Range of spectral exponents in rigor-state muscle fibers -- a 1/f noise family affair?

Using EPR spectroscopy, we have followed changes in crossbridge state in rigor-state muscle fibers as a function of time. These observed changes were of two types -- erratic fluctuations taking place on multiple time scales, and slowly-relaxing transients in response to substrate analog. For both types of change, the resulting power spectra had a 1/f-like power-law form with spectral exponents ranging from near 0 (white noise) to around 2 (brown noise). The average exponent was around 1 (pink noise). This observed broad range of spectral exponents is similar to that seen in the extended-family model of 1/f noise processes -- a model that includes members ranging from white noise to pink to brown (JM Halley, Trends. Ecol. Evoln. \underline {11}, 33, 1996). Properties of this extended family model include self-affinity, long correlation times (memory), and non-stationarity (JM Halley {\&} P Inchausti, Fluct. Noise. Lett \underline {4}, R1, 2004). We conclude that the broad range of spectral exponents observed in rigor-state muscle fibers reflects a type of underlying 1/f process. However, this particular type of process is unusual in that, although produced by a \underline {single} biological source (rigor muscle fibers), it appears to include not just one but \underline {all} of the members of the extended 1/f noise family -- from white to pink to brown.