Proteins often deform, dehydrate or otherwise denature when adsorbed or patterned directly onto an inorganic substrate, thus losing specificity and biofunctionality. One method used to maintain function is to pattern the protein of interest directly onto another underlying protein or polypeptide that acts as a buffer layer between the substrate and the desired protein. We have used microcontact printing (μcp) to cross-stamp orthogonal linear arrays of two different proteins (e.g., IgG, poly-lysine, protein A) onto glass substrates. This created three separate types of protein-substrate microenvironments, including crossover structures of protein one on protein two. We report preliminary fluorescent microscopy and scanning force microscopy characterization of these structures, including commonly encountered structural defects.

Electrical conductance of single stranded DNA (5′-TTT TTT TTT T/3 Thio MC3-D/-3′) monolayer patterns on Au surface is compared with those of various organic molecular patterns via the conductance microscope (CM) technique that allows one to take nanoscale conductance images utilizing a conducting AFM tip in contact mode AFM. In the experiment, reference molecules and ssDNA are patterned on the same substrate via direct deposition methods such as dip-pen nanolithography and microcontact printing. Then, conductance microscope image is recorded revealing the relative conductivity of ssDNA patterns relative to various reference molecules. 16-mercaptohexadecanoic acid and 2-mercaptobenzimidazole patterns are found conducting better than the ssDNA patterns. This result indicates that the ssDNA with 10T bases is a relatively poor electrical conductor. The capabilities of CM technique are also tested on various nanostructures including the single wall carbon nanotube junction.

Membrane channel and pore proteins represent a versatile class of molecules that offer opportunities to serve as engineered nano-valves. We are inserting OmpF, a voltage-gatable pore protein, into planar membranes for applications in microfluidics and sensing. To emulate and improve upon natural membranes, we have selected triblock copolymers containing UV cross-linkable end groups. We are developing a microfabricated version of a conventional black lipid membrane/copolymer characterization apparatus which will enable us to rapidly analyze composite membrane properties as a function of area and applied electrical bias. We show that only slight deviations of conventional planar lipid membrane formation procedures with triblock copolymers are sufficient for polymer monolayer membrane formation. We report the results of the preliminary tests on polymer membrane formation and stability as well as the construction of the microfabricated device.

This paper reports on the progress in developing self organized nanoparticulate arrays for magnetic recording at densities beyond 30 Gbit/cm2 (200 Gbit/in2), and in particular describes the beneficial use of biological templates in developing such arrays. Chemically synthesized, high magnetocrystalline anisotropy magnetic nanoparticles have demonstrated extremely narrow size distributions that are critical in reducing media noise. Due to their monodispersity, they also exhibit emergent self-patterning that could potentially support bit-per-particle densities up to 2–8 Tbit/cm2 (10–50 Tbit/in2).

High anisotropy L10 CoPt precursor grains are prepared within apoferritin from aqueous reactants, with synthesis conditions controlling grain size, structure and composition. Smooth films on glass disk substrates are produced by either spin- or dip-coating from aqueous dispersions of the precursor material. Films are typically annealed at 590 °C for 60 minutes with a 19 kPa (190 mBar) partial pressure of H2 to form the L10 phase.

We report on recently produced films that have demonstrated moderate-density recording using a contact drag tester with commercial, 0.35 μm-wide magnetoresistive (MR) heads. The highest areal density currently achieved for these nanoparticulate films is 0.93 Gbit/cm2 (6.0 Gbit/in2).

We describe a theory of coulomb blockade of tunneling through molecular-assembled metallic nanoparticles based on the Non-equilibrium Green's function method. We apply the theory to study current transport through a single metallic nanoparticle connected to the leads through two molecular bridges with arbitrary metal-molecule coupling and electron-molecular vibration coupling. We present model calculations of the current-voltage characteristics.

