Simple technique of coupling a diode laser into a linear power buildup cavity for Raman gas sensing.

We report a novel, to the best of our knowledge, and simple technique to lock a 642 nm multi-quantum well diode laser to an external linear power buildup cavity by directly feeding the cavity reflected light back to the diode laser for enhancement of gas Raman signals. The dominance of the resonant light field in the locking process is achieved by reducing the reflectivity of the cavity input mirror and thus making the intensity of the directly reflected light weaker than that of the resonant light. Compared with traditional techniques, stable power buildup in the fundamental transverse mode TEM00 is guaranteed without any additional optical elements or complex optical arrangements. An intracavity exciting light of 160 W is generated with a 40 mW diode laser. Using a backward Raman light collection geometry, detection limits at the ppm level are achieved for ambient gases (N2, O2) with an exposure time of 60 s.

PBX1 is a valuable prognostic biomarker for patients with breast cancer.

Pre-B-cell leukemia transcription factor (PBX) proteins have important roles in the development of numerous organs. To date, four members of the PBX family have been identified to be involved in human cancer but little is known about their expression patterns and precise functions in breast cancer (BC) progression. The aim of the present study was to determine whether they have the potential to be prognostic biomarkers in patients with BC. The expression patterns of PBXs were evaluated using Oncomine, Cancer Cell Line Encyclopedia and Gene expression-based Outcome for Breast cancer Online algorithm analyses. The prognostic value of PBX1 was determined by Kaplan-Meier plotter analysis. It was observed that, among all PBX family members, only PBX1 was significantly upregulated in BC vs. normal tissues. Meta-analysis in the Oncomine database revealed that PBX1 was significantly upregulated in invasive breast carcinoma stroma, ductal breast carcinoma, invasive lobular breast carcinoma, invasive mixed breast carcinoma and male breast carcinoma compared with normal tissues. In addition, PBX1 was significantly correlated with forkhead box protein A1. Subtype analysis indicated that PBX1 overexpression was associated with luminal-like and hormone receptor-sensitive subtypes. In the survival analysis, a high expression level of PBX1 was associated with poor prognosis of patients with estrogen receptor (ER)-positive, luminal A and luminal B subtypes of BC. The results of the present study indicate that PBX1 may serve as a specific biomarker and essential prognostic factor for ER-positive, luminal A and luminal B subtypes of BC.

FOXK transcription factors: Regulation and critical role in cancer.

Growing evidence suggests that alterations of gene expression including expression and activities of transcription factors are closely associated with carcinogenesis. Forkhead Box Class K (FOXK) proteins, FOXK1 and FOXK2, are a family of evolutionarily conserved transcriptional factors, which have recently been recognized as key transcriptional regulators involved in many types of cancer. Members of the FOXK family mediate a wide spectrum of biological processes, including cell proliferation, differentiation, apoptosis, autophagy, cell cycle progression, DNA damage and tumorigenesis. Therefore, the deregulation of FOXKs can affect the cell fate and they promote tumorigenesis as well as cancer progression. The mechanisms of FOXKs regulation including post-translational modifications (PTMs), microRNAs (miRNAs) and protein-protein interactions are well demonstrated. However, the detailed mechanisms of FOXKs activation and deregulation in cancer progression are still inconclusive. In this review, we summarize the regulatory mechanisms of FOXKs expression and activity, and their role in the development and progression of cancer. We have discussed whether FOXKs act as tumor suppressors/oncoproteins in tumor cells and their therapeutic applications in malignant diseases are also discussed. This review may assist in designing experimental studies involving FOXKs and it would strength the therapeutic potential of FOXKs as targets for cancers.

Hyper-acidic fusion minipeptides escort the intrinsic antioxidative ability of the pattern recognition receptor CRP in non-animal organisms.

