Photoinduced decarboxylation in fluorescent proteins: charge-transfer states and structure-function relationship

Area of Science:

• Biophysics
• Computational Chemistry
• Protein Science

Background:

• Photoinduced decarboxylation of acidic amino acids near the chromophore is a known phenomenon in fluorescent proteins.
• The exact mechanism and its generalizability across diverse fluorescent protein variants, especially red fluorescent proteins, are not fully understood.

Purpose of the Study:

• To investigate the photoinduced decarboxylation mechanism in various fluorescent proteins, focusing on red variants like DsRed and PSLSSmKate.
• To establish a structure-function relationship for this process across different fluorescent protein scaffolds.
• To benchmark computational methods for studying excited-state properties in fluorescent proteins.

Main Methods:

• Utilized excited-state Quantum Mechanics/Molecular Mechanics (QM/MM) calculations.
• Employed time-dependent density functional theory (TD-DFT), coupled cluster (CC2), and approximate coupled-cluster singles and doubles (ADC(2)) methods.
• Performed a benchmark study of various excited-state methods, basis sets, and embedding approaches.

Main Results:

• Provided new insights into the photoinduced decarboxylation mechanism in fluorescent proteins.
• Demonstrated the applicability of QM/MM calculations for studying excited-state processes in these systems.
• Highlighted potential differences and similarities in the mechanism across various fluorescent protein families.

Conclusions:

• The study elucidates the photoinduced decarboxylation mechanism in diverse fluorescent proteins, including red variants.
• Findings contribute to the understanding of protein photophysics.
• The research may guide the rational design of novel fluorescent probes with tailored properties.