Bio-inspired approaches to sensing for defence and security applications

Interdisciplinary research in biotechnology and related scientific areas has increased tremendously over the past decade. This rapid pace, in conjunction with advances in microfabricated systems, computer hardware, bioengineering and the availability of low-powered miniature components, has now made it feasible to design bio-inspired materials, sensors and systems with tremendous potential for defence and security applications. To realize the full potential of biotechnology and bio-inspiration, there is a need to define specific requirements to meet the challenges of the changing world and its threats. One approach to assisting the defence and security communities in defining their requirements is through the use of a conceptual model. The distributed or intelligent autonomous sensing (DIAS) system is one such model. The DIAS model is not necessarily aimed at a single component, for instance a sensor, but can include a system, or even a system of systems in the same way that a single organism, a multi-cellular organism or group of organisms is configured. This paper provides an overview of the challenges to and opportunities for bio-inspired sensors and systems together with examples of how they are being implemented. Examples focus on both learning new things from biological organisms that have application to the defence and security forces and adapting known discoveries in biology and biochemistry for practical use by these communities.     

Electrochemical insertion of lithium in mechanochemically synthesized Zn2SnO4

We studied the electrochemical insertion of Li in mechanochemically prepared Zn(2)SnO(4). The mechanism of the electrochemical reaction was investigated by using X-ray diffraction, nuclear magnetic resonance spectroscopy, and M?ssbauer spectroscopy. Changes in the morphology of the Zn(2)SnO(4) particles were studied by in situ scanning electron microscopy. The results were compared with mixtures of SnO(2) + ZnO and with Zn(2)SnO(4) prepared by conventional solid-state synthesis and showed that the mechanochemically prepared Zn(2)SnO(4) exhibits the best cyclic stability of these samples.     

Autoionization at the surface of neat water: is the top layer pH neutral, basic, or acidic?

Autoionization of water which gives rise to its pH is one of the key properties of aqueous systems. Surfaces of water and aqueous electrolyte solutions are traditionally viewed as devoid of inorganic ions; however, recent molecular simulations and spectroscopic experiments show the presence of certain ions including hydronium in the topmost layer. This raises the question of what is the pH (defined using proton concentration in the topmost layer) of the surface of neat water. Microscopic simulations and measurements with atomistic resolution show that the water surface is acidic due to a strong propensity of hydronium (but not of hydroxide) for the surface. In contrast, macroscopic experiments, such as zeta potential and titration measurements, indicate a negatively charged water surface interpreted in terms of preferential adsorption of OH(-). Here we review recent simulations and experiments characterizing autoionization at the surface of liquid water and ice crystals in an attempt to present and discuss in detail, if not fully resolve, this controversy.     

Simultaneous determination of rofecoxib and celecoxib in human plasma by high-performance liquid chromatography

An innovative reversed-phase high-performance liquid chromatographic method is validated for the simultaneous determination of rofecoxib and celecoxib in human plasma. The internal standard is 4-n-pentyl-phenyl-acetic acid. Good chromatographic separation is achieved using a Zorbax SB-CN (5 microm) analytical column operated at room temperature and mobile phase consisting of acetonitrile and water containing 0.1M potassium dihydrogen orthophosphate buffer adjusted to pH 2.4 with 85% orthophosphoric acid (42:58, v/v). UV detection is performed at 254 nm, and the flow rate is maintained at 1.0 mL/min. Plasma samples are extracted into an organic solvent (1-chlorobutane) and evaporated under an air flow. The calibration curve for rofecoxib is linear over the range of 10 to 500 microg/L, and the celecoxib calibration curve is linear over the range of 20 to 2000 microg/L. The lower limit of quantitation for rofecoxib and celecoxib is 10 and 20 microg/L, respectively, using 1.0 mL of human plasma. The validation data show that the assay is sensitive, accurate, specific, and reproducible for the determination of rofecoxib and celecoxib. This method is therefore appropriate for pharmacokinetic studies to quantitate these therapeutic agents in patients with arthritis conditions.     

Mechanistic investigation of the 2,5-diphenylpyrrolidine-catalyzed enantioselective alpha-chlorination of aldehydes

The mechanism for the 2,5-diphenylpyrrolidine-catalyzed enantioselective alpha-chlorination of aldehydes with electrophilic halogenation reagents has been investigated by using experimental and computational methods. These studies have led us to propose a mechanism for the reaction that proceeds through an initial N-chlorination of the chiral catalyst-substrate complex, followed by a 1,3-sigmatropic shift of the chlorine atom to the enamine carbon atom. The suggested reaction course is different from previously proposed mechanisms for organocatalytic enamine reactions, in which the carbon-electrophile bond is formed directly. Furthermore, the rate-determining step in the overall reaction was determined and the presence of nonlinear effects was probed.     

