Comparison of properties of titanium aluminium nitride film produced by using two different types of Ti–Al target

This work aims to study the influence of two different types of Ti–Al target (sintered and melted) which have same nominal composition (50 at% Ti, 50 at% Al) on the properties of thin films coated by using arc ion plating (AIP) method. The hardness of the melted target was of higher value than that of the sintered target. The property of the film is related to the microstructure and phase analysis of both types of target that have quite different phases. Ti and Al metals were found as major phases and TiAl₂ as minor phase in the sintered target but only TiAl compound was found in the melted target. After film coating at the same operation parameters, it was found that although the phase structures of the sintered and melted targets were quite different, the coated thin films using these targets showed the same phase structure of Ti_0.5 Al_0.5 N. However, the microstructure of films coated by using the sintered target showed higher density of droplets and pores than those of film produced by using the melted target. As a result, the hardness and adhesion strength of thin film produced by using the melted target were slightly higher than those values of film produced by using the sintered target. Copyright © 2009 John Wiley & Sons, Ltd.     

Surface-enhanced Raman scattering molecular sentinel nanoprobes for viral infection diagnostics

In this paper, we describe a surface-enhanced Raman scattering (SERS)-based detection approach, referred to as “molecular sentinel” (MS) plasmonic nanoprobes, to detect an RNA target related to viral infection. The MS method is essentially a label-free technique incorporating the SERS effect modulation scheme associated with silver nanoparticles and Raman dye-labeled DNA hairpin probes. Hybridization with target sequences opens the hairpin and spatially separates the Raman label from the silver surface thus reducing the SERS signal of the label. Herein, we have developed a MS nanoprobe to detect the human radical S-adenosyl methionine domain containing 2 (RSAD2) RNA target as a model system for method demonstration. The human RSAD2 gene has recently emerged as a novel host-response biomarker for diagnosis of respiratory infections. Our results showed that the RSAD2 MS nanoprobes exhibits high specificity and can detect as low as 1 nM target sequences. With the use of a portable Raman spectrometer and total RNA samples, we have also demonstrated for the first time the potential of the MS nanoprobe technology for detection of host-response RNA biomarkers for infectious disease diagnostics.     

From Phenotypic Hit to Chemical Probe: Chemical Biology Approaches to Elucidate Small Molecule Action in Complex Biological Systems

Biologically active small molecules have a central role in drug development, and as chemical probes and tool compounds to perturb and elucidate biological processes. Small molecules can be rationally designed for a given target, or a library of molecules can be screened against a target or phenotype of interest. Especially in the case of phenotypic screening approaches, a major challenge is to translate the compound-induced phenotype into a well-defined cellular target and mode of action of the hit compound. There is no “one size fits all” approach, and recent years have seen an increase in available target deconvolution strategies, rooted in organic chemistry, proteomics, and genetics. This review provides an overview of advances in target identification and mechanism of action studies, describes the strengths and weaknesses of the different approaches, and illustrates the need for chemical biologists to integrate and expand the existing tools to increase the probability of evolving screen hits to robust chemical probes.     

Cyclotron production of34mCl for biomedical use

A method for simple and fast production of^34mCl as tracer for biomedical research work has been developed. Different target materials have been tested, the yield of^34mCl and co-produced contaminants examined, the fast chemical separation procedure developed and target system constructed.     

L X-ray emission from fast highly charged Cu ions in collisions with gaseous targets: Saturation effect in excitation and transfer

We have measured L X-ray production cross sections for highly charged 156 MeV Be-like Cu ions in collisions with gaseous targets of H₂, Ne, Ar, Kr and Xe. In the present collision systems, measured projectile L X-ray intensity is contributed by the excitation as well as electron transfer processes. The projectile L X-ray production cross sections are found to increase initially and then saturate with increasing target atomic number. The charge state dependence of projectile L X-ray production cross sections have been measured with Kr target.     

