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Nature Communications Nov 2020Allosteric regulation is an innate control in most metabolic and signalling cascades that enables living organisms to adapt to the changing environment by tuning the...
Allosteric regulation is an innate control in most metabolic and signalling cascades that enables living organisms to adapt to the changing environment by tuning the affinity and regulating the activity of target proteins. For a microscopic understanding of this process, a protein system has been designed in such a way that allosteric communication between the binding and allosteric site can be observed in both directions. To that end, an azobenzene-derived photoswitch has been linked to the α3-helix of the PDZ3 domain, arguably the smallest allosteric protein with a clearly identifiable binding and allosteric site. Photo-induced trans-to-cis isomerisation of the photoswitch increases the binding affinity of a small peptide ligand to the protein up to 120-fold, depending on temperature. At the same time, ligand binding speeds up the thermal cis-to-trans back-isomerisation rate of the photoswitch. Based on the energetics of the four states of the system (cis vs trans and ligand-bound vs free), the concept of an allosteric force is introduced, which can be used to drive chemical reactions.
Topics: Allosteric Regulation; Azo Compounds; Binding Sites; Circular Dichroism; Disks Large Homolog 4 Protein; Fluorescence; Isomerism; PDZ Domains; Peptides; Photochemistry; Spectrophotometry, Ultraviolet; Tryptophan
PubMed: 33203849
DOI: 10.1038/s41467-020-19689-7 -
Journal of Materials Chemistry. B Dec 2019The scientific analysis of food safety issues and the establishment of rapid and efficient food safety detection methods are of great significance for safeguarding the... (Review)
Review
The scientific analysis of food safety issues and the establishment of rapid and efficient food safety detection methods are of great significance for safeguarding the health of consumers, ensuring the healthy development of food safety systems and realizing food safety strategies. As an emerging electrochemical analysis technology, photoelectrochemical (PEC) biosensors, which combine the advantages of biological analysis and optical analysis, have attracted extensive attention. Due to the complete separation of the excitation source (light) and the detection signal (current), the background signal of PEC biosensors is greatly decreased, and their sensitivity is high. The detection principle is that under illumination, the biological recognition effect between the bio-specific recognition element and the corresponding target causes a change in the signal generated by the photoactive nanomaterial. This review aims to cover the most recent advances of PEC biosensing in the field of food analysis, including mycotoxins, heavy metals, antibiotics, and pesticide residues. The future prospects in this field are also discussed.
Topics: Biosensing Techniques; Catalysis; Electrochemistry; Electrodes; Equipment Design; Food Analysis; Food Safety; Graphite; Light; Metals, Heavy; Nanostructures; Photochemistry; Polymers; Semiconductors
PubMed: 31720680
DOI: 10.1039/c9tb01644a -
Photochemistry and Photobiology Nov 2021An overview of the history, mechanistic aspects and applications is provided for p-hydroxyphenacyl (pHP) and benzoin photoremovable protecting groups, which release... (Review)
Review
An overview of the history, mechanistic aspects and applications is provided for p-hydroxyphenacyl (pHP) and benzoin photoremovable protecting groups, which release biologically important leaving groups upon photolysis with UV light. Also discussed is (7-diethylaminocoumarin-4-yl)methyl (DEACM), a photoremovable protecting group that absorbs visible light. These are followed by the α-keto amides and naphtho- and benzothiophene-2-carboxanilides as caging groups, which eliminate leaving groups via photochemically produced zwitterionic intermediates. Also covered are amino-1,4-benzoquinones, which upon exposure to green and red wavelengths of light photorearrange to an unstable photoproduct that subsequently eliminates leaving groups in aqueous media. Selected examples are given that use these photoremovable protecting (caging) groups for the light-activated release of biologically important substrates under physiological conditions in cells and tissue as practical applications in biology, biochemistry and physiology. These caging groups have found significant applications because their photochemistry is efficient and a single coproduct is formed in addition to the photoreleased substrate.
Topics: Photochemistry; Photolysis; Ultraviolet Rays
PubMed: 34101860
DOI: 10.1111/php.13462 -
International Journal of Molecular... Dec 2022In this research, the synthesis, photochemistry, and computational study of new - and -isomers of amino-thienostilbenes is performed to test the efficiency of their...
