Electron spin relaxation in myoglobin below 1 K: Positive identification of a phonon bottleneck

Abstract

Published relaxation data from ten samples of paramagnetic proteins are compared to illustrate the uncertainty which existed in identifying the anomalous low temperature relaxation mechanism in frozen solutions of proteins. Relaxation involving localized two level tunneling states or a phonon-limited direct process can explain the T2 temperature dependence of the relaxation rate that is observed in some proteins at temperatures above 1 K. Relaxation data on myoglobin at a microwave frequency of 16.545 GHz and in the temperature range between 0.4 and 1.2 K are presented. These data exhibit a coth2(ℏω/2kBT) dependence upon temperature and identify the relaxation process as phonon limited.

Electron spin relaxation measurements on the blue-copper protein plastocyanin

“…This form of the temperature dependence of a phonon bottleneck is an approximation that is valid under our operating conditions. The precise temperature dependence of an extreme phonon bottleneck [coth2(hv/2kT)], has been observed in relaxation data from myoglobin taken at 16 GHz and at temperatures below K (31).…”

Role of exchange interaction in effecting spin-lattice relaxation: Interpretations of data onCr3+inCuMisra1 1998Phys. Rev. B11050View full textAdd to dashboardCite

“…[22][23][24][25][26] This was, however, shown not to be valid by Askew and co-workers, 4 who, as pointed out above, also studied SLR in a-Si films rather extensively. The measurements of Stutzmann and Biegelson 21 using adiabatic-passage techniques in doped and undoped a-Si:H and a-Ge:H were explained on the basis of spin coupling to TLS states up to 300 K without identifying the presence of TLS centers.…”