The chemical constitution of compounds which protect erythrocytes against freezing damage.

Eleven simple neutral water-miscible compounds were tested for protective action against freezing damage to human red blood cells. All the compounds penetrated the cells at room temperature without damage, but only four, N-substituted amides, were active. These results are considered together with previously published work on freezing protection by other low molecuar weight solutes. The affinity of the compounds for water is gauged in two independent ways, and correlates well with protective ability. The chemical constitutional factors responsible for high affinity for water are discussed. It appears that basic character is most important.