Electrospray ionization mass spectrometry studies of noncovalent myosin VI complexes reveal a new specific calmodulin binding site

Among the myosin superfamily, myosin VI differs from all others by a reverse directionality and a particular motility. Little structural information is available for myosin VI. It is known that it binds one calmodulin (CaM) by means of a single "IQ motif" and that myosin VI contains a specific insert located at the junction between the motor domain (MD) and the lever arm, likely to play a critical role for the unusual motility previously observed. Electrospray ionization mass spectrometry (MS) was used to determine the CaM and Ca2+ stoichiometries in several myosin VI constructs. In particular, the experimental conditions required for the observation of multiprotein/Ca2+ noncovalent assemblies are detailed for two truncated MD constructs (less than 20 kDa) and for three full MD constructs (more than 90 KDa). The specificity of the detected stoichiometries is discussed for each construct and the resolving power of Time of Flight mass spectrometry is stressed, in particular for the detection of metal ions binding to high molecular weight complexes. MS reveals a new CaM binding site for myosin VI and highlights a different behavior for the five myosin VI constructs versus Ca2+ binding. In addition to these stoichiometry based experiments, gas-phase dissociation analyses on intact complexes are described. They reveal that Ca2+ transfer between protein partners occurs during the dissociation process for one construct with a full MD. Charge-transfer and dissociation behavior has allowed to draw structural assumptions for the interaction of the MD with the CaM N-terminal lobe.     

Evaluation of capillary isoelectric focusing in glycerol-water media with a view to hydrophobic protein applications

Capillary isoelectric focusing (CIEF) separations are usually performed with neutral coated fused-silica capillaries in aqueous anticonvective media. Glycerol, a very viscous solvent (eta = 945 mPa x s at 25 degrees C), known to help stabilize any kind of proteins and solubilize hydrophobic ones, was tested as an alternative to using commercial gels. Viscosity and electroosmotic mobility were measured as a function of gel or glycerol content in water, and a 30:70 v/v glycerol-water medium appeared as a good compromise for performing CIEF in a bare fused-silica capillary without imposing too high a viscosity. To demonstrate the feasibility of this new CIEF system, a standard mixture of nine model proteins was separated according to their pI with a good agreement between experimental and literature aqueous pIs. Moreover, better resolution was achieved with this system than with the conventional aqueous CIEF system, as two of the model proteins could not be separated in the latter system. Glycerol-water CIEF in bare silica capillary was next applied to the separation of horse radish peroxidase, a complex mixture of protein isoforms. The good concordance with the separation obtained by the conventional CIEF system indicated the adequacy of this new system. Finally, as anticipated from the results obtained for the separation of bacteriorhodopsin, a membrane protein, glycerol-water CIEF performed in bare silica capillary appears to be a promising alternative to conventional aqueous CIEF for hydrophobic protein characterization, under their native form.     

Proton to carbon-13 INEPT in solid-state NMR spectroscopy

A refocused INEPT through-bond coherence transfer technique is demonstrated for NMR of rigid organic solids and is shown to provide a valuable building block for the development of NMR correlation experiments in biological solids. The use of efficient proton homonuclear dipolar decoupling in combination with a direct spectral optimization procedure provides minimization of the transverse dephasing of coherences and leads to very efficient through-bond (1)H-(13)C INEPT transfer for crystalline organic compounds. Application of this technique to 2D heteronuclear correlation spectroscopy leads to up to a factor of 3 increase in sensitivity for a carbon-13 enriched sample in comparison to standard through-bond experiments and provides excellent selectivity for one-bond transfer. The method is demonstrated on a microcrystalline sample of the protein Crh (2 x 10.4 kDa).     

Hydroxyapatite-poly(d,l-lactide) Nanografts. Synthesis and Characterization as Bone Cement Additives

This paper reports the creation of hydroxyapatite/polyester nanografts by “graft-from” polymerization of d,l-lactide with [Ca₅(OH)(PO₄)₃]₂ as the initiator and tin(II)-2-ethylhexanoate as the catalyst. Model polymerizations were performed with cyclooctanol as initiator to confirm the grafting on the surface of the hydroxyapatite nanocrystals. Polymers with the highest molecular mass (M_n) between 4250 Da (cyclooctanol) and 6100 Da (hydroxyapatite) were produced. In both cases the molecular mass distributions of the polymers formed were monomodal. The materials obtained were characterized by size-exclusion chromatography, NMR and FT-IR spectroscopy, and thermal methods. Their suitability as additives for commercial bone cement (Simplex P Speedset, Stryker Orthopaedics) has been confirmed by thermal analysis techniques and mechanical testing. The results obtained show that addition of the hydroxyapatite/ polyester nanografts improved both thermal and mechanical properties of the bone cement.