  Recent experiments using fluorescence spectroscopy have been able to probe
the dynamics of conformational fluctuations in proteins. The fluctuations are
Gaussian but do not decay exponentially, and are therefore, non-Markovian. We
present a theory where non-Markovian fluctuation dynamics emerges naturally
from the superposition of the Markovian fluctuations of the normal modes of the
protein. A Rouse-like dynamics of the normal modes provides very good agreement
to the experimentally measured correlation functions. We provide simple scaling
arguments rationalising our results.
