ABSTRACT
Reecting the centrality of proteins in biology, their name is derived from the Greek word πρωτειοσ, which means “of primary importance.” In 1838 the Dutch chemist Gerrit Jan Mulder conferred this name to recognize the requirement for proteins in the diet of animals. Berzelius later found that all proteins have similar empirical formulas. Proteins are oligomers of amino acids joined together by amide bonds. Composed of 20 dierent building blocks, proteins display a much more varied array of functional groups and structures than either DNA or RNA, which have only four building blocks each. For DNA, structure came rst; sequencing came later. e opposite is true for proteins because a process known as the Edman degradation method made it possible to elucidate the sequence of amino acid residues in proteins long before the rst protein structures were determined.
