  Reversible switching of the complex network dynamics of proteins is mimicked
in selected network glasses and compacted small carbohydrate molecules. Protein
transitions occur on long time scales ~ us -ms, evocative of the exponentially
large viscosities found in glass-forming supercooled liquids just above the
glass transition; in searching for mechanisms for reversibly slowed "geared
activation", Kauzmann was led from proteins to glasses. I show here that
selected network glasses and small carbohydrate molecules can be used to model
such transitions, and elucidate in particular some universal aspects of tandem
repeats. The human ankyrin tandem repeat D34, with a superhelical "coiled
spring" structure which has 426 residues, folds reversibly and plastically.
Such molecules are too large for present transition-state numerical
simulations, currently limited to ~ 100 residues solvated by ~ 3000 water
molecules for times ~ ns. The transition states of D34 exhibit a surprisingly
simple collective ("geared") pattern when studied by fluorescence near its
center, in samples modified mutageneously along its 12 helical repeats. One can
understand this "plastic" pattern by taking advantage of a symmetric 45-atom
carbohydrate molecular bridge to "cross over" from proteins to inorganic
network glasses. There one easily identifies gears, and can show that the
collective pattern is the signature of nonlocal, water-mediated
[hydro(phobic/philic)] switching. Details of the transition patterns emerge
from analyzing the amino acid alpha helical repeat sequences with water-only
hydrophobicity scales. Freezing and melting of monolayer water films at
physiological temperatures can enable ankyrin repeats to direct cell dynamics
in muscles, membranes and cytoskeletons.
