ACS BIOCHEMISTRY EXAM Questions and Correct Answers the Latest Update
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Course
ACS
Institution
ACS
Henderson-Hasselbach Equation
pH = pKa + log ([A-] / [HA])
FMOC Chemical Synthesis
Used in synthesis of a growing amino acid chain to a polystyrene bead. FMOC is
used as a protecting group on the N-terminus.
Salting Out (Purification)
Changes soluble protein to solid precipitate. Protein ...
ACS BIOCHEMISTRY EXAM
Questions and Correct Answers the
Latest Update
Henderson-Hasselbach Equation
✓ pH = pKa + log ([A-] / [HA])
FMOC Chemical Synthesis
✓ Used in synthesis of a growing amino acid chain to a polystyrene bead. FMOC is
used as a protecting group on the N-terminus.
Salting Out (Purification)
✓ Changes soluble protein to solid precipitate. Protein precipitates when the charges
on the protein match the charges in the solution.
Size-Exclusion Chromatography
✓ Separates sample based on size with smaller molecules eluting later.
Ion-Exchange Chromatography
✓ Separates sample based on charge. CM attracts +, DEAE attracts -. May have
repulsion effect on like charges. Salt or acid used to remove stuck proteins.
Hydrophobic/Reverse Phase Chromatography
✓ Beads are coated with a carbon chain. Hydrophobic proteins stick better. Elute with
non-H-bonding solvent (acetonitrile).
✓ Attach a ligand that binds a protein to a bead. Elute with harsh chemicals or similar
ligand.
SDS-PAGE
✓ Uses SDS. Gel is made from cross-linked polyacrylamide. Separates based off of mass
with smaller molecules moving faster. Visualized with Coomassie blue.
SDS
✓ Sodium dodecyl sulfate. Unfolds proteins and gives them uniform negative charge.
Isoelectric Focusing
✓ Variation of gel electrophoresis where protein charge matters. Involves electrodes
and pH gradient. Protein stops at their pI when neutral.
FDNB (1-fluoro-2,3-dinitrobenzene)
✓ FDNB reacts with the N-terminus of the protein to produce a 2,4-dinitrophenol
derivative that labels the first residue. Can repeat hydrolysis to determine sequential
amino acids.
DTT (dithiothreitol)
✓ Reduces disulfide bonds.
Iodoacetate
✓ Adds carboxymethyl group on free -SH groups. Blocks disulfide bonding.
✓ Shows favorable phi-psi angle combinations. 3 main "wells" for α-helices, ß-sheets,
and left-handed α-helices.
Glycine Ramachandran Plot
✓ Glycine can adopt more angles. (H's for R-group).
Proline Ramachandran Plot
✓ Proline adopts fewer angles. Amino group is incorporated into a ring.
α-helices
✓ Ala is common, Gly & Pro are not very common. Side-chain interactions every 3 or
4 residues. Turns once every 3.6 residues. Distance between backbones is 5.4Å.
Helix Dipole
✓ Formed from added dipole moments of all hydrogen bonds in an α-helix. N-terminus
is δ+ and C-terminus is δ-.
✓ Same sheet directions (C & N-termini line up). Has angled H-bonds.
ß-turns
✓ Tight u-turns with specific phi-psi angles. Must have gly at position 3. Proline may
also be at ß-turn because it can have a cis-omega angle.
Loops
✓ Not highly structured. Not necessary highly flexible, but can occasionally move. Very
variable in sequence.
Circular Dichroism
✓ Uses UV light to measure 2° structure. Can be used to measure destabilization.
Disulfide-bonds
✓ Bonds between two -SH groups that form between 2° and 3° structure.
ß-mercaptoethanol
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