In this research, the synthesis, photochemistry, and computational study of new - and -isomers of amino-thienostilbenes is performed to test the efficiency of their production and acid resistance, and to investigate their electronic structure, photoreactivity, photophysical characteristics, and potential biological activity. The electronic structure and conformations of synthesized thienostilbene amines and their photocyclization products are examined computationally, along with molecular modeling of amines possessing two thiophene rings that showed inhibitory potential toward cholinesterases. New amino-styryl thiophenes, with favorable photophysical properties and proven acid resistance, represent model compounds for their water-soluble ammonium salts as potential styryl optical dyes. The comparison with organic dyes possessing a -aminostilbene subunit as the scaffold shows that the newly synthesized -aminostilbenes have very similar absorbance wavelengths. Furthermore, their functionalized -isomers and photocyclization products are good candidates for cholinesterase inhibitors because of the structural similarity of the molecular skeleton to some already proven bioactive derivatives.
Topics: Photochemistry; Thiophenes; Benzylamines; Models, Molecular; Coloring Agents
PubMed: 36614053
DOI: 10.3390/ijms24010610 -
Photochemistry and Photobiology Jan 2022The figure presented here illuminates the large number of variables that are necessary to adequately describe phototesting protocols. Each of these characteristics can...
The figure presented here illuminates the large number of variables that are necessary to adequately describe phototesting protocols. Each of these characteristics can be critical in understanding results presented in the photomedicine community as well as the broader photobiology and photochemistry communities. The inclusion of all of these variables within each phototesting publication will aid in discourse and further scientific discovery within our field.
Topics: Photobiology; Photochemistry
PubMed: 34312877
DOI: 10.1111/php.13493 -
Nature Oct 2021Metal-catalysed cross-couplings are a mainstay of organic synthesis and are widely used for the formation of C-C bonds, particularly in the production of unsaturated...
Metal-catalysed cross-couplings are a mainstay of organic synthesis and are widely used for the formation of C-C bonds, particularly in the production of unsaturated scaffolds. However, alkyl cross-couplings using native sp-hybridized functional groups such as alcohols remain relatively underdeveloped. In particular, a robust and general method for the direct deoxygenative coupling of alcohols would have major implications for the field of organic synthesis. A general method for the direct deoxygenative cross-coupling of free alcohols must overcome several challenges, most notably the in situ cleavage of strong C-O bonds, but would allow access to the vast collection of commercially available, structurally diverse alcohols as coupling partners. We report herein a metallaphotoredox-based cross-coupling platform in which free alcohols are activated in situ by N-heterocyclic carbene salts for carbon-carbon bond formation with aryl halide coupling partners. This method is mild, robust, selective and most importantly, capable of accommodating a wide range of primary, secondary and tertiary alcohols as well as pharmaceutically relevant aryl and heteroaryl bromides and chlorides. The power of the transformation has been demonstrated in a number of complex settings, including the late-stage functionalization of Taxol and a modular synthesis of Januvia, an antidiabetic medication. This technology represents a general strategy for the merger of in situ alcohol activation with transition metal catalysis.
Topics: Alcohols; Bromides; Carbon; Catalysis; Chlorides; Metals; Methane; Nitrogen; Oxidation-Reduction; Oxygen; Paclitaxel; Photochemistry; Simvastatin
PubMed: 34464959
DOI: 10.1038/s41586-021-03920-6 -
Spectrochimica Acta. Part A, Molecular... Nov 2021The synthesis, photoreactivity, and spectroscopic characterization of novel 1,2,3-triazole di-heterostilbenes bearing various aliphatic and aromatic substituents on the...
The synthesis, photoreactivity, and spectroscopic characterization of novel 1,2,3-triazole di-heterostilbenes bearing various aliphatic and aromatic substituents on the triazole rings were thoroughly explored. By introducing triazole rings into the o-divinylbenzene moiety, compared with the 2-furyl and 2-thienyl heteroanalogues, these compounds did not show any photochemical reactivity toward intramolecular cycloaddition reactions or electrocyclization processes. The research is further extended to the more in-depth examination of photochemical and photophysical characteristics of the investigated triazolo-stilbenes to explain the lack of reactivity in intramolecular photochemical cyclizations by configuration and substituent effects. Conformations of synthetically obtained novel triazoles are examined by Density Functional Theory (DFT). The time dependent-DFT approach was employed to obtain additional insight into the properties observed with UV/Vis spectroscopy. The frontier orbital energy was computationally investigated to determine the influence of cis-trans isomerism and the nature of substituents on the spectroscopic properties of the triazoles. Along with our previous studies of similar compounds containing furan and thiophene, respectively, this study shows that introducing various heteroaromatic rings induces diverse photochemistry and photophysics due to the conformational changes and change in electronic distribution within the molecular system.
