Conformational population distribution of acetylcholine, nicotine and muscarine in vacuum and solution

Muñoz‐Caro, Camelia; Niño, Alfonso; Mora, M. A.; Reyes, Sebastián C.; Meléndez, Francisco J.; Castro, María Eugenia

doi:10.1016/j.theochem.2005.04.015

Cited by 23 publications

(43 citation statements)

References 35 publications

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“…Indeed reoptimization of these structures at the B3-LYP/6-311ϩG(d,p) level of theory affords ACh01-ACh05 (data not shown). Muñoz-Caro et al [26] examined the MP2/cc-pVDZ PES by systematically scanning the N7-C6 -C5-O4 and C6 -C5-O4 -C2 dihedral angles (see Figure 1 for atom numbering), and located four minima. Although limited structural parameters were reported, these structures appear to correspond to ACh01, ACh02, ACh04, and ACh05.…”

Section: Dft Calculations On the Conformations Of Acetylcholinementioning

confidence: 99%

How does acetylcholine lose trimethylamine? A density functional theory study of four competing mechanisms

Lioe

Barlow

O’Hair

2009

J. Am. Soc. Mass Spectrom.

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Low-energy collision-induced dissociation (CID) of acetylcholine (ACh) yields only two fragment ions: the dominant C 4 H 7 O 2 ϩ ion at m/z 87, arising from trimethylamine loss; and protonated trimethylamine at m/z 60. Since the literature is replete with conflicting mechanisms for the loss of trimethylamine from ACh, in this article density functional theory (DFT) calculations are used to assess four competing mechanisms: (1) Path A involves a neighboring group attack to form a five-membered ring product, 2-methyl-1,3-dioxolan-2-ylium cation; (2) Path B is a neighboring group attack to form a three-membered ring product, 1-methyloxiranium ion; (3) Path C involves an intramolecular elimination reaction to form C¢O protonated vinylacetate; and (4) Path D is a 1,2-hydride migration reaction forming CH 2 -protonated vinylacetate. At the MP2/6-311ϩϩG(2d,p)//B3-LYP/6-31ϩG(d,p) level of theory path A is the kinetically favored pathway, with a transition-state energy barrier of 37.7 kcal mol Ϫ1 relative to the most stable conformer of ACh. The lowest energy pathway for the formation of protonated trimethylamine was also calculated to proceed via path A, involving proton transfer within the ion-molecule complex intermediate, with the exocylic methyl group being the proton donor. To confirm the site of proton transfer, low-energy CID of acetyl-d 3 -choline (d 3 -ACh) was carried out, which revealed loss of trimethylamine and the formation of Me 3 ND ϩ . (J Am Soc Mass Spectrom 2009, 20, 238 -246)

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Section: Dft Calculations On the Conformations Of Acetylcholinementioning

confidence: 99%

How does acetylcholine lose trimethylamine? A density functional theory study of four competing mechanisms

Lioe

Barlow

O’Hair

2009

J. Am. Soc. Mass Spectrom.

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“…Starting from the infrared (IR) spectrum (both peak positions and intensities) we computed the optical rotation (OR) at the sodium D‐line wavelength, together with vibrational circular dichroism (VCD). Because of its well‐known biological activity, (S)‐nicotine has been the subject of several studies aimed at providing better insights into its structure and properties . To the best of our knowledge, however, nicotine lacks a thorough computational study in spite of the availability of nuclear magnetic resonance (NMR), circular dichroism (CD), Raman and Raman optical activity (ROA) spectra .…”

Section: Introductionmentioning

confidence: 99%

“…Because of its well-known biological activity, (S)-nicotine has been the subject of several studies aimed at providing better insights into its structure and properties. [8][9][10][11] To the best of our knowledge, however, nicotine lacks a thorough computational study in spite of the availability of nuclear magnetic resonance (NMR), 12 circular dichroism (CD), 13,14 Raman and Raman optical activity (ROA) spectra. 15 Taking also into account that nicotine is a medium-size semirigid molecule, soluble in a variety of environments, it represents indeed an ideal benchmark for our developments.…”

Section: Introductionmentioning

confidence: 99%

Development of a Virtual Spectrometer for Chiroptical Spectroscopies: The Case of Nicotine

et al. 2013

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The impressive advances of computational spectroscopy in most recent years are providing robust and user-friendly multifrequency virtual spectrometers, which can also be used by nonspecialists to complement experimental studies. At the heart of these developments there are latest-generation models based on Density Functional Theory for the proper treatment of stereo-electronic effects, coupled to the polarizable continuum model to deal with bulk solvent effects, and low-order perturbative treatments of anharmonic effects. Continuing our efforts to increase the range of application of virtual spectrometers, we report here about chiroptical spectroscopies with special reference to optical rotation and vibrational circular dichroism. The capabilities and possible limitations of our latest tool will be analyzed for the specific case of (S)-nicotine in vacuo and in different solvents.

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“…This paper focuses on the accurate gas phase energetics and interconversion pathways of low energy conformers of positively charged acetylcholine ion using high level ab initio theoretical models. Although previous quantum theoretical studies [4][5][6][7][8][9][10][11] indicated the presence of low energy zone depending upon orientation of acetoxy group in the system where stable conformations could be identified in the potential energy surface (PES) of acetylcholine, the energy differences between these conformations and interconversion mechanism could not be delineated as most of these previous studies employed the semiempirical and low level ab initio methods while the PES of acetylcholine is expected to be floppy. Another motivation for the present study is concerned with a recent experimental and theoretical study of the infrared multiphoton dissociation (IRMPD) spectrum of this ion, where analysis of spectral peaks was performed in terms of contributions from relevant low energy conformers.…”

mentioning

confidence: 99%

“…Previous theoretical studies on acetylcholine ion using DFT and MP2 methods [9][10][11] have suggested that it could have four or five stable conformers within a few kilocalorie energy range and some of them appear to be close-lying, possibly within 1-2 kcal/mol. It has to be noted, however, that the energy difference of this small magnitude cannot be reliably predicted without proper account of electron correlation and basis set extension effect on relative energies between various conformations involved.…”

mentioning

confidence: 99%

Stability and Interconversion of Acetylcholine Conformers

Lee¹,

Park²

2014

Bulletin of the Korean Chemical Society

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The gas phase structures, energetics, and interconversion pathways of five lowest energy conformers of acetylcholine were examined employing the B3LYP, MP2, and CCSD(T) methods in conjunction with diverse basis sets including the correlation consistent aug-cc-pVDZ and aug-cc-pVTZ basis sets. It is found that use of adequate basis set containing proper polarization and diffuse functions capable of describing the floppy potential energy surface of acetylcholine is important in correctly predicting the relative stability of these conformers. The interconversion pathways and barrier heights between these conformers were elucidated by examining the potential energy surface for torsional motion, which also manifested the presence of chiral conformations of acetylcholine corresponding to the original conformations. On the basis of high level electronic energy calculations and thermal contribution analysis, four lowest energy conformers appear to be populated in the energy range of less than 1 kcal/mol at room temperature.

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Conformational population distribution of acetylcholine, nicotine and muscarine in vacuum and solution

Cited by 23 publications

References 35 publications

How does acetylcholine lose trimethylamine? A density functional theory study of four competing mechanisms

How does acetylcholine lose trimethylamine? A density functional theory study of four competing mechanisms

Development of a Virtual Spectrometer for Chiroptical Spectroscopies: The Case of Nicotine

Stability and Interconversion of Acetylcholine Conformers

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