Preparation of Organic/Inorganic Hybrid Materials Using Agregates of Poly{2-methyl-N-[2-(phenylthio)phenyl] Acrylamide-co-2-(Trimethylsyloxy)Ethyl Methacrylate} as Precursor and Vibrational Investigation of the Polymerization

Acrylamide based monomer, 2-methyl-N-[2-(phenylthio)phenyl]acrylamide (MPPA) was synthesized by reacting 2-(phenylthio) aniline with methacryloylchloride. The copolymerization of MPPA, with 2-(trimethylsyloxy)ethyl methacrylate(TSEM) was carried out with different monomer-to-monomer ratios in the feed. All the compounds were characterized by IR, Raman and ¹H- and ¹³C-NMR techniques and SEM analysis. The elemental analysis of the copolymer composition led to the determination of reactivity ratios employing Fineman-Ross, Kelen-Tüdös and Extended Kelen-Tüdös linearization methods. These parameters were also estimated using a non-linear computational fitting procedure, known as reactivity ratio errors in variable model. The molecular weights and polydispersity index of polymers was determined by gel permeation chromatography. Thermal stability of the copolymers were found to increase with increasing mole fraction of MPPA from thermogravimetric analysis. The vibrational analysis of MPPA and poly(MPPA) were also performed to explain the vibrational spectra and to confirm the polymerization on the basis of a theoretical and experimental aproach.     

Compressed images for affinity prediction (CIFAP): a study on predicting binding affinities for checkpoint kinase 1 protein inhibitors

Analyses of known protein–ligand interactions play an important role in designing novel and efficient drugs, contributing to drug discovery and development. Recently, machine learning methods have proven useful in the design of novel drugs, which utilize intelligent techniques to predict the outcome of unknown protein–ligand interactions by learning from the physical and geometrical properties of known protein–ligand interactions. The aim of this study is to work through a specific example of a novel computational method, namely compressed images for affinity prediction (CIFAP), in which binding affinities for structurally related ligands in complexes with human checkpoint kinase 1 (CHK1) are predicted. The CIFAP algorithm presented here relates published pIC ₅₀ values of 57 compounds, derived from a thienopyridine pharmacophore, in complexes with CHK1 to their two‐dimensional (2D) electrostatic potential images compressed in orthogonal dimensions. Patterns obtained from the 2D images are then used as inputs in regression and learning algorithms such as support vector regression (SVR) and adaptive neuro‐fuzzy inference system (ANFIS) methods to validate the experimental pIC ₅₀ values. This study revealed that the 2D image pixels in the vicinity of bound ligand surfaces provide more relevant information to make correlations with the empirical pIC ₅₀ values. As compared with ANFIS, SVR gave rise to the lowest root mean square errors and the greatest correlations, suggesting that SVR could be a plausible choice of machine learning methods in predicting binding affinities by CIFAP. Copyright © 2013 John Wiley & Sons, Ltd.     

Structural insights of two novel N-acetyl-glucosaminidase enzymes through in silico methods

EndoBI-1 and EndoBI-2 are two endo- β-N- acetylglucosaminidase isoenzymes that cleave N-N’- diacetylchitobiosyl moieties found in various types of native N -glycans. These N -glycans are indigestible by human infants and adults due to the lack of responsible glycosyl hydrolases and they act as selective prebiotics for a probiotic microorganism, Bifidobacterium longum subsp . infantis , in the large intestine. The selectivity and the thermostability of EndoBI-1 and EndoBI-2 suggest that these enzymes may be useful for many scientific and industrial applications. In this study, the growing numbers of homologous sequences in different databases were exploited in a comparative approach to investigate structural properties of EndoBI-1 and EndoBI-2 enzymes. Moreover, the complete and partial homology models of these two enzymes were generated and evaluated. Selected models were used for docking studies of the plus subsite ligand of these enzymes for further understanding on the substrate selectivity of EndoBI enzymes.     

