dictyNews Volume 28 Number 18

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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 <pi@jhu.edu] 
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[End dictyNews, volume 28, number 18]