-
Photochemical & Photobiological... May 2022Chemical actinometers are a useful tool in photochemistry, which allows to measure the photon flux of a light source to carry out quantitative analysis on...
Chemical actinometers are a useful tool in photochemistry, which allows to measure the photon flux of a light source to carry out quantitative analysis on photoreactions. The most commonly employed actinometers so far show minor drawbacks, such as difficult data treatment, parasite reactions, low stability or impossible reset. We propose herewith the use of 4,4'-dimethylazobenzene as a chemical actinometer. This compound undergoes a clean and efficient E/Z isomerization, approaching total conversion upon irradiation at 365 nm. Thanks to its properties, it can be used to determine the photon flux in the UV-visible region, with simple experimental methods and data treatment, and with the possibility to be reused after photochemical or thermal reset.
Topics: Photochemistry; Photons
PubMed: 35034332
DOI: 10.1007/s43630-021-00162-3 -
Postepy Biochemii 2015The article presents a short history of David Shugar studies in the field of photochemistry and UV spectroscopy of proteins and nucleic acids, carried out since the late...
The article presents a short history of David Shugar studies in the field of photochemistry and UV spectroscopy of proteins and nucleic acids, carried out since the late 1940s. to the beginning of the 1970s. of the 20th century, with some references to the state of related research in those days.
Topics: Belgium; Biochemistry; France; History, 20th Century; Nucleic Acids; Photochemistry; Poland; Proteins; Spectrophotometry, Ultraviolet
PubMed: 26677570
DOI: No ID Found -
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 -
Angewandte Chemie (International Ed. in... Feb 2023Light passes through biological tissue, and so it is used for imaging biological processes in situ. Such observation is part of the very essence of science, but... (Review)
Review
Light passes through biological tissue, and so it is used for imaging biological processes in situ. Such observation is part of the very essence of science, but mechanistic understanding requires intervention. For more than 50 years a "second function" for light has emerged; namely, that of photochemical control. Caged compounds are biologically inert signaling molecules that are activated by light. These optical probes enable external instruction of biological processes by stimulation of an individual element in complex signaling cascades in its native environment. Cause and effect are linked directly in spatial, temporal, and frequency domains in a quantitative manner by their use. I provide a guide to the basic properties required to make effective caged compounds for the biological sciences.
Topics: Photochemistry; Signal Transduction; Biology
PubMed: 36646644
DOI: 10.1002/anie.202206083 -
Chemistry (Weinheim An Der Bergstrasse,... Nov 2014The use of flow photochemistry and its apparent superiority over batch has been reported by a number of groups in recent years. To rigorously determine whether flow does... (Comparative Study)
Comparative Study
The use of flow photochemistry and its apparent superiority over batch has been reported by a number of groups in recent years. To rigorously determine whether flow does indeed have an advantage over batch, a broad range of synthetic photochemical transformations were optimized in both reactor modes and their yields and productivities compared. Surprisingly, yields were essentially identical in all comparative cases. Even more revealing was the observation that the productivity of flow reactors varied very little to that of their batch counterparts when the key reaction parameters were matched. Those with a single layer of fluorinated ethylene propylene (FEP) had an average productivity 20% lower than that of batch, whereas three-layer reactors were 20% more productive. Finally, the utility of flow chemistry was demonstrated in the scale-up of the ring-opening reaction of a potentially explosive [1.1.1] propellane with butane-2,3-dione.
Topics: Cycloaddition Reaction; Equipment Design; Photochemical Processes; Photochemistry; Polytetrafluoroethylene; Ultraviolet Rays
PubMed: 25263341
DOI: 10.1002/chem.201404347 -
Nature Chemistry Mar 2016Metal centres in biomolecules are recognized as being particularly sensitive to radiation damage by X-ray photons. This results in such molecules being both susceptible...
Metal centres in biomolecules are recognized as being particularly sensitive to radiation damage by X-ray photons. This results in such molecules being both susceptible to an effective X-ray-induced loss of function and problematic to study using X-ray diffraction methods, with reliable structures of the metal centres difficult to obtain. Despite the abundance of experimental evidence, the mechanistic details of radiation damage at metal centres are unclear. Here, using ab initio calculations, we show that the absorption of X-rays by microsolvated Mg(2+) results in a complicated chain of ultrafast electronic relaxation steps that comprise both intra- and intermolecular processes and last for a few hundred femtoseconds. At the end of this cascade the metal reverts to its original charge state, the immediate environment becomes multiply ionized and large concentrations of radicals and slow electrons build up in the metal's vicinity. We conclude that such cascades involving metal ions are essential to our understanding of radiation chemistry and radiation damage in biological environments.
Topics: Biochemistry; Electrons; Metals, Heavy; Photochemistry; X-Ray Diffraction; X-Rays
PubMed: 26892555
DOI: 10.1038/nchem.2429 -
Biochemistry Nov 2013The primary (100 fs to 10 ns) and secondary (10 ns to 100 μs) photodynamics in the type II light-oxygen-voltage (LOV) domain from the blue light YtvA photoreceptor...
