Photoinduced Interaction Research Articles

An RNA Motif That Enables Optozyme Control and Light-Dependent Gene Expression in Bacteria and Mammalian Cells.

The regulation of gene expression by light enables the versatile, spatiotemporal manipulation of biological function in bacterial and mammalian cells. Optoribogenetics extends this principle by molecular RNA devices acting on the RNA level whose functions are controlled by the photoinduced interaction of a light-oxygen-voltage photoreceptor with cognate RNA aptamers. Here light-responsive ribozymes, denoted optozymes, which undergo light-dependent self-cleavage and thereby control gene expression are described. This approach transcends existing aptamer-ribozyme chimera strategies that predominantly rely on aptamers binding to small molecules. The optozyme method thus stands to enable the graded, non-invasive, and spatiotemporally resolved control of gene expression. Optozymes are found efficient in bacteria and mammalian cells and usher in hitherto inaccessible optoribogenetic modalities with broad applicability in synthetic and systems biology.

Tuning the selectivity of photothermal CO2 hydrogenation through photo-induced interaction between Ni nanoparticles and TiO2

Photothermal CO2 hydrogenation into value-added chemicals driven by abundant solar energy is a promising and sustainable approach for achieving carbon neutralization. Herein, we demonstrate the photo-induced interaction between Ni nanoparticles and TiO2 support (Ni@TiO2) for maneuvering the selectivity of photothermal CO2 hydrogenation. According to experimental characterizations and theoretical simulations, the formed strong metal-support interaction between Ni and TiO2 can significantly enhance the adsorption of key intermediate *CO for further hydrogenation, thus tuning the CO2 hydrogenation pathway toward CH4. Consequently, the Ni@TiO2 catalyst exhibits a CH4 production rate of 286.5 mmol gcat−1 h−1 with an 81.8% selectivity under full-spectrum solar light irradiation. Moreover, in situ experimental characterizations and theoretical calculations suggest that photothermal CO2 hydrogenation over Ni@TiO2 undergoes a stepwise hydrogenation pathway to methane. This work offers insights into a simple approach for designing efficient nonprecious metal-based CO2 methanation catalysts.

Influence of the fluoride anion on photoinduced charge transfer interactions in adenine-functionalized push–pull naphthalenediimide chromophores

A new series of nucleobase adenine (A)-functionalized naphthalene diimide (NDI) derivatives to form a donor–acceptor conjugate has been designed, synthesized and characterized.

Optical force mapping at the single-nanometre scale

Three-dimensional (3D) information of the optical response in the nanometre scale is important in the field of nanophotonics science. Using photoinduced force microscopy (PiFM), we can visualize the nano-scale optical field using the optical gradient force between the tip and sample. Here, we demonstrate 3D photoinduced force field visualization around a quantum dot in the single-nanometre spatial resolution with heterodyne frequency modulation technique, using which, the effect of the photothermal expansion of the tip and sample in the ultra-high vacuum condition can be avoided. The obtained 3D mapping shows the spatially localized photoinduced interaction potential and force field vectors in the single nano-scale for composite quantum dots with photocatalytic activity. Furthermore, the spatial resolution of PiFM imaging achieved is ~0.7 nm. The single-nanometer scale photoinduced field visualization is crucial for applications such as photo catalysts, optical functional devices, and optical manipulation.

Role of Chiral Configuration in the Photoinduced Interaction of D- and L-Tryptophan with Optical Isomers of Ketoprofen in Linked Systems.