C-reactive protein (CRP) is widely used as a biomarker of inflammation. It plays important roles in innate immunity response as a member of pattern recognition receptors, by binding oxidation-specific epitopes including some intermediates of lipid oxidative chain reaction. The inferred antioxidative ability of CRP was ever demonstrated by only few in vitro evidences, and needs to be clarified especially in vivo. Herein, we expressed human CRP in three representative non-animal organisms (Escherichia coli, Saccharomyces cerevisiae, and tobacco) inherently lacking the milieu for CRP signalling, and found CRP did possess an intrinsic antioxidative ability. Heterologous CRP could confer increased oxidative resistance in its recombinant E. coli and yeast cells and transgenic tobaccos. We also revealed a positive correlation between the antioxidative effect of CRP and its solubility. Only soluble CRP could exhibit distinct antioxidative activity, while the CRP aggregates might be instead toxic (probably pro-oxidative) to cells. Moreover, fusion with hyper-acidic minipeptides could remarkably improve CRP solubility, and meanwhile guarantee or enhance CRP antioxidative ability. These results not only provide a new insight for understanding the etiology of CRP-involved inflammations and diseases, and also endorse a potential of CRP biotechnological applications in developing new pharmaceutical therapies and improving plant oxidative resistance.

Triazoles bind the C-terminal domain of SMO: Illustration by docking and molecular dynamics simulations the binding between SMO and triazoles.

Itraconazole is an antagonist of the component Smoothened of Hedgehog pathway, which can inhibit the growth of medulloblastoma, basal cell carcinoma, and melanoma, etc. To research the binding mechanism of the Smoothened and triazoles, we used docking and molecular dynamics simulations on the Smoothened crystal structure and six triazoles. Unlike vismodegib, itraconazole can effectively bind into the pocket in the C-terminal domain of the Smoothened crystal structure instead of the N-terminal domain. The binding of itraconazole can change the conformation of the N-terminal domain even although itraconazole only had limited area contacting with N-terminal domain of the Smoothened. Besides, the binding of Itraconazole will not affect the binding of vismodegib. The strong binding affinity could be demonstrated between itraconazole and the Smoothened. Posaconazole and ketoconazole also had the strong binding affinity and the similar binding mode with the Smoothened crystal structure.

Origin of Photocarrier Losses in Iron Pyrite (FeS2) Nanocubes.

Iron pyrite has received significant attention due to its high optical absorption. However, the loss of open circuit voltage (Voc) prevents its further application in photovoltaics. Herein, we have studied the photophysics of pyrite by ultrafast laser spectroscopy to understand fundamental limitation of low Voc by quantifying photocarrier losses in high quality, stoichiometric, and phase pure {100} faceted pyrite nanocubes. We found that fast carrier localization of photoexcited carriers to indirect band edge and shallow trap states is responsible for major carrier loss. Slow relaxation component reflects high density of defects within the band gap which is consistent with the observed Mott-variable range hopping (VRH) conduction from transport measurements. Magnetic measurements strikingly show the magnetic ordering associated with phase inhomogeneity, such as FeS2-δ (0 ≤ δ ≤ 1). This implies that improvement of iron pyrite solar cell performance lies in mitigating the intrinsic defects (such as sulfur vacancies) by blocking the fast carrier localization process. Photocarrier generation and relaxation model is presented by comprehensive analysis. Our results provide insight into possible defects that induce midgap states and facilitate rapid carrier relaxation before collection.

Mechanistic studies for tri-targeted inhibition of enzymes involved in cholesterol biosynthesis by green tea polyphenols.

In the present study, we found that three enzymes, MVK, MDD and FPPS, in the mevalonate pathway (MVP) of cholesterol biosynthesis, can be simultaneously inhibited by two green tea polyphenols ((-)-epicatechin-3-gallate, ECG; (-)-epigallocatechin-3-gallate, EGCG). Molecular dynamics simulations and pharmacophore studies were carried out to elucidate the tri-targeted inhibition mechanisms. Our results indicate that similar triangular binding pockets exist in all three enzymes, which is essential for their binding with polyphenols. Two distinct binding poses for ECG and EGCG were observed in our MD simulations. These results shed light on the potential for further selective and multi-targeted inhibitor design for the treatment of hyperlipidemia.

Syntheses and characterization of non-bisphosphonate quinoline derivatives as new FPPS inhibitors.

