van't hoff equation plot

TLS Online TPP Program

#Id: 8479

#Unit 1. Structure and Function of Biomolecules

Parallel sheets characteristically distribute hydrophobic side chains on both sides of the sheet

TLS Online TPP Program

#Id: 8480

#Unit 1. Structure and Function of Biomolecules

Antiparallel sheets are usually arranged with all their hydrophobic residues on one side of the sheet. 

This requires an alternation of hydrophilic and hydrophobic residues in the primary structure of peptides involved in antiparallel b-sheets because every other side chain projects to the same side of the sheet

TLS Online TPP Program

#Id: 8481

#Unit 1. Structure and Function of Biomolecules

Turns are classified into several classes, like 

β-Turn  (I, II, I’, II’) 

α -Turn 

γ- Turn

π -Turn

TLS Online TPP Program

#Id: 8482

#Unit 1. Structure and Function of Biomolecules

TLS Online TPP Program

#Id: 8483

#Unit 1. Structure and Function of Biomolecules

The central bond in this case is the peptide bond, where rotation is constrained. The peptide bond is normally (99.6% of the time) in the trans configuration, constraining  to a value of w=+_180. For a rare cis peptide bond, w=0.

TLS Online TPP Program

#Id: 8484

#Unit 1. Structure and Function of Biomolecules

The trans form is the more favoured state because in this arrangement repulsion between non-bonded atoms connected to the Cα centre are minimized. 

For most peptide bonds the ratio of cis to trans configurations is approximately 1:1000.