Hydrogen bonding dynamics of cyclodextrin–water solutions by depolarized light scattering

Depolarized light scattering measurements performed on aqueous solutions of α‐cyclodextrin are used for investigating the hydration properties of this natural cyclic oligosaccharide, which is well known for its ability to form inclusion complexes with a large variety of guest hydrophobic molecules. The spectral analysis allows the characterization of the solvent relaxation process assigned to hydration water, which is found to be seven to eight times slower than the bulk. As a structural information, the number of water molecules involved in the hydration process is also estimated at about 46. These results are a key step for understanding the role played by water in determining the properties of different forms of cyclodextrins and their derivatives, in turn related to complexation ability of these macrocycles. Copyright © 2011 John Wiley & Sons, Ltd.     

Synthesis,Crystal Structure and Thermal Properties of <Emphasis Type="Italic">N</Emphasis>-Acetyl-3-(2-furyl)-5-ferrocenyl-2-pyrazoline and <Emphasis Type="Italic">N</Emphasis>-Acetyl-3-(2-thienyl)-5-ferrocenyl-2-pyrazoline

Abstract  

Two novel ferrocenyl substituted N-acetyl-2-pyrazolines, N-acetyl-3-(2-furyl)-5-ferrocenyl-2-pyrazoline (3) and N-acetyl-3-(2-thienyl)-5-ferrocenyl-2-pyrazoline (4), have been synthesized and characterized by FTIR, ¹H-NMR, ¹³C-NMR techniques, elemental analysis and X-ray structure analysis. Thermal properties of these compounds have been determined by TGA, DTA and DSC analysis. Compound 3 (C₁₉H₁₈N₂O₂Fe) crystallizes in the monoclinic space group P21/c and Z = 4, with a = 8.6970(4) ?, b = 18.4725(9) ?, c = 11.0041(5) ?, β = 110.942(3)°. Compound 4 (C₁₉H₁₈N₂OSFe) crystallizes in the orthorhombic space group Fdd2 and Z = 16, with a = 84.242(2) ?, b = 13.5416(5) ?, c = 5.9405(2) ?, β = 90°. In terms of crystal packing, each compound shows different molecular arrangement, which are stabilized by C–H···O intermolecular weak hydrogen bonds, and/or C–H···π interactions.     

Effect of densification on the density of vibrational states of glasses

We studied the effect of densification on the vibrational dynamics of a Na(2)FeSi(3)O(8) glass. The density of vibrational states (DOS) has been measured using nuclear inelastic scattering. The corresponding changes in the microscopic, intermediate-range, and macroscopic properties have also been investigated. The results reveal that, in the absence of local structure transformations, the Debye level and the glass-specific excess of vibrational states above it have the same dependence on density, and the evolution of the DOS is fully described by the transformation of the elastic medium.     

Is there any fast sound in water?

We measured the dynamic structure factor S(Q,omega) of liquid and undercooled water down to 253 K in the Q approximately 0.02-0.1 nm;{-1} momentum transfer region. We observe the neat departure of the apparent speed of sound from the adiabatic regime as a function of decreasing temperature. Our evaluation of the infinite-frequency limit of sound velocity, c_{infinity}, matches with the results obtained in the high momentum transfer limit by inelastic neutron and x-ray scattering. These results strongly support the viscoelastic interpretation of the dynamics of water. Hence, we propose to call c_{infinity} the high-frequency speed of sound and to abandon the term fast sound, which recalls a propagation mechanism through lighter atoms, like in gas mixtures.     

Benzophenone based addition fragmentation agent for photoinitiated cationic polymerization

Photoactive allyl ammonium salt (BPEA) containing benzophenone moiety in the structure was synthesized and characterized. Its capability to act as a self-initiating addition fragmentation agent in the photoinitiated cationic polymerization of oxiranes such as cyclohexene oxide and vinyl monomers such as butylvinyl ether was investigated. These monomers turned out to be polymerizable in the presence of BPEA provided free radicals are generated photochemically at λ>300 nm by hydrogen abstraction of excited benzophenone moiety. Accordingly, a free radical adds to the carbon-carbon double bond of a ground state BPEA and fragmentation of the adduct radical results in the formation of reactive ammonium radical cation which is essentially responsible for the initiation.     