FluMag-SELEX as an advantageous method for DNA aptamer selection

Aptamers are ssDNA or RNA oligonucleotides with very high affinity for their target. They bind to the target with high selectivity and specificity because of their specific three-dimensional shape. They are developed by the so-called Systematic Evolution of Ligands by Exponential Enrichment (SELEX) process. We have modified this method in two steps—use of fluorescent labels for DNA quantification and use of magnetic beads for target immobilization. Thus, radioactive labelling is avoided. Immobilization on magnetic beads enables easy handling, use of very small amounts of target for the aptamer selection, rapid and efficient separation of bound and unbound molecules, and stringent washing steps. We have called this modified SELEX technology FluMag-SELEX. With FluMag-SELEX we have provided a methodological background for our objective of being able to select DNA aptamers for targets with very different properties and size. These aptamers will be applied as new biosensor receptors. In this work selection of streptavidin-specific aptamers by FluMag-SELEX is described. The streptavidin-specific aptamers will be used to check the surface occupancy of streptavidin-coated magnetic beads with biotinylated molecules after immobilization procedures.     

Synthesis of Imidazo[4,5-b]quinoxaline Ribonucleosides as Linear Dimensional Analogs of Antiviral Polyhalogenated Benzimidazole Ribonucleosides

We have recently found that 2,5,6-trichloro-1-(β-D-ribofuranosyl)benzimidazole (TCRB) and the corresponding 2-bromo analog have better in vitro activities against HCMV than the clinically used agents ganciclovir and foscarnet. These benzimidazole nucleosides act by a unique mechanism, however, their biological target has not been completely identified. As an approach to probing the target, we have designed imidazo[4,5-b]quinoxaline nucleosides as linear dimensional analogs of the benzimidazole nucleosides to study the spatial limitation of the binding site in the target enzyme. A convenient route was developed for the synthesis of 2-substituted 6,7-dichloroimidazo[4,5-b]quinoxalines involving a reaction of 2,3,6,7-tetrachloroquinoxaline with ammonia followed by a ring annulation as the key step. This furnished the versatile heterocycle 6,7-dichloroimidazo[4,5-b]quinoxalin-2-one. Ribosylation of 2-substituted imidazo[4,5-b]quinoxalines was influenced by the functional group at the 2-position and the 2-one compound was found to smoothly undergo ribosylation. The 2-one group of the nucleoside was converted into specifically selected 2-substituted compounds. Evaluation of the compounds for activity against two herpesviruses and for cytotoxicity showed they were less active and/or more cytotoxic than TCRB. We conclude therefore, that the binding pocket on the protein target of TCRB will tolerate some electronic and size changes.     

Colorimetric detection of proteins based on target-induced activation of aptazyme

The detection of protein is vital to fundamental research as well as practical applications. However, most detection methods depend on antibody-based assays which are faced with many shortcomings. Herein, we propose a colorimetric method for protein assays based on target-triggered activation of aptazyme, which may offer simple, rapid and cost-effective detection of the target protein. In this method, the conformation change of aptazyme induced by target protein is designed to be associated with aptazyme activation. Consequently, in the presence of the target protein, the designed DNA linkers will be cleaved into two fragments that fail to cross-link gold nanoparticles (GNPs), thus the color of GNP solution remains red, while the color will be changed in the absence of the target. Because of the advantages of aptazyme such as economic synthesis, stable, easy modification and its ability to accomplish signal recognition and signal amplification simultaneously, the method is thermostable, simple and cost-efficient. In this work, we have taken the detection of vascular endothelial growth factor (VEGF) as an example, which can present an analytical performance with as low as 0.1 nM detection limit, spanning a detection range of 3 orders of magnitude. What is more, the principle of this proposed new method can be extended as a universal assay method not only for the detection of analytes which have an aptamer but also for those analytes that have ligands.     

Comparison of two laser-induced breakdown spectroscopy techniques for total carbon measurement in soils

The potentials of two advanced laser-induced breakdown spectroscopy (LIBS) techniques which are used to determine the total carbon content in soils have been examined. The first one is the combination of a single-pulse laser ablation with spark excitation of plasma plume triggering the gap between electrodes close to the target surface. The second one is a more conventional double-pulse LIBS. In both modes the calibration graphs have a nonlinear trend in the actual range of carbon contents and present a good R² value (0.97). In the combined laser-spark approach, using low-cost and portable laser instrumentation is possible, as well as inducing a micro-damage on the target surface. Certain regularities in the spectral line intensities of soil nutritious elements have been detected and appear to be connected to the total carbon content and to the soil origin.     

