All-atom molecular dynamics (MD) simulations were performed to study the effects of different tetraalkylammonium (TAA(+)) counterions, including tetramethylammonium (TMA(+)), tetraethylammonium (TEA(+)), tetrapropylammonium (TPA(+)) and tetrabutylammonium (TBA(+)), on dodecyl sulfate (DS(-)) micelles. Structural properties, such as the radius of gyration (Rg), micelle radius (Rs), micelle size,...

The dissolution mechanism of rubbery polymers was analyzed by dividing the penetrant concentration field into three regimes that delineate three distinctly different transport processes. The solvent penetration into the rubbery polymer was assumed to be Fickian. The mode of mobility of the polymer chains was shown to undergo a change a t a critical penetrant concentration expressed as a change ...

We investigate the problem of polymer translocation through a nanopore in the absence of an external driving force. To this end, we use the two-dimensional fluctuating bond model with single-segment Monte Carlo moves. To overcome the entropic barrier without artificial restrictions, we consider a polymer which is initially placed in the middle of the pore and study the escape time tau required ...

Purified Na/K-ATPase from guinea pig renal outer medulla has been delipidated and solubilized in Brij 58 (polyoxyethylene ether; C-16, E-20). At a concentration of 2 mg of Brij 58/mg of protein, about one-half the enzyme complement was solubilized and almost 50% of Na/K-ATPase activity was retained by the enzyme-micelle complex. Guinier plots of the neutron scattering profiles yielded no eviden...

Solution small angle x-ray scattering can be used to study the association of transmembrane proteins solubilized in detergent micelles. We have used the alpha-helical transmembrane domain of the human erythrocyte glycophorin A (GpA) fused to the carboxyl terminus of monomeric staphylococcal nuclease (SN/GpA) as a model system for study. By matching the average electron density of the detergent ...

The study of evaporation of water from biological macromolecules is important for the understanding of electrospray mass spectrometry experiments. In electrospray ionization (ESI), electrically charged nanoscale droplets are formed from solutions of, for example, proteins. Then evaporation of the solvent leads to dry protein ions that can be analyzed in the mass spectrometer. In this work the d...

In order to characterize flux flow through disordered type-II superconductors, we investigate the effects of columnar and point defects on the vortex velocity / voltage power spectrum in the driven non-equilibrium steady state. We employ three-dimensional Metropolis Monte Carlo simulations to measure relevant physical observables including the force-velocity / current-voltage (I-V) characterist...

The quaternary structure of the phenylalanyl-tRNA synthetase and its complex with tRNAPhe was studied in dilute solutions by small angle X-ray scattering. For the free synthetase the radius of gyration was determined as 5.5 nm, the volume 523 nm3, the maximum diameter 17.5 nm and the molecular weight as 260,000 using an isopotential specific volume of 0.735. The overall shape could be best appr...

Solution x-ray scattering using synchrotron radiation as an x-ray source has been used to study the solution structure of calmodulin complexed with substance P, a undecapeptide neurotransmitter. The x-ray data indicate that the complex has a compact globular structure, the formation of which is dependent upon the binding of Ca2+ to calmodulin. In the Ca(2+)-saturated condition, the radius of gy...

We have developed a graphical user interface based dendrimer builder toolkit (DBT) which can be used to generate the dendrimer configuration of desired generation for various dendrimer architectures. The validation of structures generated by this tool was carried out by studying the structural properties of two well known classes of dendrimers: ethylenediamine cored poly(amidoamine) (PAMAM) den...