Spin transition molecular materials: intelligent contrast agents for magnetic resonance imaging

Some preliminary results from a model of temperature-sensitive contrast agents are reported. This paramagnetic system switches from a spin S = 0 diamagnetic state to a S = 2 paramagnetic one at a temperature that can be tuned according to chemical composition. The magnetic susceptibility jump and the subsequent R2* effect as a function of temperature have been followed by means of spectroscopy, relaxometry, and imaging, demonstrating sharp and reversible transitions. Potential applications of this kind of system could be found in therapy by hyperthermia or in material science.     

Human-centric intelligent systems for exploration and knowledge discovery

This speculative article discusses research and development relating to computational intelligence (CI) technologies comprising powerful machine-based search and exploration techniques that can generate, extract, process and present high-quality information from complex, poorly understood biotechnology domains. The integration and capture of user experiential knowledge within such CI systems in order to support and stimulate knowledge discovery and increase scientific and technological understanding is of particular interest. The manner in which appropriate user interaction can overcome problems relating to poor problem representation within systems utilising evolutionary computation (EC), machine-learning and software agent technologies is investigated. The objective is the development of user-centric intelligent systems that support an improving knowledge-base founded upon gradual problem re-definition and reformulation. Such an approach can overcome initial lack of understanding and associated uncertainty.     

Integrating virtual screening and combinatorial chemistry for accelerated drug discovery

Virtual screening is increasingly being used in drug discovery programs with a growing number of successful applications. Experimental methodologies developed to speed up the drug discovery processes include high-throughput screening and combinatorial chemistry. The complementarities between computational and experimental screenings have been recognized and reviewed in the literature. Computational methods have also been used in the combinatorial chemistry field, in particular in library design. However, the integration of computational and combinatorial chemistry screenings has been attempted only recently. Combinatorial libraries (experimental or virtual) represent a notable source of chemically related compounds. Advances in combinatorial chemistry and deconvolution strategies, have enabled the rapid exploration of novel and dense regions in the chemical space. The present review is focused on the integration of virtual and experimental screening of combinatorial libraries. Applications of virtual screening to discover novel anticancer agents and our ongoing efforts towards the integration of virtual screening and combinatorial chemistry are also discussed.     

Macromolecular coupling agents for flame retardant materials

Polypropylene (PP) is a large-consumed polymer employed in many applications. For some uses, good flame resistance is desirable and this can be achieved by the addition of metallic hydroxides. However, high loads of metallic hydroxides are needed causing marked deterioration of the physical properties. Addition of interfacial agents is a useful way of minimizing these effects. In this study, PP was modified with vinyltriethoxysilane (VTES) and maleic anhydride (MA) and the products were used as coupling agents for PP/aluminum hydroxide (ATH) composites. The composites were characterized by TGA, SEM, tensile and flammability tests. It was observed that both coupling agents were efficient but PP modified with VTES showed better effect on the mechanical properties. Two types of ATH were used for comparison.     

Critical considerations for the accelerated ageing of high-density polyethylene potable water materials

Accelerated ageing conditions with chlorinated water were identified that minimize variations in solution chemistry and water sorption, and that also enable the interpretation of HDPE physical and chemical changes during 20 week (3884 h) immersion periods. Of the ten conditions tested, three conditions with an alkalinity concentration of 50 ppm as CaCO₃ at pH 6.5 and at 23 and 37 °C performed best. These three conditions exhibited stable pH, free available chlorine, and alkalinity concentration during 20 weeks of HDPE immersion with 72 h changes of ageing solution. HDPE was periodically characterized using differential scanning calorimetry, thermogravimetric analysis, tensile analysis, a density gradient column, moisture analysis, and optical and infrared spectroscopy. Formation of surface carbonyl bonds and gradual reductions in oxidation induction time were detected, as well as water sorption into HDPE. Ageing solution and water sorption monitoring recommendations from this work should be incorporated into accelerated ageing protocols and considered when characterizing aged PE drinking water pipe.     

High-throughput screening: speeding up porous materials discovery

A new tool (Infrasorb-12) for the screening of porosity is described, identifying high surface area materials in a very short time with high accuracy. Further, an example for the application of the tool in the discovery of new cobalt-based metal-organic frameworks is given.     

