Our laboratory is investigating the use of mass spectrometry to determine ligands which can be classified into structural frameworks, i.e. the determination of structural features such as, molecular weight, disulfide bond number and connectivity pattern, posttranslationally modified and novel amino acids.

Disulfide bonds beteen cysteine residues are one of the most important means for stabilising protein conformations [1] to maintain the tertiary structure of small peptides (mini-proteins) and hence promote specific receptor interactions. The determination of cystine connectivity is of importance for both functional and structural studies. Recent papers by W.R. Gray [2] and our laboratory [3] have demonstrated the feasibility of connectivity determination using reduction alkylation procedures under conditions to limit the scrambling or rearranging of disulfide bonds, ie. acidic pH and rapid alkkylation.

Here we present the results of a differential alkylation procedure for the determination of disulfide bond connectivity together with chemical and enzymatic manipulation of the peptides in an attempt to classify ligands based on a number of structural features.

1. Thornton, J M., J. Mol,. Biol 1981, 151, 261-287.
2. Gray, W.R., Protein Science 1993, 2, 1732-1148.
3. Jones, A., Bingham, J-P. and Alewood, P.F., 41st ASMS Conference, San Francisco, May, 1993.