When the RNA polymerase reaches the termination site, rho first freezes the structure of the polymerase and then invades the exit channel to destabilize the enzyme, causing it to release the RNA.

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polylysine is a random coil at pH values below about 11, where repulsion of positive charges prevents helix formation. At pH 12, where polylysine is a neutral peptide chain, it readily forms an a-helix.

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polyGlu is a random coil at pH values above about 5, where repulsion of negative charges prevents helix formation. 

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#Unit 1. Molecules and their Interaction Relevant to Biology

The RHH (L amino acids) α helix, which ideally has ϕ = −57° and ψ = −47°

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The two forms of poly(Pro)

all cis (I) or all trans (II) peptide bonds. 

poly(Pro) I as a right-handed helix with 3.3 residues per turn 

poly(Pro) II is a left-handed helix with 3 residues per turn.

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poly(Pro) helix are stabilized by water molecule hydrogen bonding

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Poly(Gly) chains also adopt secondary conformations. 

In the solid state poly(Gly) has been shown to adopt two regular conformations designated I and II. 

State I has an extended conformation like a β strand whilst state II has three resides per turn and is similar to poly(Pro).