ac5023666_si_001.pdf (706.67 kB)
Flavin Adenine Dinucleotide Structural Motifs: From Solution to Gas Phase
journal contribution
posted on 2015-12-17, 05:20 authored by Juan Camilo Molano-Arevalo, Diana R. Hernandez, Walter G. Gonzalez, Jaroslava Miksovska, Mark E. Ridgeway, Melvin A. Park, Francisco Fernandez-LimaFlavin
adenine dinucleotide (FAD) is involved in important metabolic
reactions where the biological function is intrinsically related to
changes in conformation. In the present work, FAD conformational changes
were studied in solution and in gas phase by measuring the fluorescence
decay time and ion-neutral collision cross sections (CCS, in a trapped
ion mobility spectrometer, TIMS) as a function of the solvent conditions
(i.e., organic content) and gas-phase collisional partner (i.e., N2 doped with organic molecules). Changes in the fluorescence
decay suggest that FAD can exist in four conformations in solution,
where the abundance of the extended conformations increases with the
organic content. TIMS-MS experiments showed that FAD can exist in
the gas phase as deprotonated (M = C27H31N9O15P2) and protonated forms (M = C27H33N9O15P2) and
that multiple conformations (up to 12) can be observed as a function
of the starting solution for the [M + H]+ and [M + Na]+molecular ions. In addition, changes in the relative abundances
of the gas-phase structures were observed from a “stack”
to a “close” conformation when organic molecules were
introduced in the TIMS cell as collision partners. Candidate structures
optimized at the DFT/B3LYP/6-31G(d,p) were proposed for each IMS band,
and results showed that the most abundant IMS band corresponds to
the most stable candidate structure. Solution and gas-phase experiments
suggest that the driving force that stabilizes the different conformations
is based on the interaction of the adenine and isoalloxazine rings
that can be tailored by the “solvation” effect created
with the organic molecules.