Topics: Cyclization; Molecular Conformation; Photochemistry; Spectrum Analysis; Triazoles
PubMed: 34146829
DOI: 10.1016/j.saa.2021.120056 -
Chemical Reviews Apr 2020A detailed understanding of radiative and nonradiative processes in peptides containing an aromatic chromophore requires the knowledge of the nature and energy level of... (Review)
Review
A detailed understanding of radiative and nonradiative processes in peptides containing an aromatic chromophore requires the knowledge of the nature and energy level of low-lying excited states that could be coupled to the bright ππ* excited state. Isolated aromatic amino acids and short peptides provide benchmark cases to study, at the molecular level, the photoinduced processes that govern their excited state dynamics. Recent advances in gas phase laser spectroscopy of conformer-selected peptides have paved the way to a better, yet not fully complete, understanding of the influence of intramolecular interactions on the properties of aromatic chromophores. This review aims at providing an overview of the photophysics and photochemistry at play in neutral and charged aromatic chromophore containing peptides, with a particular emphasis on the charge (electron, proton) and energy transfer processes. A significant impact is exerted by the experimental progress in energy- and time-resolved spectroscopy of protonated species, which leads to a growing demand for theoretical supports to accurately describe their excited state properties.
Topics: Amino Acids, Aromatic; Energy Transfer; Fluorescence; Fluorescence Resonance Energy Transfer; Peptides; Photochemistry; Protein Conformation; Protons; Spectrophotometry, Ultraviolet; Ultraviolet Rays
PubMed: 31424927
DOI: 10.1021/acs.chemrev.9b00316 -
Natural Product Reports Feb 2020Covering: 1978 to 2019 The synthetically challenging [3.3.3]propellane core has caught a lot of attention over the last 50 years. This comprehensive review details all... (Review)
Review
Covering: 1978 to 2019 The synthetically challenging [3.3.3]propellane core has caught a lot of attention over the last 50 years. This comprehensive review details all synthetic strategies reported in the period 1978-2019 to facilitate the synthesis of carbocyclic [3.3.3]propellanes. The described strategies span from acid-catalyzed rearrangements and photo-mediated cycloadditions of ketones, heteropropellanes and dispiroundecanes to thermal rearrangements of acetylenes and alkenes. Other approaches, such as radical reactions with halogenated alkenes, domino cyclizations, the smart use of epoxide-carbonyl rearrangements and intramolecular palladium-catalyzed ring contractions are discussed as well. A special section is dedicated to triptindanes, a subclass of [3.3.3]propellanes which are of interest to material sciences.
Topics: Alkynes; Biological Products; Bridged-Ring Compounds; Catalysis; Cyclization; Cycloaddition Reaction; Epoxy Compounds; Ketones; Molecular Structure; Palladium; Photochemistry; Polycyclic Sesquiterpenes
PubMed: 31140489
DOI: 10.1039/c8np00086g -
Molecules (Basel, Switzerland) Jun 2022The structure, tautomerization pathways, vibrational spectra, and photochemistry of 2-amino-4-methylthiazole (AMT) molecule were studied by matrix isolation FTIR...
The structure, tautomerization pathways, vibrational spectra, and photochemistry of 2-amino-4-methylthiazole (AMT) molecule were studied by matrix isolation FTIR spectroscopy and DFT calculations undertaken at the B3LYP/6-311++G(3df,3pd) level of theory. The most stable tautomer with the five-membered ring stabilized by two double C=C and C=N bonds, was detected in argon matrices after deposition. When the AMT/Ar matrices were exposed to 265 nm selective irradiation, three main photoproducts, N-(1-sulfanylprop-1-en-2-yl)carbodiimide (fp1), N-(1-thioxopropan-2-yl)carbodiimide (fp2) and N-(2-methylthiiran-2-yl)carbodiimide (fp3), were photoproduced by a cleavage of the CS-CN bond together with hydrogen atom migration. The minor photoreaction caused by the cleavage of the CS-CC bond and followed by hydrogen migration formed 2-methyl-1H-azirene-1-carbimidothioic acid (fp15). We have also found that cleavage of the CS-CN bond followed by disruption of the N-C bond produced cyanamide (fp11) and the C(CH3)=CH-S biradical that transformed into 2-methylthiirene (fp12) and further photoreactions produced 1-propyne-1-thiole (fp13) or methylthioketene (fp14). Cleavage of the CS-CC bond followed by disruption of the N-C bond produced propyne (fp22) and the S-C(NH)=N biradical that transformed into 3-aminethiazirene (fp23); further photoreactions produced N-sulfanylcarbodiimide (fp25). As a result of these transformations, several molecular complexes were identified as photoproducts besides new molecules in the AMT photolysis process.
Topics: Carbodiimides; Hydrogen; Models, Molecular; Photochemistry; Spectroscopy, Fourier Transform Infrared
PubMed: 35745029
DOI: 10.3390/molecules27123897