We present the spectrum of the S 1 ← S 0 transition of an anionic model for the chromophore of the green fluorescent protein in vacuo at cryogenic temperatures, showing previously unresolved vibrational features, and resolving the band origin at 20 930 cm −1 (477.8 nm) with unprecedented accuracy. The vibrational spectrum establishes that the molecule is in the Z isomer at low temperature. At increased temperature, the S 1 ← S 0 band shifts to the red, which we tentatively attribute to emergent population of the E isomer.
The interactions between molecular hosts and ionic guests and how the chemical environment in aqueous solutions changes these interactions are challenging to disentangle from solution data alone. The vibrational spectra of cold complexes of ethylenediaminetetraacetic acid (EDTA) chelating alkaline earth dications in vacuo encode structural characteristics of these complexes and their dependence on the size of the bound ion. The correlation between metal binding geometry and the relative intensities of vibrational bands of the carboxylate groups forming the binding pocket allows us to characterize changes in molecular geometry by interaction with other molecules. The evolution of these structural markers from bare ions to water adducts to aqueous solution illustrates the role of water for the structure of ion binding sites in chelators. The results show that the binding pocket of EDTA opens up in aqueous solution, bringing the bound ion closer to the mouth of the binding site, and leading to an increased exposure of the bound ion to the chemical environment.
We present electronic spectra containing the Qx and Qy absorption bands of singly and doubly deprotonated protoporphyrin IX, prepared as mass selected ions in vacuo at cryogenic temperatures, revealing vibronic...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.