Evolutionary chemical space exploration for functional materials: computational organic semiconductor discovery

Computational methods, including crystal structure and property prediction, have the potential to accelerate the materials discovery process by enabling structure prediction and screening of possible molecular building blocks prior to their synthesis. However, the discovery of new functional molecular materials is still limited by the need to identify promising molecules from a vast chemical space. We describe an evolutionary method which explores a user specified region of chemical space to identify promising molecules, which are subsequently evaluated using crystal structure prediction. We demonstrate the methods for the exploration of aza-substituted pentacenes with the aim of finding small molecule organic semiconductors with high charge carrier mobilities, where the space of possible substitution patterns is too large to exhaustively search using a high throughput approach. The method efficiently explores this large space, typically requiring calculations on only ∼1% of molecules during a search. The results reveal two promising structural motifs: aza-substituted naphtho[1,2-a]anthracenes with reorganisation energies as low as pentacene and a series of pyridazine-based molecules having both low reorganisation energies and high electron affinities.

Evolutionary optimisation and crystal structure prediction are used to explore chemical space for molecular organic semiconductors.     

Use of cationic agents for fixing coloration of textile materials

Russian Journal of Applied Chemistry - Ways to increase the degree of utilization of active dyes, enhance the economic and environmental efficiency of coloration, and improve the quality parameters...     

Mechanoacoustic method for production of composite Chitosan finishing agents for textile materials

Theory and practice of fibrous materials modification using chitosan finishing agents with functional additives are discussed. Efficiency of the mechanoacoustic method for production of composite finishing agents is proved.     

Solution-phase parallel synthesis of an isoflavone library for the discovery of novel antigiardial agents

Combinatorial chemistry has become a dramatically useful tool for the development of new medicinal agents. In the search to discover a novel and effective lead for the treatment of giardiasis, solution-phase synthesis of a library of isoflavone derivatives has been accomplished. Of the products screened, several compounds such as P(A1,B1) and P(A1,B11) exhibited potent antigiardial activity. The details of synthesis, in vitro antigiardial assay, and preliminary structure-activity relationships of these compounds are described.     

Drug discovery studies on quinoline-based derivatives as potential antimalarial agents

Molecular modelling studies were performed to identify the essential structural requirements of quinoline-based derivatives for improving their antimalarial activity. The developed CoMFA, CoMSIA and HQSAR models for a training set comprising 37 derivatives showed good statistical significance in terms of internal cross validation (q²) 0.70, 0.69 and 0.80 and non-cross validation (r²) 0.80, 0.79 and 0.80. Also, the predicted r² values (r²_pred) of 0.63, 0.61 and 0.72 for a test set consisting of 12 compounds suggested significant predicting ability of the models. Structural features were correlated in terms of steric, electrostatic, hydrophobic, hydrogen bond donor and hydrogen bond acceptor interactions. Furthermore, the bioactive conformation was explored and explained by docking compounds #28, 32 and 40 into the active binding site of lactate dehydrogenase of Plasmodium falciparum. The QSAR models, contour map and docking binding affinity obtained could be successfully utilized as a guiding tool for the design and discovery of novel quinoline-based derivatives with potent antimalarial activity.     

Conducting polymers in redox devices and intelligent materials systems

Applications opportunities are described for conducting polymer devices, including (1) batteries and redox capacitors, (2) electromechanical actuators, (3) electrochromic windows and displays, (4) chemical separation and chemical delivery systems, and (5) indicators and sensors. Each of these potential application areas depends upon the dramatic property changes which occur during chemical or electrochemical doping. Since the properties profiles of conducting polymers can be reversibly changed either chemically or electrochemically, these polymers also provide exciting candidates for intelligent materials systems - where sensor, logic element, and actuator functions can be either partially or fully integrated. Results of device and properties investigations are used to evaluate future possibilities for conducting polymers in intelligent material systems.     

Functionalizing inorganic solids: towards organic-inorganic nanostructured materials for intelligent and bioinspired systems

The design, preparation, and properties of organic-inorganic hybrid compounds are described and discussed with respect to their potential uses as intelligent and bioinspired materials. Several synthesis strategies based on intercalation in 2D solids, the grafting of organic groups onto silica and silicates, and the self-assembly of organo-silica materials are presented, focusing on the soft procedures that are used to modify the functionality of the inorganic substrates. The combination of both organic and inorganic moieties at the nanometer level forms the basis for preparing multifunctional solids that are provided with specific functions in response to different types of stimuli. In some cases these resemble materials that are found in biological systems. Examples include organic-inorganic membranes that are based on intercalated macrocyclic compounds and bi-layer vesicles that consist of alkyl long-chains arranged either in the confined region of layered silicates or as self-organized organo-silica micelles. The role of certain hybrid materials such as membranes provides a different approach to the development of artificial liposomes and other mimetic systems that have an organic-inorganic composition and nanostructural organization. Their potential uses for DDS or DNA-dense phases are also discussed and novel alternatives to bioinspired systems development are proposed.     