Monitoring Humic Acid Photodegradation by CUPRAC Colorimetric and HPLC Determination of Dihydroxybenzoate Isomers Produced From a Salicylate Probe

Abstract

Novel analytical methods were designed for monitoring humic acid photodegradation in environmental waters. Modified CUPric Reducing Antioxidant Capacity (CUPRAC) spectrophotometric and chromatographic methods were used for the determination of dihydroxybenzoate isomers (DHBAs) produced from a salicylate probe, which was hydroxylated by hydroxyl radicals (^?OH) produced from the photodegradation of humic acid under ultraviolet A-radiation. The combined use of CUPRAC colorimetry and HPLC was shown to effectively monitor humic acid photodegradation and ^?OH generation for the first time. The formation of 2,5-dihydroxybenzoate and 2,3-dihydroxybenzoate, as major and minor products, respectively, from the hydroxylation of a salicylate probe was demonstrated by HPLC and confirmed by a modified CUPRAC method to indicate ^?OH formation from humic acid, which acted as both a generator and absorber of hydroxyl radicals. Salicylate hydroxylation showed an increase between 30 and 50?min of illumination, and was affected by the initial concentration of humic acid up to 0.01% but not by solution pH around the neutral values. Traces of Fe(III) and Mn(II) present in natural waters decreased the ^?OH production, but EDTA partly restored the probe hydroxylation by chelating these metal cations. Since humic acid-mediated ^?OH generation may aid in natural disinfection processes, this work may extend our comprehension of concentration- and time-dependent generation of ^?OH in environmental waters and of the possible effects of other antioxidants.     

Novel Nanocomposites of Polypyrrole Doped with Fullerene C60

This paper reports on the structural, thermal, and dielectric properties of polypyrrole/fullerene C₆₀ nanocomposites synthesized by a interfacial polymerization method. Fourier transform infrared (FT-IR) and ultraviolet-visible (UV-vis) analyses clearly indicated the existence of interactions between polypyrrole (PPy) and the fullerene C₆₀ nanoparticles. Thermal analyses indicated that the extrapolated onset degradation temperature (T_deg) of PPy increased with increasing doping level. Scanning electron microscopy (SEM) images showed that the fullerene C₆₀ changed the morphology of PPy. Dielectric analyses showed a temperature dependent dielectric relaxation behavior. The relaxation time of the nanocomposites with high doping levels tended to increase with increasing temperature. This behavior of the polypyrrole/fullerene C₆₀ nanocomposites indicated that they could be used as a high temperature ultrasonic transducer.     

Synthesis of new hydrogels based on the macromolecular reaction of citraconic anhydride copolymers with γ‐aminopropyltriethoxysilane (APTS)

This work describes the synthesis and macromolecular reactions of citraconic anhydride (CA)–acrylamide (AAm) binary reactive copolymers with γ‐aminopropyltriethoxysilane (APTS) as a polyfunctional crosslinker. Copolymers with given composition of poly(CA‐alt‐AAm) were synthesized by radical binary copolymerization with benzoyl peroxide (BPO) as an initiator in benzene at 70°C in nitrogen atmosphere with initial monomer ratio 1 : 1. It was shown that the network structure is formed in poly(CA‐alt‐AAm)/APTS in water by intermolecular reactions between the anhydride unit and the amine group, as well as between the ethoxysilyl fragment and free carboxyl groups of the CA unit and amide unit of AAm. Swelling parameters such as beginning time of the hydrogel‐formation, initial rate of the swelling, swelling rate constant, equilibrium swelling and equilibrium water content were determined for the copolymer/APTS/water system with certain (2.75 : 1) copolymer/crosslinker ratio. Formation of a hyperbranched network structure through the fragmentation of side‐chain reactive groups in studied systems was confirmed by Fourier transform infrared spectroscopy (FT‐IR) method. Copyright © 2004 John Wiley & Sons, Ltd.     

