scholarly journals Using photocaging for fast time-resolved structural biology studies

2021 ◽  
Vol 77 (10) ◽  
pp. 1218-1232
Author(s):  
Diana C. F. Monteiro ◽  
Emmanuel Amoah ◽  
Cromarte Rogers ◽  
Arwen R. Pearson
Keyword(s):  
Structural Biology ◽  
Spectroscopic Properties ◽  
Decay Rates ◽  
Quantum Yields ◽  
Fast Time ◽  
Time Resolved ◽  
Extinction Coefficients ◽  
Reaction Initiation ◽  
Selection Of ◽  
Molar Extinction Coefficients

Careful selection of photocaging approaches is critical to achieve fast and well synchronized reaction initiation and perform successful time-resolved structural biology experiments. This review summarizes the best characterized and most relevant photocaging groups previously described in the literature. It also provides a walkthrough of the essential factors to consider in designing a suitable photocaged molecule to address specific biological questions, focusing on photocaging groups with well characterized spectroscopic properties. The relationships between decay rates (k in s−1), quantum yields (φ) and molar extinction coefficients (ɛmax in M −1 cm−1) are highlighted for different groups. The effects of the nature of the photocaged group on these properties is also discussed. Four main photocaging scaffolds are presented in detail, o-nitrobenzyls, p-hydroxyphenyls, coumarinyls and nitrodibenzofuranyls, along with three examples of the use of this technology. Furthermore, a subset of specialty photocages are highlighted: photoacids, molecular photoswitches and metal-containing photocages. These extend the range of photocaging approaches by, for example, controlling pH or generating conformationally locked molecules.

The Synthesis, Characterisation, Photophysical and Thermal Properties, and Photovoltaic Performance of 7-Coumarinoxy-4-Methyltetrasubstituted Metallophthalocyanines

2015 ◽  
Vol 68 (7) ◽  
pp. 1025 ◽  
Author(s):  
Jun-Jie Guo ◽  
Shi-Rong Wang ◽  
Xiang-Gao Li ◽  
Fei Zhang ◽  
Yin Xiao ◽  
...  
Keyword(s):  
Thermal Properties ◽  
Transition Metal Complexes ◽  
Photovoltaic Performance ◽  
Quantum Yields ◽  
Stability Studies ◽  
Time Resolved ◽  
Extinction Coefficients ◽  
Fluorescence Quantum Yields ◽  
Photoluminescence Decay ◽  
Molar Extinction Coefficients

The synthesis, characterisation, photophysical and thermal properties of 2(3),9(10),16(17),23(24)-tetrakis(7-coumarinoxy-4-methyl)-phthalocyaninatozinc(ii) (ZnPc-Coumarin) and 2(3),9(10),16(17),23(24)-tetrakis(7-coumarinoxy-4-methyl)-phthalocyaninatocobalt(ii) (CoPc-Coumarin) are reported. The ground state absorbance of ZnPc-Coumarin shows molar extinction coefficients as high as 1.80 × 105 dm3 mol–1 cm–1. The fluorescence spectrum and fluorescence quantum yields of compounds ZnPc-Coumarin and CoPc-Coumarin are also investigated. The photoluminescence decay of the two transition-metal complexes in DMF solution, in poly(methyl methacrylate) (PMMA), and on TiO2 films has been studied with time-resolved emission. This study shows that the electron transfer from the dye to TiO2 is through space. The thermal stability studies indicate that both of the two complexes are stable up to 390°C. The ZnPc-Coumarin achieved a higher overall conversion efficiency than the reported SnPcCl2-Coumarin, InPcCl-Coumarin, and RuPcCl-Coumarin because of its slower charge recombination rate and faster electron injection from the dye to the conduction band of the conducting glass.

scholarly journals Effect of the Substitution Position on the Electronic and Solvatochromic Properties of Isocyanoaminonaphthalene (ICAN) Fluorophores

Molecules ◽  
2019 ◽  
Vol 24 (13) ◽  
pp. 2434 ◽  
Author(s):  
Sándor Lajos Kovács ◽  
Miklós Nagy ◽  
Péter Pál Fehér ◽  
Miklós Zsuga ◽  
Sándor Kéki
Keyword(s):  
Radiative Decay ◽  
Fluorescence Emission ◽  
Solvent Polarity ◽  
Decay Rates ◽  
Quantum Yields ◽  
Time Resolved Fluorescence ◽  
Solvatochromic Shift ◽  
Fluorescence Emission Spectra ◽  
Time Resolved ◽  
Donor And Acceptor