Pyrolysis mass spectrometry for distinguishing potential hoax materials from bioterror agents

Pyrolysis mass spectrometry (PyMS) was investigated as a rapid tool to distinguish potential bioterror hoax materials from samples containing pathogenic bacteria. A pyrolysis time-of-flight (TOF) mass spectrometer equipped with an alternative ionization technique, metastable atom bombardment (MAB), was used to produce sample spectra. These spectra were analyzed by principal component and discriminant analysis for pattern recognition. Materials investigated were two strains of Vibrio parahaemolyticus, one of which produced the tdh toxin, two Salmonella enterica serotypes, a biological mosquito control product containing spores of Bacillus thuringiensis, and several white to off-white powders (which could be used as hoax materials), such as flour, corn starch, methyl cellulose, and xanthan gum. PyMS distinguished bacterial samples from hoax materials. Furthermore, pattern analysis differentiated Vibrios from Salmonellae, Salmonella enterica Anatum from S. enterica Heidelberg, and the two V. parahaemolyticus strains from each other. The B. thuringiensis mixture was distinguished from other bacteria and powders, suggesting that PyMS with pattern recognition may differentiate samples containing pathogens, including Bacillus spp., from nonbiological agents and that it can be a rapid method for detection of bacteria. MS data acquisition took only 7 min for each sample.     

Enhanced trace element analysis of plant materials after accelerated pulsed UV digestion

A method for measuring trace concentration of Fe, Co, Ni, Cu, Zn and Pb in plant materials was developed, optimized, validated and compared using reference standards and fresh samples. The method is based on rapid material digestion by radicals produced with laser-assisted pulsed UV (PUV) photolysis of aqueous solutions containing H₂O₂. Metals in the resulting solution were pre-concentrated as carbamates. Samples were analyzed with particle induced X-ray emission (PIXE). Combined PUV digestion and pre-concentration techniques resulted in enhanced detection levels of selected trace elements in foods and non-food commodities. The method was applied to measure trace elements in wastewater irrigated fruits, vegetables and crops.     

Co-crystallisation as a modular approach to the discovery of spin-crossover materials

Herein we present co-crystallisation as a strategy for materials discovery in the field of switchable spin crossover (SCO) systems. Using [Fe(3-bpp)₂]·2A (where 3-bpp = 2,6-bis(pyrazol-3-yl)pyridine, A = BF₄⁻/PF₆⁻) as a starting point, a total of 11 new cocrystals have been synthesised with five different dipyridyl coformers. Eight of these systems show spin crossover behaviour, and all show dramatically different switching properties from the parent complex. The cocrystals have been studied by variable temperature single-crystal X-ray diffraction and SQUID magnetometry to develop structure–property relationships. The supramolecular architecture of the cocrystals depends on the properties of the coformer. With linear, rigid coformer molecules leading to 1D supramolecular hydrogen-bonded chains, while flexible coformers form 2D sheets and bent coformers yield 3D network structures. The SCO behaviour of the cocrystals can be modified through changing the coformer and thus co-crystallisation presents a rapid, facile and highly modular tool for the discovery of new switchable materials. The wider applicability of this strategy to the design of hybrid multifunctional materials is also discussed.

The switching behaviour of spin crossover cocrystals can be modified through changing the coformer and thus co-crystallisation presents a rapid, facile and highly modular tool for the discovery of new switchable materials.     

Applications of total synthesis toward the discovery of clinically useful anticancer agents

This tutorial review provides a historical sampling of synthetic efforts undertaken in our laboratory, which have led to the total syntheses of a range of small molecule natural products of potential interest in oncology. It has become evident that natural products, and structures clearly derivable from natural products, have a remarkable record in the treatment of cancer at the clinical level. It is likely that, with the growing power of chemical synthesis, small molecule natural products will play a continuing role in providing lead anticancer compounds.     

Bioactive polymeric materials for targeted administration of active agents: synthesis and evaluation

Bioerodible polymers displaying both stealth and targeting properties for the preparation of nanosystems for targeted and controlled delivery of fibrinolytic drugs to the thrombus were prepared by straightforward synthetic routes and characterized. Poly[(maleic anhydride)-alt-(butylvinyl ether)]s were synthesized in the presence of dodecyl mercaptan as chain transfer agent allowing for the preparation of copolymers with tunable molecular weight. 2-Methoxyethanol hemiesters containing antiopsonizing molecules of poly(ethylene glycol) were prepared and further biofunctionalized with a Fab fragment by a two-step reaction. In vitro biocompatibility investigation of the prepared materials supported their suitability for biomedical applications.