Rates of amino acid changes in fibrinopeptides, hemoglobin, and cytochrome c ... tantalizing findings was the observation that protein sequence change seemed to occur at a rate proportional ...

"One can reconstruct this evolution by comparing the sequence of amino acid units in the several molecular chains of human hemoglobin and in hemoglobin chains from other animals" ...

The proteins analyzed included hemoglobin (Zuckerkandl & Pauling ... F. & Blombäck, B. Amino-acid sequence investigations of fibrinopeptides from various mammals: Evolutionary implications.

Proteins have four levels of structure: primary (amino acid sequence), secondary (local folding patterns like alpha helices and beta sheets), tertiary (overall 3D shape), and quaternary (assembly of ...