Alpha Helices

Alpha Helices

1. Structure:

   • 1. Structure Repeats every 5.4 Angstroms
     • 2. Hydrogen bonds stabilize the structure every 4 amino acids
       • 3. Every turn Contains 3.6 amino acids
         • Right handed corkscrew

2. Polarity Considerations

   • Net positive charge at the amino end, as no hydrogen bonds available for stabilization
     • Therefore, Negative aa are preferred on the amino end...
   • Net Negative charge at carboxyl end as no hydrogen bonding available to stabilize chargfe
     • ...and positive amino acids are preferred on the carboxyl end

3. Glycine is too flexible for amino acids

4. Proline, because of inability to hydrogren bond (due to proline being cyclized) will introduce a kink in the alpha helix "helix breaker"

5. Alanine, smallest amino acid (exception of glycine), is the most common aa in alpha helices

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