Proteins

• (-phi,+psi) for beta strands
• (-phi,-psi) for alpha helices

Beta strands are in the +y region, alpha helices are in the -y region. They both only occur on the -x axis side. See slide #13

The protein structures would be unstable due to large possibility of steric clashes between atoms.

14

(# of H bonds) = (# of residues) - 4

See slide #4

3.6

• Ex. 1: 18 residues x (1 turn/3.6 residues) = 5 turns
• Ex. 2: 7 turns x (3.6 residues/1 turn) = 25 residues when rounded to the nearest whole #

DEKR (all charged molecules)

(also participate in H bonding)

strengthens the shape of a protein or peptide

1 disulfide bond = 2 Cysteines

Beta strands. There would be steric constraints between the H bonds within 1 strand. Interstrand H bonding occurs between 2 strands to help them stabilize.

See slide #10

Alpha helixes & beta turns. In alpha helixes, intrahelical H bonding occurs between the carbonyl O & amide N

See slide #3 & 11A

18 (See slide #6)

• 35 H bonds + 4 = 39 residues.
• 39 residues x (1 layer/18 residues) = 2.17 layers

• 8 turns x (3.6 residues/1 turn) = 28.8 residues
• 28.8 residues x (1 layer/18 residues) = 1.60 layers

42/7 = 6 perfect heptad repeats. Each heptad has 2 a & d residues making a total of 12 a & d positions.

See slide #9

A heptad has 2 a & d positions so there would be 4 heptad repeats. Each heptad has 7 residues so 4 x 7 = 28 residues

N-C(alpha); carbonyl C

C(alpha)-C; amide N

C-N (no rotation due to partial double bond); alpha C