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Chemical Society Reviews Sep 2021There has been a significant push in recent years to deploy fundamental knowledge and methods of photochemistry toward biological ends. Photoreactive groups have enabled... (Review)
Review
There has been a significant push in recent years to deploy fundamental knowledge and methods of photochemistry toward biological ends. Photoreactive groups have enabled chemists to activate biological function using the concept of photocaging. By granting spatiotemporal control over protein activation, these photocaging methods are fundamental in understanding biological processes. Peptides and proteins are an important group of photocaging targets that present conceptual and technical challenges, requiring precise chemoselectivity in complex polyfunctional environments. This review focuses on recent advances in photocaging techniques and methodologies, as well as their use in living systems. Photocaging methods include genetic and chemical approaches that require a deep understanding of structure-function relationships based on subtle changes in primary structure. Successful implementation of these ideas can shed light on important spatiotemporal aspects of living systems.
Topics: Biological Phenomena; Peptides; Photochemistry; Proteins
PubMed: 34320043
DOI: 10.1039/d0cs01434f -
Photochemistry and Photobiology Mar 2022The photolysis of vanillin produces a short-lived triplet state where its lifetime is controlled by efficient self-quenching (k ~ 2 × 10 m s ) which also...
The photolysis of vanillin produces a short-lived triplet state where its lifetime is controlled by efficient self-quenching (k ~ 2 × 10 m s ) which also generates radicals. Free radical reactions, including vanillin dimer formation, are responsible for the degradation of vanillin and is accompanied by yellowing of the acetonitrile solutions. Laser flash photolysis studies reveal a triplet absorbing at 390 nm, readily quenched by naphthalenes, conjugated dienes and oxygen. Vanillin is also a good singlet oxygen sensitizer as revealed by its characteristic NIR emission at 1270 nm.
Topics: Benzaldehydes; Photochemistry; Photolysis; Singlet Oxygen
PubMed: 34570372
DOI: 10.1111/php.13520 -
Photochemical & Photobiological... Jan 2022Cholesta-5,7,9(11)-trien-3β-ol (9,11-dehydroprovitamin D, CTL) is used as a fluorescent probe to track the presence and migration of cholesterol in vivo. CTL is known...
Cholesta-5,7,9(11)-trien-3β-ol (9,11-dehydroprovitamin D, CTL) is used as a fluorescent probe to track the presence and migration of cholesterol in vivo. CTL is known to be photochemically active, but little consideration has been given to the formation efficiency and possible toxicity of its photoproducts. In degassed tetrahydrofuran (THF) solution, we isolated the photoproduct of CTL and of its 25-hydroxy derivative (HOCTL), and X-ray crystal structures were obtained for HOCTL and the photorearrangement product. The X-ray crystal structure and its H NMR spectrum confirm the product structure as a pentacyclic HOCTL isomer. In the presence of air in THF, endoperoxide formation via [2+4] addition of O* across the B ring of CTL or HOCTL becomes the dominant photoreaction. The UV spectrum and decay kinetics of the triplet state of HOCTL, the precursor of O*, are determined by transient absorption spectroscopy. We confirm the proposed structure of the endoperoxide by X-ray crystallography. Kinetics analysis of quantum yields provides rate constants for photophysical and photochemical events.
Topics: Cholesterol; Crystallography, X-Ray; Magnetic Resonance Spectroscopy; Photochemistry; Trientine
PubMed: 35000147
DOI: 10.1007/s43630-021-00131-w -
Molecules (Basel, Switzerland) Jan 2020The last decade has witnessed a remarkable development towards improved and new photochemical transformations in response to greener and more sustainable chemical... (Review)
Review
The last decade has witnessed a remarkable development towards improved and new photochemical transformations in response to greener and more sustainable chemical synthesis needs. Additionally, the availability of modern continuous flow reactors has enabled widespread applications in view of more streamlined and custom designed flow processes. In this focused review article, we wish to evaluate the standing of the field of continuous flow photochemistry with a specific emphasis on the generation of bioactive entities, including natural products, drugs and their precursors. To this end we highlight key developments in this field that have contributed to the progress achieved to date. Dedicated sections present the variety of suitable reactor designs and set-ups available; a short discussion on the relevance of greener and more sustainable approaches; and selected key applications in the area of bioactive structures. A final section outlines remaining challenges and areas that will benefit from further developments in this fast-moving area. It is hoped that this report provides a valuable update on this important field of synthetic chemistry which may fuel developments in the future.
Topics: Biological Products; Humans; Photochemical Processes; Photochemistry
PubMed: 31952244
DOI: 10.3390/molecules25020356 -
The Journal of Physical Chemistry. B Nov 2023Microbial rhodopsins are photoreceptive membrane proteins of microorganisms that express diverse photobiological functions. All--retinylidene Schiff base, the so-called... (Review)
Review
Microbial rhodopsins are photoreceptive membrane proteins of microorganisms that express diverse photobiological functions. All--retinylidene Schiff base, the so-called all--retinal, is a chromophore of microbial rhodopsins, which captures photons. It isomerizes into the 13- form upon photoexcitation. Isomerization of retinal leads to sequential conformational changes in the protein, giving rise to active states that exhibit biological functions. Despite the rapidly expanding diversity of microbial rhodopsin functions, the photochemical behaviors of retinal were considered to be common among them. However, the retinal of many recently discovered rhodopsins was found to exhibit new photochemical characteristics, such as highly red-shifted absorption, isomerization to 7- and 11- forms, and energy transfer from a secondary carotenoid chromophore to the retinal, which is markedly different from that established in canonical microbial rhodopsins. Here, I review new aspects of retinal found in novel microbial rhodopsins and highlight the emerging problems that need to be addressed to understand noncanonical retinal photochemistry.
