Theoretical studies of the excited states of p-cyanophenylalanine and comparisons with the natural amino acids phenylalanine and tyrosine

Meloni, Stephen L.; Matsika, Spiridoula

doi:10.1007/s00214-014-1497-2

Cited by 4 publications

(7 citation statements)

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“…Both of these absorption bands are attributed to p* ' p transitions of the benzonitrile chromophore 34,51 and the l abs max of the S 1 ' S 0 transition is in strong agreement with theory. 37 At 280 nm, the molar absorptivities, e, of aqueous 2-Phe CN , 3-Phe CN , and 4-Phe CN were determined to be 1180 AE 20 M À1 cm À1 , 800 AE 200 M À1 cm À1 and 750 AE 50 M À1 cm À1 , respectively; see Table 1. The value of e at 280 nm determined for 4-Phe CN is in reasonable agreement with the previously reported value 18 (850 AE 50 M À1 cm À1 ).…”

Section: Absorbance Properties Of 2-phe Cn and 3-phe Cnmentioning

confidence: 99%

“…First, both the molar absorptivity (e) and fluorescence quantum yield (F F ) of the Phe CN species are roughly 4 times larger than those of Phe (e = 200 M À1 cm À1 at 260 nm and F F = 0.024) 35,36 due to mixing of the np* state (located on the amino group) and the pp* state wavefunctions upon addition of the nitrile group to the phenyl ring. 37 Consequently, the photophysical properties of the Phe CN species are quite similar to tryptophan, a commonly used probe for peptides. Equally, Phe CN is theoretically tractable 37,38 and a multi-spectroscopic probe, displaying utility in fluorescence, 31,39 UV-Vis absorption, 18 infrared, 40,41 2D-infrared, 42,43 raman, 44 and NMR 45,46 studies, thus allowing for correlation between spectroscopic techniques.…”

Section: Introductionmentioning

confidence: 99%

“…37 Consequently, the photophysical properties of the Phe CN species are quite similar to tryptophan, a commonly used probe for peptides. Equally, Phe CN is theoretically tractable 37,38 and a multi-spectroscopic probe, displaying utility in fluorescence, 31,39 UV-Vis absorption, 18 infrared, 40,41 2D-infrared, 42,43 raman, 44 and NMR 45,46 studies, thus allowing for correlation between spectroscopic techniques. Phe CN is also easily incorporated into peptides or proteins using common synthesis methods, including the Fmoc protocol in solid phase peptide synthesis, 24 through genome modification, 41 or by protein ligation methods.…”

Section: Introductionmentioning

confidence: 99%

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Comparison of biological chromophores: photophysical properties of cyanophenylalanine derivatives

Martin

Fetto

Tucker

2016

Phys. Chem. Chem. Phys.

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Within this work, the family of cyanophenylalanine spectroscopic reporters is extended by showing the ortho and meta derivatives have intrinsic photophysical properties that are useful for studies of protein structure and dynamics. The molar absorptivities of 2-cyanophenylalanine and 3-cyanophenylalanine are shown to be comparable to that of 4-cyanophenylalanine with similar spectral features in their absorbance and emission profiles, demonstrating that these probes can be utilized interchangeably. The fluorescence quantum yields are also on the same scale as commonly used fluorophores in peptides and proteins, tyrosine and tryptophan. These new cyano-fluorophores can be paired with either 4-cyanophenylalanine or tryptophan to capture distances in peptide structure through Förster resonance energy transfer. Additionally, the spectroscopic properties of these chromophores can report the local solvent environment via changes in fluorescence emission intensity as a result of hydrogen bonding and/or hydration. A decrease in the quantum yield is also observed in basic environments due to photoinduced electron transfer from a deprotonated amine in the free PheCN species and at the N-terminus of a short peptide, providing an avenue to detect pH in biological systems. Our results show the potential of these probes, 2-cyanophenylalanine and 3-cyanophenylalanine, to be incorporated into a single peptide chain, either individually or in tandem with 4-cyanophenylalanine, tryptophan, or tyrosine, in order to obtain information about peptide structure and dynamics.