The primary (100 fs to 10 ns) and secondary (10 ns to 100 μs) photodynamics in the type II light-oxygen-voltage (LOV) domain from the blue light YtvA photoreceptor extracted from Bacillus subtilis were explored with transient absorption spectroscopy. The photodynamics of full-length YtvA were characterized after femtosecond 400 nm excitation of both the dark-adapted D447 state and the light-adapted S390 state. The S390 state relaxes on a 43 min time scale at room temperature back into D447, which is weakly accelerated by the introduction of imidazole. This is ascribed to an obstructed cavity in YtvA that hinders access to the embedded FMN chromophore and is more open in type I LOV domains. The primary photochemistry of dark-adapted YtvA is qualitatively similar to that of the type I LOV domains, including AsLOV2 from Avena sativa, but exhibits an appreciably higher (60% greater) terminal triplet yield, estimated near the maximal ΦISC value of ≈78%; the other 22% decays via non-triplet-generating fluorescence. The subsequent secondary dynamics are inhomogeneous, with three triplet populations co-evolving: the faster-decaying (I)T* population (38% occupancy) with a 200 ns decay time is nonproductive in generating the S390 adduct state, a slower (II)T* population (57% occupancy) exhibits a high yield (Φadduct ≈ 100%) in generating S390 and a third (5%) (III)T*population persists (>100 μs) with unresolved photoactivity. The ultrafast photoswitching dynamics of the S390 state appreciably differ from those previously resolved for the type I AcLOV2 domain from Adiantum capillus-veneris [Kennis, J. T., et al. (2004) J. Am. Chem. Soc. 126, 4512], with a low-yield dissociation (Φdis ≈ 2.5%) reaction, which is due to an ultrafast recombination reaction, following photodissociation, and is absent in AcLOV2, which results in the increased photoswitching activity of the latter domain.
Topics: Bacillus subtilis; Bacterial Proteins; Photochemistry; Protein Structure, Secondary
PubMed: 24171435
DOI: 10.1021/bi4012258 -
Environmental Science & Technology Dec 2022Photocatalysis is regarded as one of the most promising technologies for indoor volatile organic compounds (VOCs) elimination due to its low cost, safe operation, energy... (Review)
Review
Photocatalysis is regarded as one of the most promising technologies for indoor volatile organic compounds (VOCs) elimination due to its low cost, safe operation, energy efficiency, and high mineralization efficiency under ambient conditions. However, the practical applications of this technology are limited, despite considerable research efforts in recent decades. Until now, most of the works were carried out in the laboratory and focused on exploring new catalytic materials. Only a few works involved the immobilization of catalysts and the design of reactors for practical applications. Therefore, this review systematically summarizes the research and development on photocatalytic oxidation (PCO) of VOCs, with emphasis on recent catalyst's immobilization and reactor designs in detail. First, different types of photocatalytic materials and the mechanisms for PCO of VOCs are briefly discussed. Then, both the catalyst's immobilization techniques and reactor designs are reviewed in detail. Finally, the existing challenges and future perspectives for PCO of VOCs are proposed. This work aims to provide updated information and research inspirations for the commercialization of this technology in the future.
Topics: Volatile Organic Compounds; Air Pollution, Indoor; Photochemistry; Catalysis; Oxidation-Reduction
PubMed: 36367480
DOI: 10.1021/acs.est.2c05444 -
Nature Nanotechnology Dec 2016Phototaxis is commonly observed in motile photosynthetic microorganisms. For example, green algae are capable of swimming towards a light source (positive phototaxis) to...
Phototaxis is commonly observed in motile photosynthetic microorganisms. For example, green algae are capable of swimming towards a light source (positive phototaxis) to receive more energy for photosynthesis, or away from a light source (negative phototaxis) to avoid radiation damage or to hide from predators. Recently, with the aim of applying nanoscale machinery to biomedical applications, various inorganic nanomotors based on different propulsion mechanisms have been demonstrated. The only method to control the direction of motion of these self-propelled micro/nanomotors is to incorporate a ferromagnetic material into their structure and use an external magnetic field for steering. Here, we show an artificial microswimmer that can sense and orient to the illumination direction of an external light source. Our microswimmer is a Janus nanotree containing a nanostructured photocathode and photoanode at opposite ends that release cations and anions, respectively, propelling the microswimmer by self-electrophoresis. Using chemical modifications, we can control the zeta potential of the photoanode and program the microswimmer to exhibit either positive or negative phototaxis. Finally, we show that a school of microswimmers mimics the collective phototactic behaviour of green algae in solution.
Topics: Light; Locomotion; Microscopy, Electron, Scanning; Nanowires; Photochemistry; Phototaxis; Surface Properties; Titanium
PubMed: 27749832
DOI: 10.1038/nnano.2016.187 -
Current Opinion in Neurobiology Oct 2009Neurobiology has entered a new era in which optical methods are challenging electrophysiological techniques for their value in measuring and manipulating neuronal... (Review)
Review
Neurobiology has entered a new era in which optical methods are challenging electrophysiological techniques for their value in measuring and manipulating neuronal activity. This change is occurring largely because of the development of new photochemical tools, some synthesized by chemists and some provided by nature. This review is focused on the three types of photochemical tools for neuronal control that have emerged in recent years. Caged neurotransmitters, including caged glutamate, are synthetic molecules that enable highly localized activation of neurotransmitter receptors in response to light. Natural photosensitive proteins, including channelrhodopsin-2 and halorhodopsin, can be exogenously expressed in neurons and enable rapid photocontrol of action potential firing. Synthetic small molecule photoswitches can bestow light-sensitivity on native or exogenously expressed proteins, including K(+) channels and glutamate receptors, allowing photocontrol of action potential firing and synaptic events. At a rapid pace, these tools are being improved and new tools are being introduced, thanks to molecular biology and synthetic chemistry. The three families of photochemical tools have different capabilities and uses, but they all share in enabling precise and noninvasive exploration of neural function with light.
Topics: Animals; Neurons; Neurotransmitter Agents; Photic Stimulation; Photochemistry
PubMed: 19828309
DOI: 10.1016/j.conb.2009.09.004