The synthetic calmodulin peptpide fragments were synthesized using solid phase peptide synthesizer, each containing one calcium binding domain. The conformation of the peptides were studied using two dimensional NMR spectroscopy. The techniques used were double quantum filtered correlation spectroscopy (DQF-COSY), nuclear overhauser effect spectroscopy (NOESY) and total correlation spectroscopy (TOCSY). Detailed investigations have been completed for the fragment, containing the first calcium binding domain, in the presence and absence of calcium. At higher calcium concentrations, the conformation of the peptide was found to be changed, as indicated by the appearance of the cross peaks in the NH-NH regions of the NOESY spectra. It has been found that when the E and F helix size was less than optimal size, the fragments invariably adopt a random coil structure. However, the peptide in structure forming solvents such as trifluoroethanol showed considerable helicity in circular dichorism. Attempts to study the three dimensional structure has been hampered by strong solvent peaks and the associated dynamic range problems. However one dimensional NMR is being carried out to understand possible protein folding patterns in the presence and absence of calcium in structure forming solvents such as trifluoroethanol.
