Tuesday, March 4, 2014

What are the organising principles of biological physics?

In last months Physics Today Steve Hagen has a very interesting and informative review of the book, Biophysics: Searching for Principles by William Bialek.
He begins, that the title of the book,
makes an important point: Even the top practitioners in the field do not completely agree on its main principles or where to find them.
He then describes some different perspectives, including those enunciated in leading texts, such as Phil Nelson's wonderful book [I have used it in a course and blogged about it before].

He then goes on to describe two of Bialek's principles.
sensory and regulatory systems have mechanisms for managing thermal noise, particle number fluctuation, and other types of background, and that those mechanisms in many cases reduce noise almost to its fundamental physical limits. Examples include reaction dynamics in photosynthetic enzymes, bacterial chemotaxis, embryonic development, and bat echolocation.
the principle of efficient representation, the view that sensory systems represent and transmit the information that they gather in a way that is optimal, subject to physical limits. This idea is made quantitative through information theory, which Bialek presents in tutorial fashion before exploring examples from such areas as embryogenesis, neural spike train encoding, bacterial growth, and animal learning.
Steve Hagen has an impressive career history. After a Ph.D and postdoc working on experiments on strongly correlated electron materials he made a transition to biophysics.
The webpage for the undergraduate biophysics course he teaches at U. Florida has some frank rules for students about classroom behaviour and plagiarism.

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