Impact of compatible solutes on the mechanical properties of fibronectin: a single molecule analysis

Abstract

The influence of ectoine and sarcosine on the mechanical properties of surface bound fibronectin has been investigated by means of force microscopy. Single molecule stretching experiments of fibronectin molecules reveal that ectoine and sarcosine increase the tendency of the polypeptide to coil, thus decreasing its apparent persistence length. This behavior can be explained by means of the preferential exclusion model implying that the osmolytes are expelled from the protein surface due to the increase in chemical potential of the denatured, i.e. stretched, state forcing the protein into a more compact structure. Detailed analysis of the unfolding forces, which are extracted from the successive unfolding of the individual subunits of fibronectin, shows that neither ectoine nor sarcosine influence the binding strength in a significant way even if the concentration of osmolytes exceeds 1 M.