First-principles calculations of 0D/2D GQDs-MoS2 mixed van der Waals heterojunctions for photocatalysis: a transition from type I to type II.

The fabrication of type II heterojunctions is an efficient strategy to facilitate charge separation in photocatalysis. Here, mixed dimensional 0D/2D van der Waals (vdW) heterostructures (graphene quantum dots (GQDs)-MoS2) for generating hydrogen from water splitting are investigated based on density functional theory (DFT). The electronic and photocatalytic properties of three heterostructures, namely, C6H6-MoS2, C24H12-MoS2 and C32H14-MoS2 are estimated by analyzing the density of states, charge density difference, work function, Bader charge, absorption spectra and band alignment. The results indicated that the built-in electric fields from GQDs to MoS2 boost charge separation. Meanwhile, all the GQDs-MoS2 exhibit strong absorption in the visible light region. Surprisingly, the transition of heterojunctions from type I to type II is realized by tuning the size of GQDs. In particular, C32H14-MoS2 with enhanced visible-light absorption and an appropriate band edge position, as a type II heterostructure, may be a promising photocatalyst for generating hydrogen from water splitting. Thus, in this work a novel type II 0D/2D nanocomposite as a photocatalyst is constructed that provides a strategy to regulate the type of heterostructure from the perspective of theoretical calculation.

Theoretical insights on type I/II photoreactions of potential Zn(II) polypyridyl photosensitizers for two-photon photodynamic therapy.

Large two-photon absorption cross-sections are vital to photosensitizers (PSs) in TP-PDT, which can be used to develop in-depth treatment for diseased cells and minimize the harm to surrounding cells. Here, we conduct a study about photophysical properties of one Ru(II) polypyridyl complex and two designed Zn(II) polypyridyl complexes by means of DFT and TD-DFT methods. The main results are as follows: firstly, the two-photon absorption spectrum of two designed complexes Zn-OMe and Zn-OCOOCH3 are all within the phototherapeutic window (550-900 nm). Secondly, large SOC values and small energy gaps ΔES-T of these complexes guarantee the efficiency of ISC process. Thirdly, their T1 energy is greater than that required for generating 1O2 (0.98 eV) via Type II photoreaction. In addition, the calculated results of vertical electron affinities (VEA) and vertical ionization potentials (VIP) show that these complexes are able to form superoxide ions O2(-) via Type I photoreaction. Specifically, both of two designed Zn-centric complexes have larger TPA cross-sections than that of Ru-centric complex. In a word, we are pleased to report two potential photosensitizers with excellent performance and reasonable price for Type I/II photoreactions. We expect our study will offer some theoretical guidance and help in TP-PDT.

Theoretical insight into the photophysical properties of long-lifetime Ir(iii) and Rh(iii) complexes for two-photon photodynamic therapy.

Two-photon photodynamic therapy (TP-PDT) plays crucial roles in curing tumors because it involves deep penetration of drugs into the tissue and has minimal damage to the surrounding cells. Our theoretical study was aimed at providing fresh insights into photosensitizers, such as [Ir(N^C)2(N^N)]+ (N^C = 2-phenylpyridine, N^N = bis-benzimidazole) and [Rh(N^C)2(N^N)]+, to treat cancer via the TP-PDT route. To better understand the properties of the complexes [Ir(N^C)2(N^N)]+ and [Rh(N^C)2(N^N)]+, the one-photon and two-photon absorption electronic spectra, energy gap (ΔES-T), strength of two-photon absorption cross-section (δ), spin-orbit matrix element (S1|HSO|Tj), and phosphorescence lifetimes (τ) were calculated by DFT and TD-DFT. The calculation results suggested that both complexes met the criteria (i.e. an efficient ISC process, enough energy to produce 1O2 and phototherapeutic window of the absorption wavelength) of photosensitizers; importantly, the designed complex [Rh(N^C)2(N^N)]+ had better performance than [Ir(N^C)2(N^N)]+, especially in the long-lived triplet excited state. It is expected that our research can make quite a few contributions to the development of photosensitizers and establish some guidelines for experiments based on TP-PDT.

Theoretical study on photophysical properties of three high water solubility polypyridyl complexes for two-photon photodynamic therapy.

