Dynamical structure of peptide molecules: Fourier transform microwave spectroscopy and ab initio calculations of N-methylformamide

Kawashima, Yasunaru; Usami, Tsuyoshi; Suenram, R. D.; Golubiatnikov, G. Yu.; Hirota, Eizi

doi:10.1016/j.jms.2010.06.004

Cited by 19 publications

(26 citation statements)

References 34 publications

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“…The same is true for the centrifugal distortion constants. At the same time, the change in V 3 value is in good agreement with the prediction made in Kawashima et al (2010) where a quite large V 6 term in the potential function was postulated by analogy with acetamide (Ilyushin et al 2004). The data set available in Kawashima et al (2010) was limited to the ground torsional state transitions only and did not give the opportunity to determine the V 6 value.…”

Section: Methodssupporting

confidence: 83%

“…The interstellar detection of the next stable isomer of the C 2 H 5 NO family, CH 3 C(OH)NH, may therefore become possible once its rotational spectrum will have been measured in the laboratory. Table 2 of Kawashima et al (2010). …”

Section: Discussionmentioning

confidence: 99%

“…We follow the definition of the Rho-axis method given in Hougen et al (1994) and, in our case, the A and E species are treated together with a single set of rotational parameters. On the contrary, Kawashima et al (2010) treated the A and E species with distinct sets of rotational parameters (see their Table 2). As a result, a direct comparison of the changes in the rotational parameters is not possible.…”

Section: Methodsmentioning

confidence: 99%

“…The V 3 barrier of the methyl group internal rotation was determined to be 55.17 ± 0.84 cm −1 . Recently, Kawashima et al (2010) carried out a new spectroscopic investigation of N-methylformamide. In that study, rotational spectra of both trans and cis conformers of the normal as well as deuterated CH 3 NHCHO isotopologues were measured in the frequency range of 5-118 GHz.…”

Section: Introductionmentioning

confidence: 99%

“…Fantoni & Caminati (1996) and Fantoni et al (2002) • was named trans. Kawashima et al (2010) used another convention widely accepted for molecules with a peptide bond. According to this convention applied for N-methylformamide, one should use the D * (Y − N − C − X) dihedral angle, where X is the carbonyl hydrogen and Y is the methyl group.…”

Section: Introductionmentioning

confidence: 99%

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Rotational spectroscopy, tentative interstellar detection, and chemical modeling of N-methylformamide

Беллоче

Meshcheryakov

Garrod

et al. 2017

A&A

155

261

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Context. N-methylformamide, CH 3 NHCHO, may be an important molecule for interstellar pre-biotic chemistry because it contains a peptide bond, which in terrestrial chemistry is responsible for linking amino acids in proteins. The rotational spectrum of the most stable trans conformer of N-methylformamide is complicated by strong torsion-rotation interaction due to the low barrier of the methyl torsion. For this reason, the theoretical description of the rotational spectrum of the trans conformer has up to now not been accurate enough to provide a firm basis for its interstellar detection. Aims. In this context, as a prerequisite for a successful interstellar detection, our goal is to improve the characterization of the rotational spectrum of N-methylformamide. Methods. We use two absorption spectrometers in Kharkiv and Lille to measure the rotational spectra over the frequency range 45-630 GHz. The analysis is carried out using the Rho-axis method and the RAM36 code. We search for N-methylformamide toward the hot molecular core Sagittarius (Sgr) B2(N2) using a spectral line survey carried out with the Atacama Large Millimeter/submillimeter Array (ALMA). The astronomical spectra are analyzed under the assumption of local thermodynamic equilibrium. The astronomical results are put into a broader astrochemical context with the help of a gas-grain chemical kinetics model. Results. The new laboratory data set for the trans conformer of N-methylformamide consists of 9469 distinct line frequencies with J ≤ 62, including the first assignment of the rotational spectra of the first and second excited torsional states. All these lines are fitted within experimental accuracy for the first time. Based on the reliable frequency predictions obtained in this study, we report the tentative detection of N-methylformamide towards Sgr B2(N2). We find N-methylformamide to be more than one order of magnitude less abundant than formamide (NH 2 CHO), a factor of two less abundant than the unsaturated molecule methyl isocyanate (CH 3 NCO), but only slightly less abundant than acetamide (CH 3 CONH 2 ). We also report the tentative detection of the 15 N isotopologue of formamide ( 15 NH 2 CHO) toward Sgr B2(N2). The chemical models indicate that the efficient formation of HNCO via NH + CO on grains is a necessary step in the achievement of the observed gas-phase abundance of CH 3 NCO. Production of CH 3 NHCHO may plausibly occur on grains either through the direct addition of functional-group radicals or through the hydrogenation of CH 3 NCO. Conclusions. Provided the detection of N-methylformamide is confirmed, the only slight underabundance of this molecule compared to its more stable structural isomer acetamide and the sensitivity of the model abundances to the chemical kinetics parameters suggest that the formation of these two molecules is controlled by kinetics rather than thermal equilibrium.

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Section: Methodssupporting

confidence: 83%

Section: Discussionmentioning

confidence: 99%