Enzymichromism: Determination of the dielectric properties of an enzyme active site

Solvatochromism in a Pyridinium Cyclopentadienylide: Insights from a Sequential Car–Parrinello QM/MM and TD-DFT/Semicontinuum Approach

“…As can be seen, the N-point average appears to converge beyond 30 configurations. Overall, the experimentally reported negative solvatochromic shift has been reproduced in excellent agreement with experiments . Interestingly, the solvents involved in microsolvation of the CO group yield a red shift in the spectra while the inclusion of all solvent molecules up to the second solvation shell brings the correct sign for the solvatochromic shift.…”

“…The second intense band appearing in the UV region also shows a decrease in intensity and displays a small red shift. Overall, the absolute value of λ max for CPYC in benzene and water solvents are underestimated approximately by 34 and 49 nm when compared to experimental values . However, the computed solvatochromic shift (which is 59 nm) for CPYC from benzene to water solvent is in good agreement with experiment, i.e., 44 nm.…”

“…The atomic charges used for this analysis are of the D-RESP type and are obtained from best fitting to the molecular electrostatic potential. As has been proposed, the positive charge is accumulated on the pyridinium ring and the negative charge is accumulated on the cyclopentadiene group. There is also a small negative charge on the amide group.…”

“…Refer to Figure to see the molecular structure of CPYC. This molecule has been reported to be a probe for studying the dielectric nature of enzyme active sites . As we have mentioned the molecular size of CPYC is comparably smaller than other optical probes and so appears to be a promising probes to study such small active sites in enzymes.…”

“…As we have mentioned the molecular size of CPYC is comparably smaller than other optical probes and so appears to be a promising probes to study such small active sites in enzymes. There are experimental reports on the absorption spectra of CPYC in different solvents. , In a nonpolar solvent like benzene, the CPYC has an absorption maximum at 562 nm and it blue shifts to 518 nm in water solvent. Interestingly, going from water solvent to the binding site of horse-liver alcohol dehydrogenase protein, the absorption maximum shifts to 597 nm which reveals the hydrophobic nature of the active site .…”