| 1. |
- Benitez-Martin, Carlos, 1994, et al.
(författare)
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Fluorescent Molecular Photoswitches for the Generation of All-Optical Encryption Keys
- 2023
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Ingår i: Chemphotochem. - 2367-0932.
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Tidskriftsartikel (refereegranskat)abstract
- Herein, we report a tri-component photochromic molecular cocktail that can be used to encrypt and decrypt information. The time-dependent fluorescent response of this cocktail is highly non-linear with respect to the set of inputs used (concentrations of the three photochromic components, excitation- and emission wavelengths), a property required for the generation of so-called encryption keys. The all-optical system can generate more than 80 million unique fluorescence responses by applying different input combinations and is operated using a conventional fluorimeter.
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| 2. |
- Björk, Linnea, et al.
(författare)
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Amino-Acid Side-Chain Nanoarchitectonics for Tuning the Chiroptical Properties and Supramolecular Structure of Pentameric Oligothiophenes
- 2024
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Ingår i: ChemPhotoChem. - : WILEY-V C H VERLAG GMBH. - 2367-0932.
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Tidskriftsartikel (refereegranskat)abstract
- Oligothiophenes with specific photophysical properties and molecular organization are of great interest, since this class of materials are used in organic electronics and bioelectronics, as well as biosensing. Herein, 8 different pentameric oligothiophenes, denoted proteophenes, with different amino acid substitution patterns at distinct positions along the thiophene backbone were investigated. Spectroscopic and microscopic studies of the ligands revealed the formation of optically active self-assembled materials under acidic or basic conditions. The distinct photophysical characteristics, including induced circular dichroism, as well as the supramolecular structures of the assemblies deduced from light scattering and transmission electron microscopy, were highly influenced by the positioning of distinct amino acid moieties along the thiophene backbone. Proteophenes functionalized with only glutamate residues or these functionalities in combination with hydrophobic valine moieties formed fibrillar structures with excellent chiroptical properties under acidic conditions. In addition, the amino acid functionality at the beta-position of distinct thiophene moieties influenced the induced circular dichroism pattern observed from the proteophenes. Overall, the obtained results demonstrate how changes in the position of various amino acid functionalities, as well as the chemical nature of the amino acid side chain functionality greatly affect the optical properties as well as the architecture of the self-assembled materials. Self-assembled Proteophenes. Oligothiophenes with distinct amino acid side-chain functionalities along the conjugated backbone displayed distinct chiroptical and structural properties in acidic or alkaline solutions. The distinct photophysical characteristics, as well as the supramolecular structures of the assemblies were highly influenced by the chemical nature of the amino acid, as well as the positioning of distinct amino acid moieties along the thiophene backbone.image
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| 3. |
- Blaise, Nadine, et al.
(författare)
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Isomerization dynamics of a novel cis/trans-only merocyanine
- 2024
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Ingår i: ChemPhotoChem. - 2367-0932. ; 8:3
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Tidskriftsartikel (refereegranskat)abstract
- Merocyanines (MC) usually adopt ring opened zwitterionic structures that are interconvertible with their ring-closed spiropyran photoisomers. By methylating the phenolate oxygen, and thereby blocking the ring-closure reaction, a cis/trans-only MC photoswitch was obtained, yielding a perfect candidate for a detailed examination of the cis/trans isomerization mechanism for this class of compounds. This photoswitch displays outstanding properties including excellent photoreaction quantum yields and photoswitching turnovers. Due to the central polymethine bridge of MC, in principle eight cis (C)/trans (T) isomers are possible. Density Functional Theory (DFT) calculations revealed the CCT and TTT-isomers of the studied compound as most stable cis and trans ground state isomers, respectively. UV/vis transient absorption studies combined with conical intersection computations with the complete active space self-consistent field (CASSCF) method show that both trans/cis- and cis/trans-photoisomerizations are initiated by a rotation of the central doubled bond fragment. A hot ground state species is then formed, which undergoes a second isomerization. Thus, the cis/trans reaction proceeds via a CCT-CTT-TTT sequence and the reverse reaction via TTT-TCT-CCT.
