 The difficulty in purifying proteins in large quantities made them very difficult for early protein biochemists to study . Hence , early studies focused on proteins that could be purified in large quantities , e.g. , those of blood , egg white , various toxins , and digestive / metabolic enzymes obtained from slaughterhouses . In the 1950s , the Armour Hot Dog Co. purified 1 kg of pure bovine pancreatic ribonuclease A and made it freely available to scientists ; this gesture helped ribonuclease A become a major target for biochemical study for the following decades . 
 The difficulty in purifying proteins in large quantities made them very difficult for early protein biochemists to study . Hence , early studies focused on proteins <a href='null_relcl' title='1'><mark>that</mark></a>could be purified in large quantities , e.g. , those of blood , egg white , various toxins , and digestive / metabolic enzymes obtained from slaughterhouses . In the 1950s , the Armour Hot Dog Co. purified 1 kg of pure bovine pancreatic ribonuclease A and made it freely available to scientists ; this gesture helped ribonuclease A become a major target for biochemical study for the following decades . 
The difficulty in purifying proteins in large quantities made them very difficult fa early protein biochemists to study . Hence , early studies focused on proteins could b purified in large quantities , e.g. , those of blood , egg white , various toxins , and digestive / metabolic enzymes obtained from slaughterhouses . In da 1950s , the Armour Hot Dog Co. purified 1 kg of pure bovine pancreatic ribonuclease A and made it freely available to scientists ; dis gesture helped ribonuclease A become a major finishline ffirbiochemical study for the following decades .