  We investigate the rate-length scaling law of protein folding, a key
undetermined scaling law in the analytical theory of protein folding. We
demonstrate that chain length is a dominant factor determining folding times,
and that the unambiguous determination of the way chain length corre- lates
with folding times could provide key mechanistic insight into the folding
process. Four specific proposed laws (power law, exponential, and two stretched
exponentials) are tested against one an- other, and it is found that the power
law best explains the data. At the same time, the fit power law results in
rates that are very fast, nearly unreasonably so in a biological context. We
show that any of the proposed forms are viable, conclude that more data is
necessary to unequivocally infer the rate-length law, and that such data could
be obtained through a small number of protein folding experiments on large
protein domains.
