Attachment of proteins to metal surfaces has the potential to improve our understanding of protein adhesion and has applications in sensor technology. Repeating polypeptides able to bind to metallic gold or chromium were selected from a population of approximately 5 million different polypeptides. Each polypeptide contained several direct repeats of identical peptide units 14 or 28 amino acids long. The metal-recognizing polypeptides were found to retain their binding properties when freed from the protein used to select them. One gold-binding polypeptide's avidity for gold was found to be dependent on the number of repeats and the presence of salt.

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In the absence of RecA-mediated cleavage of the repressor, the lambda prophage is exceptionally stable. We develop a stochastic model that predicts the stability of such epigenetic states from affinities of the molecular components. We find that the stability, in particular, depends on the maximum possible cI protein production, and on the number of translated cro proteins per transcribed mRNA. We apply the model to the behavior of recently published mutants of O(R) and find, in particular, that a mutant that overexpress cro behaves in a different way than what was predicted, thus suggesting that the current view of the O(R) switch is incomplete. The approach described here should be generally applicable to the stability of expressed states.

Escherichia coli able to specifically adhere to iron oxide and not adhere to other metal oxides were constructed by genetic engineering. Concatamers of random oligonucleotides were introduced into a portion of a plasmidborne lamB gene encoding an external domain of the phage A receptor. Bacteria able to adhere to iron oxide were selected by serial enrichment from the population of plasmid transformants. The concatameric nature of the inserted DNA allows a genetic analysis analogous to exon shuffling. Results of this genetic analysis indicate that in some isolates, part of the binding site is encoded by flanking vector sequences. This strategy may prove generally useful for identifying protein sequences able to recognize specific surfaces.

Structural DNA nanotechnology, and specifically scaffolded DNA origami, is rapidly developing as a versatile method for bottom-up fabrication of novel nanometer-scale materials and devices. However, lengths of conventional single-stranded scaffolds, for example, 7,249-nucleotide circular genomic DNA from the M13mp18 phage, limit the scales of these uniquely addressable structures. Additionally, increasing DNA origami size generates the cost burden of increased staple-strand synthesis. We addressed this 2-fold problem by developing the following methods: (1) production of the largest to-date biologically derived single-stranded scaffold using a λ/M13 hybrid virus to produce a 51 466-nucleotide DNA in a circular, single-stranded form and (2) inexpensive DNA synthesis via an inkjet-printing process on a chip embossed with functionalized micropillars made from cyclic olefin copolymer. We have experimentally demonstrated very efficient assembly of a 51-kilobasepair origami from the λ/M13 hybrid scaffold folded by chip-derived staple strands. In addition, we have demonstrated two-dimensional, asymmetric origami sheets with controlled global curvature such that they land on a substrate in predictable orientations that have been verified by atomic force microscopy.