218799-33-8Relevant academic research and scientific papers
Long-lived charge-separated species observed on flash photolysis of peptide conjugates. Interplay of local and radical ion pair triplet states
Jones II, Guilford,Lu, Lily N.
, p. 8938 - 8945 (1998)
Peptides composed of alanine (Ala) and tryptophan (Trp), modified with the (nitro)pyrenesulfonyl chromophore (Pyr and NPyr) at the N-terminus have been examined by nanosecond laser flash photolysis. A common phototransient for Pyr-AlaOEt and Pyr-Ala-TrpOEt was observed that exhibited broad absorption at 410-550 nm and decay time constants in the range, τ(1/2) = 20- 40 μs. This species was assigned to the triplet excited state that is local to the pyrene chromophore (3Pyr). For the conjugates having a stronger electron acceptor group at the N-terminus, NPyrAla-TrpOEt and NPyr-Ala-Ala- TrpOEt, the local triplet was replaced with a phototransient whose principal feature is a sharp band at 440 nm (assigned to the NPyr-. radical anion). The radical ion transients for the NPyr peptide derivatives were assigned to intermediates that result from the intramolecular electron transfer quenching of NP excited species by pendant groups (i.e., the indole ring of tryptophan). The lifetimes observed for the radical ion transients associated with the NPyr series were relatively long (extending to ca. 400 ns) and depended in an interesting way on the structure of the peptide linkage. A mechanism of electron transfer in the singlet manifold and recombination yielding a local Pyr triplet state is important for the Pyr series.
