The conformation response of calf thymus DNA and beta-lactoglobulin (BLG) to solvent conditions altered by varying amounts of ethanol (EtOH) and tert-butanol (TBA) has been monitored by viscosimetry and circular dichroism measurements. A correlation between the effects of EtOH and TBA on DNA condensation and BLG denaturation clearly appears from the data, suggesting that a similar molecular mechanism is responsible for the alcohol effects on these two very different systems and processes. These alcohol-induced transitions appear in the concentration range (alcohol mole fraction X = 0.22 and X = 0.07 for EtOH and TBA, respectively) where changes in the association state of the alcohol molecule occur (see compressibility and IR data). (C) 2010 Elsevier B. V. All rights reserved.