Figure 1.

Cryoprotectant concentration required to obtain an ice-free scattering curve. (a) Photographs of ∼1 μL drops of PEG 200—water mixtures held in ∼700 μm nylon loops after cooling to 100 K in a N₂ gas stream. PEG concentrations for drops (A–H) ranged from 0% to 45% (w/w) (indicated in the legends of (b) and (c)). Opacity of the drop arises from light scattering by ice crystals. (b) SAXS curves show increasing scattering intensity at $q\lesssim 0.02{\text{Å}}^{-1}$ as the PEG concentration increases from 0% to 35% (w/w). (c) At 40% (w/w) PEG and above the drops are visually clear and the $q\lesssim 0.02{\text{Å}}^{-1}$ intensity drops dramatically. However, scattering at low-q values still shows the presence of small amounts of ice. Using 45% (w/w) (drop H), the excess low-q scattering is absent. (d) The scattering curves from (b) and (c) are shown on log-log axes, revealing the characteristic power-law scattering of ice crystallites at all concentrations.