The properties of 1,4-isocyanoaminonaphthalene (1,4-ICAN) and 2,6-isocyanoaminonaphthalene (2,6-ICAN) isomers are discussed in comparison with those of 1,5-isocyanoaminonaphthalene (1,5-ICAN), which exhibits a large positive solvatochromic shift similar to that of Prodan. In these isocyanoaminonaphthalene derivatives, the isocyano and the amine group serve as the donor and acceptor moieties, respectively. It was found that the positions of the donor and the acceptor groups in these naphthalene derivatives greatly influence the Stokes and solvatochromic shifts, which decrease in the following order: 1,5-ICAN > 2,6-ICAN > 1,4-ICAN. According to high-level quantum chemical calculations, this order is well correlated with the charge transfer character of these compounds upon excitation. Furthermore, unlike 1,5-ICAN, the 1,4-ICAN and 2,6-ICAN isomers showed relatively high quantum yields in water, that were determined to be 0.62 and 0.21, respectively. In addition, time-resolved fluorescence experiments revealed that both the radiative and non-radiative decay rates for these three ICAN isomers varied unusually with the solvent polarity parameter ET(30). The explanations of the influence of the solvent polarity on the resulting steady-state and time-resolved fluorescence emission spectra are also discussed.

Photochemical cross sections in cytidylyl-(3′-5′)-cytidine

1968 ◽  
Vol 46 (8) ◽  
pp. 911-918 ◽  
Author(s):  
P. V. Hariharan ◽  
H. E. Johns
Keyword(s):  
Cross Sections ◽  
Quantum Yields ◽  
Important Class ◽  
Extinction Coefficients ◽  
Dark Reaction ◽  
Dna And Rna ◽  
Biological Interest ◽  
Thymine Dimers ◽  
The Cross ◽  
Molar Extinction Coefficients

Ultraviolet irradiation of cytidylyl-(3′-5′)-cytidine (CpC) results in the production of only one dimer, [Formula: see text], and for ultraviolet exposures in the range of biological interest, only the single hydrate (CpC)*. A second dimer of CpC, [Formula: see text], arises from [Formula: see text] through a dark reaction. Both these dimers deaminate in the dark to dimers of uridylyl-(3′-5′)-cytidine (UpC) and then to [Formula: see text]. The cross sections and quantum yields for the production of [Formula: see text] and (CpC)* have been determined at a number of wavelengths. In the wavelength range 240–289 mμ, the cross sections for dimer production are at least two times that for hydrate production. Approximate molar extinction coefficients have been determined for a mixture of [Formula: see text] and [Formula: see text], yielding values at ail wavelengths which are at least four times larger than for thymine dimers. The cross sections for dimer reversal of [Formula: see text] and [Formula: see text] are about the same and are larger than those of thymine dimers by at least a factor of 6.0. The quantum yield for reversal of CpC dimers is about 1.0 and independent of wavelength. These photochemical findings prove that in CpC, dimers are a much more important class of photoproduct than hydrates at low ultraviolet exposures. A similar result could be expected in polymers containing cytosine such as occur in DNA and RNA.

Near-infrared Ag2Se quantum dots with distinct absorption features and high fluorescence quantum yields

RSC Advances ◽  
2016 ◽  
Vol 6 (44) ◽  
pp. 38183-38186 ◽  
Author(s):  
Li-Juan Shi ◽  
Chun-Nan Zhu ◽  
He He ◽  
Dong-Liang Zhu ◽  
Zhi-Ling Zhang ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Near Infrared ◽  
Quantum Yields ◽  
Extinction Coefficients ◽  
Fluorescence Quantum Yields ◽  
High Fluorescence ◽  
Absorption Features ◽  
Molar Extinction Coefficients

Near-infrared Ag2Se QDs with distinct absorption features ranging between 830–954 nm and fluorescence quantum yields up to 23.4% were controllably synthesized, and the molar extinction coefficients of the Ag2Se QDs were determined.

Influence of molecular weight on the spectroscopic properties of a series of well-defined poly(3-hexylthiophene) polymers

2011 ◽  
Vol 89 (1) ◽  
pp. 27-33 ◽  
Author(s):  
Qiliang Peng ◽  
Ian W. Wyman ◽  
Dehui Han ◽  
Guojun Liu
Keyword(s):  
Molecular Weight ◽  
Refractive Index ◽  
Fluorescence Spectroscopy ◽  
Spectroscopic Properties ◽  
Extinction Coefficients ◽  
Maximum Absorbance ◽  
Molar Extinction Coefficients

A series of five poly(3-hexylthiophene) (P3HT) polymers were prepared, and their spectroscopic properties were studied. These polymers were well defined, with polydispersity indices no larger than 1.20 and regioregularities that were above 90% for each member of the series. The P3HT polymers were characterized using UV–vis and fluorescence spectroscopy, and their specific refractive index increments were measured in tetrahydrofuran. The influence of the molecular weight of these polymers on their maximum absorbance and emission wavelengths, molar extinction coefficients, and refractive index increments was studied.

scholarly journals Determination of the main spectral characteristics and conditions for the extraction of the cationic dye pyronine G with higher carboxylic acids

