Sorbitol is a natural cryoprotectant for some organisms. In order to reveal the mechanism of a protection some organisms against low temperatures, we studied the interaction between sorbitol and phosphatidylcholine (PC) which is one of major component of cell membranes. Small-angle neutron-scattering contrast variation method was used to characterize dihexanoyl-PC (dC(6)PC) micelles in the presence of sorbitol (2 M). As a result, the aggregation number for the dC(6)PC micelle and the volume per a single molecule in the micelle were estimated to be ∼, 32 and ∼ 640 Å3, respectively. By comparing these data and those for the dC(6)PC micelle in pure water (Lin et al., J Am Chem Soc 108:3499-3507), it was concluded that sorbitol reduces the contact area between the lipid and the aqueous phase. On the basis of this conclusion, we discuss the role of sorbitol for the ability of some organisms to survive in low temperatures.
- Contrast-variation method
- Neutron scattering