Mostly Biomathematics Lunchtime Seminar

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Beyond Berg–Purcell: effects of communication constraints and time-varying signals on precision of cellular sensing

Speaker: Ilya Nemenman, Emory University (currently at Flatiron Institute at Simons Foundation)

Location: Warren Weaver Hall 1314

Date: Tuesday, November 10, 2026, 12:45 p.m.

Synopsis:

The Berg–Purcell bound is a foundational result in theoretical biophysics: it sets how accurately a cell of linear size a can measure a chemical concentration in a given time. Yet two of its assumptions have gone underexamined for decades — that the sensor is also the actuator that acts on the measurement, and that the concentration is constant. I will show what happens when each of these assumptions is lifted. First, the sensor surface captures molecules at distance a from the origin, but must still communicate what it has learned to the actuator at the origin, and this communication imposes its own constraint on the accuracy of sensing. I will present experimental and theoretical results for diffusive communication in mammary gland development, and theoretical results for polymer-diffusion-driven communication in fly development. Second, I will ask what becomes of the Berg–Purcell bound when the concentration varies in time. For Ornstein–Uhlenbeck variation, precision improves more slowly than 1/√t. For predictable variation, the sensor can predict the concentration with sub-shot-noise accuracy.