At slightly lower concentrations (intermediate concentrations), activin (about 100 molecules per cell) activated the Xbra gene and instructed the cell to become muscle.

TLS Online TPP Program

#Id: 8448

#Unit 1. Molecules and their Interaction Relevant to Biology

In a typical a-helix of 12 (or n) residues, there are 8 (or n-4) hydrogen bonds.

TLS Online TPP Program

#Id: 8449

#Unit 1. Molecules and their Interaction Relevant to Biology

The first 4 amide hydrogens and the last 4 carbonyl oxygens cannot participate in helix H bonds.

TLS Online TPP Program

#Id: 8450

#Unit 1. Molecules and their Interaction Relevant to Biology

Right-handed helical conformation has 3.6 residues per turn with height of 5.4A

TLS Online TPP Program

#Id: 8451

#Unit 1. Molecules and their Interaction Relevant to Biology

The diameter of a typical α helix is about 12 Å, which matches the 12 Å wide and 6–8 Å deep major groove of B-form DNA. 

TLS Online TPP Program

#Id: 8452

#Unit 1. Molecules and their Interaction Relevant to Biology

If the α helix lies parallel to the direction of the major groove, the straight α helix can contact 4–6 bp before the bases curve out of the plane of the amino acids in the α helix.

TLS Online TPP Program

#Id: 8453

#Unit 1. Molecules and their Interaction Relevant to Biology