The study of the L- and D-amino acid properties in proteins and peptides has attracted considerable attention in recent years, as the replacement of even one L-amino acid by its D-analogue due to aging of the body is resulted in a number of pathological conditions, including Alzheimer’s and Parkinson’s diseases. A recent trend is using short model systems to study the peculiarities of proteins with D-amino acids. In this report, the comparison of the excited states quenching of L- and D-tryptophan (Trp) in a model donor–acceptor dyad with (R)- and (S)-ketoprofen (KP-Trp) was carried out by photochemically induced dynamic nuclear polarization (CIDNP) and fluorescence spectroscopy. Quenching of the Trp excited states, which occurs via two mechanisms: prevailing resonance energy transfer (RET) and electron transfer (ET), indeed demonstrates some peculiarities for all three studied configurations of the dyad: (R,S)-, (S,R)-, and (S,S)-. Thus, the ET efficiency is identical for (S,R)- and (R,S)-enantiomers, while RET differs by 1.6 times. For (S,S)-, the CIDNP coefficient is almost an order of magnitude greater than for (R,S)- and (S,R)-. To understand the source of this difference, hyperpolarization of (S,S)-and (R,S)- has been calculated using theory involving the electron dipole–dipole interaction in the secular equation.

A study on the interaction of nile blue with Uracils: A spectroscopic and computational approach.

The present work focuses the investigation on fluorescence quenching of nile blue (NB) in presence of various substituted uracil molecules. UV-Visible absorption studies signify the possibility of ground state complex formation between NB and uracil molecules. The increase in concentration of quencher molecules greatly influences the emission spectra of NB. The bimolecular quenching rate constant (kq) were calculated and found to depend on the position and electronic properties of substituent in quencher molecules. Fluorescence quenching experiments were performed at different temperature to calculate the thermodynamic parameters. The fluorescence lifetime measurements show that the quenching process proceeds through static quenching. The mechanism of fluorescence quenching includes the possibility of proton transfer. The bond dissociation enthalpy (BDE) reveals the release of H from the quencher molecules. The quencher molecules possess antioxidant activity and identified using deoxyribose degradation assay. The position of substituent and its electronic property are key features to address the antioxidant activity of uracil molecules.

Electron transfer governed by light\u2013matter interaction at metal\u2013semiconductor interface

The photoexcitation of heterostructures consisting of metallic nanoclusters and a semiconductor has been extensively investigated in relation to interests in photocatalysis and optical devices. The optoelectronic functions of the heterostructures originate from localized surface plasmon resonance, which can induce electron and resonance energy transfers. While it is well known that photoinduced electronic interaction between a metallic nanocluster and a semiconductor is responsible for the resonance energy transfer, the electron transfer associated with the photoinduced electronic interaction has not been discussed. In this paper, we elucidate the photoexcitation dynamics of a silver nanocluster/TiO2 heterostructure using an original first-principles computational approach that explicitly deals with light–matter interactions. It is shown that the photoinduced silver–TiO2 electronic interaction causes excited electrons to be directly transferred from the silver nanocluster to the TiO2 layer without passing through the conduction band of the silver nanocluster.

"Expression of Concern to Photoinduced interaction studies on N-(2-methylthiophenyl)-2-hydroxy-1-naphthadiamine with TiO2 nanoparticles: A Combined Experimental and Theoretical (DFT and Spectroscopic) approach" [Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 133 (2014) 80-86

"Expression of Concern to Photoinduced interaction studies on N-(2-methylthiophenyl)-2-hydroxy-1-naphthadiamine with TiO2 nanoparticles: A Combined Experimental and Theoretical (DFT and Spectroscopic) approach" [Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 133 (2014) 80-86

Photoinduced interaction of arylamine dye with carbon quantum dots ensued from Centella asiatica

Developing new carbon nano-materials and interaction studies with organic dye molecules are raising interest in the current scenario for photovoltaic applications. Herein, a simple, economical and green method is adopted for the synthesis of carbon quantum dots via hydrothermal process using Centella asiatica as a carbon source (CQDs). The synthesized CQDs were characterized by vital techniques such as atomic force microscope (AFM), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), UV−vis absorption, steady-state and time-resolved fluorescence spectroscopy. The results reveal that the synthesized CQDs were spherical shape with an average diameter of ~ 2nm. It shows the emission maximum at 440nm with a quantum yield of 3% and it exhibit broad and excitation-dependent emission spectra, which is a unique property of CDs. Further, fluorescence quenching of an arylamine dye, 2-Cyano-3-(4-diphenylamino-phenyl)-acrylic acid (TCC) with CQDs has also been studied. The quenching mechanism of TCC with CQDs was evaluated by Stern–Volmer equation and the time-resolved fluorescence lifetime studies. The results explored that the dominant process of fluorescence quenching is attributed to electron transfer from excited TCC to CQDs. As a consequence of the work, CQDs can be used as a acceptor material for various emerging fields such as in photovoltaics, photocatalytic water treatment and etc.

