dictyNews Electronic Edition Volume 28, number 18 June 22, 2007 Please submit abstracts of your papers as soon as they have been accepted for publication by sending them to dicty@northwestern.edu or by using the form at http://dictybase.org/db/cgi-bin/dictyBase/abstract_submit. Back issues of dictyNews, the Dicty Reference database and other useful information is available at dictyBase - http://dictybase.org. ========= Abstracts ========= Dihydrodictyopyrone A and C: New members of dictyopyrone family isolated from Dictyostelium cellular slime molds. Kikuchi H*, Nakamura K, Kubohara Y, Gokan N, Hosaka K, Maeda Y, & Oshima Y*. *Corresponding authors Graduate School of Pharmaceutical Sciences Tohoku University, Japan Tetrahedron Lett. In press. Abstract We have explored the diversity of secondary metabolites produced by cellular slime molds to evaluate if they are valuable resources for biologically potential substances. From the methanol extract of fruiting bodies of Dictyostelium firmibasis, we obtained new alpha-pyranoids, dihydrodictyopyrone A (1) and C (2). Compounds 1 and 2 are new members of the dictyopyrone family, which are characteristic secondary metabolites of various species of Dictyostelium cellular slime molds. Submitted by: Yuzuru Kubohara [kubohara@showa.gunma-u.ac.jp] -------------------------------------------------------------------------------- An information-theoretic characterization of the optimal gradient sensing response of cells Burton W. Andrews and Pablo A. Iglesias Department of Electrical and Computer Engineering The Johns Hopkins University, Baltimore, MD 21218 PLoS Computational Biology, Accepted Abstract Many cellular systems rely on the ability to interpret spatial heterogeneities in chemoattractant concentration to direct cell migration. The accuracy of this process is limited by stochastic fluctuations in the concentration of the external signal and in the internal signaling components. Here we use information theory to determine the optimal scheme to detect the location of an external chemoattractant source in the presence of noise. We compute the minimum amount of mutual information needed between the chemoattractant gradient and the internal signal to achieve a prespecified chemotactic accuracy. We show that more accurate chemotaxis requires greater mutual information. We also demonstrate that a priori information can improve chemotaxis efficiency. We compare the optimal signaling schemes to existing experimental measurements and models of eukaryotic gradient sensing. Remarkably, there is good quantitative agreement between the optimal response when no a priori assumption is made about the location of the existing source, and the observed experimental response of unpolarized D. discoideum cells. In contrast, the measured response of polarized D. discoideum cells matches closely the optimal scheme assuming prior knowledge of the external gradient - for example, through prolonged chemotaxis in a given direction. Our results demonstrate that different observed classes of responses in cells (polarized and unpolarized) are optimal under varying information assumptions. Submitted by: [Pablo Iglesias