Sentence:  The latter procedure gave rise to a small active <WSD>protein</WSD> peak ( Region 1a ) between Regions 1 and 2 . 
Meaning of the word marked with <WSD> tags:  any of a large group of nitrogenous organic compounds that are essential constituents of living cells; consist of polymers of amino acids; essential in the diet of animals for growth and for repair of tissues; can be obtained from meat and eggs and milk and legumes