Smart bio-nano interface derived from zein protein as receptors for biotinyl moiety.

Proteinaceous, tunable nanostructures of zein (prolamine of corn) were developed as biotinyl-specific receptors using a molecular imprinting technique. Sacrificial templates, such as latex beads (LB3) and anodized alumina membrane (AAM), have been used to control nanostructural patterns in biotin-imprinted zein (BMZ). Briefly, a methanolic solution of the zein-biotin complex was drop cast upon a self-organized LB3 and AAM templates on Au/quartz surfaces. Subsequent dissolution of these sacrificial templates affords highly oriented, predetermined, and uniformly grown hyperporous (300 nm) and nanowires (150 nm) motifs of zein (BMZ-LB3 and BMZ-AAM), as shown by scanning electron microscopy (SEM). Selective extraction of biotin molecular template cast-off site-selective biotin imprints within these zein nanostructures complementary to biotinyl moieties. Alternatively, biotin-imprinted zein nanoparticles (BMZ-Np) and thin film (BMZ-MeOH) were prepared by coacervation and drop casting methods, respectively. Density functional theoretical (DFT) studies reveal strong hydrogen-bonded interaction of biotin with serine and glutamine residues of zein. Quartz crystal microbalance (QCM) studies show remarkable sensitivity of the hyperporous-BMZ-LB3 and nanowires of BMZ-AAM towards biotin derivative (biotin methyl ester) by five (24.75 ± 1.34 Hz/mM) and four (18.19 ± 0.75 Hz/mM) times, respectively, higher than the BMZ-MeOH. Enhanced permeability features of the zein nanostructures, when templated with LB3, enable the QCM detection of biotin- or its derivatives down to 12.9 ng mL-1 from dairy products (Kefir). The outcome of this study shall be a key aspect in interfacing biological materials with micro-/nano-sensors and electronic devices for detecting pertinent analytes using sustainably developed biopolymer-based nanostructures.

Phage display screening in low dielectric media.

Here we report the first application of phage display screening in low dielectric media. Two series of phage clones with affinity for alpha-chymotrypsin (CT) were selected from a Ph.D.(TM)-C7C library, using either a buffer or acetonitrile in buffer (50%, v/v). The affinity of lysates, individual clones or selected cyclic peptides for the enzyme was studied by examining their influence on CT activity. Peptides displayed on phage selected in buffer provided significant protection from enzyme autolysis resulting in marked increase in CT activity (>100%). Phage selected in ACN provided some, albeit weak, protection from the detrimental influence on CT from ACN. In conclusion, the results demonstrate the potential for the application of phage display screening protocols to targets in media of low dielectricity.

Mode of heavy meromyosin adsorption and motor function correlated with surface hydrophobicity and charge.

The in vitro motility assay is valuable for fundamental studies of actomyosin function and has recently been combined with nanostructuring techniques for the development of nanotechnological applications. However, the limited understanding of the interaction mechanisms between myosin motor fragments (heavy meromyosin, HMM) and artificial surfaces hampers the development as well as the interpretation of fundamental studies. Here we elucidate the HMM-surface interaction mechanisms for a range of negatively charged surfaces (silanized glass and SiO2), which is relevant both to nanotechnology and fundamental studies. The results show that the HMM-propelled actin filament sliding speed (after a single injection of HMM, 120 microg/mL) increased with the contact angle of the surfaces (in the range of 20-80 degrees). However, quartz crystal microbalance (QCM) studies suggested a reduction in the adsorption of HMM (with coupled water) under these conditions. This result and actin filament binding data, together with previous measurements of the HMM density (Sundberg, M.; Balaz, M.; Bunk, R.; Rosengren-Holmberg, J. P.; Montelius, L.; Nicholls, I. A.; Omling, P.; Tågerud, S.; Månsson, A. Langmuir 2006, 22, 7302-7312. Balaz, M.; Sundberg, M.; Persson, M.; Kvassman, J.; Månsson, A. Biochemistry 2007, 46, 7233-7251), are consistent with (1) an HMM monolayer and (2) different HMM configurations at different contact angles of the surface. More specifically, the QCM and in vitro motility assay data are consistent with a model where the molecules are adsorbed either via their flexible C-terminal tail part (HMMC) or via their positively charged N-terminal motor domain (HMMN) without other surface contact points. Measurements of zeta potentials suggest that an increased contact angle is correlated with a reduced negative charge of the surfaces. As a consequence, the HMMC configuration would be the dominant configuration at high contact angles but would be supplemented with electrostatically adsorbed HMM molecules (HMMN configuration) at low contact angles. This would explain the higher initial HMM adsorption (from probability arguments) under the latter conditions. Furthermore, because the HMMN mode would have no actin binding it would also account for the lower sliding velocity at low contact angles. The results are compared to previous studies of the microtubule-kinesin system and are also discussed in relation to fundamental studies of actomyosin and nanotechnological developments and applications.