Tests-Biochemistry I – 1 Aminoacids + Peptides
Structures – formulas of important aminoacids
e.g.
Write formulas of:
tyrosine, tryptophan, arginine, methionine … etc.
Describe by formula the structure of peptide
Glycylaspartate … etc.
Properties and reactions of amino acids and peptides
e.g.
a) Describe by formula the structure of peptide: Lysylglutamate
b) Describe all ionization forms of that peptide from pH 1 to 14 and append pK values to the dissociation
equlibria.
Glu: pK1=2,1, pK2=9,5, pK3 = 4,1. Lys: pK1 = 2, 2; pK2 = 9,2, pK3 = 10,8.
c) Calculate pI of that dipeptide!
Mixture of aminoacids (Cys, Glu, Ser, Ala, Lys and His, their pKa3 values are Cys 10,8; Lys 10,5; His 6.0. COOH has pKa 2,0 and -NH2 9.0) was applied on annex column at pH 10. Which amino acids will be bound and
which will be eluted?
Při elektroforéze v pufru o pH 5,0 se aminokyseliny Lys, His, Gly were separated by electrophoresis in buffer
with pH 5.0 in a manner described below.
Shortly: pKa values of -COOH and -NH2 are 2,0 and 9.0, resp., pKa of Lys -NH2 is 10.5, and pKa of
imidazole 6,0.
start
Append individual amino acids to the positions shown and give a reason.
What is a generally used method for amino acid determination?
Describe using chemical equations or at least by words.
Desribe the ninhydrine reaction – formulas, equations. What is the importance of this reaction?