where S and s denote the 'solute'-the emitter, and the 'solvent,' respectively. The "solvent" which involves in our case the protein and its internal and surrounding water molecules. The π-electron contribution to the emitter's N th excited state is represented by 𝑉 𝜋 𝑁 , while 𝑉 𝜎 is the σ-electron contribution to the chromophore surface. 𝑉 Ss is the potential that couples the protein (solvent) and the chromophore and Vss is the protein force field of the protein and solvent system. The surfaces 𝑉 𝜋 and 𝑉 𝜎 are derived using the QCFF/PI method, which employs the Zero Differential Overlap (ZDO) approximation. This approximation sets 𝜑 𝑎 * (1) 𝜑 𝑏 (1) to zero for 𝑎 ≠ 𝑏 under the Pariser-Parr-Pople approximation. This method assumes a separation between σ and π electrons in 𝑉 𝜋 𝑁 , while 𝑉 𝜎 is represented by an empirical force field. This approach makes the computational process more practical, facilitating the modeling of conjugated heteroatomic molecules in both ground and excited π to π* states by theoretically disentangling σ and π electrons. The QCFF/PI method is well documented and widely available. It has been used extensively in studies of retinal and related systems and is more efficient than QM/MM approaches. In the current study, all coelenteramide atoms are included within the QM region. The QM treatment involves a configuration interaction treatment of all the single excitations for the three highest occupied and the three lowest unoccupied orbitals. The full parameters for our systems used are those from our earlier study. The coupling potential between the solute and solvent, denoted as 𝑉 Ss is derived using the method presented in detail in our prior studies. This integration involves including the electrostatic potential from the solvent (or protein) into the solute Hamiltonian, as explained in ref , using,