The R2PI Spectroscopy of Tyrosine: A Vibronic Analysis

Grace, Louis; Cohen, Rami; Dunn, Thomas M.; Lubman, David M.; Vries, Mattanjah S. de

doi:10.1006/jmsp.2002.8639

Cited by 103 publications

(79 citation statements)

References 26 publications

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“…[23] As the "catalytic" pathway does not occur in the Y193F variant it suggests that the Ty rresidue is involved in formation of the "reactive" excited-state species.T aken together,i ti s likely that excited-state H-bonding interactions between the OH group of the Ty rr esidue and the carbonyl at the C17 position have an electron-withdrawing effect on the neighboring C17-C18 double bond to create an electron-deficient site (see the reaction scheme in Figure 3). Although vibrational modes associated with the OH group of Ty rare known to be observed at about 1250 cm À1 [25] these are beyond the spectral limits of our measurements for direct detection. However,r emoval of the OH group in the Y193F variant prevents the excited-state H-bonding interactions that create the decrease in local electron density at C17-C18, leading to catalytic inefficiency.…”

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confidence: 77%

Excited‐State Charge Separation in the Photochemical Mechanism of the Light‐Driven Enzyme Protochlorophyllide Oxidoreductase

et al. 2014

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The unique light-driven enzyme protochlorophyllide oxidoreductase (POR) is an important model system for understanding how light energy can be harnessed to power enzyme reactions.T he ultrafast photochemical processes, essential for capturing the excitation energy to drive the subsequent hydride-and proton-transfer chemistry,h ave so far proven difficult to detect. We have used ac ombination of time-resolved visible and IR spectroscopy, providing complete temporal resolution over the picosecond-microsecond time range,t op ropose an ew mechanism for the photochemistry. Excited-state interactions between active site residues and acarboxyl group on the Pchlide molecule result in apolarized and highly reactive double bond. This so-called "reactive" intramolecular charge-transfer state creates an electron-deficient site across the double bond to trigger the subsequent nucleophilic attacko fN ADPH, by the negatively charged hydride from nicotinamide adenine dinucleotide phosphate. This work provides the crucial, missing link between excitedstate processes and chemistry in POR. Moreover,i tp rovides important insight into how light energy can be harnessed to drive enzyme catalysis with implications for the design of lightactivated chemical and biological catalysts.

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confidence: 77%

Excited‐State Charge Separation in the Photochemical Mechanism of the Light‐Driven Enzyme Protochlorophyllide Oxidoreductase

et al. 2014

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“…Natural amino acids bearing a chromophoric group in their structure, namely, tyrosine, tryptophan, and phenylalanine, have been widely studied in the gas phase with various techniques which combine electronic and vibrational spectroscopy with supersonic expansions. [14][15][16][17][18][19] However, for none of them has been repotrted a rotationally resolved investigation capable of providing structural information on the various conformers. Hence, this study is the first gas-phase investigation of the unnatural a-amino acid PG, the simplest one bearing a chromophoric group.…”

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confidence: 99%

The Conformers of Phenylglycine

Sanz

Cortijo

Camináti

et al. 2006

Chemistry A European J

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The neutral form of the unnatural amino acid phenylglycine was vaporized by laser ablation, and the presence of two conformers was detected in a supersonic expansion by Fourier transform microwave spectroscopy. Both conformers were unequivocally identified by comparison of their experimental rotational and quadrupole coupling constants with those calculated ab initio. The most stable conformer is stabilized by intramolecular hydrogen bonds N-H...O=C, N-H...pi (with the closest C-C bond in the aromatic ring), and a cis-COOH interaction. The other conformer exhibits a O-H...N hydrogen bond between the hydrogen atom of the hydroxyl group and the lone pair at the nitrogen atom.

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“…However, the use of electronic spectroscopy is limited to favorable cases that present aromatic chromophores. Only three of the 20 natural amino acids have aromatic side chains that meet this criterion: phenylalanine, tyrosine, and tryptophan (4,(8)(9)(10)(11)(12)(13)(14).Microwave spectroscopy, often considered the most definitive gas-phase structural probe, can distinguish unambiguously between different conformational structures and provide accurate structural information directly comparable to the in vacuo theoretical predictions. Without any chromophore restriction, all amino acids are potentially amenable to pure rotational studies.…”

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Revealing the multiple structures of serine

Blanco

Sanz

López

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

117

141

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We explored the conformational landscape of the proteinogenic amino acid serine [CH2OHOCH(NH2)OCOOH] in the gas phase. Solid serine was vaporized by laser ablation, expanded in a supersonic jet, and characterized by Fourier transform microwave spectroscopy. In the isolation conditions of the jet there have been discovered up to seven different neutral (non-zwitterionic) structures of serine, which are conclusively identified by the comparison between the experimental values of the rotational and quadrupole coupling constants with those predicted by ab initio calculations. These seven forms can serve as a basis to represent the shape of serine in the gas phase. From the postexpansion abundances we derived the conformational stability trend, which is controlled by the subtle network of intramolecular hydrogen bonds formed between the polar groups in the amino acid backbone and the hydroxy side chain. It is proposed that conformational cooling perturbs the equilibrium conformational distribution; thus, some of the lower-energy forms are ''missing'' in the supersonic expansion.amino acids ͉ conformations ͉ laser ablation ͉ microwave spectroscopy ͉ supersonic expansion A mino acids are distinguished by an outstanding conformational flexibility originating from multiple torsional degrees of freedom, which makes folding and functionality of proteins possible (1). Whereas covalent forces determine the molecular skeleton, conformational isomerism is controlled by weaker nonbonded interactions within the molecule, especially hydrogen bonding. Amino acids are also very sensitive to the chemical medium chosen for their study. In traditional studies in the condensed phase, the extensive intermolecular hydrogen bond interactions fix amino acids as doubly charged zwitterions (2, 3), wiping out the conformational variety of these molecules. The intrinsic structural preferences of amino acids can be revealed only when they are studied as free species in the gas phase, where neutral forms (present in polypeptide chains) are the most stable in detriment of ionic or zwitterionic forms. Levy and coworkers (4) were the first to measure highly resolved electronic spectra of amino acids in the gas phase by seeding tryptophan in a supersonic expansion. Since then, different experimental methods have been used to investigate the electronic spectrum of amino acids and a variety of biological molecules in the gas phase (5-7). The electronic spectrum is interpreted with the help of theoretical calculations to identify different conformations with a high degree of confidence. However, the use of electronic spectroscopy is limited to favorable cases that present aromatic chromophores. Only three of the 20 natural amino acids have aromatic side chains that meet this criterion: phenylalanine, tyrosine, and tryptophan (4,(8)(9)(10)(11)(12)(13)(14).Microwave spectroscopy, often considered the most definitive gas-phase structural probe, can distinguish unambiguously between different conformational structures and provide accurate structural inform...

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The R2PI Spectroscopy of Tyrosine: A Vibronic Analysis

Cited by 103 publications

References 26 publications

Excited‐State Charge Separation in the Photochemical Mechanism of the Light‐Driven Enzyme Protochlorophyllide Oxidoreductase

Excited‐State Charge Separation in the Photochemical Mechanism of the Light‐Driven Enzyme Protochlorophyllide Oxidoreductase

The Conformers of Phenylglycine

Revealing the multiple structures of serine

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