BACKGROUND: Farnesyl pyrophosphate synthase (FPPS) is a key regulatory enzyme in the biosynthesis of cholesterol and in the post-translational modification of signaling proteins. It has been reported that non-bisphosphonate FPPS inhibitors targeting its allosteric binding pocket are potentially important for the development of promising anti-cancer drugs. METHODS: The following methods were used: organic syntheses of non-bisphosphonate quinoline derivatives, enzyme inhibition studies, fluorescence titration assays, synergistic effect studies of quinoline derivatives with zoledronate, ITC studies for the binding of FPPS with quinoline derivatives, NMR-based HAP binding assays, molecular modeling studies, fluorescence imaging assay and MTT assays. RESULTS: We report our syntheses of a series of quinoline derivatives as new FPPS inhibitors possibly targeting the allosteric site of the enzyme. Compound 6b showed potent inhibition to FPPS without significant hydroxyapatite binding affinity. The compound showed synergistic inhibitory effect with active-site inhibitor zoledronate. ITC experiment confirmed the good binding effect of compound 6b to FPPS, and further indicated the binding ratio of 1:1. Molecular modeling studies showed that 6b could possibly bind to the allosteric binding pocket of the enzyme. The fluorescence microscopy indicated that these compounds could get into cancer cells. CONCLUSIONS: Our results showed that quinoline derivative 6b could become a new lead compound for further optimization for cancer treatment. GENERAL SIGNIFICANCE: The traditional FPPS active-site inhibitors bisphosphonates show poor membrane permeability to tumor cells, due to their strong polarity. The development of new non-bisphosphonate FPPS inhibitors with good cell membrane permeability is potentially important.

Advances in the studies of roles of Rho/Rho-kinase in diseases and the development of its inhibitors.

RhoA/Rho-kinase pathway plays a pivotal role in numerous fundamental cellular functions including contraction, motility, proliferation, differentiation and apoptosis. The pathway is also involved in the development of many diseases such as vasospasm, pulmonary hypertension, cancer and central nervous systems (CNS) disorders. The inhibitors of Rho kinase have been extensively studied since the Rho/Rho-kinase pathway was verified as a target for a number of diseases. Herein, we reviewed the advances in the studies of the roles of Rho/Rho-kinase in diseases and the development of Rho-kinase inhibitors in recent five years.

Salvianolic acid A, a polyphenolic derivative from Salvia miltiorrhiza bunge, as a multifunctional agent for the treatment of Alzheimer's disease.

The effects of Salvianolic acid A (Sal A) on the treatment of Alzheimer's disease (AD) were investigated. Sal A significantly inhibits amyloid beta [Formula: see text] self-aggregation and disaggregates pre-formed [Formula: see text] fibrils, reduces metal-induced [Formula: see text] aggregation through chelating metal ions, and blocks the formation of reactive oxygen species (ROS) in SH-SY5Y cells. Sal A protects cells against [Formula: see text]-induced toxicity. Furthermore, Sal A, possibly because of the effects of decreasing toxicity effects of [Formula: see text] species, alleviates [Formula: see text]-induced paralysis in transgenic Caenorhabditis elegans. Circular dichroism (CD) experiments and Molecular dynamic (MD) simulations demonstrate that Sal A inhibits [Formula: see text] self-aggregation through binding to the C-terminus of [Formula: see text], and therefore stabilizing the [Formula: see text]-helical conformations. Altogether, our data show that Sal A, as the multifunctional agent, is likely to be promising therapeutics for AD.

Loop motion and base release in purine-specific nucleoside hydrolase: a molecular dynamics study.

Although various Trypanosoma vivax purine-specific inosine-adenosine-guanosine nucleoside hydrolase (IAG-NH) crystal structures have been determined and the chemical reaction mechanism of substrate hydrolysis has been studied recently, the mechanistic details for the release of base and ribose are still unclear. Herein molecular dynamics (MD) simulations combined with umbrella sampling technique were utilized to explore the regulation mechanisms of key residues and loops 1 and 2 for the base release. Our results have indicated that the base release process is not the rate-limiting step in the entire hydrolysis process, and the very low barrier of ~5.6kcal/mol can be washed out easily by the notable exothermicity from the substrate hydrolysis step. Moreover, the MD simulations have revealed that Glu82/Trp83 in loop 1 and His247/Arg252 in loop 2 are important to modulate the base release. The partial helix-to-coil change of loop 2 along with the base release process has been observed, showing good agreement with the IAG-NH crystal structures. The local binding site around the ribose after the base release is also discussed.

On the value of homology models for virtual screening: discovering hCXCR3 antagonists by pharmacophore-based and structure-based approaches.

