trans-cis Isomerism and acylimine formation in DsRed chromophore models: Intrinsic rotation barriers

We report barriers to internal rotation of the acylimine (peptide) linkage in simple models of mature (immature) forms of the red fluorescent protein DsRed. The results indicate a substantial barrier lowering following acylimine formation, providing prima facie evidence that bond rotation follows acylimine formation in DsRed chromophores.