Figure 2.

Difference absorption spectra of the PHYB adducts with PCB, PΦB, and analogs having side-chain substituents in the A-ring (analogs 1–4; see Table 1). The difference spectra were obtained by subtracting the absorption spectra determined after far-red light irradiation from that measured after red light irradiation. The sample volumes were 800 μl. Difference spectra were recorded after two consecutive red/far-red cycles. Black and gray dotted lines indicate the difference spectra obtained after the first and second cycles, respectively. The vertical bars represent 0.002 absorbance difference units.