Fourth heart sound (S4)

Not audible in normal adults

Heard in ventricular hypertrophy, where ventricular compliance is decreased

TLS Online TPP Program

#Id: 8465

#Unit 1. Molecules and their Interaction Relevant to Biology

The magnitude of this dipole moment corresponds to about 0.5-0.7 unit charge at each end of the helix. These charges would be expected to attract ligands of opposite charge and negatively charged ligands, especially when they contain phosphate groups and frequently bind at the N-termini of a helices. In contrast, positively charged ligands rarely bind at the C-terminus

TLS Online TPP Program

#Id: 8466

#Unit 1. Molecules and their Interaction Relevant to Biology

Polyleucine and polyalanine readily form a-helical structures.

TLS Online TPP Program

#Id: 8467

#Unit 1. Molecules and their Interaction Relevant to Biology

polylysine is a random coil at pH values below about 11, where repulsion of positive charges prevents helix formation. At pH 12, where polylysine is a neutral peptide chain, it readily forms an a-helix.

TLS Online TPP Program

#Id: 8468

#Unit 1. Molecules and their Interaction Relevant to Biology

polyGlu is a random coil at pH values above about 5, where repulsion of negative charges prevents helix formation. 

TLS Online TPP Program

#Id: 8469

#Unit 1. Molecules and their Interaction Relevant to Biology

The RHH (L amino acids) α helix, which ideally has ϕ = −57° and ψ = −47°

TLS Online TPP Program

#Id: 8470

#Unit 1. Molecules and their Interaction Relevant to Biology

The two forms of poly(Pro)

all cis (I) or all trans (II) peptide bonds. 

poly(Pro) I as a right-handed helix with 3.3 residues per turn 

poly(Pro) II is a left-handed helix with 3 residues per turn.