There are manifest scientific and technological interests in organizing nanocrystals (NC) into controlled architectures and work is rapidly expanding in exploiting opportunities through bio-assembly processes. In this research, we have applied biologically assembled nano-scale template to direct formation of precisely defined 2D nanocrystal arrays. We explored purple membrane (PM), a naturally occurring membrane protein (bacteriorhodopsin, BR) crystal patch from halobacteria, as a precisely structured nanometer-scale template. We have developed genetically engineered PMs that display unique functional group (cystein) on the membrane surfaces with precisely defined nano-scale symmetry. These reactive functional groups were used as specific anchoring sites for NC immobilization. We show that the cystein mutants of BR mutated at the surface of the PM are capable of forming stable PM-like hexagonal crystal lattices in the host cell membrane. These crystal patches are easily purified by ultracentrifugation and can be used to react with functionallized gold nanoclusters. We also present the variation of crystal lattice by detergent treatment and recrystallization techniques. The PM has been known to posses good materials properties and is expected to allow formation of robust nanocrystal array that can withstand variety of optical and electrical characterization conditions.

In this paper we present techniques, utilizing dielectrophoresis and electrohydrodynamics, which can possibly be used for assembling devices suspended in a solution onto a binding site on a substrate. We explored the concepts using micro-scale negatively charged polystyrene beads and rectangular silicon blocks. Dielectrophoretic forces on devices in buffer solutions were examined as a function of frequency of the applied AC signal. The observed results can be explained by taking in account electro-thermal and AC electroosmotic effects. The study described in the paper can be used for placing and assembling micro and nano-electronic devices and objects at specific sites on various substrates, in combination with bio-inspired biological binding techniques such as DNA hybridization, antigen-antibody interactions, and ligand-receptor (avidin-biotin) interactions.

Tissue engineering aims at resolving problems such as donor shortage and immune rejection faced in transplantation. Scaffolds (artificial extracellular matrices) play critical roles in tissue engineering. Recently, we developed nano-fibrous poly(L-lactic acid) (PLLA) scaffolds under the hypothesis that synthetic nano-fibrous scaffolding, mimicking the structure of natural collagen fibers, could create a more favorable microenvironment for cells. This is the first report that the nano-fibrous architecture built in three-dimensional scaffolds improved the features of protein adsorption, which mediates cell interactions with scaffolds. Scaffolds with nano-fibrous pore walls adsorbed 4 times more serum proteins than scaffolds with solid pore walls. More interestingly, the nano-fibrous architecture selectively enhanced protein adsorption including fibronectin and vitronectin, even though both scaffolds were made from the same PLLA material. Furthermore, nano-fibrous scaffolds also allowed more than 1.7 times of osteoblastic cell attachment than scaffolds with “solid” pore walls. These results demonstrate that the biomimetic nano-fibrous architecture serves as superior scaffolding for tissue engineering.

With the aim of fabricating highly integrated protein microarrays, functional proteins were occluded into a protein crystal, consisting of a proteinaceous occlusion body termed polyhedrin, and the crystals were individually fixed onto a polymer film by using laser trapping and bonding techniques. Individual crystals were trapped by the 1064 nm beam of a Nd3+:YAG laser and placed to the film. The bonding to the film was achieved by irradiating with the single shot of the 800 nm beam of a femtosecond Ti:sapphire laser. Enhanced green fluorescent protein (EGFP) was occluded into the polyhedrin crystal and the crystals were patterned and observed by florescence imaging and single crystal florescence spectroscopy. From these experiments, the biological activity of the bonded crystal was confirmed and their potential as element in protein microarrays was discussed.

We present extensive molecular dynamics simulations of DNA duplexes and duplex dimers based on the Amber force field to determine the distribution of ions as a function of salt (NaCl) concentration over the range 0.2–1.0M. Periodic boundary conditions are used to model an infinite DNA chain, and particle mesh Ewald summation is used to describe long range electrostatic interactions. We have used these simulations to determine the ion distributions associated with a 10 base pair duplex, and we find that the positive and negative ion distributions are identical for distances greater than a radius Rcounter which is on the order of 25 Å from the DNA axis, and which decreases as the bulk salt concentration is varied. Based on the calculated Rcounter, we determine the local counterion concentration as a function of bulk salt concentration. Similar studies of DNA duplex dimers separated by 30–40 Å leads to a determination of the local counterion concentration around these dimers. Here we find that dimerization leads to greatly enhanced counterion concentrations. If this information is combined with the measured results concerning the dependence of DNA melting temperature on bulk salt concentration, we find that dimerization leads to a several degree increase in melting temperature, with the increase being 10°C for a dimer separation of 30 Å. This result provides justification for a recently developed cooperative melting model of DNA duplex aggregates.