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| 4. |
- Bozal-Ginesta, Carlota, et al.
(författare)
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Self-Recovery of Photochemical H2 Evolution with a Molecular Diiron Catalyst Incorporated in a UiO-66 Metal-Organic Framework
- 2020
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Ingår i: ChemPhotoChem. - : Wiley. - 2367-0932. ; 4:4, s. 287-290
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Tidskriftsartikel (refereegranskat)abstract
- Photochemical hydrogen evolution from a UiO‐66‐incorporated Fe2(dcbdt)(CO)6 catalyst in conjunction with a ruthenium photosensitizer and an ascorbate donor ceases after a period of irradiation, but is restored after a 60 min. resting period in the dark. Control experiments show that neither product inhibition nor pore clogging is responsible for this surprising behaviour, and intra‐crystal linker scrambling is proposed as a potential explanation.
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| 5. |
- Colas, Kilian, et al.
(författare)
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Photophysical Characteristics of Polarity-Sensitive and Lipid Droplet-Specific Phenylbenzothiadiazoles
- 2021
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Ingår i: ChemPhotoChem. - : Wiley. - 2367-0932. ; 5:7, s. 632-643
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we present a series of solvatochromic phenylbenzothiadiazoles that display dual emission from the locally excited (LE) and intramolecular charge transfer (ICT) excited states. The donor-acceptor derivatives are highly sensitive to polarity changes, which can be monitored by differences in emission efficiency, spectroscopic shifts and variations of the LE/ICT ratio. One of the compounds in the series, containing a thiomethyl substituent, emerged as an excellent blue emitting stain for intracellular lipid droplets, a biomarker for various types of cancer. In addition, a non-emissive nitro derivative becomes fluorescent upon bioreduction in hypoxic cancer cells and accumulates in lipid droplets with a high signal-to-background ratio.
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| 6. |
- Corbella, Marina, et al.
(författare)
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Spectral Variability in Phycocyanin Cryptophyte Antenna Complexes is Controlled by Changes in the alpha-Polypeptide Chains
- 2019
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Ingår i: ChemPhotoChem. - : WILEY-V C H VERLAG GMBH. - 2367-0932. ; 3:9, s. 945-956
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Tidskriftsartikel (refereegranskat)abstract
- Quantitative models of light harvesting in photosynthetic antenna complexes depend sensitively on the challenging determination of the relative site energies of the pigments. Herein we analyze the basis of the light harvesting properties of four antennae from cryptophyte algae, phycocyanines PC577, PC612, PC630 and PC645, by comparing two alternative theoretical strategies to derive the excitonic Hamiltonian. The first is based on molecular dynamics simulations and subsequent polarizable quantum/molecular mechanics (QM/MMPol) calculations, whereas the second is based on three-layer QM/MMPol/ddCOSMO calculations performed on optimized geometries of the pigments, where the water solvent is described using the ddCOSMO continuum model. We find the latter approach to be remarkably accurate, suggesting that these four phycobiliproteins share a common energetic ordering PCB82 < PCB158 < DBV51/61 for pigments located in the highly-conserved beta chains, whereas bilins in the more divergent alpha chains cause their spectral differences. In addition, we predict a strong screening of the coupling among central dihydrobiliverdins (DBVs) in "open" form complexes PC577 and PC612 compared to "closed" form ones, which together with the increased interpigment separation explains the attenuation of coherence beatings observed for these complexes.
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| 7. |
- Doloczki, Susanne, et al.
(författare)
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An Indolin-3-imine Photobase and pH Sensitive Fluorophore
- 2023
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Ingår i: ChemPhotoChem. - : John Wiley & Sons. - 2367-0932.
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Tidskriftsartikel (refereegranskat)abstract
- This work presents the pH sensing ability of a fluorescent indolin-3-imine derivative. Protonation of the weakly basic imine (pKa = 8.3 of its conjugate acid) results in a significant redshift of the absorption band. The fluorophore acts as a photobase, with a basicity increase of approximately 6 units upon photoexcitation. This behavior promotes excited state proton transfer from weak acids such as protic solvents. The characteristics of the fluorophore enable sensing of water fractions in organic solvents and differentiation between methanol, ethanol, and longer chain alcohols. Initial cell studies indicated the future potential of indolin-3-imines as fluorophores for bioimaging applications.
