The cystine knot structure of homodimeric recombinant human growth and differentiation factor 5 (rGDF5) was identified de novo applying a combination of proteolytic degradation and subsequent analyses of the disulfide-linked peptides by electrospray- and MALDI-TOF mass spectrometry, amino acid analysis, and Edman degradation.
The generated fragments by MALDI-TOF mass spectrometry facilitated an unambiguous assignment of the disulfide bridge pattern.

This work was carried out in the groups of PD Dr. Stefan Schürch and Prof. Johann Schaller.

References:

• Christian Trachsel, Urs Kämpfer, Rolf Bechtold, Johann Schaller and Stefan Schürch;
  "Elucidation of the disulfide bridge pattern of the recombinant human growth and differentiation factor 5 dimer and the interchain Cys/Ala mutant monomer"
  Anal. Biochem., 390, 103-108, (2009); doi:10.1016/j.ab.2009.04.024.