Photocyclization and Photoisomerization Mechanisms of an Indolylfulgide Derivative in Acetonitrile Solution by Using the QM (MS-CASPT2)/MM Method.

The indolylfulgide systems have been extensively investigated due to their potential applications as photochromic materials. In this work, the photoinduced ring-closure/opening and isomerization reactions of a photochromic indolylfulgide in vacuum and acetonitrile solvent have been investigated by means of MS-CASPT2//CASSCF and QM(MS-CASPT2)//CASSCF/MM. The deactivation mechanisms of indolylfulgide have been proposed based on the optimized structures in the S and S states, S/S conical intersections, and the calculated minimum-energy paths.

Mechanistic Insights into the Excited-State Intramolecular Proton Transfer (ESIPT) Process of 2-(2-Aminophenyl)naphthalene.

The 2-(2-aminophenyl)naphthalene molecule attracted much attention due to excited-state intramolecular proton transfer (ESIPT) from an amino NH group to a carbon atom of an adjacent aromatic ring. The ESIPT mechanisms of 2-(2-aminophenyl)naphthalene are still unclear. Herein, the decay pathways of this molecule in vacuum were investigated by combining static electronic structure calculations and nonadiabatic dynamics simulations.

Photochemical Mechanisms of Hydroxyquinoline Benzimidazole: Insights from Electronic Structure Calculations and Nonadiabatic Dynamics Simulations.

Excited-state intramolecular double proton transfer (ESIDPT) has received much attention because of its widespread existence in the life reactions of living organisms, and materials with this property are significant for their special luminescent properties. In this work, the complete active space self-consistent field (CASSCF) and OM2/multireference configuration interaction (OM2/MRCI) methods have been employed to study the static electronic structure calculations of the photochemistry and the possibility of ESIDPT process of hydroxyquinoline benzimidazole (HQB) molecule, along with the nonadiabatic dynamics simulations. The computational results show that the HQB molecule is relaxed to the S1-ENOL minimum after being excited to the Franck-Condon point in the S state.

Structures and Energetics of EH (E = As, Sb, and Bi) Cations.

EH (E = As, Sb, Bi) structures involving multiple bonds have attracted much attention recently. The EH cations (protonated EH) are predicted to be viable with substantial proton affinities (>180 kcal/mol). Herein, the bonding characters and energetics of a number of EH isomers are explored through CCSD(T) and DFT methods.

Excited-state relaxation mechanisms of 2,2'-(1-phenyl-1-1,2,4-triazole-3,5-diyl)diphenol: single- or double-proton transfer?

Triazole compounds are important organic systems with excellent electronic properties, which have diagnostic potential in the fields of organic electronics and organic photovoltaics. The important photophysical nature of these systems is the transformation between the enol and keto forms after excited-state proton transfer. In this study, the IR vibrational spectrum, ESIPT mechanism, and excited-state decay dynamics of 2,2'-(1-phenyl-1-1,2,4-triazole-3,5-diyl)diphenol (ExPh) were explored using electronic structure calculations and non-adiabatic dynamics simulations.

Non-adiabatic dynamics simulations of the S excited-state relaxation of diacetyl phenylenediamine.

The small molecule built around the benzene ring, diacetyl phenylenediamine (DAPA), has attracted much attention due to its synthesis accessibility, large Stokes shift, However, its meta structure m-DAPA does not fluoresce. In a previous investigation, it was found that such a property is due to the fact that it undergoes an energy-reasonable double proton transfer conical intersection during the deactivation of the S excited-state, then returns to the ground state by a nonradiative relaxation process eventually. However, our static electronic structure calculations and non-adiabatic dynamics analysis results indicate that only one reasonable non-adiabatic deactivation channel exists: after being excited to the S state, m-DAPA undergoes an ultrafast and barrierless ESIPT process and reaches the single-proton-transfer conical intersection.

Combined QM (MS-CASPT2)/MM studies on photocyclization and photoisomerization of a fulgide derivative in toluene solution.