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| 8. |
- Falklöf, Olle, 1986-, et al.
(författare)
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Computational Identification of Pyrrole Ring C as the Preferred Donor for Excited-State Proton Transfer in Bacteriophytochromes
- 2018
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Ingår i: ChemPhotoChem. - Weinheim, Germany : Wiley-VCH Verlagsgesellschaft. - 2367-0932. ; 2:6, s. 453-457
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Tidskriftsartikel (refereegranskat)abstract
- The engineering of bacteriophytochrome photoreceptors into near-infrared fluorescent proteins is a promising route toward deep-tissue imaging of living cells with many challenges ahead. One key objective is to increase the fluorescence quantum yields, which are limited by competing non-radiative relaxation processes involving not only the well-known double-bond photoisomerization of the tetrapyrrole chromophore, but also a potential excited-state proton transfer from the chromophore to the protein. Motivated by the lack of mechanistic knowledge about this proton transfer, we here use hybrid quantum mechanics/molecular mechanics methods to investigate three possible scenarios for how the process is initiated. Through calculated excited-state pKa values of the chromophore inside the protein matrix of Deinococcus radiodurans bacteriophytochrome, it is found that pyrrole ring C is a much more likely donor for excited-state proton transfer than rings A and B, which are also possible donors discussed in the literature. This finding offers a starting point for establishing a strategy to strengthen the fluorescence of engineered bacteriophytochromes through biochemical inhibition of the proton transfer.
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| 9. |
- Fernández Galván, Ignacio, 1977-, et al.
(författare)
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Chemiexcitation without the Peroxide Bond? : Replacing oxygen with other heteroatoms
- 2019
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Ingår i: ChemPhotoChem. - : Wiley. - 2367-0932. ; 3:9, s. 957-967
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Tidskriftsartikel (refereegranskat)abstract
- Chemiexcitation is the population of electronic excited states from the electronic ground state via radiationless non-adiabatic transitions upon thermal activation. The subsequent emission of the excess of energy in the form of light is called chemiluminescence or bioluminescence when occurring in living organisms. Key intermediates in these reactions have been shown to contain a high-energy (often cyclic) peroxide which decomposes. The simplest molecules, 1,2-dioxetane and 1,2-dioxetanone, have thus been used extensively both theoretically and experimentally as model systems to understand the underlying mechanisms of chemiexcitation. An outstanding question remains whether the peroxide bond is a necessity and whether equivalent processes could happen in other simple molecules not containing an OO bond. In the present work, the decomposition reactions of four analogs of 1,2-dioxetane not containing a peroxide bond, the 1,2-oxazetidine anion, the 1,2-diazetidine anion, (neutral) 1,2-oxazetidine and 1,2-dithietane, have been studied theoretically using ab initio multicongurational methods. In particular, the reaction energy barriers and spin-orbit coupling strengths were calculated; the electronic degeneracy was studied and compared to the case of 1,2-dioxetane to assess the potentiality of chemiexcitation in the analog molecules.
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| 10. |
- Fleming, Cassandra L., et al.
(författare)
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On-Command Regulation of Kinase Activity using Photonic Stimuli
- 2019
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Ingår i: ChemPhotoChem. - : Wiley. - 2367-0932. ; 3:6, s. 318-326
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Forskningsöversikt (refereegranskat)abstract
- The underlying role that many kinases play in complex cellular pathways as well as disease remains unclear. To better understand the role that kinases play in both health and disease states, the use of light as an external stimulus to modulate kinase activity with high spatiotemporal resolution has gained increasing interest over the years. Herein we highlight the progress made towards the development of light-responsive kinase enzymes and small molecule inhibitors. In these examples, photolabile caging groups and photoswitchable entities have been utilised to modulate either kinase activation or inhibition in a light-controlled manner.
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