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![[Figure 2]](di5016fig2mag.jpg)
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Figure 2
(a) Density ρ (g ml−1) versus CPA concentration [%(w/w)] at T = 77 K as measured here, with the accepted density of low-density amorphous (LDA) ice of 0.94 g cm−3 (Loerting et al., 2011  ) plotted at x = 0. The solid lines are fourth-order polynomial fits with the coefficients given in Table 2. Density data for methanol solutions at concentrations above ∼80%(w/w), indicated by open circles, are likely to be for the α crystalline phase or a mixture of α and β crystal phases and possibly a vitreous component. Uncertainties in measured densities are dominated by the difference between the minimum nitrogen/argon mixture density at which a drop sinks and the maximum density at which it floats; the corresponding error bars are in most cases smaller than the symbols. (b) Electron density (e− Å−3) calculated from the densities in (a), equation (1) and Table 3. (c) Normalized forward scattering for protein versus CPA concentration at T = 77 K, calculated using (2). Corresponding results for nucleic acids are shown in Supplementary Fig. S2(b). Normalization is by forward scattering in pure LDA ice at T = 77 K; Supplementary Fig. S1 normalizes by the forward scattering in pure water at T = 300 K. (d) Excess specific volume vE versus CPA concentration, calculated using (3) and (4) from the densities in (a). Values for methanol are based on the measured specific volume of pure methanol at 77 K, which is likely to be in a crystalline rather than a vitreous phase. |
![[Figure 2]](di5016fig2.jpg)
 | STRUCTURAL BIOLOGY |
ISSN: 2059-7983
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