Amino acids, proteins and DNA

• All amino acids are optically active ( has a chiral carbon)
• Zwitterion - molecules which have a permanent positive charge and a permanent negative charge. Overall charge is neutral. So they have ionic properties
• Zwitterion formed

  The bond between the OH in the carboxylic group goes to the nitrogen on the amino group

  A) Amino acid

  B) +

  C) -

  
• In low pH conditions, there is more H+ ions so the carboxylic group has its hydrogen restored

  A)

  B)

  
• In high pH conditions (alkaline) there is less H+ ions so the hydrogen would be removed from the amino group

  A)

  B)

  C)

  
• Reaction of amino acids

  Due to it having a amino group and a carboxylic group it would have the same reactions as them

  Amine group

  • Protonated by acids
  • Acylation
  • Nucleophilic substitution with haloalkanes

  Carboxylic group

  • Deprotonated by bases
  • Esterification with alcohols
• A polypeptide and a polyamide is not the same thing.

  Polyamides are made from diamines and dicarboxylic acids. Polypeptides are made from two amino acid groups
• Polypeptides are broken down by either base or acid hydrolysis
• This base is guanine.

  Hydrogen bonding takes place at

  • The oxygen
  • the NH next to the oxygen
  • NH2 next to the NH

  The deoxyribose sugar bonds at the NH between the Nitrogen

  
• This base is adenine

  Hydrogen bonding takes place at:

  • NH2
  • The nitrogen between NH2 and N

  The deoxyribose sugar bonds at the NH

  
• This is cytosine

  Hydrogen bonding takes place at the

  • NH2
  • N
  • Oxygen

  Deoxyribose sugar bonds at the NH

  
• This is thymine

  Hydrogen bonding takes place at the

  • Oxygen between the CH3 and NH
  • At the NH

  Deoxyribose sugar bonds at the NH

  
• The sugar used in DNA is called 2-deoxyribose.

  On the left side the OH groups is where the phosphate bonds to it.

  On the right side the OH group is where base bonds to it

  
• Anticancer drugs

  Cisplatin the Pt(||) complex  s used as an anticancer drug.

  Cisplatin prevents DNA replication in cancer cells by a ligand replacement reaction with DNA in which a coordinate bond is formed between platinum and a nitrogen atom on guanine.
• Cisplatin is an important drug to prolong life of cancer patients but has some side effects:

  • Prevents normal cells in the body from replicating
  • Can cause nausea and vomiting
  • Patients can become resistant to cisplatin
• Cisplatin drug

  A) NH3

  B) Cl

  C) Cl

  D) NH3

  E) Pt