Photo-induced interaction of thioglycolic acid (TGA)-capped CdTe quantum dots with cyanine dyes

The photo-induced interaction of three different sizes of thioglycolic acid (TGA)-capped CdTe quantum dots (CdTe QDs) with two monomethine cyanine dyes belonging to the thiazole orange (TO) family has been studied. Positively charged cyanines interact with QDs surface which is negatively charged due to capping agent carboxylate ions. The energy transfer parameters including Stern-Volmer constant, Ksv, number of binding sites, n, quenching sphere radius, r, the critical energy transfer distance, R0, and energy transfer efficiencies, E have been calculated. The effect of structure and the number of aggregating molecules have been studied as a function of CdTe QDs particle size. Combining organic and inorganic semiconductors leads to increase of the effective absorption cross section of the QDs which can be utilized in novel nanoscale designs for light-emitting, photovoltaic and sensor applications. A synthesized triplet emission of the studied dyes was observed using CdTe QDs as donors and this is expected to play a potential role in molecular oxygen sensitization and in photodynamic therapy (PDT) applications.

Thermo- and photoinduced interaction between the components of a poly(n-butyl methacrylate)–fullerene C60 composite

Dispersity of fullerene C60 in poly(n-butyl methacrylate), thermo- and photoinduced binding of components of the composite and the influence of this interaction on the composite thermal destruction kinetics were investigated by means of optical absorption and mass spectrometry.

Photoinduced interactions of supramolecular ruthenium(II) complexes with plasmid DNA: synthesis and spectroscopic, electrochemical, and DNA photocleavage studies.

Two new bridging ligands have been synthesized by combining substituted benzaldehydes with phenanthrolinopyrrole (php), resulting in new polyazine bridging ligands. The ligands have been characterized by (1)H NMR, mass spectroscopy, and elemental analysis. These new ligands display π-π* transitions above 500 nm with modest molar absorptivities. Upon excitation at the ligand-centered charge-transfer transition, weak emission with a maximum wavelength of 612 nm is observed. When coordinated to two ruthenium(II) bis(bipyridyl) groups, the new bimetallic complexes generated give an overall 4+ charge. The electronic transitions of the bimetallic ruthenium(II) complexes display traditional π-π* transitions at 287 nm and metal-to-ligand charge-transfer transitions at 452 nm with molar absorptivities greater than 30000 M(-1) cm(-1). Oxidation of the ruthenium(II) metal centers to ruthenium(III) occurs at potentials above 1.4 V versus the Ag/AgCl reference electrode. Spectroscopic and electrochemical measurements indicate that the ruthenium(II) moieties behave independently. Both complexes are water-soluble and show the ability to photonick plasmid DNA when irradiated with low-energy light above 550 nm. In addition, one of the complexes, [Ru(bpy)2php]2Van(4+), shows the ability to linearize plasmid DNA and gives evidence, by gel electrophoresis, of photoinduced binding to plasmid DNA.

