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A number of biological materials owe their unusual structural characteristics and mechanical properties to long-range order induced by the lamination of -sheet proteins between layers of inorganic mineral. 1 In such composites, both the protein layer and the mineral layer adopt structures different from those they assume in isolation. Interactions between such layers and the ordered structures that result from these interactions enable nature to produce biomaterials that are simultaneously hard, strong, and tough.With the long-term goal of constructing artificial biomaterials with laminated structures, we developed a biomimetic system using a highly ordered surface to template the assembly of a de noVo designed -sheet protein. The surface used is highly ordered pyrolytic graphite (HOPG), which forms individual crystallite domains extending over several microns. 2 The graphite lattice is hexagonal; therefore structures templated by HOPG are expected to show 3-fold symmetry.The protein used in this study was chosen from a combinatorial library of amino acid sequences designed de noVo to form -sheet proteins. 3,4 The library design specified that each protein should contain 6 -strands, and each -strand would be 7 residues long, with polar and nonpolar amino acids arranged in an alternating pattern (Figure 1). This polar/nonpolar pattern (binary patterning [3][4][5] ) is consistent with the formation of a -sheet having all polar side chains projecting from one face, and all nonpolar side chains projecting from the opposing face ( Figure 3). Formation of such facial amphiphiles would be favored at an interface between polar and nonpolar phases such as water and graphite.Combinatorial diversity was incorporated into the library of de noVo proteins by allowing polar residues to be His, Lys, Asn, Asp, Gln, or Glu; and nonpolar residues to be Leu, Ile, Val, or Phe. 3 These combinatorial sets of amino acids were encoded by libraries of synthetic genes with polar residues specified by the degenerate DNA codon VAS, and nonpolar residues by the degenerate DNA codon NTC (where V ) A, G, or C; S ) G or C; and N ) A, G, C, or T). The proteins in this library have a total length (including six -strands and intervening turns) of 63 residues. Their design and synthesis has been described. 3 Previous studies of proteins from this library demonstrated that they self-assemble into (i) amyloid-like fibrils in a homogeneous aqueous environment 3 and (ii) -sheet monolayers at an air/water interface. 4 Given the tendency of these de noVo proteins to selfassemble in the absence of an external template, we sought to assess whether the presence of a highly ordered surface (template) would induce structures that recapitulate the order and symmetry of the template.To assess the propensity of our de noVo proteins to undergo template-directed assembly, 6 we focused on one protein, 17-6 (Figure 1), from our -sheet library. When probing the ability of a surface to template protein assembly, it is important to present the template with a pro...

In field studies based on pre-test market and scanner data, researchers have found evidence of pioneering advantage in the form of an order-of-entry effect: a permanent share advantage that is greatest for the first brand to enter a market and smaller for each subsequently entering brand. Conceptually, an order-of-entry effect implies that the share advantage of a market pioneer over the second entrant is constant, regardless of the length the of time the pioneer is alone in the market or the length of time since the entry of the second brand. We argue that pioneering advantage is also related to a brand's length of time in the market: the longer the brand's time in market (during which time it can impact consumer learning and influence consumer perceptions and preferences), the greater its relative share advantage. We present a parsimonious model of this time-in-market effect and test of model using two data sources: cross-category data collected and analyzed by Urban et al. (1986) and regional roll-out data for a single product category.pioneering advantage, order-of-entry