Information goods, such as journal articles, require substantial initial investment, but low incremental reproduction and distribution costs. Advances in computing and digital communications have nearly eliminated these incremental costs. Thus, positive per-item prices are ineÆcient because they discourages consumption with value greater than marginal cost. Further, very low per item prices wil...

We develop an analytical model that presents optimal pricing strategies for a multi-product software firm selling consumer security software. Our model highlights two aspects unique to this kind of software. The first is a supply-side effect that alters its cost structure due to the nonnegligible costs of providing security updates and patches to minimize vulnerabilities and prevent security br...

We examine a mechanism by which bundling may inefficiently deter entry into the market. The model considers an incumbent monopolist in two complementary components that faces a series of entry attempts by rivals. It is shown that the incumbent can practice bundling to buttress its monopoly position by keeping specialist innovators out of the market. Bundling prevents specialist rivals from coor...

The scaffolding protein insulin receptor tyrosine kinase substrate p53 (IRSp53), a ubiquitous regulator of the actin cytoskeleton, mediates filopodia formation under the control of Rho-family GTPases. IRSp53 comprises a central SH3 domain, which binds to proline-rich regions of a wide range of actin regulators, and a conserved N-terminal IRSp53/MIM homology domain (IMD) that harbours F-actin-bu...

A monomeric actin bundling protein with a native molecular weight of approximately 50,000 (ABP-50) has been isolated from amoebae of Dictyostelium discoideum. ABP-50 cross-links F-actin to form tightly packed bundles, some of which are highly ordered. It exhibits a Kd of 2.1 microM and a molar ratio to actin of 1:1 in bundles. Calcium and ATP at physiological concentrations have no effect on th...

This paper studies a model of interpersonal bundling, in which a monopolist offers a good for sale under a regular price and a group purchase discount if the number of consumers in a group– the bundle size– belongs to some menu of intervals. We find that this is often a profitable selling strategy in response to demand uncertainty, and it can achieve the highest profit among all possible sellin...

Villin is a major F-actin-bundling protein present in the microfilament bundle underlying the plasma membrane of the microvilli present on intestinal epithelial cells. Mild in vitro proteolysis converts villin (Mr, 95,000) into a large fragment, the villin core (apparent Mr, 90,000). Villin core has lost the F-actin-bundling activity expressed by villin in the absence of calcium but retains the...

Escherichia coli and other bacteria use rotating helical filaments to swim. Each cell typically has about four filaments, which bundle or disperse depending on the sense of motor rotation. To study the bundling process, we built a macroscopic scale model consisting of stepper motor-driven polymer helices in a tank filled with a high-viscosity silicone oil. The Reynolds number, the ratio of visc...

Fascin is an evolutionarily conserved actin-binding protein that plays a key role in forming filopodia. It is widely thought that this function involves fascin directly bundling actin filaments, which is controlled by an N-terminal regulatory serine residue. In this paper, by studying cellular processes in Drosophila melanogaster that require fascin activity, we identify a regulatory residue wi...