Hexa-BODIPY Linked-Triazole Based on a Cyclotriphosphazene Core as a Highly Selective and Sensitive Fluorescent Sensor for Fe<Superscript>2+</Superscript> Ions

A new type of fluorescent chemosensor based on tethered hexa-borondipyrromethene cyclotriphosphazene platform (HBTC) linked via triazole groups was designed and synthesized. Its sensing behavior toward metal ions was investigated by ultraviolet-visible and fluorescence spectroscopies. Addition of a Fe²⁺ ion to a tetrahydrofuran solution of HBTC gave a visual color change as well as a significantly quenched fluorescence emission, while other tested 19 metal ions induced no color or spectral changes. This compound was found to be highly selective and sensitive for Fe²⁺ with a low limit of detection (2.03 μM) which is, to the best of our knowledge, the superior than the previously studied chemosensors for Fe²⁺.

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Prostate Cancer Biomarker Detection with Carbon Nanotubes Modified Screen Printed Electrodes

DNA hypermethylation is an epigenetic alteration and a promising biomarker for early prostate cancer detection. Simple, sensitive, easy to handle and rapid detection methodologies are imperative for point of care diagnostics especially for cancer. Herein, we describe for the first time a regenerable and compatible electrochemical biosensor for detection of Glutathione S‐Transferase P‐1 (GSTP‐1) gene hypermethylation related to prostate cancer via DNA hybridization onto the disposable Carbon and Multi Walled Carbon Nanotubes (MWCNT) Screen Printed Electrodes (SPEs). In the study, capture probes were adsorbed onto the SPEs by simple passive adsorption and then hybridization was achieved by sending the complementary target onto the probe‐modified electrodes. The selectivity of the biosensor was proved by control studies. Differential Pulse Voltammetry (DPV) technique was used to detect hybridization via guanine oxidation signals changes. The total time of the optimized method was nearly 1h, measurements took for less than 1 min, and the biosensor response was stable up to 40 days of storage period at 4 °C. The main advantages of the biosensor are very low detection limit (picomolar range) and capability of reusing the biosensor for at least 3 times after very simple regeneration process that is a unique property to reduce the cost of the assay. In addition, this is the first study that demonstrates the detection of GSTP‐1 hypermethylation electrochemically by using SPEs in order to create point of care diagnostics. The optimum parameters for the biosensor, as well as its future prospects to enhance the performance of DNA biosensors were also presented.     

Application of stripping voltammetry method for the analysis of available copper,zinc and manganese contents in soil samples

Determination of copper (Cu), zinc (Zn) and manganese (Mn) micronutrients in soil samples have been studied for an efficient fertiliser application. Plant-available micronutrients of soils were extracted with DTPA extraction procedure, then differential pulse stripping voltammetry (DPSV) and square wave stripping voltammetry (SWSV) methods were performed with inexpensive and disposable pencil graphite electrode for determination of Cu(II), Zn(II) and Mn(II). Parameters such as deposition potential, deposition time, pH and concentration of the supporting electrolyte were optimised for these ions. Under optimised conditions, the limits of detection were found as 0.01 mg L^?1 for Cu(II) and 0.02 mg L^?1 for Zn(II) and 0.25 mg L^?1 for Mn(II). Relative standard deviation (%RSD) was 6.80, 8.86 and 3.29 for Cu(II), Zn(II) and Mn(II), respectively. The experimental study was conducted using a flame atomic absorption spectroscopy. The described stripping voltammetry methods were successfully applied for the determination of Mn(II), Cu(II) and Zn(II) in soil samples.