Evolutionary constraint are restrictions, limitations, or biases on the course or outcome of adaptive evolution.

TLS Online TPP Program

#Id: 8455

#Unit 1. Molecules and their Interaction Relevant to Biology

α helices are common components of polypeptide chains, they need to be of a certain minimum length of 6 amino acid

TLS Online TPP Program

#Id: 8456

#Unit 1. Molecules and their Interaction Relevant to Biology

The α helices have rotation of 100 degree per amino acid

TLS Online TPP Program

#Id: 8457

#Unit 1. Molecules and their Interaction Relevant to Biology

Gly is often observed at the C-cap & N cap both positions, Pro at the Ncap and Asp and Glu at N2 and N3.

TLS Online TPP Program

#Id: 8458

#Unit 1. Molecules and their Interaction Relevant to Biology

Helix can form in polypeptides consisting of either L- or D-amino acids but never exist to contain both types.

TLS Online TPP Program

#Id: 8459

#Unit 1. Molecules and their Interaction Relevant to Biology

Five types of constraints affect the stability of an  helix: 

(1) the intrinsic propensity of an amino acid residue to form an  helix; 

(2) the interactions between R groups, particularly those spaced three (or four) residues apart; 

(3) the bulkiness of adjacent R groups; 

(4) the occurrence of Pro and Gly residues; and 

(5) interactions between amino acid residues at the ends of the helical segment and the electric dipole inherent to the  helix.

TLS Online TPP Program

#Id: 8460

#Unit 1. Molecules and their Interaction Relevant to Biology

The intrinsic propensity of an amino acid residue to form an  helix