Photophysics of phenylalanine analogues

Rzeska, Alicja; Malicka, Joanna; Stachowiak, Krystyna; Szymańska, Aneta; Łankiewicz, Leszek; Wiczk, Wiesław

doi:10.1016/s1010-6030(01)00394-x

Cited by 9 publications

(8 citation statements)

References 77 publications

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“…13,14 The rotamer model for tyrosine and tryptophan photophysics is now widely accepted, but the existence of rotamers in phenylalanine has hitherto lacked supporting evidence because of its apparent monoexponential decay in solution. 6,9,10 Our findings differ from these previous results and confirm that there is much more commonality between the photophysics of all three fluorescent aromatic amino acids than has hitherto been recognized. Our data suggest that there are at least two ground state rotamers of phenylalanine, which coexist on a time scale longer than their fluorescence decay times.…”

contrasting

confidence: 99%

“…Unlike the other two fluorescent amino acids tyrosine and tryptophan, previous studies on aqueous phenylalanine over a range of pH ͑including pH of 6 reported here͒ and in other homogeneous solvents, 6,9,10 seem only to have reported evidence for a monoexponential fluorescence decay. On reflection this is in some ways surprising given that the identical side-chain containing carboxyl and amino groups ͑Fig.…”

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confidence: 83%

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Excitation of fluorescence decay using a 265nm pulsed light-emitting diode: Evidence for aqueous phenylalanine rotamers

McGuinness

Macmillan

Sagoo

et al. 2006

Applied Physics Letters

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Selective excitation of tryptophan fluorescence decay in proteins using a subnanosecond 295 nm light-emitting diode and time-correlated single-photon counting Appl. Phys. Lett. 86, 261911 (2005); 10.1063/1.1984088 Ultraviolet light-emitting diodes operating in the 340 nm wavelength range and application to time-resolved fluorescence spectroscopy Blue light-emitting diode demonstrated as an ultraviolet excitation source for nanosecond phase-modulation fluorescence lifetime measurements Rev.

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confidence: 99%

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confidence: 83%

Excitation of fluorescence decay using a 265nm pulsed light-emitting diode: Evidence for aqueous phenylalanine rotamers

McGuinness

Macmillan

Sagoo

et al. 2006

Applied Physics Letters

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“…Shorter fluorescence decay time can give evidence of the protonation process of carboxylic groups or formation of aggregates, which induces faster fluorescence decay. 38,39 It is known that water molecules do absorb NIR wavelengths, 40 as well as -NH and -OH groups 1 existing in the structure of L-phe aqueous solutions. All groups are involved in the hydrogen bonding network in the interface of waterbiological system complexes.…”

Section: Resultsmentioning

confidence: 99%

Influence of Near-Infrared Radiation on the pK_a Values of L-Phenylalanine

2006

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The effect of pH on L-phenylalanine (L-phe) before and after exposure to near-infrared (NIR) radiation (15 min, 700-2000 nm) was investigated by attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy. Characteristic bands of L-phe were described and the pK(a) values were retrieved from IR spectra by using an intensity ratio method according to our recent paper (Olsztynska et al., Appl. Spectrosc. 55, 901 (2001)). It has been found that the irradiation process modifies pK(a) values of L-phe. The spectroscopic study clearly shows the shift of acid-base equilibrium after exposure to NIR radiation. The phenomenon is due to modification of the water structure. Intra- and intermolecular hydrogen bonds weaken, which could induce conformational changes of the phe molecule. Subsequently, hydrophobic interactions strongly increase. These processes favor aggregation of phe molecules, which leads to deprotonation of the -NH(3)(+) to -NH(2) group and protonation of the -COO(-) to -COOH group, changing the pK(a) values.

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“…The existence of nonradiative deactivations (NRD) in electronically excited proteins is of paramount importance for the stability of one of the major constituents of the living matter. − Progress toward understanding of these photochemical pathways is most readily made through studying small model peptides, as protein building blocks. ,− The multifaceted photochemistry of peptides is mainly due to the valence transitions involving three groups of chromophores: the aromatic side chains of phenylalanine, tryptophan, tyrosine, and histidine, as well as terminal amino and carboxyl groups and the peptide bonds. The latter have long been recognized as a possible source for phenomena like fluorescence quenching. ,,,− In this context, model peptides containing aromatic amino acids and having modified, protected termini, such as N -acetylphenylalaninylamide (NAPA) and N -acetyltryptophanylmethylamide (NATMA), are considered invaluable because they retain complete peptide bonds, which qualifies them as protein chain model species. ,,,− …”

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confidence: 99%

Unraveling the Mechanisms of Nonradiative Deactivation in Model Peptides Following Photoexcitation of a Phenylalanine Residue

et al. 2012

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The mechanisms of nonradiative deactivation of a phenylalanine residue after near-UV photoexcitation have been investigated in an isolated peptide chain model (N-acetylphenylalaninylamide, NAPA) both experimentally and theoretically. Lifetime measurements at the origin of the first ππ* state of jet-cooled NAPA molecules have shown that (i) among the three most stable conformers of the molecule, the folded conformer NAPA B is ∼50-times shorter lived than the extended major conformer NAPA A and (ii) this lifetime is virtually insensitive to deuteration at the NH(2) and NH sites. Concurrent time-dependent density functional theory (TDDFT) based nonadiabatic dynamics simulations in the full dimensionality, carried out for the NAPA B conformer, provided direct insights on novel classes of ultrafast deactivation mechanisms, proceeding through several conical intersections and leading in fine to the ground state. These mechanisms are found to be triggered either (i) by a stretch of the N(Phe)H bond, which leads to an H-transfer to the ring, or (ii) by specific backbone amide distortions. The potential energy surfaces of the NAPA conformers along these critical pathways have been characterized more accurately using the coupled cluster doubles (CC2) method and shown to exhibit barriers that can be overcome with moderate excess energies. These results analyzed in the light of the experimental findings enabled us to assign the short lifetime of NAPA B conformer to a number of easily accessible exit channels from the initial ππ* surface, most importantly the one involving a transfer of electronic excitation to an nπ* surface, induced by distortions of the backbone peptide bond.

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Photophysics of phenylalanine analogues

Cited by 9 publications

References 77 publications

Excitation of fluorescence decay using a 265nm pulsed light-emitting diode: Evidence for aqueous phenylalanine rotamers

Excitation of fluorescence decay using a 265nm pulsed light-emitting diode: Evidence for aqueous phenylalanine rotamers

Influence of Near-Infrared Radiation on the pK_a Values of L-Phenylalanine

Unraveling the Mechanisms of Nonradiative Deactivation in Model Peptides Following Photoexcitation of a Phenylalanine Residue

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Photophysics of phenylalanine analogues

Cited by 9 publications

References 77 publications

Excitation of fluorescence decay using a 265nm pulsed light-emitting diode: Evidence for aqueous phenylalanine rotamers

Excitation of fluorescence decay using a 265nm pulsed light-emitting diode: Evidence for aqueous phenylalanine rotamers

Influence of Near-Infrared Radiation on the pKa Values of L-Phenylalanine

Unraveling the Mechanisms of Nonradiative Deactivation in Model Peptides Following Photoexcitation of a Phenylalanine Residue

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Influence of Near-Infrared Radiation on the pK_a Values of L-Phenylalanine