Application of octadecanethiol self-assembled monolayer to cholesterol biosensor based on surface plasmon resonance technique

Octadecanethiol (ODT) self-assembled monolayer (SAM) prepared onto gold-coated glass plate has been modified by using nitrene reaction of 1-fluoro-2-nitro-4-azidobenzene (FNAB) that further covalently binds to cholesterol oxidase (ChOx) via thermal reaction. FNAB acts as a bridge (cross-linker) between SAM and ChOx. The ChOx/FNAB/ODT/Au electrode thus fabricated has been characterized using contact angle (CA) measurements, UV-vis spectroscopy, electrochemical techniques and X-ray photoelectron spectroscopy (XPS) technique, respectively. This ChOx/FNAB/ODT/Au bioelectrode has been utilized for estimation of cholesterol in solution using surface plasmon resonance (SPR) technique. This SPR based cholesterol biosensor has linearity from 50 to 500 mg/dl of cholesterol in solution with lower detection limit of 50 mg/dl and shelf life of about 2 months when stored at 4 °C.     

Preparation and Characterization of Chiral Oxazaborolidine Complex Immobilized SBA‐15 and Its Application in the Asymmetric Reduction of Prochiral Ketones

The immobilization of chiral oxazaborolidine complex in the well‐ordered mesochannels of SBA‐15 is demonstrated by a postsynthetic approach using 3‐aminopropyltriethoxysilane as a reactive surface modifier. The immobilized catalysts are characterized by various techniques, such as XRD, nitrogen adsorption, HRSEM, UV/Vis diffuse reflectance spectroscopy, and FTIR spectroscopy. The catalysts are used for the enantioselective reduction of aromatic prochiral ketones. The activity of the chiral oxazaborolidine complex immobilized SBA‐15 catalysts is also compared with that of the pure chiral oxazaborolidine complex, which is a homogeneous catalyst. It is found that the activity of the chiral complex immobilized SBA‐15 heterogeneous catalyst is comparable with that of the homogeneous catalyst.     

Pressure perturbation calorimetric studies of the solvation properties and the thermal unfolding of proteins in solution--experiments and theoretical interpretation

We used pressure perturbation calorimetry (PPC), a relatively new and efficient technique, to study the solvation and volumetric properties of amino acids and peptides as well as of proteins in their native and unfolded state. In PPC, the coefficient of thermal expansion of the partial volume of the protein is deduced from the heat consumed or produced after small isothermal pressure jumps, which strongly depends on the interaction of the protein with the solvent or cosolvent at the protein-solvent interface. Furthermore, the effects of various chaotropic and kosmotropic cosolvents on the volume and expansivity changes of proteins were measured over a wide concentration range with high precision. Depending on the type of cosolvent and its concentration, specific differences were found for the solvation properties and unfolding behaviour of the proteins, and the volume change upon unfolding may even change sign. To yield a molecular interpretation of the different terms contributing to the partial protein volume and its temperature dependence, and hence a better understanding of the PPC data, molecular dynamics computer simulations on SNase were also carried out and compared with the experimental data. The PPC studies introduced aim to obtain more insight into the basic thermodynamic properties of protein solvation and volume effects accompanying structural transformations of proteins in various cosolvents on one hand, as these form the basis for understanding their physiological functions and their use in drug designing and formulations, but also to initiate further valuable applications in studies of other biomolecular and chemical systems.     

Microbial dynamics in oil-impacted prairie soil

A remote site in the Tallgrass Prairie Preserve (Osage County, OK) was contaminated with crude oil by a pipeline break in 1992. In 1996, the contaminated soil was bioremediated by blending with uncontaminated soil, prairie hay, buffalo manure, and commercial fertilizers, and spreading in a shallow layer over uncontaminated soil to create a landfarm. The landfarm was monitored for two years for aerobic and anaerobic bacteria, soil gases indicative of microbial activity, and for changes in the concentration of total petroleum hydrocarbons (TPH). Levels of hydrocarbon degraders and soil gas indicators of aerobic degradation were stimulated in the landfarm during the first warm season relative to uncontaminated prairie soil. However, these same indicators were less conclusive during the second warm season, indicating depletion of the more easily degradable hydrocarbons, although the landfarm still contained 6,800 mg/kg TPH on the average at the beginning of the second warm season. Methane formation and methanogen counts were clearly stimulated in the first warm season relative to uncontaminated prairie soil, in dicating that methanogenesis plays an important role in the mineralization of hydrocarbons even in these shallow soils.     

