Helicity propensity and interaction of synthetic peptides from heptad-repeat domains of herpes simplex virus 1 glycoprotein H: a circular dichroism study

The secondary structure of two synthetic peptides from heptad-repeat domains of herpes simplex virus 1 glycoprotein H was determined by circular dichroism. In particular, the propensity of these peptides to assume an ordered structure was investigated upon by changing the solvent's polarity and the temperature. A reduction of solvent polarity led to a significant increase in the alpha-helix content in the case of HR1, whereas only a slight change in the secondary structure was observed in the case of HR2. In both cases the conformational change followed a two-state transition model. The interaction of the peptides was monitored by the conformational change in the mixture with respect to the single peptides. However, formation of the complex did not significantly enhance thermal stability. A reliable estimation of the secondary structure was obtained by optimising the experimental conditions to collect CD data down to 180 nm, and by comparing the structure data yielded by different software packages.