2020 ◽  
Vol 64 (12) ◽  
pp. 83-87
Author(s):  
Viachaslau U. Zhylko ◽  
◽  
Natalia V. Nekhan ◽  
Keyword(s):  
Carboxylic Acids ◽  
Polar Phase ◽  
Cationic Dye ◽  
Alkaline Ph ◽  
Photometric Analysis ◽  
Extinction Coefficients ◽  
Ph Values ◽  
Selection Of ◽  
Molar Extinction Coefficients

The selection of the suitable cationic dye is one of the key steps in extraction-photometric methods for the quantitative determination of hydrophobic anions, in particular, higher carboxylic acids. No less important is the reasonable selection of the required polar phase pH for extraction systems. It is because higher carboxylic acids are well extracted by non-polar phase in molecular form. It was found that, in contrast to other cationic dyes, pyronine G, which is stable in high alkaline pH values, is well extracted in form of ionic associates with higher carboxylic acids. The optimal composition of organic phase (5% solution by volume of n-octanol-1 in heptane) was found for quantitative analysis of higher carboxylic acids in the form of associates with pyronine G, at which the blank sample has a rather low optical density. Molar extinction coefficient of dyes for quantitative photometric analysis is an equally important characteristic of their optical properties. These properties depend on not only the nature of the substance itself, but also on the solvent. The molar extinction coefficients for organic (5.3·104 l·mol-1·cm-1) and aqueous phases (3.6·104 l·mol-1·cm-1) were determined for the above-found optimal extraction system for pyronine G with palmitic acid (water – 5% solution by volume of n-octanol-1 in heptane). They are 1.5-2 times higher than the molar extinction coefficients of safranin T and other cationic dyes used in the photometric analysis of hydrophobic acids in high alkaline pH values. Thus, the cationic dye pyronine G use for quantitative extraction-photometric analysis of higher carboxylic acids seems to be very promising.

scholarly journals Detectors for fast time-resolved studies at SSRC, status and future

2020 ◽  
Author(s):  
L. I. Shekhtman ◽  
A. S. Arakcheev ◽  
V. M. Aulchenko ◽  
V. N. Kudryavtsev ◽  
V. D. Kutovenko ◽  
...  
Keyword(s):  
Fast Time ◽  
Time Resolved

Photodissociation of ClONO2:  2. Time-Resolved Absorption Studies of Product Quantum Yields

1997 ◽  
Vol 101 (36) ◽  
pp. 6667-6678 ◽  
Author(s):  
R. J. Yokelson ◽  
James B. Burkholder ◽  
R. W. Fox ◽  
A. R. Ravishankara
Keyword(s):  
Quantum Yields ◽  
Time Resolved ◽  
Absorption Studies

Mechanistic studies of aromatic ketone-sensitized photoreduction of bis(acetylacetonato)copper(II)

1983 ◽  
Vol 61 (5) ◽  
pp. 801-808 ◽  
Author(s):  
Yuan L. Chow ◽  
Gonzalo E. Buono-Core ◽  
Bronislaw Marciniak ◽  
Carol Beddard
Keyword(s):  
Rate Constant ◽  
Rate Constants ◽  
Flash Photolysis ◽  
Decay Rates ◽  
Polynuclear Aromatic Hydrocarbons ◽  
Aromatic Ketone ◽  
Quantum Yields ◽  
Triplet States ◽  
Quenching Rate ◽  
Triplet Energy

Bis(acetylacetonato)copper(II), Cu(acac)2, quenches triplet excited states of ketones and polynuclear aromatic hydrocarbons efficiently, but only aromatic ketones with high triplet energy successfully sensitize photoreduction of Cu(acac)2 in alcohols under nitrogen to give derivatives of aeetylacetonatocopper(I), Cu(acac). For the triplet state benzophenone-sensitized photoreduction of Cu(acac)2, the quantum yields of photoreduction (ΦC) and those of benzophenone disappearance (ΦB) were determined in methanol with various concentrations of Cu(acac)2. The values of the quenching rate constant, kq, determined from these two types of monitors on the basis of the proposed mechanism were in good agreement (6.89 ~ 7.35 × 109 M−1 s−1). This value was higher, by a factor of about two, than that obtained from the monitor of the benzophenone triplet decay rates generated by flash photolysis in the presence of Cu(acac)2. The quenching rate constants of various aromatic ketone and hydrocarbon triplet states by Cu(acac)2 were determined by flash photolysis to be in the order of the diffusion rate constant and the quantum yields of these photoreductions were found to be far from unity. Paramagnetic quenching, with contributions of electron exchange and charge transfer, was proposed as a possible quenching mechanism. For a series of aromatic ketone sensitizers with higher triplet energy, this mechanism was used to rationalize the observed high quenching rate constants in contrast to the low quantum yields of photoreduction.

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