Photo-induced inter-protein interaction changes in the time domain; a blue light sensor protein PixD

ABSTRACT : For understanding molecular mechanisms of photochemical reactions, in particular reactions of proteins with biological functions, it is important to elucidate both the initial reactions from the photoexcited states and the series of subsequent chemical reactions, e.g., conformation, intermolecular interactions (hydrogen bonding, hydrophobic interactions), and inter-protein interactions (oligomer formation, dissociation reactions). Although time-resolved detection of such dynamics is essential, these dynamics have been very difficult to track by traditional spectroscopic techniques. Here, relatively new approaches for probing the dynamics of protein photochemical reactions using time-resolved transient grating (TG) are reviewed. By using this method, a variety of spectrally silent dynamics can be detected and such data provide a valuable description about the reaction scheme. Herein, a blue light sensor protein TePixD is the exemplar. The initial photochemistry for TePixD occurs around the chromophore and is detected readily by light absorption, but subsequent reactions are spectrally silent. The TG experiments revealed conformational changes and changes in inter-protein interactions, which are essential for TePixD function. The TG experiments also showed the importance of fluctuations of the intermediates as the driving force of the reaction. This technique is complementary to optical absorption detection methods. The TG signal contains a variety of unique information, which is difficult to obtain by other methods. The advantages and methods for signal analyses are described in detail in this review. ultraviolet

Photoinduced interactions of two dirhodium complexes with d(GTCGAC)2 probed by 2D NOESY.

The interactions between the 6-mer duplex oligonucleotide d(GTCGAC)2 and the photoactive dirhodium complexes cis-H,H-[Rh2(HNOCCH3)2(L)(CH3CN)4](2+), where L represents bpy (1, 2,2'-bipyridine) and dppz (2, dipyrido[3,2-a:2',3'-c]phenazine), were probed using 2D (1)H-(1)H NOESY NMR spectroscopy. Complex does not interact with the duplex in the dark, but binds covalently to the terminal guanine following irradiation with visible light. Similar behavior was observed for 2, but in addition to the photoinduced covalent DNA binding, the planar dppz ligand of the complex shields the terminal cytosine protons after irradiation. The results are consistent with photoinduced guanine coordination and end-capping of the duplex through π-stacking interactions with the terminal GC base pair. These data show that in the presence of the 6-mer duplex oligonucleotide, 1 and 2 exhibit photoinduced covalent binding to DNA. In addition, the π-stacking interactions of 2 with the duplex are enhanced upon irradiation.

Photoinduced interaction of CdSe quantum dot with coumarins

Cadmium selenide (CdSe) quantum dots (QDs) were synthesized with a cubic shape having a diameter of ~5.24nm. The prepared CdSe QDs were characterized by using UV–visible, Fourier transform infrared (FTIR), powder X-ray diffraction (XRD) and transmission electron microscope (TEM) measurements. The UV–visible absorption spectra indicate that the optical band gap of CdSe QDs is ~622nm and the peak shift can mainly be due to the quantum size effects. The fluorescence decay kinetics for the synthesized QDs was followed by time-resolved fluorescence spectroscopy, and the spectra were analyzed in regard to a bi-exponential model to identify two lifetime values, that is, shorter-lifetime 1.37ns (55%) and longer-lifetime 6.58ns (45%). The interaction of coumarin 152 (C152) and coumarin 153 (C153) with QDs surface brings about further considerable changes in the absorption and fluorescence patterns. The calculated binding constant from fluorescence quenching method matches well with that determined from the absorption spectral changes. The static quenching mechanism was confirmed by large magnitude of KSV and unaltered fluorescence lifetime.

Ultrafast pump-probe spectroscopy in gallium arsenide at 25 T.

We have performed high-fluence, nondegenerate pump-probe spectroscopy in the Split Florida-Helix magnet at 25 T and 15 K. The electronic component of our ultrafast differential reflectivity can be described with a simplified four-level approximation to determine the scattering and recombination rates. Ultrafast oscillations are well described by a coherent acoustic phonon model. Our free-space ultrafast spectroscopic technique will permit future experimental investigations to study novel photoinduced phase transitions and complex interactions in correlated electron systems, which will require the high pulse energies of our free-space alternative.

