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TLS Online TPP Program

#Id: 7859


#Unit 1. Structure and Function of Biomolecules #OPTICAL Properties of Monosaccharides #Part B Pointers
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TLS Online TPP Program

#Id: 8444

#Unit 1. Structure and Function of Biomolecules

Both the pi helix and the 310 helix occur rarely and usually only at the ends of a helices or as single-tum helices. They are not energetically favorable, since the backbone atoms are too tightly packed in the 310 helix and so loosely packed in the n helix that there is a hole through the middle. 
Only in the a helix are the backbone atoms properly packed to provide a stable structure.
TLS Online TPP Program

#Id: 8445

#Unit 1. Structure and Function of Biomolecules

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

#Id: 8446

#Unit 1. Structure and Function of Biomolecules

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. 
TLS Online TPP Program

#Id: 8447

#Unit 1. Structure and Function of Biomolecules

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

#Id: 8448

#Unit 1. Structure and Function of Biomolecules

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. Structure and Function of Biomolecules

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