Introduction to Proteins

• DNA is transcribed to form mRNA in the nucleus. The mRNA is then exported to the cytoplasm. mRNA is then translated into a linear sequence of amino acids that folds into a 3D structure.
• Amino acids have an alpha carbon central to it. Surrounding the alpha carbon is the amino group, carboxylic acid, and amino acid specific side chain (R group).
• When the R group is not a hydrogen atom, the alpha carbon is an asymmetric center.
• At a neutral pH, the amino acid nitrogen is protonated and the carboxylic acid is deprotonated to yield a zwitterion.
• When four different groups are attached to a carbon atom, the atom is said to be chiral, a stereocenter, or an asymmetric carbon.
• A Fischer projection is a 2D stereochemical representation.
• All 20 alpha amino acids, except glycine, contain an asymmetric alpha carbon.
• L-alanine is the mirror image of D-alanine, so they are enantiomers.
• The classifications of amino acids are nonpolar aliphatic, nonpolar, nonpolar aromatic, polar, positively charged polar, and negativity charged polar amino acids.
• The nonpolar aliphatic amino acids are glycine, alanine, valine, leucine, and isoleucine.
• The nonpolar amino acids are proline and methionine.
• The nonpolar amino acids are phenylalanine, tyrosine, and tryptophan.
• The polar amino acids are serine, cysteine, threonine, asparagine, and glutamine.
• The positively charged polar amino acids are histidine, lysine, and arginine.
• The negatively charged polar amino acids are aspartic acid and glutamic acid.
• Glycine (Gly, G)

  
• Alanine (Ala, A)

  
• Valine (Val, V)

  
• Leucine (Leu, L)

  
• Isoleucine (Ile, I)

  
• Proline (Pro, P)

  
• Methionine (Met, M)

  
• Phenylalanine (Phe, F)

  
• Tyrosine (Tyr, Y)

  
• Tryptophan (Trp, W)

  
• Serine (Ser, S)

  
• Cysteine (Cys, C)

  
• Threonine (Thr, T)

  
• Asparagine (Asn, N)

  
• Glutamine (Gln, Q)

  
• Histidine (His, H)

  
• Lysine (Lys, K)

  
• Arginine (Arg, R)

  
• Aspartic acid (Asp, D)

  
• Glutamic acid (Glu, E)

  
• The one letter abbreviation for alanine is A.
• The three letter abbreviation for alanine is Ala.
• The one letter abbreviation for arginine is R.
• The three letter abbreviation for arginine is Arg.
• The one letter abbreviation for asparagine is N.