Measuring the Densities of Aqueous Glasses at Cryogenic Temperatures

Abstract

We demonstrate a method for determining the vitreous phase cryogenic temperature densities of aqueous mixtures, and other samples that require rapid cooling, to prepare the desired cryogenic temperature phase. Microliter to picoliter size drops are cooled by projection into a liquid nitrogen-argon (N2-Ar) mixture. The cryogenic temperature phase of the drop is evaluated using a visual assay that correlates with X-ray diffraction measurements. The density of the liquid N2-Ar mixture is adjusted by adding N2 or Ar until the drop becomes neutrally buoyant. The density of this mixture and thus of the drop is determined using a test mass and Archimedes principle. With appropriate care in drop preparation, management of gas above the liquid cryogen mixture to minimize icing, and regular mixing of the cryogenic mixture to prevent density stratification and phase separation, densities accurate to <0.5% of drops as small as 50 pL can readily be determined. Measurements on aqueous cryoprotectant mixtures provide insight into cryoprotectant action, and provide quantitative data to facilitate thermal contraction matching in biological cryopreservation.

The impact of cryosolution thermal contraction on proteins and protein crystals: volumes, conformation and order

“…Cooling is known to increase the true crystal mosaicity severalfold (Vahedi-Faridi et al, 2003). Information about the effects of the cryoprotective agent as well as concentration on contraction are available (Juers & Matthews, 2004a;Alcorn & Juers, 2010;Shen et al, 2016Shen et al, , 2017. More information may thus be uncovered by using a synchrotron-radiation source, especially without focusing optics, in which case mosaicity changes with cooling will represent a larger fraction of the base mosaicity (Bellamy et al, 2000) Cryo-optimization processes can then include knowledge about the cryosolvent thermal contraction.…”

“…Even when cooling conditions are found to be adequate for a particular purpose, they can often be further optimized by adjusting the concentration or the identity of the cryoprotective agent (Mitchell & Garman, 1994). The average contractions of many different cryosolutions between RT and 77 K have been measured both in macroscopic samples ($1 ml; Marshall et al, 2012;Juers & Matthews, 2001, 2004aAlcorn & Juers, 2010) and in microlitre-sized drops (Shen et al, 2016(Shen et al, , 2017, but systematic testing of contraction-based cryo-optimization has not yet been reported. The thermal behavior of such a system is complex, with potentially different thermal responses of the protein, internal solvent and external solvent.…”

Characterization of Aluminum Matrix Metal Composite Hybrid Reinforced With SiCw/(Al2O3-Mg) on Thermal Conductivity and Hardness

“…Density is a physical quantity, the ratio of the mass to the volume of the object [20]. Measurement of density in solid form using the Archimedes method can be calculated from equation ( 2) [21].…”

A comparison of gas stream cooling and plunge cooling of macromolecular crystals

“…Here this would lead to larger volumes with plunge cooling. Confirming whether a factor of ten in the cooling rate could lead to a $1% change in cell volume awaits further experiments, for example by varying the cooling rate in vitrified density measurements of cryosolvents (Alcorn & Juers, 2010;Shen et al, 2017). Solvent transport may also explain the cell volume difference, because greater resistance to solvent flow due to faster cooling may limit the total volume of solvent flowing out of any particular unit cell, resulting in smaller unitcell reductions for plunging.…”