%0 Journal Article %T pH-Dependent Interaction between C-Peptide and Phospholipid Bicelles %A Sofia Unnerst le %A Lena M ler %J Journal of Biophysics %D 2012 %I Hindawi Publishing Corporation %R 10.1155/2012/185907 %X C-peptide is the connecting peptide between the A and B chains of insulin in proinsulin. In this paper, we investigate the interaction between C-peptide and phospholipid bicelles, by circular dichroism and nuclear magnetic resonance spectroscopy, and in particular the pH dependence of this interaction. The results demonstrate that C-peptide is largely unstructured independent of pH, but that a weak structural induction towards a short stretch of β-sheet is induced at low pH, corresponding to the isoelectric point of the peptide. Furthermore, it is demonstrated that C-peptide associates with neutral phospholipid bicelles as well as acidic phospholipid bicelles at this low pH. C-peptide does not undergo a large structural rearrangement as a consequence of lipid interaction, which indicates that the folding and binding are uncoupled. In vivo, local variations in environment, including pH, may cause C-peptide to associate with lipids, which may affect the aggregation state of the peptide. %U http://www.hindawi.com/journals/jbp/2012/185907/