PROTEIN

• There are 4 levels of protein structure

  1. primary
  2. secondary
  3. tertiary
  4. quaternary
• Primary structure is composed of single covalently-bonded amino acids
• There are 2 types of secondary structure

  1. alpha helix structure
  2. beta-sheet structure
• The alpha helix structure contains one strand of amino acid chain that is bonded by intramolecular hydrogen bonds
• Two chains that are linked by hydrogen bonds described the beta-sheet structure
• The tertiary structure of the protein refers to the combination of either pure helix or of pure beta or combination of both
• The stabilizing interactions in the tertiary level are

  (a) salt linkages

  (b) hydrogen bonds

  (c) disulfides linkages

  (d) hydrophobic interactions
• Denaturation is the unfolding of the complex secondary, tertiary, and quarternary structure of proteins
• Heat causes the atom within the protein molecule to vibrate more rapidly, causing the hydrogen bonds and hydrophobic interaction to break
• combining the free carboxylate anions of the acidic amino acids with the metal, causing precipitation
• Organic acids, like picric acids and tannic acids, are used to precipitate the alkaloids giving rise to the name “alkaloidal reagents”
• Leather is manufactured by coating animal skins with tannic acids, hence the process is known as tanning
• Biuret Test

  • for compound that contains 2 or more peptide linkages
  • color : purple
• Ninhydrin Test

  • color : blue to violet
• Xanthoproteic Test

  • Nitration of amino acids that contain benzene ring
  • color : yellow to orange
• Millon's Test

  • prensence of phenol group
  • darker pink or red
• Hopkin‘s Cole Test

  • aldehyde present in the test
  • blue or vilet
• Sakaguchi Test

  • combination of alpha napthol and sodium hypobromite
  • to identify the presence of arginine
  • red to orange
• Lead Acetate Test (Test for Sulfur)

  • sulfur containing amino acids
  • brownish-black
• Color test of proteins:

  1. Biuret Test
  2. Ninhydrin Test
  3. Xanthoproteic Test
  4. Millon's Test
  5. Hopkin's Cole Test
  6. Sakaguchi Test
  7. Lead Acetate Test