Positive selection in pray population leads to an “arm’s race” with predator (Host-pathogen same).

#Id: 7704

#Unit 1. Molecules and their Interaction Relevant to Biology

                                                           Loops and Turn

Small loops with regular hydrogen bond pattern and specific dihedral angles are termed as turns

#Id: 7705

#Unit 1. Molecules and their Interaction Relevant to Biology

                                                               β-turns

Most common turns, also termed as ẞ-bends, tight turns, reverse turns, generally connects

β-sheets.

The conformation of i+1 and i+2 are crucial and on the basis of this, they are classified

Consists of 4 amino acids, generally termed as i, i + 1 , i + 2 and i + 3

H-bond is seen between i and i+3 (First and Fourth residue)

#Id: 7706

#Unit 1. Molecules and their Interaction Relevant to Biology

                                                                                                Type I β turn

#Id: 7707

#Unit 1. Molecules and their Interaction Relevant to Biology

H bonding i-i+3, i+1 in BS while i+2 in below LHH which virtually not allowed region

for most of amino acid except Gly that is why Gly is most conserved in type II B turns

                                                                Type II β turn

#Id: 7708

#Unit 1. Molecules and their Interaction Relevant to Biology

                  Type l'β turn

#Id: 7709

#Unit 1. Molecules and their Interaction Relevant to Biology

                              Type II β turn