Olefins and Vinyl Polar Monomers: Bridging the Gap for Next Generation Materials

The inherent differences in reactivity between activated and non‐activated alkenes prevents copolymerization using established polymer synthesis techniques. Research over the past 20 years has greatly advanced the copolymerization of polar vinyl monomers and olefins. This Review highlights the challenges associated with conventional polymerization systems and evaluates the most relevant methods which have been developed to “bridge the gap” between polar vinyl monomers and olefins. We discuss advancements in heteroatom tolerant coordination–insertion polymerizations, methods of controlling radical polymerizations to incorporate olefinic monomers, as well as combined approaches employing sequential polymerizations. Finally, we discuss state‐of‐the‐art stimuli‐responsive systems capable of facile switching between catalytic pathways and provide an outlook towards applications in which tailored copolymers are ideally suited.     

Metasurface‐Based Molecular Biosensing Aided by Artificial Intelligence

Molecular spectroscopy provides unique information on the internal structure of biological materials by detecting the characteristic vibrational signatures of their constituent chemical bonds at infrared frequencies. Nanophotonic antennas and metasurfaces have driven this concept towards few‐molecule sensitivity by confining incident light into intense hot spots of the electromagnetic fields, providing strongly enhanced light‐matter interaction. In this Minireview, recently developed molecular biosensing approaches based on the combination of dielectric metasurfaces and imaging detection are highlighted in comparison to traditional plasmonic geometries, and the unique potential of artificial intelligence techniques for nanophotonic sensor design and data analysis is emphasized. Because of their spectrometer‐less operation principle, such imaging‐based approaches hold great promise for miniaturized biosensors in practical point‐of‐care or field‐deployable applications.     

Determination of the effective correlation time modulating 1H NMR relaxation processes of bound water in protein solutions

The relaxation in protein solutions has mainly been studied by nuclear magnetic relaxation dispersion (NMRD) techniques. NMRD data have mostly been analyzed in terms of fast chemical exchange of water between free water and water bound to proteins. Several approaches were used for the estimation of correlation time modulating the relaxation mechanism of bound water. On the other hand, in a nuclear magnetic resonance experiment, the relaxation rates of protein solutions (1/T1 and 1/T2) and also those of free water (1/T1f and 1/T2f) are measurable. However, the relaxation rates of bound water (1/T1b and 1/T2b) are not. Despite this, equating (1/T1-1/T1f)/2(1/T2-1/T2f) to (1/T1b)/2(1/T2b) leads to an expression involving only an effective tau that is related to the rotational correlation time (tau r) of proteins. Equating the ratios may therefore give a simple alternative method for the determination of tau r even if this method is limited to a single resonance frequency. In this work, a formula was derived for the solution of the effective tau. Then, the 1/T1 and 1/T2 in solutions of two globular proteins (lysozyme and albumin) and one nonglobular protein (gamma-globulin) were measured for different amounts of each protein. Next, the values of 1/T1 and 1/T2 were plotted vs. protein concentrations, and then the slopes of the fits were used in the derived equation for determining the effective tau values. Finally, the rotational correlation time tau r, calculated from tau, was used in the Stokes-Einstein relation to reproduce relevant radii. The effective tau values of lysozyme, albumin and gamma-globulin were found to be 5.89 ns, 7.03 ns and 8.8 ns, respectively. tau r values of albumin and lysozyme produce their Stokes radii. The present data suggest that use of the measurable ratio in the derived formula may give a simple way for the determination of the correlation times of lysozyme and albumin.     

Synthesis,crystal structures,characterization and antimicrobial activities of 5-hydroxyisophthalate complexes

Two 5-hydroxyisophthalate complexes of nickel(II), formulated as [Ni(μ-Hhip)(2-hepy)₂] _n (1) and [Ni₂(μ-Hhip)₂(dap)₄] _n (2) (H₃hip = 5-hydroxyisophthalic acid, 2-hepy = 2-(2-hydroxyethyl)pyridine, dap = 1,3-diaminopropane), have been synthesized and characterized by chemical and spectroscopic methods. The molecular structures of the complexes have been determined by single-crystal X-ray diffraction analysis. The Ni(II) centres have distorted octahedral geometries in both crystals. Furthermore, both complexes have 1D chain structures in which the individual chains are linked together via hydrogen bonds to give 3D frameworks. Evaluation of the complexes by the agar diffusion method showed that they have weak antibiotic activities against the tested microorganisms.