UNASSIGNED: The effects of the solvent and protonation state on the electronic absorption spectrum of the @entity25371 ( @entity4901 ), a model of the photoactive yellow protein (PYP), have been studied using the ASEP/ @entity601 (averaged solvent electrostatic potential from molecular dynamics) method. Even though, in the protein, the chromophore is assumed to be in its @entity52998 monoanionic form, when it is found in water solution pH control can favor neutral, monoanionic, and dianionic species. As the @entity4901 has two hydrogens susceptible of deprotonation, both @entity3338 and @entity52998 monoanions are possible. Their relative stabilities are strongly dependent on the medium. In gas phase, the most stable isomer is the @entity52998 while in aqueous solution it is the @entity3338 , although the population of the @entity52998 form is not negligible. The s-cis, s-trans, @entity15735 , and anti conformers have also been included in the study. Electronic excited states of the chromophore have been characterized by SA-CAS(14,12)-PT2/cc-pVDZ level of theory. The bright state corresponds, in all the cases, to a     >    * transition involving a charge displacement in the system. The magnitude and direction of this displacement depends on the protonation state and on the environment (gas phase or solution). In the same way, the calculated solvatochromic shift of the absorption maximum depends on the studied form, being a red shift for the neutral, @entity3338 monoanion, and dianionic chromophores and a blue shift for the @entity52998 monoanion. Finally, the contribution that the solvent electronic polarizability has on the solvent shift was analyzed. It represents a very important part of the total solvent shift in the neutral form, but its contribution is completly negligible in the mono- and dianionic forms.

Solvent Effects on the Absorption Spectra of the XXXX Chromophore in Its Different Protonation Forms.

@entity15735 :: ('23336', 'Gene') :: ['syn'] @entity52998 :: ('CHEBI:50526', 'Chemical') :: ['phenolate'] @entity601 :: ('MESH:D009436', 'Disease') :: ['MD'] @entity4901 :: ('CHEBI:36751', 'Chemical') :: ['pCA'] @entity25371 :: ('MESH:C032171', 'Chemical') :: ['para-coumaric acid'] @entity3338 :: ('CHEBI:35757', 'Chemical') :: ['carboxylate']
@entity25371 :: (MESH:C032171,Chemical) :: ['para-Coumaric Acid']
