Photophysics of phenylalanine analogues

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

doi:10.1016/s1010-6030(00)00229-x

Cited by 10 publications

(10 citation statements)

References 39 publications

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“…This value of 6.97 ns is characteristic for the monomeric form of phe. 37 After NIR radiation, the second decay time (s 2 ¼ 2.61 ns) appears in water solution of phe. Shorter fluorescence decay time can give evidence of the protonation process of carboxylic groups or formation of aggregates, which induces faster fluorescence decay.…”

Section: Resultsmentioning

confidence: 99%

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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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Section: Resultsmentioning

confidence: 99%

“…On the other hand, the aggregation process induced by modifications of the water structures involves changes of pK a values. 37,48 As a final consequence of this process, the pK a values of L-phe are shifted.…”

Section: Resultsmentioning

confidence: 99%

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

2006

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“…Our analysis of the excited-state dynamics of the Phe/Ser protonated dimer is supported by the known photochemistry of Phe and Phe analogs in solution and in the gas phase. In neutral and acidic aqueous solution at room temperature, Phe has a fluorescence lifetime of ∼5–7 ns , and undergoes ISC with a quantum yield of 0.4 to the T 1 state, which has a lifetime of ∼2–3 μs . The T 1 state was identified as the precursor for the dissociation of the C α -C β bond under formation of a benzyl radical, the same neutral fragment that accompanies the m / z 180 photofragment ion of the protonated Phe/Ser dimer.…”

Section: Resultsmentioning

confidence: 99%

Structural Melting of an Amino Acid Dimer upon Intersystem Crossing

Lorenz

Rizzo

2014

J. Am. Chem. Soc.

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We present a spectroscopic investigation of the excited-state dynamics of the phenylalanine (Phe)/serine (Ser) protonated dimer in the gas phase. Using an ultraviolet (UV) laser pulse, we promote individual isomers to the S1 state and probe their fate with an infrared (IR) pulse. We find that the S1 state has a lifetime of ~70 ns and undergoes intersystem crossing (ISC) to the T1 state. Time-resolved IR spectra allow us to follow the structural evolution of the dimer. In the S1 state, the different isomers retain the hydrogen-bonding pattern of the ground state. Intersystem crossing triggers a sudden increase of the vibrational energy, so that the dimers can overcome isomerization barriers and explore large parts of the potential energy surface (PES). Their broad IR spectra largely resemble one another and indicate that the dimers adopt a molten structure.

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“…3-C-B Neutral phenylalanine. Although UV absorption and uorescence spectra of phenylalanine and its derivatives have been studied by Wiczk's group, 63 to our knowledge, there is no extensive theoretical report on the relaxation dynamics and deactivation pathways of this molecule. Nevertheless, the long lifetime of the S 1 excited phenylalanine (nanosecond range), reported by Lee et al, 30 indicates a stable S 1 character of isolated Phe.…”

Section: -C Photophysical Behavior: Potential Energy Prolesmentioning

confidence: 99%