TABLE 1.

Dielectric parameters for hydration of F-actin and myoglobin

Relaxation component	1st				2nd
Protein	fc1 (GHz)	δ1	φ1/c*	N1	fc2 (GHz)	δ2	φ2/c*
F-actin†	6.5	45	0.506	1190	40	75	0.600
Myoglobin	6.2	79	0.588	581‡	–	–	–

^*N₁ = φ₁M_w/18c, where M_w is mass weight of protein. See text for other details. c is the protein concentration (g/ml). The values of the partial specific volume s_v (F-actin, 0.743 ml/g; myoglobin, 0.74 ml/g) were measured with a density meter (Anton Paar DMA-58). φ₁/c and φ₂/c are the volume fractions of the hydration shells per unit protein concentration.

^†The values were calculated from the averaged and smoothed spectrum as described in Materials and Methods. The individual spectra (not averaged but smoothed) were also analyzed to estimate the errors accompanying the best-fit values given here to show the precision of eight independent measurements. The means were almost identical to the values obtained for the averaged spectrum, and the relative standard errors of the means for f_c1, δ₁, and φ₁ were 3.0%, 4.0%, and 3.0%, respectively, and those for f_c2, δ₂, and φ₂ were 4.6%, 4.8%, and 7.0%, respectively.

^‡This value was much larger than the one reported previously (∼380). This discrepancy is most likely due to the difference in the frequency range employed, 2–20 GHz in the present work compared to the earlier of 2–10 GHz. Increasing the frequency range may be equivalent to taking into account the hydrating water with a higher mobility. Taking into consideration weakly and strongly restrained water (Suzuki et al., 1996; Yokoyama et al., 2001), these values are roughly consistent with those estimated by MD calculations (Makarov et al., 2000).