Structural Properties and Stability of Proteins in Dihydrolevoglucosenone/Water Mixtures

Dihydrolevoglucosenone
(DHL) shows great promise as an alternative
to conventional toxic organic solvents widely used for industrial
purposes. In this framework, evaluating the potential of DHL (commercially
known as Cyrene) as a solvent for dissolving proteins is of great
importance. Here, the effect of DHL/water mixtures on protein stability
and solubility has been assessed. Several proteins, namely, hemoglobin,
ferritin, ribonuclease, and albumin, were readily dissolved in buffer
solutions containing up to 50–60% DHL and were stable at room
temperature, as indicated by gel electrophoresis and matrix-assisted
laser desorption/ionization analysis. Turbidimetry assays were performed
in order to assess the solubility limitations derived from DHL/water
mixtures. Finally, protein secondary structures in such mixtures,
investigated by attenuated total reflectance Fourier-transform infrared
spectroscopy, were found to be comparable to those obtained in phosphate
buffer up to 50% DHL/water, with small spectral changes in the case
of ribonuclease. DHL/water mixtures may thus represent highly convenient
solvents for studies of protein chemistry.