Photocyclization and photoisomerization of fulgides have been extensively studied experimentally and computationally due to their significant potential applications for example as photoswitches in memory devices. However, the reported excited-state decay mechanisms of fulgides do not include the effects of solvation explicitly to date. Herein, calculations using the high-level MS-CASPT2//CASSCF method were conducted to explore the photoinduced excited-state decay processes of the conformer of a fulgide derivative in toluene with solvent effects treated by implicit PCM and explicit QM/MM models, respectively.

Excited-state photochemistry dynamics of 2-(1-naphthyl) phenol: electronic structure calculations and non-adiabatic dynamics simulations.

The excited-state proton transfer processes and the formation mechanism of quinone methide of (1-naphthyl)phenol were investigated by combining static electronic structure calculations and non-adiabatic dynamics simulations in vacuum. The results indicated the existence of two minimum energy structures (S0-ENOL-1 and S0-ENOL-2) in the ground and excited states, which correspond to two ESIPT pathways. Upon excitation of S0-ENOL-1 to the bright S state, the system relaxes to the S minimum quickly in the enol region, for which two decay pathways have been described.

Excited-State Deactivation Mechanism of 3,5-bis(2-hydroxyphenyl)-1-1,2,4-triazole: Electronic Structure Calculations and Nonadiabatic Dynamics Simulations.

3,5-bis(2-Hydroxyphenyl)-1-1,2,4-triazole (bis-HPTA) has attracted wide attention due to the important application in the detection of microorganisms and insecticidal activity. However, the mechanisms of excited-state intramolecular proton transfer (ESIPT) process and decay pathways are still a matter of debate. In this work, we have comprehensively investigated the photodynamics of bis-HPTA by executing combined electronic structure calculations and nonadiabatic surface-hopping dynamics simulations.

Comprehensive analysis of the differential expression profile of microRNAs in missed abortion.

To screen the key circulating microRNAs (miRNAs) involved in missed abortion (MA) and explore their role in MA process. We examined the miRNA profile from the serum of three MA patients and three early pregnancy induced abortion patients (controls) by next-generation sequencing. We analyzed the target genes of the differentially expressed (DE) miRNAs to analyze the function and pathway enrichment using Gene Ontology and Kyoto Encyclopedia of Genes and Genomes, respectively.

Photochemical mechanism of 1,5-benzodiazepin-2-one: electronic structure calculations and nonadiabatic surface-hopping dynamics simulations.

Due to the significant applications in bioimaging, sensing, optoelectronics etc., photoluminescent materials have attracted more and more attention in recent years. 1,5-Benzodiazepin-2-one and its derivatives have been used as fluorogenic probes for the detection of biothiols.

Electronic structure calculations and nonadiabatic dynamics simulations of excited-state relaxation of Pigment Yellow 101.

Pigment Yellow 101 (PY101) is widely used as a typical pigment due to its excellent excited-state properties. However, the origin of its photostability is still elusive. In this work, we have systematically investigated the photodynamics of PY101 by performing combined electronic structure calculations and trajectory-based nonadiabatic dynamics simulations.

A theoretical study of ruthenium complexes with 2,2'-biimidazole-like ligands: structural, optical and emissive properties.

The structural and optical properties of five ruthenium complexes, recently synthesized for their photooxidative and photophysical properties, have been studied by means of density functional theory (DFT) and time-dependent DFT (TD-DFT). The structures of [Ru(bpy)2(BiimH2)](2+) (bpy = 2,2'-bipyridine; BiimH2 = 2,2'-biimidazole) 1, [Ru(bpy)2(TMBiimH2)](2+) (TM BiimH2 = 4,5,4',5'-tetramethyl-2,2'-biimidazole) 5, [Ru(bpy)2(L1H2)](2+) (L1H2 = 4,5-dimethyl-2(N,N-diacetyl)(carboximidamide-1H-imidazole)) 6, [Ru(bpy)2(L2H2)](2+) (L2H2 = N(1),N(1),N(2),N(2)-tetrakis(acetyl)ethanediimidamide) 7 and [Ru(phen)2(TMBiimH2)](2+) (phen = 1,10'-phenanthroline) 8 have been fully optimized in the electronic ground state as well as in the lowest triplet T1 excited state. The theoretical absorption spectra of the five complexes that compare rather well with the experimental spectra have been analyzed on the basis of TD-DFT calculations without and with spin-orbit coupling (SOC).

