Helix-coil transition of poly-gamma-N-carbobenzoxy-L-alpha, gamma-diaminobutyrate and poly-delta-N-carbobenzoxy-L-ornithine |
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Authors: | F Gaskin J T Yang |
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Abstract: | The helix–coil transition of poly-γ-N-carbobenzoxy-L -α,γ-diaminobutyrate (PCLB) and poly-δ-N-carbobenzoxy-L -ornithine (PCLO) in chloroform–dichloroacetic acid mixtures was followed by optical rotatory dispersion. PCLB displays a “normal” temperature-induced transition, but PCLO an “inverse” one. The thermodynamic parameters for helix formation of the two polymers were determined using the Zimm-Bragg theory. The enthalpy for adding an amide residue to a helical region, ΔH, and the initiation factor σ were ΔH = ?180 cal/mole and σ = 9.2 × 10?5 for PCLB and ΔH = +490 cal/mole and σ = 1.9 × 10?5 for PCLO. |
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