Structural changes accompanying chloroform-induced contraction of the filamentous phage fd

Contact with a chloroform/water interface at 2 o C induces contraction of fd filamentous phage into rodlike I-forms; this contraction is accompanied by a decrease in the magnitude of circular dichroism spectral intensity near 222 nm and an increase near 210 nm. Comparisons with circular dichroism spectra of 100% helical poly-L-lysine and N-bromosuccinimide-oxidized fd phage indicate that the spectral change accompanying the fd to I-forms transition is due primarily to a change in the contributions from the single tryptophan (W26) of the major coat protein, with probably no significant change in the α-helix content