Protein Terms: Structure of Protein Amino Acids (AA)

Protein Terms: Amino Acids (AA) All AA have an amino (NH2 ) group and a carboxyl(COOH) group.

All AA contain carbon (C), Hydrogen (H), oxygen (O), and nitrogen (N). Methionine & cystine also contain sulfur (S).

Structure of Protein 4 Structures

1. Primary structure; AA- polypeptides with peptide bond.

2. Secondary structure; Structure of Protein Helic-polypeptide chain with hydrogen/disulfide bond.

3. Tertiary structure; Structure of Protein Globular-polypeptide chain with hydrogen/disulfide bond, hydrophobic bond, nonpolar bond. Fibrous protein; keratin , collagen ,etc.

4. Quaternary structure; Oligomeric protein, or mix of polypeptide chain with a weak bond

Total Crude Protein

• CP = Nitrogen (N) x 6.25

• 100 g CP = 16 g N

• 100 / 16 = 6.25

• Example: Soybean = 7% N x 6.25 = 43.75% CP

Nonprotein Nitrogen (NPN)

• NPN not in a protein
• True protein is N in a long chain of amino acids and peptide bond
• NPN must be incorporated into microbial protein to be beneficial
• Examples of NPN
– Urea
– Monoammonium phosphate
– Free amino acids


Available Protein

• Protein available for digestion
• Should be 90% or more of CP
• Less than 90% CP available indicates:
– Heat damage
– Excessive maturity at harvest

Unavailable Protein

• Protein unavailable for digestion
• Should be less than 10% of CP
• If greater than 10% of CP indicates:
– Heat damage
– Malliard Reaction
– Carmelized protein
– Bound protein
– ADF-N


Avoid Heating & Carmelization

• Proper stage of maturity
• Correct moisture content
– Conventional (55 - 60%)
– Bunkers & bags (65 - 70%)
• Length of chop
• A tight silo or pack
• Fill rapidly
• Seal if needed