Exploring photoinduced electron transfer and excited-state proton transfer reactions involving 9-aminoacridine hydrochloride hydrate and methyl viologen using laser flash photolysis

In this letter photoinduced interactions of methyl viologen (MV2+) with 9-aminoacridine hydrochloride hydrate (9AA-HCl) have been studied. In homogeneous medium, both photoinduced electron transfer (PET) and excited-state proton transfer (ESPT) are occurring whereas in micellar medium only PET is prevalent. Magnetic field effect confirms that the PET takes place primarily in the triplet state. Discrepancy in theoretically calculated and experimentally obtained B1/2 values indicates the presence of electron hopping mechanism. Amalgamation of this letter with our previous report indicates that 9AA-HCl may either act as an electron donor or acceptor in PET reactions under suitable condition of redox potentials.

Photoinduced interaction studies on N-(2-methylthiophenyl)-2-hydroxy-1-naphthadiamine with TiO2 nanoparticles: A combined experimental and theoretical (DFT and spectroscopic) approach

Schiff base derivative synthesized by the reaction of 2-(methylthio) aniline and 2-hydroxy-1-naphthaldehyde exhibits keto-amine tautomerism in methanol solvent. The fluorescence quenching of N-(2-methyl thiophenyl)-2-hydroxy-1-naphthadiamine (NMTHN) by TiO2 nanoparticles in methanol has been studied. The excitation and emission peaks have been observed at 439 and 509nm respectively. The apparent association constant has been deduced from the absorption spectral changes of NMTHN–TiO2 nanoparticles using Bensi-Hildebrand equation. The number of binding sites and the binding constant have been calculated from the relevant fluorescence data. Quenching of fluorescence of NMTHN by TiO2 could be due to a dynamic mode. Density Functional Theory (DFT) calculations also have been performed to study the charge distribution of NMTHN–TiO2 both in ground and excited states. The HOMO–LUMO analysis of NMTHN–TiO2 in the ground state has been made.

A spectroscopic investigation of the photophysical behaviour of 9-aminoacridine hydrochloride hydrate in presence of organic amines in homogeneous and heterogeneous media

Photoinduced interactions of 9-aminoacridine hydrochloride hydrate (9AA-HCl) with aromatic and aliphatic amines, N,N'-dimethylaniline (DMA) and triethylamine (TEA) respectively have been investigated in homogeneous water–acetonitrile (1:1) mixture as well as in heterogeneous cetyltrimethyl ammonium bromide (CTAB) micellar media using UV–vis absorption, steady-state as well as time-resolved fluorescence spectroscopies and laser flash photolysis technique associated with a weak external magnetic field (MF). Differential modes of fluorescence quenching of 9AA-HCl with DMA and TEA corroborated with absorption studies reveal their disparity in the mechanism of interactions. Excited state proton transfer (ESPT) and photoinduced electron transfer (PET) are the phenomenon that have been found to be involved in with DMA, whereas with TEA ground-state complex formation, ground-state proton transfer and PET are prevalent. Discrepancy in pH of the interfacial and hydrophobic regions of CTAB facilitates the partitioning of the protonated and neutral forms of 9AA-HCl leading to differential occupational sites of the acceptor and donor moieties in the micellar medium, thus making the study more intriguing. Another important aspect of the present study is the use of MF to confirm the occurrence of PET, authenticate the spin-state of the intermediates thus formed and also to resolve the process of PET and ESPT.

Photosensitized formation of peroxyl radicals in aqueous solutions of adenine at 77 K

Conditions for the formation of peroxyl radicals photosensitized by near-UV irradiation in frozen aqueous solutions of adenine containing 0.1 M NaCl (pH 4–7) are studied. Analysis of the EPR spectra shows that the systems under study contain two types of peroxyl radicals presumably classified earlier as O2−· and HO2··. The effect of freezing methods on the production of the radicals is shown. The signal from O2−· predominates in the spectra of samples with open surfaces and is likely due to the reduction of adsorbed O2 molecules with photoejected electrons. The signal from HO2· could be due to photoinduced interaction between the sensitizer and solvent. Possible mechanisms of these processes are considered.