Figure 7.

Light-induced FTIR absorption difference spectrum of JSiR1. The top spectrum in red reflects the vibrational changes that take place upon illumination by an LED emitting at 470 nm of Iso (negative bands) to a Meta-Rho mixture (positive bands). The frequencies of some of the difference bands are indicated and discussed in the text. The absence of pronounced bands in the carboxylic region above 1700 cm⁻¹ is in contrast to the photoactivation of bovine rhodopsin (bottom spectrum) in which strong carboxylic bands arise. Formation of Meta II is accompanied by strong carboxylic bands as a consequence of the deprotonation of the Schiff base.