Human chemokine receptor CXCR3 (hCXCR3) antagonists have potential therapeutic applications as antivirus, antitumor, and anti-inflammatory agents. A novel virtual screening protocol, which combines pharmacophore-based and structure-based approaches, was proposed. A three-dimensional QSAR pharmacophore model and a structure-based docking model were built to virtually screen for hCXCR3 antagonists. The hCXCR3 antagonist binding site was constructed by homology modeling and molecular dynamics (MD) simulation. By combining the structure-based and ligand-based screenings results, 95% of the compounds satisfied either pharmacophore or docking score criteria and would be chosen as hits if the union of the two searches was taken. The false negative rates were 15% for the pharmacophore model, 14% for the homology model, and 5% for the combined model. Therefore, the consistency of the pharmacophore model and the structural binding model is 219/273 = 80%. The hit rate for the virtual screening protocol is 273/286 = 95%. This work demonstrated that the quality of both the pharmacophore model and homology model can be measured by the consistency of the two models, and the false negatives in virtual screening can be reduced by combining two virtual screening approaches.

Nanofibers doped with a novel red-emitting Europium complex: synthesis, characterization, photophysical property and sensing activity toward molecular oxygen.

In this paper, we synthesize a novel diamine ligand of DIQ-Et and its corresponding Eu(III) complex of Eu(TTA)(3)DIQ-Et, where DIQ-Et=N-ethyl-10H-dipyrido-[f,h]-indolo-[3,2-b]-quinoxaline, and TTA=2-thenoyltrifluoroacetonate. The UV-vis absorption, photoluminescence, low temperature phosphorescence, energy transfer mechanism, and excited state lifetime of Eu(TTA)(3)DIQ-Et are investigated in detail. Data suggest that the emission of Eu(TTA)(3)DIQ-Et is quenchable by molecular oxygen due to the back-energy transfer process. By doping Eu(TTA)(3)DIQ-Et into a polymer matrix of poly(vinylpyrrolidone) (PVP), oxygen sensing performance of the resulted nanofibers is investigated. Finally, the 0.7 wt% doped sample exhibits a linear response toward molecular oxygen, with a sensitivity of 2.4 and response/recovery time of 12s/16s.

A new protocol for predicting novel GSK-3ß ATP competitive inhibitors.

Glycogen synthase kinase 3ß (GSK-3ß) is a potential therapeutic target for cancer, type-2 diabetes, and Alzheimer's disease. This paper proposes a new lead identification protocol that predicts new GSK-3ß ATP competitive inhibitors with topologically diverse scaffolds. First, three-dimensional quantitative structure-activity relationship (3D QSAR) models were built and validated. These models are based upon known GSK-3ß inhibitors, benzofuran-3-yl-(indol-3-yl) maleimides, by means of comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA). Second, 28 826 maleimide derivatives were selected from the PubChem database. After filtration via Lipinski's rules, 10 429 maleimide derivatives were left. Third, the FlexX-dock program was employed to virtually screen the 10 429 compounds against GSK-3ß. This resulted in 617 virtual hits. Fourth, the 3D QSAR models predicted that from the 617 virtual hits, 93 compounds would have GSK-3ß inhibition values of less than 15 nM. Finally, from the 93 predicted active hits, 23 compounds were confirmed as GSK-3ß inhibitors from literatures; their GSK-3ß inhibition ranged from 1.3 to 480 nM. Therefore, the hits rate of our virtual screening protocol is greater than 25%. The protocol combines ligand- and structure-based approaches and therefore validates both approaches and is capable of identifying new hits with topologically diverse scaffolds.

Molecular mechanism of action for reversible P2Y12 antagonists.

Recently, reversible antagonists of the P2Y(12) receptor have been reported. However, the mechanisms of binding have not been elucidated. To this end, a number of homology models were built by means of three programs from four templates. A consensus model was derived from those initial models. The final model was created by refining the consensus model with molecular dynamics simulations. The agonist and antagonists of P2Y(12) have been docked in the final model. For the agonist, the Arg256, Lys280, and Phe252 are "hot" residues. For the antagonists, the Lys280 and Phe252 are "hot" residues that have hydrogen bonding contacts and π-π interactions, respectively. These results can explain the observations of mutation experiments and can guide the design of new inhibitors.