scholarly journals Спектры РКР и механизмы тушения флуоресценции beta-нитро-тетрафенилпорфирина

2019 ◽  
Vol 126 (3) ◽  
pp. 285
Author(s):  
Н.В. Ивашин ◽  
С.Н. Терехов
Keyword(s):  
Fluorescence Quenching ◽  
Excited States ◽  
Density Functional ◽  
Fluorescence Decay ◽  
Excitation Wavelength ◽  
Decay Kinetics ◽  
Vibrational States ◽  
The Density Functional Theory ◽  
The Matrix ◽  
Fluorescence Decay Kinetics

AbstractThe study of the excited states and photophysical characteristics of β-nitro-tetraphenylporphyrin (TPP–NO_2) has been carried out using resonance Raman scattering (RRS) spectroscopy and methods of the density functional theory. The appearance of new lines, the intensity of which depends on the composition of the matrix and excitation wavelength, has been found in the TPP–NO_2 RRS spectra in the low-temperature matrix. The calculation of the vibrational states of TPP–NO_2 allowed the linking of the additional lines with the asymmetric vibrations of the nitro group and valence C–C vibrations of the phenyl ring (Ph1) that was nearest to it. The activation of these modes is related to the specific features of the TPP–NO_2 geometry in the charge transfer (CT) state from Ph1 to the porphyrin macrocycle. It has been concluded on the basis of the analysis of the data of the study of the RRS spectra and the results of calculations that use the СAM-B3LYP and wB97XD functionals that the CT states do not play a significant role in the TPP–NO_2 fluorescence quenching, as previously assumed. The fluorescence quenching owes to strengthening channels of internal and inter-conversion by reducing the energy gaps Δ E ( S _1 – T _1) and Δ E ( S _1 – S _0) as well as increasing the spin-orbit coupling between the S _1 and T _1 states. It has been shown that TPP–NO_2 is characterized by conformational heterogeneity both in the ground and in the excited states, which explains the absence of the monoexponentiality of fluorescence decay kinetics.

scholarly journals Study of Anharmonicity in Zirconium Hydrides Using Inelastic Neutron Scattering and Ab-Initio Computer Modeling

Inorganics ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 29
Author(s):  
Jiayong Zhang ◽  
Yongqiang Cheng ◽  
Alexander I. Kolesnikov ◽  
Jerry Bernholc ◽  
Wenchang Lu ◽  
...  
Keyword(s):  
Neutron Scattering ◽  
Excited States ◽  
Lattice Dynamics ◽  
Density Functional ◽  
Inelastic Neutron Scattering ◽  
Inelastic Neutron ◽  
Vibrational States ◽  
Functional Theory ◽  
Hydrogen Deuterium ◽  
Zirconium Hydrides

The anharmonic phonon behavior in zirconium hydrides and deuterides, including ϵ-ZrH2, γ-ZrH, and γ-ZrD, has been investigated from aspects of inelastic neutron scattering (INS) and lattice dynamics calculations within the framework of density functional theory (DFT). The harmonic model failed to reproduce the spectral features observed in the experimental data, indicating the existence of anharmonicity in those materials and the necessity of further explanations. Here, we present a detailed study on the anharmonicity in zirconium hydrides/deuterides by exploring the 2D potential energy surface of hydrogen/deuterium atoms and solving the corresponding 2D single-particle Schrödinger equation to obtain the eigenfrequencies, which are then convoluted with the instrument resolution. The convoluted INS spectra qualitatively describe the anharmonic peaks in the experimental INS spectra and demonstrate that the anharmonicity originates from the deviations of hydrogen potentials from quadratic behavior in certain directions; the effects are apparent for the higher-order excited vibrational states, but small for the ground and first excited states.

The tryptophan fluorescence lifetime puzzle. A study of decay times in aqueous solution as a function of pH and buffer composition

1981 ◽  
Vol 59 (7) ◽  
pp. 1037-1044 ◽  
Author(s):  
Eva Gudgin ◽  
Ricardo Lopez-Delgado ◽  
William R. Ware
Keyword(s):  
Tryptophan Fluorescence ◽  
Fluorescence Decay ◽  
Low Ph ◽  
Decay Kinetics ◽  
Decay Component ◽  
Diffusion Controlled ◽  
Double Exponential ◽  
Decay Times ◽  
Fluorescence Decay Kinetics ◽  
Buffer Composition

Tryptophan fluorescence decay kinetics have been systematically investigated in aqueous solutions as a function of pH as well as in a variety of buffer solutions. Below pH 7.0, the decay appears to be double exponential with a subnanosecond component confirming the previous findings of Rayner and Szabo (3). In the low pH region, where the proton concentration becomes kinetically significant, tryptophan fluorescence is collisionally quenched by [H+] with diffusion controlled rate and no experimental evidence is found regarding the appearance at low pH of a new tryptophan molecular species, namely the cationic form. At pH ≥ 7.0, the decay becomes triple-exponential with the appearance of a long component whose contribution to the total emission intensity increases rapidly with increasing pH at the expense of the other two. Lifetimes and relative intensities of each decay component depend in a complex way on pH and on the buffer chemical composition.

