Gas-phase acid-base properties of 1-aminocycloalkane-1-carboxylic acids from the extended kinetic method

Muetterties, Corbin; Touzani, Ali Drissi; Hardee, Isabel; Huynh, Kathy T.; Poutsma, John C.

doi:10.1016/j.ijms.2014.07.010

Cited by 5 publications

(3 citation statements)

References 58 publications

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“…Due to the small differences between the recommended scaling factors and the unscaled harmonic frequencies, we chose to use the unscaled harmonic frequencies to derive ZPE and thermal corrections. This combination of triple-zeta single-point energy calculations at double-zeta geometries has been shown to give predictions for proton affinities for a variety of amino acids and other nitrogencontaining compounds that are in excellent agreement with experimental determinations from our lab [39][40][41][42].…”

Section: Theoretical Proceduressupporting

confidence: 67%

Spectroscopic Evidence for Lactam Formation in Terminal Ornithine b₂⁺ and b₃⁺ Fragment Ions

Smith

Wang

Scheerer

et al. 2019

J. Am. Soc. Mass Spectrom.

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Infrared multiple photon dissociation action spectroscopy was performed on the AlaOrn b 2 + and AlaAlaOrn b 3 + fragment ions from ornithine-containing tetrapeptides. Infrared spectra were obtained in the fingerprint region (1000-2000 cm −1 ) using the infrared free electron lasers at the Centre Laser Infrarouge d'Orsay (CLIO) facility in Orsay, France, and the free electron lasers for infrared experiments (FELIX) facility in Nijmegen, the Netherlands. A novel terminal ornithine lactam AO + b 2 + structure was synthesized for experimental comparison and spectroscopy confirms that the b 2 + fragment ion from AOAA forms a lactam structure. Comparison of experimental spectra with scaled harmonic frequencies at the B3LYP/6-31+G(d,p) level of theory shows that AO + b 2 + forms a terminal lactam protonated either on the lactam carbonyl oxygen or the N-terminal nitrogen atom. Several low-lying conformers of these isomers are likely populated following IRMPD dissociation. Similarly, a comparison of the experimental IRMPD spectrum with calculated spectra shows that AAO + b 3 + -ions also adopt a lactam structure, again with multiple different protonation sites, during fragmentation. This study provides spectroscopic confirmation for the lactam cyclization proposed for the Bornithine effect^and represents an alternative b n + structure to the oxazolone and diketopiperazine/macrocycle structures most often formed.

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Section: Theoretical Proceduressupporting

confidence: 67%

Spectroscopic Evidence for Lactam Formation in Terminal Ornithine b₂⁺ and b₃⁺ Fragment Ions

Smith

Wang

Scheerer

et al. 2019

J. Am. Soc. Mass Spectrom.

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“…As to further experimental work, the extended kinetic method could be employed to examine entropic effects. [24][25][26] However, such experiments are not feasible with our ion-trap methodology: we 1 and others 27 have observed that the product ratio changes only very slightly as the amplitude is changed. For example, the ratio [butyl acetate]•••Ag + /[propyl acetate]•••Ag + observed in the ion-trap CID spectrum of the silver-bound dimer changes only slightly from (1.7 ± 0.1) at high amplitudes (where the precursor ion has completely dissociated) to (1.9 ± 0.1) at the lowest possible amplitude, corresponding to 2% fragmentation.…”

Section: Metal Ion Bidentate Bonding In 1-alkenesmentioning

confidence: 83%

Metal Ion Hydrocarbon Bidentate Bonding in Alkyl Acetates, Methyl Alkanoates, Alcohols and 1-Alkenes: A Comparative Study

Burgers¹,

Holmes

Terlouwc

2016

Eur J Mass Spectrom (Chichester)

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The relative affinity of the monovalent metal ions Li, Na, Cu and Ag towards a series of aliphatic alkyl acetates and some selected 1-alkenes (P) was examined using the kinetic method. A detailed analysis of the dissociation characteristics of a series of mixed metal-bound dimer ions of the type P-M-P and the evaluated proton affinities (PAs) of the monomers shows that the affinity of the cation towards long-chain alkyl acetates and alkenes (having a chain length ≤ C) is markedly enhanced. In line with recent studies of nitriles, alcohols and methyl alkanoates, this is attributed to a bidentate interaction of the metal ion with the functional group or double bond and the aliphatic chain. In particular, the longer chain alkyl acetates, methyl alkanoates and alcohols show a remarkably similar behaviour with respect to silver ion hydrocarbon bonding. The Ag adducts of the alkyl acetates dissociate by loss of CHCOOH. This reaction becomes more pronounced at longer chain lengths, which points to metal ion bidentate formation in [Ag···1-alkene] product ions having a long hydrocarbon chain. In the same vein, the heterodimers [1- hexene···Ag···1-heptene] and [1- heptene···Ag···1-octene] dissociate primarily into [Ag···1-heptene] and [Ag···1-octene] ions, respectively. Hydrocarbon bidentate formation in [Ag···1-octene] also reveals itself by the reluctance of this ion to react with water in an ion trap, as opposed to [Ag···1-hexene] which readily undergoes hydration.

