Experimental Approaches to Adsorption-Desorption Dynamism of Human Serum Albumin (HSA) onto Crosslinked N,N′-Diethylaminoethyl (DEAE) Dextran Microbeads

Crosslinked N,N′-Diethylaminoethyl (DEAE) groups containing dextran microbeads have been used in human serum albumin (HSA) adsorption-desorption studies. For the HSA adsorption onto positively charged hydrophilic DEAE dextran microbeads, the adsorption kinetic was slightly decreased by the changing concentration of the protein solution. Adsorption kinetics and equilibrium isotherms for the adsorption of HSA on crosslinked DEAE dextran have been determined experimentally. Modeling of the adsorption processes on DEAE dextran microbeads were realized by applying different adsorption isotherms. Among the several isotherm equations, Langmuir and Freundlich adsorption isotherms were investigated depending on the two temperatures. These were only slightly dependent on the initial concentration of HSA but were considerably affected by the pH of the medium. The HSA adsorption capacity factor and the adsorption equilibrium constant were obtained and mathematical modeling of adsorption, adsorption rate constants and maximum adsorption were determined. Besides the adsorption mechanism, optimum ionic strength and optimum pH also were investigated. Desorption studies and desorption ratio of the system were determined for optimum medium conditions. It was been proved both experimentally and theoretically that human HSA is adsorbed by electrostatic attraction, ion-exchange, hydrophobic interaction and/or hydrogen bonding.     

Bioengineered Chimeric Spider Silk‐Uranium Binding Proteins

Heavy metals constitute a source of environmental pollution. Here, novel functional hybrid biomaterials for specific interactions with heavy metals are designed by bioengineering consensus sequence repeats from spider silk of Nephila clavipes with repeats of a uranium peptide recognition motif from a mutated 33‐residue of calmodulin protein from Paramecium tetraurelia. The self‐assembly features of the silk to control nanoscale organic/inorganic material interfaces provides new biomaterials for uranium recovery. With subsequent enzymatic digestion of the silk to concentrate the sequestered metals, options can be envisaged to use these new chimeric protein systems in environmental engineering, including to remediate environments contaminated by uranium.

     

Nonlinearity and time-resolved studies of ion emission in ultrafast laser ablation of graphite

We have investigated the laser fluence dependence of the ion emission process in ultrafast laser ablation of graphite using a time-of-flight technique. Two regimes of ion emission have been identified: (1) a highly nonlinear laser absorption process accompanied by generation of a transient electrical field on the surface and collisionless emission of ions due to electrostatic repulsion; (2) a saturation regime for laser power absorption characterised by nearly equal kinetic energy of ejected carbon clusters. We also show the effect of the surface temperature on the emitted clusters’ stability and the influence of nonlinearity on the intensity autocorrelation traces.     

Hypersonic modulation of light in three-dimensional photonic and phononic band-gap materials

The elastic coupling between the a-SiO2 spheres composing opal films brings forth three-dimensional periodic structures which besides a photonic stop band are predicted to also exhibit complete phononic band gaps. The influence of elastic crystal vibrations on the photonic band structure has been studied by injection of coherent hypersonic wave packets generated in a metal transducer by subpicosecond laser pulses. These studies show that light with energies close to the photonic band gap can be efficiently modulated by hypersonic waves.     

Newly developed semi-empirical formulas for (<Emphasis Type="Italic">p,α</Emphasis>) at 17.9 MeV and (<Emphasis Type="Italic">p,np</Emphasis>) at 22.3 MeV reaction cross-sections

In this study, we have investigated the asymmetry term effect for the (p, α) and (p, np) reaction cross-sections and obtained new coefficients for the (p, α) and (p, np) reaction cross-sections at 17.9 and 22.3 MeV energies. We have suggested semi-empirical formulas including the non-elastic effects of optical model found by fitting two parameters for proton-induced reactions. The coefficients were determined by least-square fitting method. The obtained cross-section formulas with new coefficients have been discussed and compared with the available experimental data.     

Infrared regular reflectance and transmittance instrumentation and standards at NIST

Instrumentation is described that has been constructed at the National Institute of Standards and Technology (NIST) for the measurement of regular reflectance and transmittance over the 2–25 μm wavelength region. This includes both specialized accessories used with Fourier-transform infrared (FT-IR) spectrometers and laser-based systems for high optical density transmittance measurements. The FT-IR systems have been used to develop standard reference materials for IR regular transmittance.     

A new analysis of tuned circuit levitators

Investigations of a relatively new magnetic levitation device are described. This device uses an electromagnet, which is the inductive part of a resonant circuit. If the circuit is properly tuned, static stability is attainable.In order to understand the dynamic instabilities and to enable systematic design of tuned circuit levitators. a method is needed, which permits rapid analysis. In the models investigated, the frequency of supply is much higher than that associated with the mechanical vibrations, and as a result, a direct digital simulation of the equations is inefficient. This difficulty is overcome by using an approximation of slowly varying quantities. Due to the omission of the detailed high frequency oscillation from this new representation, it has been found possible to obtain a solution of an example by using only a few steps of integration. The results agree with those observed in an experimental model. They also agree with analogue simulations.