When the 5′ end of the siRNA of a RISC complex base-pairs precisely with a target mRNA over a distance of one turn of an RNA helix (10–12 base pairs), this domain of AGO2 cleaves the phosphodiester bond of the target RNA across from nucleotides 10 and 11 of the siRNA

TLS Online TPP Program

#Id: 8454

#Unit 1. Molecules and their Interaction Relevant to Biology

The α helices of proteins have an average length of ∼12 residues, which corresponds to more than three helical turns, and a length of ∼18 A.

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.