Effect of chromophore encapsulation on linear and nonlinear optical properties: the case of “miniSOG”, a protein-encased flavin

Abstract

Linear and nonlinear spectroscopic parameters of flavin mononucleotide, FMN, have been examined both experimentally and computationally under conditions in which FMN is (1) solvated in a buffered aqueous solution, and (2) encased in a protein that is likewise solvated in a buffered aqueous solution. The latter was achieved using "miniSOG" which is an FMN-containing protein engineered from Arabidopsis thaliana phototropin 2. Although it is reasonable to expect that the encasing protein could have an appreciable effect, certainly on the nonlinear two-photon absorption cross section, we find that replacing the dynamic aqueous environment with the more static protein environment does little to influence the spectroscopic properties of FMN. The experimental and computational studies are consistent in this regard, and this agreement indicates that comparatively high-level computational methods can indeed be used with success on large chromophores with a complicated local environment. The results of the present study facilitate the much-needed development of well-characterized and readily-controlled chromophores suitable for use as intracellular sensitizers and fluorophores.

Spectroscopic Properties of Lumiflavin: A Quantum Chemical Study

“…In the previous section, we have shown that the first two bright states from ADC(2), CC2, and CAM‐B3LYP calculations involve π H → π * L and π H‐1 → π * L transitions, and their positions are found in qualitative agreement with the experimental peaks (Table ). However, the gas‐phase results are blueshifted with respect to the absorption peaks of lumiflavin measured in water and within the protein embedded system . Our recorded spectrum in chloroform is shown in Figure that is consistent to the previous experimental studies by Sikorski et al .…”

“…Also the long-range corrected functional CAM-B3LYP can give accurate description for state ordering among the low-lying excited states. This has been shown for double-zeta basis set by List et al (73) as well as triple-zeta basis set in Table 2. The fact that CAM-B3LYP is adjusting the energetic order indicates a partial charge transfer character of the S 4 state which is not correctly described using B3LYP.…”

“…This has been shown for double‐zeta basis set by List et al . as well as triple‐zeta basis set in Table . The fact that CAM‐B3LYP is adjusting the energetic order indicates a partial charge transfer character of the S 4 state which is not correctly described using B3LYP.…”

“…A comprehensive understanding of the electronic structure associated with the absorption peaks of the lumiflavin spectrum is the main target of numerous computational studies (21,22,(24)(25)(26)(70)(71)(72)(73). The nature of the excited states and their energetic order is also important for the study of the photochemical reaction initiated at the Frank-Condon point.…”

Molecular quantum mechanical gradients within the polarizable embedding approach—Application to the internal vibrational Stark shift of acetophenone

“…It has been successfully applied to model the environmental effects on both electric and magnetic molecular properties. 8,27,28 The aim of the present study is to broaden the scope of the PE model to vibrational properties of molecules embedded in large and complex environments. To this end, we have implemented molecular gradients with respect to nuclear displacements in the quantum region within the PE framework.…”