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Updated: Oct 24, 2026

Photo-Induced Cross-Linking of Unmodified Proteins (PICUP) Applied to Amyloidogenic Peptides
Published on: January 12, 2009
A novel protein cross-linking reaction in stressed Neutral Protamine Hagedorn formulations of insulin
R C Beavis1, M D Kneirman, D Sharknas
1Lilly Research Laboratories, Eli Lilly and Company, Lilly Corporate Center, DC 3811, Indianapolis, Indiana 46285, USA.
Abstract:
The covalent insulin-protamine product molecules formed by heat stress in Neutral Protamine Hagedorn formulations of insulin and the insulin analogue [LysB28,ProB29] were examined by mass spectrometry. The results demonstrated that the covalent cross-link between insulin and protamine was not caused by linkage through the protamine N-terminal amino group, as had been previously thought. Our results indicate that the linkage was formed between the side chain of a protamine arginine and a histidine in the insulin B chain, resulting in a net mass change of -5 Da, compared to the sum of the protamine and insulin molecular masses. A mechanism for this new type of covalent cross-linking reaction is proposed.
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