Figure 5.

The 9,11-bridged retinal acts to rescue the long-lived O intermediate in the double mutant Leu-93 → Ala, Asp-96 → Asn independent of the lifetime of the M intermediate. (A) Transient changes in absorbance with native retinal showing the presence of long-lived M (measured at 405 nm) and O (measured at 605 nm) intermediates. The increased lifetime of the M intermediate is due to the Asp-96 → Asn mutation. (Inset) The addition of ≈4 mM sodium azide accelerates the decay of the M intermediate and the rise of the O intermediate, but not the decay of the O intermediate. (B) Same as in A except native retinal was replaced by the 9,11-bridged retinal and sodium azide (≈4 mM) was added.