Laser Based Optical Emission Studies of Zinc Oxide (ZnO) Plasma

We present the optical emission characteristics of the zinc oxide (ZnO) plasma produced by the first (1,064 nm) and second (532 nm) harmonics of a Q switched Nd: YAG laser. The target material was placed in front of laser beam in air (at atmospheric pressure).The experimentally observed line profiles of neutral zinc (Zn I) have been used to extract the electron temperature using the Boltzmann plot method, whereas, the electron number density has been determined from the Stark broadening. The electron temperature is calculated by varying distance from the target surface along the line of propagation of plasma plume and also by varying the laser irradiance. Beside we have studied the variation of number density as a function of laser irradiance as well as its variation with distance from the target surface. It is observed that electron temperature and electron number density increases as laser energy is increased.     

A novel technology for the detection, enrichment, and separation of trace amounts of target DNA based on amino-modified fluorescent magnetic composite nanoparticles

A novel, highly sensitive technology for the detection, enrichment, and separation of trace amounts of target DNA was developed on the basis of amino-modified fluorescent magnetic composite nanoparticles (AFMN). In this study, the positively charged amino-modified composite nanoparticles conjugate with the negatively charged capture DNA through electrostatic binding. The optimal combination of AFMN and capture DNA was measured by dynamic light scattering (DLS) and UV–vis absorption spectroscopy. The highly sensitive detection of trace amounts of target DNA was achieved through enrichment by means of AFMN. The detection limit for target DNA is 0.4 pM, which could be further improved by using a more powerful magnet. Because of their different melting temperatures, single-base mismatched target DNA could be separated from perfectly complementary target DNA. In addition, the photoluminescence (PL) signals of perfectly complementary target DNA and single-base mismatched DNA as well as the hybridization kinetics of different concentrations of target DNA at different reaction times have also been studied. Most importantly, the detection, enrichment, and separation ability of AFMN was further verified with milk. Simple and satisfactory results were obtained, which show the great potential in the fields of mutation identification and clinical diagnosis.     

A systematic investigation of ionization occurring in few electron collision systems: H0, He0 impact on He

Absolute doubly differential cross sections for electron emission occurring in fast (0.5 MeV/amu) H⁰ — and He⁰ — He collisions have been measured using standard non-coincidence techniques as well as emitted electron — charge state analysed projectile coincidence techniques. The comparison of these data with results obtained for H⁺ and He⁺ impact provides insight into the influence of one or two loosely bound projectile electrons on the probabilities for projectile, target, and simultaneous projectile — target ionization. PWBA calculations for these systems demonstrate good agreement with the experimental data for target and projectile ionization and indicate the importance of including simultaneous ionization processes in the theoretical treatment.     

A Self-immolative Molecular Beacon for Amplified Nucleic Acid Detection**

Fluorogenic hybridization probes allow the detection of RNA and DNA sequences in homogeneous solution. Typically, one target molecule activates the fluorescence of a single probe molecule. This limits the sensitivity of nucleic acid detection. Herein, we report a self-immolative molecular beacon (iMB) that escapes the one-target/one-probe paradigm. The iMB probe includes a photoreductively cleavable N-alkyl-picolinium (NAP) linkage within the loop region. A fluorophore at the 5’-end serves, on the one hand, as a reporter group and, on the other hand, as a photosensitizer of a NAP-linker cleavage reaction. In the absence of target, the iMB adopts a hairpin shape. Quencher groups prevent photo-induced cleavage. The iMB opens upon hybridization with a target, and both fluorescent emission as well as photo-reductive cleavage of the NAP linker can occur. In contrast to previous chemical amplification reactions, iMBs are unimolecular probes that undergo cleavage leading to products that have lower target affinity than the probes before reaction. Aided by catalysis, the method allowed the detection of 5 pm RNA target within 100 min.     

