Ans: Used in synthesis of a growing amino acid chain to a polystyrene bead. FMOC is
used as a protecting group on the N-terminus.
3). Salting out (purification)
Ans: Changes soluble protein to solid precipitate. Protein precipitates when the
charges on the protein match the charges in the solution.
4). Size-exclusion chromatography
Ans: Separates sample based on size with smaller molecules eluting later.
5). Ion-exchange chromatography
Ans: Separates sample based on charge. CM attracts +, DEAE attracts -. May have
repulsion effect on like charges. Salt or acid used to remove stuck proteins.
6). Hydrophobic/reverse phase chromatography
Ans: Beads are coated with a carbon chain. Hydrophobic proteins stick better. Elute
with non-H-bonding solvent (acetonitrile).
7). Affinity chromatography
Ans: Attach a ligand that binds a protein to a bead. Elute with harsh chemicals or
similar ligand.
PaperStoc.com Page 1 of 31
, 8). Sds-page
Ans: Uses SDS. Gel is made from cross-linked polyacrylamide. Separates based off of
mass with smaller molecules moving faster. Visualized with Coomassie blue.
9). Sds
Ans: Sodium dodecyl sulfate. Unfolds proteins and gives them uniform negative
charge.
10). Isoelectric focusing
Ans: Variation of gel electrophoresis where protein charge matters. Involves
electrodes and pH gradient. Protein stops at their pI when neutral.
11). Fdnb (1-fluoro-2,3-dinitrobenzene)
Ans: 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.
12). Dtt (dithiothreitol)
Ans: Reduces disulfide bonds.
13). Iodoacetate
Ans: Adds carboxymethyl group on free -SH groups. Blocks disulfide bonding.
14). Homologs
Ans: Shares 25% identity with another gene
15). Orthologs
Ans: Similar genes in different organisms
16). Paralogs
Ans: Similar "paired" genes in the same organism
PaperStoc.com Page 2 of 31
, 17). Ramachandran plot
Ans: Shows favorable phi-psi angle combinations. 3 main "wells" for α-helices, ß-
sheets, and left-handed α-helices.
18). Glycine ramachandran plot
Ans: Glycine can adopt more angles. (H's for R-group).
19). Proline ramachandran plot
Ans: Proline adopts fewer angles. Amino group is incorporated into a ring.
20). Α-helices
Ans: 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.
21). Helix dipole
Ans: Formed from added dipole moments of all hydrogen bonds in an α-helix. N-
terminus is δ+ and C-terminus is δ-.
22). Ss-sheet
Ans: Either parallel or anti-parallel. Often twisted to increase strength.
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