Glutathione-s-transferase based electrochemical biosensor for the detection of captan

The proposed electrochemical biosensor based on the inhibition of glutathione-s-transferase (GST) onto SAM modified gold due to captan was developed and determined by CV technique. The bioelectrode exhibited improved fast response time (12 s) with the detection limits 0.25–16 ppm, percentage inhibition >72% and high sensitivity 4.5 uA/ppm at standard optimal conditions. The recovery experiment results were found between 77% and 144% from spiked water sources. The bioelectrode was regenerated by DTT and reusable. The bioelectrodes were characterized by UV–visible, CV, AFM and STM. Thus, the proposed electrochemical biosensor is not only detected captan but also its metabolite and promising for real-time analysis of small molecules of environmental interest.     

Sweep Tests on Vibrating Systems with Power-Law Damping

The non-stationary response in vibrating systems with power-law damping, subjected to sweep tests is considered. Using the method of averaging, it is shown that the bifurcation delay persists in all forms of power-law damping, viz., Coulomb, orifice and cubic damping models. Experimental investigations on a soft type of isolator confirm the existence of delay in the jump phenomenon. These results also indicate that the softening nature of non-linearity can be profitably employed in the design of isolators and vehicle suspensions.     

Structure of p-tert-butylcalix[5]arene·ethyl acetate. A polymeric array of neighbor-included calixarenes

p-tert-Butylcalix[5]arene crystallizes from ethyl acetate in the monoclinic space groupC2/c witha=34.793(9),b=13.637(3),c=25.577(7), =114.28(2)°, andD _c =1.08 g cm^–3 forZ=8 (C₅₉H₇₈O₇). Refinement based on 2789 observed reflections led toR=0.071. The complex crystallizes with one molecule of ethyl acetate per calixarene molecule, with the solvent residing between calixarene units instead of within the cavity. The calixarene units neighbor-include to form a polymeric array: a t-butyl group of one calixarene is housed in the cavity of an adjacent calixarene. The packing arrangement of the calixarene molecules bears a remarkable resemblance to a zeolitic array.     

A new equation for modeling nonisothermal reactions

Based on previously reported approximations of the temperature integral, a new approximation $$\int {\exp ( - E/RT)dT = \frac{{RT^2 }}{E}} \left[ {\frac{{1 - 2(RT/E)}}{{1 - 5(RT/E)^2 }}} \right]\exp ( - E/RT)$$ has been proposed for modeling nonisothermal reactions. It has been found that the equation of Coats and Redfern deviates by less than 1 % from the exact solution forE/RT ratio greater than 23 and by less than 10% forE/RT ratio greater than 6. The exact solution was obtained independently by solving the exponential temperature integral numerically by the Simpson's rule and the Trapezoidal rule. The Gorbachev equation deviates by less than 0.1% forE/RT ratio greater than 41 and by less than 1 % forE/RT ratio greater than 11. The Li equation deviates by less than 0.1 % forE/RT ratio greater than 21 and by less than 1% forE/RT ratio greater than 9. The proposed equation deviates by less than 0.1% forE/RT greater than 7.     

Interstrand communication between 2'-N-(pyren-1-yl)methyl-2'-amino-LNA monomers in nucleic acid duplexes: directional control and signalling of full complementarity

Very efficient interstrand communication systems in nucleic acid duplexes, based on pyrene excimer formation between 2'-N-(pyren-1-yl)methyl-2'-amino-LNA monomers, demonstrate the versatility of functionalized 2'-amino-LNA monomers for Angstrom-scale chemical engineering.     

A novel synthetic route to fused propenochlorin and benzochlorin photodynamic therapy probes

Reaction of meso-(2-formylvinyl)octaethylporphyrin with (CH3)3SiCN-Cu(OTf)2 produced unexpected 10(3)-trimethylsiloxyl and 10(3)-hydroxyl fused propenochlorins which, in H2SO4, underwent subsequent migration of the 8-ethyl group to the 10(3)-position of the exocyclic benzene ring to form a novel benzochlorin.