Different effects of (L)-arginine on the heat-induced unfolding and aggregation of proteins

Circular dichroism spectroscopy was used to study the effect of l-arginine on the temperature related unfolding and aggregation of three growth hormones, i.e. human, porcine and mink growth hormones, and human interferon-α2b. (L)-arginine can stabilize some proteins and suppress their aggregation as it was exemplified by porcine and mink growth hormones. For some other proteins, on the contrary, the effect of arginine can be negative. Even at low concentrations the amino acid is able to promote the aggregation as it was demonstrated by the experiments with human growth hormone and interferon-α2b. (L)-arginine seems not to be a universal excipient for preventing the temperature related aggregation of proteins in contrast to its widespread application in the refolding process.