Mechanism for long-acting chimeras based on fusion with the   carboxyl-terminal peptide (CTP) of human chorionic gonadotropin beta-subunit   3
  Thermodynamic scaling explains the dramatic successes of CTP fused human growth proteins as regards lifetime in vivo and enhanced functionality compared to their wild-type analogues, like Biogen. The theory is semi-quantitative and contains no adjustable parameters. It shows how hydrophilic terminal spheres orient fused proteins in the neighborhood of a membrane surface, extending lifetimes and improving functionality. 
J. C. Phillips
q-bio.QM