Structural changes induced in proteins by therapeutic ultrasounds

The structural effect induced by therapeutic ultrasound on proteins in aqueous solution has been investigated with FTIR spectroscopy, UV–VIS spectroscopy, circular dichroism and light scattering. Six proteins (cytochrome, lysozyme, myoglobin, bovine serum albumin, trypsinogen, and α-chymotrypsinogen A) with different molecular weight and secondary structure have been studied. The experiment has been performed using an ultrasound source at resonant frequency of 1 MHz and sonication times of 10, 20, 30, 40, 50, and 60 min. A different behaviour of proteins under sonication depends on the dominant secondary structure type (α-helix or β-sheets) and on the grade of the ordered structure. The results suggest that the free radicals, produced by water sonolysis, have an important role in the changes of structural order.