Condensed Matter Physics Seminar

Thursday, September 28, 2000, 2 p.m.

Plant Sciences Building, Room 1130

Engineering Aspects of Enzymatic Signal Transduction: Photo-receptors in Retina

Anirvan Sengupta

(Bell Laboratories, NJ)

Abstract: The basic module of enzymatic amplification is an irreversible cycle of messenger activation/deactivation by a pair of ``push-pull" enzymes.  We analyze this module in terms of gain, bandwidth, noise and power consumption.  The enzymatic signal transduction cascade is viewed as as information channel,  the design of which is governed by the statistical properties of the input and the noise and dynamic range constraint of the output.  On the example of vertebrate photo-transduction cascade, we demonstrate that of the relevant  engineering parameters are controlled by enzyme concentrations.  From functional constraints, we could derive bounds on the protein numbers and compare with observed values.  We also study a possible mechanism underlying the low variability of single photon response despite stochastic   fluctuations in the life span of an activated Rhodopsin molecule.

Host: Amitava Chattopadhyay

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