Optical supermicrosensor responses for simple recognition and sensitive removal of Cu (II) Ion target

The field of optical chemosensor technology demands a simple yet general design for fast, sensitive, selective, inexpensive, and specific recognition of a broad range of toxic metal ions. The suitable accommodation of chromogenic receptors onto ordered porous carriers have led to selective and sensitive chemosensors of target species. In this study, we offer real evidence on the potential use of two- and three-dimensional (2D and 3D) ordered supermicroporous monoliths as selective shape and size carriers for immobilizing the chromogenic probe. Among all the chemosensors, 3D supermicropore has exhibited easy accessibility of target ions, such as ion transports and high affinity responses of receptor-metal analyte binding events. This leads to an optical color signal that is easily generated and transduced even at trace levels of Cu(II) target ions. The supermicrosensors have shown the ability to create Cu(II) ion-sensing responses up to nanomolar concentrations (∼10⁻⁹ mol/dm³) with rapid response time (in the order of seconds). Supermicrosensors have the ability to create easily modified sensing systems with multiple regeneration/reuse cycles of sensing systems of Cu(II) analytes. The simple treatment using ClO₄⁻ anion as a stripping agent has removed effectively the Cu(II) ions and formed a “metal-free” probe surface. The supermicrosensors have exhibited the specificity behavior permitting Cu(II) ion-selective determination in real-life samples, such as in wastewater, despite the presence of active component species. Extensive analytical results indicate that the use of the supermicrosensor as Cu(II) ion strips for field screening can be a time- and cost-alternative tool to current effective laboratory assays.     

Iron-promoted one-pot approach: Synthesis of isothiocyanates

Abstract

We have established a facile and versatile synthesis for the construction of isothiocyanates from their respective amines in the presence of an eco-friendly, inexpensive, easily available Iron catalyst under mild conditions. This reaction provides the target products through the formation of thiocarbamate salt as an intermediate. Both aromatic amines and aliphatic amines provided the respective target products in moderate to high yield under optimized reaction conditions. However, electron withdrawing substituents were difficult to give target product at room temperature, whereas, they obtained final products in good yield at moderate temperature. In addition, mechanistic studies were revealed that the synthetic route involved iron based subsequent reactions of addition and removal of sulfur.     

A general purpose XUV laser spectrometer: some applications to N2, O2 and CO2

Coherent radiation is generated from 90 to 105 nm by frequency tripling the frequency-doubled output of a pulsed Nd: YG-pumped dye laser using a synchronized pulsed jet of various gases as the nonlinear medium. The XUV radiation is isolated by a pair of dichroic mirrors before interacting with a supersonically cooled gas target. Provisions have been made to measure the photoion yield as a function of wavelength using a time-of-flight mass spectrometer. In addition absorption by the target gas or fluorescence from the excited target and/or its fragments can be detected. Some applications are presented which illustrate the versatility of this XUV laser spectrometer involving 1+1 resonance-enhanced multiphoton ionization of N₂ and excitation of Rydberg states of O₂ and CO₂.     

Estimation of calcified tissues hardness via calcium and magnesium ionic to atomic line intensity ratio in laser induced breakdown spectra

Calcified tissues representing three different matrices, namely enamel of human teeth, shells and eggshell, have been studied via Laser Induced Breakdown Spectroscopy (LIBS) technique. The experimental CaII/CaI and MgII/MgI ratios have been measured, in view of the expected correlation between the extent of ionization caused by the laser induced shock wave (SW) and the hardness of the target. The ratio CaII/CaI between the ionic calcium line at 373.69 nm and the neutral line at 428.9 nm is obtained for enamel, shells and eggshell spectra, as well as the ratio MgII/MgI between the ionic magnesium line at 280.26 nm and the neutral line at 285.22 nm. The results show that such spectral lines intensities ratio differs for different matrices and is indeed related to the target materials hardness. It is also found that the MgII/MgI ratio is preferable as an indicator of hardness since these lines are less affected by self absorption. The SW front speed has been measured in the three cases and the obtained values confirm the proportionality to the target hardness. The results here obtained suggest the feasibility of the quantitative estimation of hardness for any other calcified tissues.     

Mechanism of DNA-drug interactions

Over the last two decades many strategies have been planned to design specific drugs for rare diseases to target their action at the DNA level. Advancements in our understanding of the interactions of small nonpeptide molecules with DNA have opened the doors for “rational” drug design. Special methods have now been developed to give accurate account of the precise location of ligand-DNA adducts on target DNA. We are now in a position to think of designing ligands that recognize particular sequences of base pairs. This work will allow us to enter into a new era of gene therapy for diseases like Cystic fibrosis, Alzheimer’s disease and many related disorders at genetic level. These ligands can also be employed in the treatment of various types of cancers. They may also be useful as highly specific probes to locate particular sequences in the genomic DNA.