Two-photon photodynamic therapy (TP-PDT) is a very promising treatment that has drawn much attention in recent years due to its ability to penetrate deeper into tissues and minimize the damage to normal cells. Here, the properties of three highly water soluble Ru(ii) and Zn(ii) polypyridyl complexes as photosensitizers (PSs) were examined, including the one-photon and two-photon absorption (OPA and TPA) spectra, singlet-triplet energy gap (ΔH-L), TPA cross-section and spin-orbit coupling constant via Density Function Theory (DFT) and Time-Dependent Density Functional Theory (TD-DFT). Their potential therapeutic use as photosensitizers in TP-PDT is proposed, where the reasoning is as follows: first, they possess strong absorption in the therapeutic window; second, the vertical excitation energy is greater than 0.98 eV, which can generate a singlet oxygen species and the remarkable coupling between the S1 and T1 states. Moreover, the spin-orbit matrix elements are greater than 0.24 cm-1 for Ru-bpy and Zn-tpy, indicating that the intersystem spin crossing processes are efficient. It is expected that these complexes will be applied to PSs in TP-PDT, and we hope this research can serve as a guideline for the development of efficient two-photon PSs.

A theoretical study of a series of water-soluble triphenylamine photosensitizers for two-photon photodynamic therapy.

In this study, the therapeutic activity of a series of water-soluble triphenylamine (TP) photosensitizers (Ps) was explored by using theoretical simulations. The key photophysical parameters which determined the efficiency of Ps, such as absorption electronic spectra, singlet-triplet energy gaps and spin-orbit matrix elements were calculated at density functional theory and its time-dependent extension (DFT, TD-DFT). The calculated results showed that these TP photosensitizers possessed large two-photon absorption cross-section in the near-infrared region (NIR), efficient intersystem crossing (ISC) transition from the first singlet excited state to the low lying triplet excited states and sufficient energy for generating reactive oxygen species (ROS). These suitable features made these TP series holding great promise for applications in two-photon photodynamic therapy (PDT). These TP photosensitizers studied here in principle extended the application range of two-photon PDT in water solution.

Dynamic evolution of a vesicle formed by comb-like block copolymer-tethered nanoparticles: a dissipative particle dynamics simulation study.

Vesicles are well-sealed capsules that can store or transport substances. Their dynamic evolution mechanisms are important to fulfill specific functions. In the present study, dissipative particle dynamics (DPD) simulation was employed to study the formation, fusion, and fission pathways of vesicles. Our results show that comb-like block copolymer-tethered nanoparticles can self-assemble into stable vesicles, which may be a good candidate for drug entrapment and controlled release of drug. The spontaneous fusion of this type of vesicles has been studied, whose mechanism is different from that of the vesicles formed from comb-like block copolymers. However, the fission mechanisms of the two types of vesicles are similar. To summarize, the introduction of nanoparticles alters the fusion mechanism, but causes no difference in the fission pathway of vesicles. The reason may be attributed to the nature of nanoparticles. The fusion and fission processes always experience the congregation of nanoparticles. The large and rigid nanoparticles inevitably result in changes of surface tension of the vesicle that is a key factor influencing the membrane dynamics.

Multi-algorithm and multi-model based drug target prediction and web server.

AIM: To develop a reliable computational approach for predicting potential drug targets based merely on protein sequence. METHODS: With drug target and non-target datasets prepared and 3 classification algorithms (Support Vector Machine, Neural Network and Decision Tree), a multi-algorithm and multi-model based strategy was employed for constructing models to predict potential drug targets. RESULTS: Twenty one prediction models for each of the 3 algorithms were successfully developed. Our evaluation results showed that ∼30% of human proteins were potential drug targets, and ∼40% of putative targets for the drugs undergoing phase II clinical trials were probably non-targets. A public web server named D3TPredictor (http://www.d3pharma.com/d3tpredictor) was constructed to provide easy access. CONCLUSION: Reliable and robust drug target prediction based on protein sequences is achieved using the multi-algorithm and multi-model strategy.

Li2 trapped inside tubiform [n] boron nitride clusters (n=4-8): structures and first hyperpolarizability.