Theoretical study on photooxidation mechanism of ruthenium complex [Ru(II)-(bpy)2 (TMBiimH2 )](2+) with molecular oxygen.

Photoinduced reactions of ruthenium complexes with molecular oxygen have attracted a lot of experimental attention; however, the reaction mechanism remains elusive. In this work, we have used the density functional theory method to scrutinize the visible-light induced photooxidation mechanism of the ruthenium complex [Ru(II)-(bpy)2 (TMBiimH2 )](2+) (bpy: 2, 2-bipyridine and TMBiimH2 : 4, 5, 4, 5-tetramethyl-2, 2-biimidazole) initiated by the attack of molecular oxygen. The present computational results not only explain very well recent experiments, also provide new mechanistic insights.

How Photoisomerization Drives Peptide Folding and Unfolding: Insights from QM/MM and MM Dynamics Simulations.

Photoswitchable azobenzene cross-linkers can control the folding and unfolding of peptides by photoisomerization and can thus regulate peptide affinities and enzyme activities. Using quantum mechanics/molecular mechanics (QM/MM) methods and classical MM force fields, we report the first molecular dynamics simulations of the photoinduced folding and unfolding processes in the azobenzene cross-linked FK-11 peptide. We find that the interactions between the peptide and the azobenzene cross-linker are crucial for controlling the evolution of the secondary structure of the peptide and responsible for accelerating the folding and unfolding events.

Excited-State Proton-Transfer-Induced Trapping Enhances the Fluorescence Emission of a Locked GFP Chromophore.

The chemical locking of the central single bond in core chromophores of green fluorescent proteins (GFPs) influences their excited-state behavior in a distinct manner. Experimentally, it significantly enhances the fluorescence quantum yield of GFP chromophores with an ortho-hydroxyl group, while it has almost no effect on the photophysics of GFP chromophores with a para-hydroxyl group. To unravel the underlying physical reasons for this different behavior, we report static electronic structure calculations and nonadiabatic dynamics simulations on excited-state intramolecular proton transfer, cis-trans isomerization, and excited-state deactivation in a locked ortho-substituted GFP model chromophore (o-LHBI).

Photophysics of Auramine-O: electronic structure calculations and nonadiabatic dynamics simulations.

Diphenylmethane dyes are very useful photoinduced molecular rotors; however, their photophysical mechanisms are still elusive until now. In this work, we adopted combined static electronic structure calculations (MS-CASPT2//CASSCF) and trajectory-based surface-hopping dynamics simulations (OM2/MRCI) to study the S1 excited-state relaxation mechanism of a representative diphenylmethane dye Auramine-O. On the basis of the optimized S1 minima and the computed emission bands, we have for the first time assigned experimentally proposed three transient states (i.

Photodissociation dynamics of CH3C(O)SH in argon matrix: A QM/MM nonadiabatic dynamics simulation.

In this work, we have first employed the combined quantum mechanics/molecular mechanics (QM/MM) method to study the photodissociation mechanism of thioacetic acid CH3C(O)SH in the S1, T1, and S0 states in argon matrix. CH3C(O)SH is treated quantum mechanically using the complete active space self-consistent field and complete active space second-order perturbation theory methods; argon matrix is described classically using Lennard-Jones potentials. We find that the C-S bond fission is predominant due to its small barriers of ca.

Surface-hopping dynamics simulations of malachite green: a triphenylmethane dye.

