[bioundgrd] Cell Decision Process Group (Lauffenburger) hosts Dr. Martin Feinberg (The Ohio State University), this Thursday, April 26, at 9:30 in 68-181

[Gurukarm Khalsa]

You are invited to attend this week's Cell Decision Processes (CDP)  
meeting, Thursday, April 26, at 9:30 in 68-181.

This week's CDP invited speaker is Martin Feinberg, Prof. of Chem.  
Eng and Math at The Ohio State University (on sabbatical at the  
Systems Biology Dept, HMS).

Title: Stability and Instability in Complex Chemical Reaction  
Networks: The Big Picture

NOTE: This talk is meant for a broad audience and should be suitable  
for people who are not on the friendliest of terms with advanced  
mathematics.

Abstract:
In nature there are millions of distinct networks of chemical  
reactions that might present themselves for study at one time or  
another. Written at the level of elementary reactions taken with  
classical mass action kinetics, each new network gives rise to its  
own (usually large) system of polynomial equations for the species  
concentrations. In this way, chemistry presents a huge and  
bewildering array of polynomial systems, each determined in a precise  
way by the underlying network up to parameter values (e.g., rate  
constants). Polynomial systems in general, even simple ones, are  
known to be rich sources of interesting and sometimes wild dynamical  
behavior. It would appear, then, that chemistry too should be a rich  
source of dynamical exotica.
Yet there is a remarkable amount of stability in chemistry. Indeed,  
chemical engineers generally expect homogeneous isothermal reactors,  
even highly complex ones, to behave in quite dull ways. Although this  
tacit doctrine of stable behavior is supported by a long  
observational record, there are certainly instances of homogeneous  
isothermal reactors that give rise, for example, to bistability or  
even chaotic behavior. The vast landscape of chemical reaction  
networks, then, appears to have wide regions of intrinsic stability  
(regardless of parameter values) punctuated by smaller regions in  
which instability might be extant (for at least certain parameter  
values).

In this talk, I will present some recent work (with George Craciun  
and Phillipp Ellison) that goes a long way toward explaining this  
landscape -- in particular, toward explaining how biological  
chemistry "escapes" the stability doctrine to (literally) make life  
interesting. Indeed, theory indicates just why enzyme-driven  
chemistry is strikingly different from "regular" chemistry. Although  
it is commonly supposed that biochemical instability results from  
gross feedback across a pathway, whereby the product of one enzyme- 
catalyzed reaction promotes or inhibits another such reaction along  
the pathway, the fact is that sources of instability are already to  
be found in quite classical and elementary mechanisms for enzyme  
catalysis of a single reaction. (This seems to be poorly appreciated  
and might perhaps confound the interpretation of experiments.)

-- 
-----------------------------------------------------
John M. Burke, Ph.D.
Assistant Research Director
Cell Decision Processes Center

Systems Biology - HMS
Sorger Lab

Biological Engineering - MIT
Lauffenburger Lab
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