scholarly journals Evidence that D1 Processing Is Required for Manganese Binding and Extrinsic Protein Assembly into Photosystem II

2004 ◽  
Vol 279 (44) ◽  
pp. 45417-45422 ◽  
Author(s):  
Johnna L. Roose ◽  
Himadri B. Pakrasi
Keyword(s):  
Photosystem Ii ◽  
Mutant Cell ◽  
Protein A ◽  
D1 Protein ◽  
Fluorescence Decay ◽  
Normal Function ◽  
Temporal Position ◽  
Decay Kinetics ◽  
Fluorescence Decay Kinetics ◽  
Extrinsic Proteins

Photosystem II (PSII) is a large membrane protein complex that catalyzes oxidation of water to molecular oxygen. During its normal function, PSII is damaged and frequently turned over. The maturation of the D1 protein, a key component in PSII, is a critical step in PSII biogenesis. The precursor form of D1 (pD1) contains a C-terminal extension, which is removed by the protease CtpA to yield PSII complexes with oxygen evolution activity. To determine the temporal position of D1 processing in the PSII assembly pathway, PSII complexes containing only pD1 were isolated from a CtpA-deficient strain of the cyanobacteriumSynechocystis6803. Although membranes from the mutant cell had nearly 50% manganese, no manganese was detected in isolated ΔctpAHT3 PSII, indicating a severely decreased manganese affinity. However, chlorophyll fluorescence decay kinetics after a single saturating flash suggested that the donor YZwas accessible to exogenous Mn2+ions. Furthermore, the extrinsic proteins PsbO, PsbU, and PsbV were not present in PSII isolated from this mutant. However, PsbO and PsbV were present in mutant membranes, but the amount of PsbV protein was consistently less in the mutant membranes compared with the control membranes. We conclude that D1 processing precedes manganese binding and assembly of the extrinsic proteins into PSII. Interestingly, the Psb27 protein was found to be more abundant in ΔctpAHT3 PSII than in HT3 PSII, suggesting a possible role of Psb27 as an assembly factor during PSII biogenesis.

scholarly journals Analysis of Fluorescence Decay Kinetics of Indocyanine Green Monomers and Aggregates in Brain Tumor Model In Vivo

Nanomaterials ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 3185
Author(s):  
Dina Farrakhova ◽  
Igor Romanishkin ◽  
Yuliya Maklygina ◽  
Lina Bezdetnaya ◽  
Victor Loschenov
Keyword(s):  
Brain Tumor ◽  
Indocyanine Green ◽  
Fluorescence Lifetime ◽  
Tumor Model ◽  
Fluorescence Decay ◽  
Decay Kinetics ◽  
Lifetime Analysis ◽  
Fluorescence Decay Kinetics ◽  
Brain Tumor Model

Spectroscopic approach with fluorescence time resolution allows one to determine the state of a brain tumor and its microenvironment via changes in the fluorescent dye’s fluorescence lifetime. Indocyanine green (ICG) is an acknowledged infra-red fluorescent dye that self-assembles into stable aggregate forms (ICG NPs). ICG NPs aggregates have a tendency to accumulate in the tumor with a maximum accumulation at 24 h after systemic administration, enabling extended intraoperative diagnostic. Fluorescence lifetime analysis of ICG and ICG NPs demonstrates different values for ICG monomers and H-aggregates, indicating promising suitability for fluorescent diagnostics of brain tumors due to their affinity to tumor cells and stability in biological tissue.

scholarly journals Examination of chlorophyll fluorescence decay kinetics in sulfur deprived algae Chlamydomonas reinhardtii

2007 ◽  
Vol 1767 (6) ◽  
pp. 559-564 ◽  
Author(s):  
A.A. Volgusheva ◽  
V.E. Zagidullin ◽  
T.K. Antal ◽  
B.N. Korvatovsky ◽  
T.E. Krendeleva ◽  
...  
Keyword(s):  
Chlorophyll Fluorescence ◽  
Chlamydomonas Reinhardtii ◽  
Fluorescence Decay ◽  
Decay Kinetics ◽  
Fluorescence Decay Kinetics

Excited-state properties of hypericin: electronic spectra and fluorescence decay kinetics

1993 ◽  
Vol 97 (30) ◽  
pp. 7870-7875 ◽  
Author(s):  
Tomoko Yamazaki ◽  
Nobuhiro Ohta ◽  
Iwao Yamazaki ◽  
Pill Soon Song
Keyword(s):  
Excited State ◽  
Electronic Spectra ◽  
Fluorescence Decay ◽  
Decay Kinetics ◽  
Fluorescence Decay Kinetics
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