TLS Online TPP Program

#Id: 8472

#Unit 1. Structure and Function of Biomolecules

Poly(Gly) chains also adopt secondary conformations. 

In the solid state poly(Gly) has been shown to adopt two regular conformations designated I and II. 

State I has an extended conformation like a β strand whilst state II has three resides per turn and is similar to poly(Pro).

TLS Online TPP Program

#Id: 8473

#Unit 1. Structure and Function of Biomolecules

Beta sheets usually have their B strands either parallel or antiparallel

TLS Online TPP Program

#Id: 8474

#Unit 1. Structure and Function of Biomolecules

β Sheets in proteins contain 2 to as many as 22 polypeptide strands, with an average of 6 strands. 

Each strand may contain up to 15 residues, the average being 6 residues.

TLS Online TPP Program

#Id: 8475

#Unit 1. Structure and Function of Biomolecules

Repeat period is shorter for the parallel conformation (6.5 Å, vs. 7 Å for antiparallel)

TLS Online TPP Program

#Id: 8476

#Unit 1. Structure and Function of Biomolecules

TLS Online TPP Program

#Id: 8477

#Unit 1. Structure and Function of Biomolecules

Each single strand of the b-sheet structure can be pictured as a twofold helix, that is, a helix with two residues per turn.

The arrangement of successive amide planes has a pleated appearance due to the tetrahedral nature of the Ca atom.