Proteins fold to their native conformations via directed pathways rather than stumbling on them through random conformational searches.

TLS Online TPP Program

#Id: 8445

#Unit 1. Molecules and their Interaction Relevant to Biology

Right-handed helical conformation has 3.6 residues per turn and 1.5A/aa.

TLS Online TPP Program

#Id: 8446

#Unit 1. Molecules and their Interaction Relevant to Biology

In the α helix, the backbone hydrogen bonds are arranged such that the peptide CO bond of the nth residue points along the helix axis toward the peptide NH group of the (n + 4)th residue. 

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#Id: 8447

#Unit 1. Molecules and their Interaction Relevant to Biology

This results in a strong hydrogen bond that has the nearly optimum N…O distance of 2.8 A.

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#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.

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#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