Sequential oligopeptides carrying naphthalene and protoporphyrin IX as fluorophores, covalently bound to α-amino groups of lysine residues, were investigated in methanol and water/methanol 75/25 (v/v) solutions by steady-state fluorescence, transient absorption spectra and time resolved emission measurements. Quenching of excited naphthalene chiefly takes place by transfer of excitation energy, 1N∗→P, and proceeds on a time scale of 3–8 ns (25 °C), depending on the helical periodicity of the backbone chain. According to earlier IR and CD spectral results, the oligopeptides investigated attain an α-helix conformation, which is responsible for the periodic variation of the interprobe distances. A slower ( ≈45 ns) and minor fluorescence decay was also measured, which is ascribed to exciplex emission. This finding differs from that earlier obtained with the same chromophores bound to α-helical poly(l-lysine) in water, where quenching of naphthalene was mainly due to electron transfer from ground-state porphyrin, P → 1N∗ Molecular mechanics calculations show a different topology of N and P molecules bound to the α-helix in the two systems, which is thought to be primarily responsible for the observed transition between photoinduced electron transfer and energy transfer.
Pispisa, B., Venanzi, M., Palleschi, A., Zanotti, G. (1997). Intramolecular transfer of excitationenergy in short linear peptides carrying naphthalene and protoporphyrin molecules. A molecular model of electron transfer/energy transfer transition. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY. A, CHEMISTRY, 105(2-3), 225-233 [10.1016/S1010-6030(96)04494-2].
Intramolecular transfer of excitationenergy in short linear peptides carrying naphthalene and protoporphyrin molecules. A molecular model of electron transfer/energy transfer transition
PISPISA, BASILIO;VENANZI, MARIANO;PALLESCHI, ANTONIO;
1997-01-01
Abstract
Sequential oligopeptides carrying naphthalene and protoporphyrin IX as fluorophores, covalently bound to α-amino groups of lysine residues, were investigated in methanol and water/methanol 75/25 (v/v) solutions by steady-state fluorescence, transient absorption spectra and time resolved emission measurements. Quenching of excited naphthalene chiefly takes place by transfer of excitation energy, 1N∗→P, and proceeds on a time scale of 3–8 ns (25 °C), depending on the helical periodicity of the backbone chain. According to earlier IR and CD spectral results, the oligopeptides investigated attain an α-helix conformation, which is responsible for the periodic variation of the interprobe distances. A slower ( ≈45 ns) and minor fluorescence decay was also measured, which is ascribed to exciplex emission. This finding differs from that earlier obtained with the same chromophores bound to α-helical poly(l-lysine) in water, where quenching of naphthalene was mainly due to electron transfer from ground-state porphyrin, P → 1N∗ Molecular mechanics calculations show a different topology of N and P molecules bound to the α-helix in the two systems, which is thought to be primarily responsible for the observed transition between photoinduced electron transfer and energy transfer.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.