Nucleotides and Amino Acids

PR 613 Structural Biology I

Dr. Eric Wickstrom

Structure dictates function

Nucleic Acids

Triple helix

Southern Northern

Catalytic RNA

Antiparallel B-form (Southern) double helix

Ring stacking and hydrophobic repulsion stabilize helix. Hydrogen bonds permit close approach, but don’t add stability!

Dynein TcTex1

C to N, over the bridge

Sidechain on the left in an L-amino acid

Aromatic (-orbital) amino acids

pK 4 pK 4

pK 10.5

pK 8

pK 10.5 pK 12.5 pK 6

Sperm whale myoglobin

helix3.6 aa/turn5.4 Å/turn1.5 Å/aa

8 helices

sheet2.0 aa/turn7 Å/turn3.5 Å/aa

Prealbumin

16 sheets

-turns