Topics: Rhodopsins, Microbial; Rhodopsin; Photochemistry; Retina; Carotenoids
PubMed: 37853716
DOI: 10.1021/acs.jpcb.3c05467 -
Photochemistry and Photobiology Jan 2023Interest in Criegee intermediates (CIs), often termed carbonyl oxides, and their role in tropospheric chemistry has grown massively since the demonstration of... (Review)
Review
Interest in Criegee intermediates (CIs), often termed carbonyl oxides, and their role in tropospheric chemistry has grown massively since the demonstration of laboratory-based routes to their formation and characterization in the gas phase. This article reviews current knowledge regarding the electronic spectroscopy of atmospherically relevant CIs like CH OO, CH CHOO, (CH ) COO and larger CIs like methyl vinyl ketone oxide and methacrolein oxide that are formed in the ozonolysis of isoprene, and of selected conjugated carbene-derived CIs of interest in the synthetic chemistry community. Of the aforementioned atmospherically relevant CIs, all except CH OO and (CH ) COO exist in different conformers which, under tropospheric conditions, can display strikingly different thermal loss rates via unimolecular and bimolecular processes. Calculated photolysis rates based on their absorption properties suggest that solar photolysis will rarely be a significant contributor to the total loss rate for any CI under tropospheric conditions. Nonetheless, there is ever-growing interest in the absorption cross sections and primary photochemistry of CIs following excitation to the strongly absorbing ππ* state, and how this varies with CI, with conformer and with excitation wavelength. The later part of this review surveys the photochemical data reported to date, including a range of studies that demonstrate prompt photo-induced fission of the terminal O-O bond, and speculates about possible alternate decay processes that could occur following non-adiabatic coupling to, and dissociation from, highly internally excited levels of the electronic ground state of a CI.
Topics: Spectrum Analysis; Oxides; Photochemistry
PubMed: 35713380
DOI: 10.1111/php.13665 -
Photochemistry and Photobiology Nov 2021Sulfoximines are popular scaffolds in drug discovery due to their hydrogen bonding properties and chemical stability. In recent years, the role of reactive intermediates...
Sulfoximines are popular scaffolds in drug discovery due to their hydrogen bonding properties and chemical stability. In recent years, the role of reactive intermediates such as nitrenes has been studied in the synthesis and degradation of sulfoximines. In this work, the photochemistry of N-phenyl dibenzothiophene sulfoximine [5-(phenylimino)-5H-5λ -dibenzo[b,d]thiophene S-oxide] was analyzed. The structure resembles a combination of N-phenyl iminodibenzothiophene and dibenzothiophene S-oxide, which generate nitrene and O( P) upon UV-A irradiation, respectively. The photochemistry of N-phenyl dibenzothiophene sulfoximine was explored by monitoring the formation of azobenzene, a photoproduct of triplet nitrene, using direct irradiation and sensitized experiments. The reactivity profile was further studied through direct irradiation experiments in the presence of diethylamine (DEA) as a nucleophile. The studies demonstrated that N-phenyl dibenzothiophene sulfoximine underwent S-N photocleavage to release singlet phenyl nitrene which formed a mixture of azepines in the presence of DEA and generated moderate amounts of azobenzene in the absence of DEA to indicate formation of triplet phenyl nitrene.
Topics: Molecular Structure; Oxides; Photochemistry; Thiophenes
PubMed: 34022069
DOI: 10.1111/php.13456 -
Photochemical & Photobiological... May 2022Although reported several decades ago, 3,3',5,5'-tetramethoxybenzoin esters have not been used as a common photolabile protecting group, contrary to their unsymmetrical...
Although reported several decades ago, 3,3',5,5'-tetramethoxybenzoin esters have not been used as a common photolabile protecting group, contrary to their unsymmetrical 3',5'-dimethoxybenzoin analogues. While the properties of the latter are superior, their tedious synthesis and chemical instability represent a drawback. In this article, we describe a reliable synthetic access to the symmetrical tetramethoxybenzoin derivatives, and show that their photochemical behaviour remain interesting, in particular chromatically orthogonality with respect to nitroveratryl esters.
Topics: Esters; Photochemistry; Photolysis
PubMed: 35028893
DOI: 10.1007/s43630-021-00150-7 -
Methods (San Diego, Calif.) Sep 2019
Topics: Biosensing Techniques; Cell Membrane Permeability; Coloring Agents; Electrochemistry; Fluorescent Dyes; HeLa Cells; Humans; Hydrogen-Ion Concentration; Ions; Luminescence; Metals; Microscopy, Fluorescence; Nanotechnology; Organic Chemicals; Photochemistry; Quantum Dots
PubMed: 31521733
DOI: 10.1016/j.ymeth.2019.09.010 -
Angewandte Chemie (International Ed. in... Jan 2021Amino acids (AAs) are key structural motifs with widespread applications in organic synthesis, biochemistry, and material sciences. Recently, with the development of... (Review)
Review
Amino acids (AAs) are key structural motifs with widespread applications in organic synthesis, biochemistry, and material sciences. Recently, with the development of milder and more versatile radical-based procedures, the use of strategies relying on radical chemistry for the synthesis and modification of AAs has gained increased attention, as they allow rapid access to libraries of novel unnatural AAs containing a wide range of structural motifs. In this Minireview, we provide a broad overview of the advancements made in this field during the last decade, focusing on methods for the de novo synthesis of α-, β-, and γ-AAs, as well as for the selective derivatisation of canonical and non-canonical α-AAs.
Topics: Amino Acids; Humans; Peptides; Photochemistry
PubMed: 32841470
DOI: 10.1002/anie.202010157