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“…111 It has since become standard practice in our lab to present proton affinities based on Boltzmann-weighted enthalpies for the neutral and protonated amino acids under study. 110,138 We use G 298 to determine the Boltzmann population for each low-energy conformer to determine the weighting factor for the H 298 values. In this case, we were pleased to find that the lowest enthalpy neutral conformer that we based our proton affinity value on in 2006 is the lowest free-energy conformer from our current more robust search.…”

Section: Resultsmentioning

confidence: 99%

Infrared multiple photon dissociation spectroscopy of cationized canavanine: Side-chain substitution influences gas-phase zwitterion formation

Smith

Steinmetz

Martens

et al. 2018

International Journal of Mass Spectrometry

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Infrared multiple photon dissociation spectroscopy was performed on protonated and cationized canavanine (Cav), a non-protein amino acid oxy-analog of arginine. Infrared spectra in the XH stretching region (3000 - 4000 cm) were obtained at the Centre Laser Infrarouge d'Orsay (CLIO) facility. Comparison of the experimental infrared spectra with scaled harmonic frequencies at the B3LYP/6-31+G(d,p) level of theory indicates that canavanine is in a canonical neutral form in CavH, CavLi, and CavNa; therefore, these cations are charge-solvated structures. The infrared spectrum of CavK is consistent with a mixture of Cav in canonical and zwitterionic forms leading to both charge-solvated and salt-bridged cationic structures. The Cav moiety in CavCs is shown to be zwitterionic, forming a salt-bridged structure for the cation. Infrared spectra in the fingerprint region (1000 - 2000 cm) obtained at the FELIX Laboratory in Nijmegen, Netherlands support these assignments. These results show that that a single oxygen atom substitution in the side chain reduces the stability of the zwitterion compared to that of the protein amino acid arginine (Arg), which has been shown previously to adopt a zwitterionic structure in ArgNa and ArgK. This difference can be explained in part due to the decreased basicity of Cav (PA = 1001 kJ/mol) as compared to arginine (PA = 1051 kJ/mol), but not entirely, as lysine, which has nearly the same proton affinity as Cav, (~993 kJ/mol) forms only canonical structures with Na, K, and Cs. A major difference between the zwitterionic forms of ArgM and CavM is that the protonation site is on the side chain for Arg and on the N-terminus for Cav. This results in systematically weaker salt bridges in the Cav zwitterions. In addition, the presence of another hydrogen-bonding acceptor atom in the side chain contributes to the stability of the canonical structures for the smaller alkali cations.

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Gas-phase acid-base properties of 1-aminocycloalkane-1-carboxylic acids from the extended kinetic method

Cited by 5 publications

References 58 publications

Spectroscopic Evidence for Lactam Formation in Terminal Ornithine b₂⁺ and b₃⁺ Fragment Ions

Spectroscopic Evidence for Lactam Formation in Terminal Ornithine b₂⁺ and b₃⁺ Fragment Ions

Metal Ion Hydrocarbon Bidentate Bonding in Alkyl Acetates, Methyl Alkanoates, Alcohols and 1-Alkenes: A Comparative Study

Infrared multiple photon dissociation spectroscopy of cationized canavanine: Side-chain substitution influences gas-phase zwitterion formation

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Gas-phase acid-base properties of 1-aminocycloalkane-1-carboxylic acids from the extended kinetic method

Cited by 5 publications

References 58 publications

Spectroscopic Evidence for Lactam Formation in Terminal Ornithine b2+ and b3+ Fragment Ions

Spectroscopic Evidence for Lactam Formation in Terminal Ornithine b2+ and b3+ Fragment Ions

Metal Ion Hydrocarbon Bidentate Bonding in Alkyl Acetates, Methyl Alkanoates, Alcohols and 1-Alkenes: A Comparative Study

Infrared multiple photon dissociation spectroscopy of cationized canavanine: Side-chain substitution influences gas-phase zwitterion formation

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Spectroscopic Evidence for Lactam Formation in Terminal Ornithine b₂⁺ and b₃⁺ Fragment Ions

Spectroscopic Evidence for Lactam Formation in Terminal Ornithine b₂⁺ and b₃⁺ Fragment Ions