Malachite green is a typical triphenylmethane dye widely used in fundamental and industrial research; however, its excited-state relaxation dynamics remains elusive. In this work we simulate its photodynamics from the S2 and S1 states using the fewest-switches surface-hopping scheme. In the S2 photodynamics, the system first relaxes to the S2 minimum, which immediately hops to the S1 state via an S2/S1 conical intersection.

Excited-state ring-opening mechanism of cyclic ketones: a MS-CASPT2//CASSCF study.

We have employed complete active space self-consistent field (CASSCF) and its second-order perturbation (MS-CASPT2) methods to study the S1 and T1 excited-state ring-opening mechanisms and S1 excited-state deactivation channels of cyclopropanone, cyclobutanone, cyclopentanone, and cyclohexanone. On the basis of optimized minima, transition states, conical intersections, refined energies, and relaxed two-dimensional S1 and T1 potential energy surfaces, we find that, with the ring-strain decrease from cyclopropanone to cyclohexanone, (1) the ring-opening S1 and T1 barrier increases from 0.0 and 0.

Excited-state intramolecular proton transfer to carbon atoms: nonadiabatic surface-hopping dynamics simulations.

Excited-state intramolecular proton transfer (ESIPT) between two highly electronegative atoms, for example, oxygen and nitrogen, has been intensely studied experimentally and computationally, whereas there has been much less theoretical work on ESIPT to other atoms such as carbon. We have employed CASSCF, MS-CASPT2, RI-ADC(2), OM2/MRCI, DFT, and TDDFT methods to study the mechanistic photochemistry of 2-phenylphenol, for which such an ESIPT has been observed experimentally. According to static electronic structure calculations, irradiation of 2-phenylphenol populates the bright S1 state, which has a rather flat potential in the Franck-Condon region (with a shallow enol minimum at the CASSCF level) and may undergo an essentially barrierless ESIPT to the more stable S1 keto species.

Proteomic profiling of proteins dysregulted in Chinese esophageal squamous cell carcinoma.

Esophageal squamous cell carcinoma (ESCC) is one of the leading causes of cancer death in China. In the present study, proteins in tumors and adjacent normal esophageal tissues from 41 patients with ESCC were extracted, and two-dimensional electrophoresis (2-DE) was performed using the pH 3-10 and 4-7 immobilized pH gradient strips. The protein spots expressed differentially between tumors and normal tissues were identified by matrix-assisted laser desorption/ionization and liquid chromatography electrospray/ionization ion trap mass spectrometry.

Decreased n-6/n-3 fatty acid ratio reduces the invasive potential of human lung cancer cells by downregulation of cell adhesion/invasion-related genes.

Recent studies have shown opposing effects of n-6 and n-3 fatty acids on the development of cancer and suggest a role for the ratio of n-6 to n-3 fatty acids in the control of cancer. However, whether an alteration in the n-6/n-3 fatty acid ratio of cancer cells affects their invasive potential has not been well investigated. We recently developed a genetic approach to modify the n-6/n-3 ratio by expression of the Caenorhabditis elegans fat-1 gene encoding an n-3 desaturase that converts n-6 to n-3 fatty acids in mammalian cells.

[Analysis of proteins with altered expression in human esophageal squamous cell carcinomas].

Background & Objective: Esophageal squamous cell carcinoma is characterized by high incidence and high mortality. This study was designed to identify the proteins dysregulated in ECSS by.

Methods: Microdissection of routinely unstained frozen sections was used to procure cancer cells from seven esophageal squamous cell carcinomas, and esophageal epithelial cells from normal tissues adjacent to the tumors.

Elevated expression of p63 protein in human esophageal squamous cell carcinomas.

p63 is a recently identified homologue of the tumor suppressor gene TP53, which encodes multiple isotypes with transactivating, death-inducing and dominant-negative activities. p63 is expressed in basal cells of squamous epithelia and many kinds of tumors. To explore the penetrance of p63 in esophageal cancer, we analyzed p63 expression in squamous cell carcinomas, adjacent dysplasia and histologically normal mucosa of the esophagus by combination of immunohistochemistry and reverse transcriptase-polymerase chain reaction (RT-PCR).