The geometries and electronic properties of tubiform [n] boron nitride clusters entrapping Li(2) (Li(2)@BN-cluster(n,0); n=4-8), obtained by doping BN-cluster(n,0) with Li(2) molecules, are investigated by means of DFT. The effects of tube diameter n on the dipole moment µ(0), static polarizability α(0), and first hyperpolarizability ß(0) are elucidated. Both the dipole moment and polarizability increase with increasing tube diameter, whereas variation of the static first hyperpolarizability with tube diameter is not monotonic; ß(0) follows the order 1612 (n=4)<3112 (n=5)<5534 (n=7)<8244 (n=6)<12,282 a.u. (n=8). In addition, the natural bond orbital (NBO) charges show that charge transfer takes place from the Li(2) molecule to the BN cluster, except for BN-cluster(8,0) with larger tube diameter. Since the large-diameter tubular BN-cluster(8,0) can trap the excess electrons of the Li(2) molecule, Li(2)@BN-cluster(8,0) can be considered to be a novel electride compound.

Spontaneous fusion between the vesicles formed by A2n(B2)n type comb-like block copolymers with a semiflexible hydrophobic backbone.

The spontaneous vesicle formation and fusion of A(2n)(B(2))(n) (n = 2-10) type comb-like block copolymers with semiflexible hydrophobic backbone are studied via dissipative particle dynamics (DPD) simulations. By systemically varying the solvent condition, we construct a phase diagram to indicate the thermodynamically stable region for vesicles. The spontaneous fusion between the vesicles is studied, whose mechanism is as follows: first, a stalk is formed between the vesicles; then, the holes appear in both vesicles near the feet of the stalk; finally, the stalk bends to circle the holes and the fusion process is completed. This fusion pathway is similar to that observed in Monte Carlo simulations and dynamic self-consistent filed theory but different from those reported in coarse-grained molecular dynamics and DPD simulations. The main reason for the difference may be attributed to the molecular structures used in different simulation techniques.

Silencing of IQGAP1 by shRNA inhibits the invasion of ovarian carcinoma HO-8910PM cells in vitro.

BACKGROUND: IQGAP1 is a scaffolding protein and overexpressed in many human tumors, including ovarian cancer. However, the contribution of IQGAP1 to invasive properties of ovarian cancer cells remains unknown. Here, we investigated the effect of IQGAP1-specific short hairpin RNA (shRNA) expressing plasmids on metastatic potential of ovarian cancer HO-8910PM cells. METHODS: We used RT-PCR and Western blot analysis to characterize expression of IQGAP1 in three human ovarian cancer-derived cell lines SK-OV-3, HO-8910 and HO-8910PM. We then determined whether expression of endogenous IQGAP1 correlated with invasive and migratory ability by using an in vitro Matrigel assay and cell migration assay. We further knocked down IQGAP1 using shRNA expressing plasmids controlled by U1 promoter in HO-8910PM cells and examined the proliferation activity, invasive and migration potential of IQGAP1 shRNA transfectants using MTT assay, in vitro Matrigel-coated invasion assay and migration assay. RESULTS: IQGAP1 expression level seemed to be closely associated with the enhanced invasion and migration in ovarian cancer cell lines. Levels of both IQGAP1 mRNA and protein were significantly reduced in HO-8910PM cells transfected with plasmid-based IQGAP1-specific shRNAs. RNAi-mediated knockdown of IQGAP1 expression in HO-8910PM cells resulted in a significant decrease in cell invasion and migration. CONCLUSION: Our findings support the hypothesis that IQGAP1 promotes tumor progression and identify IQGAP1 as a potential therapeutic strategy for ovarian cancer and some other tumors with over-expression of the IQGAP1 gene.

Environmental influence of Wuhan urban agglomeration development and strategies of environmental protection.

In Wuhan urban agglomeration (WUA), the population growth and concentration, the industrial development and urban sprawl have been affecting the environment fundamentally. Comparing with Yangtze delta metropolitan region, the level of urbanization and industrialization of WUA has lagged behind for about 10 years; but the problems in environmental protection and rehabilitation are commonly serious. In the future, WUA should avoid unnecessary mistakes and seek a win-win strategy for economy and environment in its large-scale development stage. Based on the analysis of the changing of main environmental pollutants and the coupled curves in past decades, the paper discussed the important links among the urban environmental pollutions, industry growth and urban sprawl in WUA. It is concluded that the integration of economic and environmental policies in urban development is more required and significant at the large urban agglomeration region. Four proactive and long-term strategies need to be adopted to provide prior guidance and better protection for the development of WUA.