found that the absorption maximum was shifted toward the red as the refractive index of the solvent increased. This is in accordance with Kundt’s law. The absorption in water, however, differs markedly from that in organic solvents. In the latter the spectrum consists of a prominent band in the orange and a half-shade nearer the blue. In water this half-shade has become a separate band comparable in intensity with the orange. Absorption curves in alcohol and water are shown. It is convenient to term the band near the red the β-(organic) band, the one nearer the blue the α -(water) band. It appeared desirable to investigate this difference further.

scholarly journals THE PHOTOSYNTHETIC EFFICIENCY OF PHYCOCYANIN IN CHROOCOCCUS, AND THE PROBLEM OF CAROTENOID PARTICIPATION IN PHOTOSYNTHESIS

1942 ◽  
Vol 25 (4) ◽  
pp. 579-595 ◽  
Author(s):  
Robert Emerson ◽  
Charlton M. Lewis
Keyword(s):  
Quantum Yield ◽  
Absorption Spectra ◽  
Photosynthetic Efficiency ◽  
High Efficiency ◽  
Wave Length ◽  
Visible Spectrum ◽  
Living Cells ◽  
Reasonable Doubt ◽  
Carotenoid Pigments ◽  
Relative Absorption

The absorption spectra of the principal pigment components extracted from Chroococcus cells have been measured, and their sum compared with the absorption of a suspension of living cells. The agreement was sufficiently close so that it was concluded the absorption spectra of the extracted and separated pigment components could be used to obtain estimates of the relative absorption of the various components in the living cells. The quantum yield of Chroococcus photosynthesis was measured at a succession of wave lengths throughout the visible spectrum, and the dependence of yield on wave length was compared with the proportions of light absorbed by the pigment components. This comparison showed beyond reasonable doubt that the light absorbed by phycocyanin is utilized in photosynthesis with an efficiency approximately equal to that of the light absorbed by chlorophyll. The light absorbed by the carotenoid pigments of Chroococcus seems for the most part to be unavailable for photosynthesis. The results leave open the possibility that light absorbed by the carotenoids is active in photosynthesis, but with an efficiency considerably lower than that of chlorophyll and phycocyanin. It is also possible that the light absorbed by one or a few of the several carotenoid components is utilized with a high efficiency, while the light absorbed by most of the components is lost for photosynthesis.

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