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Section: Absorbance Properties Of 2-phe Cn and 3-phe Cnmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Comparison of biological chromophores: photophysical properties of cyanophenylalanine derivatives

Martin

Fetto

Tucker

2016

Phys. Chem. Chem. Phys.

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“…Selective fluorophore excitation is possible due to differences in preferred electronic transitions of the two chromophores. Previous studies have suggested that Phe 4CN favors the S 2 ← S 0 transition, which is centered around ∼230 nm in the absorption spectrum, while Phe 2CN favors the S 1 ← S 0 transition, which is centered around ∼280 nm . These transitions are favored due to the relative orientation between the transition dipole moment and the permanent dipole moment, μ p .…”

Section: Introductionmentioning

confidence: 95%

Selective Excitation of Cyanophenylalanine Fluorophores for Multi-Site Binding Studies

et al. 2017

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Recently, it has been shown that nitrile-derivatized phenylalanines possess distinct fluorescent properties depending on the position of the cyano-group within the aromatic ring. These fluorophores have potential as probes for studying protein dynamics due to their sensitivity to local environment. Herein, we demonstrate that 2-cyanophenylalanine (Phe) and Phe can independently monitor multiple sites during the Ca dependent binding of a skeletal muscle myosin light chain kinase (MLCK) peptide fragment to the protein calmodulin (CaM). These cyano-probes were incorporated at two different positions along the peptide chain and monitored simultaneously via selective excitation of the two chromophores. The peptide was labeled with Phe at a residue known to bind to a hydrophobic binding pocket of CaM, while Phe was designed to acquire dynamics external to the binding pocket. By selectively exciting each of the chromophores, it was determined that the fluorescence emission of Phe located at position 581 of MLCK was quenched in the presence of CaM, while no significant change in Phe emission was observed at exposed position 594. The CaM binding affinity (K) of the double labeled MLCK peptide was calculated to be approximately 64 nM, which is in agreement with previous measurements. These results indicate that multiple Phe reporters within the same peptide can simultaneously detect variations in the local environment, and that these fluorophores could be utilized to investigate a wide variety of biological problems.

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“…The broad spectroscopic utility of this unnatural amino acid, which is a structural derivative of tyrosine (Tyr) or phenylalanine (Phe) [2], stems from the fact that its fluorescence quantum yield and lifetime are sensitive to environment [3], as well as its easy incorporation into peptides and proteins [4]. For example, dehydration leads to a significant decrease in the fluorescence intensity of Phe CN , thus making it a useful probe of processes that involve exclusion of water, such as protein folding [5,6], binding [7,8], aggregation [9–11], and interaction with membranes [12–15].…”

Section: Introductionmentioning

confidence: 99%

Sensing pH via p-cyanophenylalanine fluorescence: Application to determine peptide pKa and membrane penetration kinetics

Pazos

Ahmed

Berríos

et al. 2015

Analytical Biochemistry

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We expand the spectroscopic utility of a well-known infrared and fluorescence probe, p-cyanophenylalanine, by showing that it can also serve as a pH sensor. This new application is based on the notion that the fluorescence quantum yield of this unnatural amino acid, when placed at or near the N-terminal end of a polypeptide, depends on the protonation status of the N-terminal amino group of the peptide. Using this pH sensor, we are able to determine the N-terminal pKa values of nine tripeptides and also the membrane penetration kinetics of a cell-penetrating peptide. Taken together, these examples demonstrate the applicability of using this unnatural amino acid fluorophore to study pH-dependent biological processes or events that accompany a pH change.

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Theoretical studies of the excited states of p-cyanophenylalanine and comparisons with the natural amino acids phenylalanine and tyrosine

Cited by 4 publications

References 45 publications

Comparison of biological chromophores: photophysical properties of cyanophenylalanine derivatives

Comparison of biological chromophores: photophysical properties of cyanophenylalanine derivatives

Selective Excitation of Cyanophenylalanine Fluorophores for Multi-Site Binding Studies

Sensing pH via p-cyanophenylalanine fluorescence: Application to determine peptide pKa and membrane penetration kinetics

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