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# H-bonds between H 2O
and peptide linkages
= 33 x 2 = 66
Ignores groups at the ends of the
a-helix which are assumed to
maintain their H-bonds with water
in the folded state FOLDED STATE
# of H-bonds between
H2O molecules = 66/2 = 33 # of H-bonds in
the α-helix 33
a-helices have 4 less H-bonds
than the number of residues Energy required to break
H-bonds in the unfolded state Energy required to break H-bonds
in the folded state = 66 x 12 = 792 kJ = (33 x 12) + (33 x 15) = 891 kJ Because it requires more energy to break the H-bonds in the final state,
the final state is more strongly bonded thus ∆HH-bond ~ -99 kJ (b) Based on ∆HH-bond alone, should the protein fold in water? YES (YES/NO) Question #10 (TUTORIAL Content, 10 points)
(a) In an effort to purify histone proteins from nuclear extracts, a biochemist applies a sample of nuclear
proteins to a column containing a matrix composed of cellulose derivatized with DNA Following application
of the sample in buffer at pH = 7, the column is washed with an NaCl gradient in buffer at pH = 7.
What kind(s) of column chromatography is the biochemist using?
(i) Cation exchange chromatography Recall that histones are +vely charged at pH =7.
(ii) Anion exchange chromatography
(iii) Affinity chromatography Histones bind to DNA.
(iv) Size exclusion chromatography
(b) You are investigating the properties of three monomeric proteins A, B and C, and find:
When a mixture of the three proteins is subjected to native polyacrylamide gel electrophoresis, protein C lies
nearest the bottom of the gel followed by A, and finally B which lies nearest the top of the gel (the point
of sample application)
Protein A binds to diethylaminoethylcellulose at pH 5.5 but not at pH 4.5.
In 2-D gel e...
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This test prep was uploaded on 04/01/2014 for the course BIOL 201 taught by Professor Chowrira during the Winter '13 term at UBC.
- Winter '13