12C 15N Research Articles

Spectroscopic parameter and molecular constant investigations on X 2Σ + and A 2Π i states of 12C 14N, 12C 15N, 13C 14N and 13C 15N species

The potential energy curves of X 2Σ + and A 2Π i states of CN radical have been investigated using the complete active space self-consistent-field method followed by the highly accurate valence internally contracted multireference configuration interaction approach in combination with the cc-pV5Z basis set. With the second-order Douglas–Kroll Hamiltonian approximation, the effect on the PECs by the relativistic corrections has been taken into considerations. Employing the cc-pcV5Z basis set, the effect on the spectroscopic parameters by the core-correlate corrections has been evaluated. For the X 2Σ + and A 2Π i electronic states, the spectroscopic parameters of these four species ( 12C 14N, 13C 14N, 12C 15N and 13C 15N) have been studied. With the CN potential energy curves obtained here, 43 vibrational states for the X 2Σ + and 60 for the A 2Π i states are predicted when the rotational quantum number J is equal to zero ( J = 0). The vibrational manifolds are determined for the first 40 vibrational states when J = 0. And the rovibrational energy levels of four species are calculated until J = 29. The results of spectroscopic parameters and molecular constants have been compared in detail with those of the investigations reported in the literature.

Supported Membrane Composition Analysis by Secondary Ion Mass Spectrometry with High Lateral Resolution

The lateral organization of lipid components within membranes is usually investigated with fluorescence microscopy, which, though highly sensitive, introduces bulky fluorophores that might alter the behavior of the components they label. Secondary ion mass spectroscopy performed with a NanoSIMS 50 instrument also provides high lateral resolution and sensitivity, and many species can be observed in parallel without the use of bulky labels. A tightly focused beam (∼100 nm) of Cs ions is scanned across a sample, and up to five of the resulting small negative secondary ions can be simultaneously analyzed by a high-resolution mass spectrometer. Thin layers of 15N- and 19F-labeled proteins were microcontact-printed on an oxidized silicon substrate and imaged using the NanoSIMS 50, demonstrating the sensitivity and selectivity of this approach. Supported lipid bilayers were assembled on an oxidized silicon substrate, then flash-frozen and freeze-dried to preserve their lateral organization. Lipid bilayers were analyzed with the NanoSIMS 50, where the identity of each specific lipid was determined through detection of its unique secondary ions, including 12C 1H −, 12C 2H −, 13C −, 12C 14N −, and 12C 15N −. Steps toward obtaining quantitative composition analysis of lipid membranes that varied spatially in isotopic composition are presented. This approach has the potential to provide a composition-specific analysis of membrane organization that compliments other imaging modalities.

Transport of 13C-oleate in adipocytes measured using multi imaging mass spectrometry

The mechanism of long chain free fatty acid (FFA) transport across cell membranes is under active investigation. Here we describe the use of multi imaging mass spectrometry (MIMS) to monitor intracellular concentrations of FFA and provide new insight into FFA transport in cultured adipocytes. Cells were incubated with 13C-oleate:BSA and either dried directly or dried after washing with a medium deprived of 13C-oleate:BSA. Cells were analyzed with MIMS using a scanning primary Cs+ ion beam and 12C-, 13C-, 12C14N-, 13C14N-) (or 12C 15N-) were imaged simultaneously. From these quantitative images the values of the 13C/ 12C ratios were determined in the intracellular lipid droplets, in the cytoplasm and outside the 3T3F442A adipocytes. The results indicate that after incubation with 13C-oleate:BSA the droplet 13C/ 12C ratio was 15 +/- 6%. This value is about 14-fold higher than the 13C/ 12C terrestrial ratio (1.12%). After washing the 13C-oleate:BSA, the droplet 13C/ 12C ratios decreased to 1.6 +/- 0.1%, about 40% greater than the natural abundance. Results for washed cells indicate that relatively little FFA was esterified. The unwashed cell results, together with the value of the lipid water partition coefficient, reveal that intracellular unbound FFA (FFAu) concentrations were on average about 4.5-fold greater than the extracellular FFAu concentrations. These results are consistent with the possibility that FFA may be pumped into adipocytes against their electro-chemical potential. This work demonstrates that MIMS can be used to image and quantitate stable isotope labeled fatty acid in intracellular lipid droplets.

Fourier transform infrared spectroscopy of the 2 ν3 overtone band of different ICN isotopomers: an improved evaluation of the anharmonic force field of cyanogen iodide

The weak 2 ν 3 overtone band of the three isotopomers of cyanogen iodide, I 12C 14N, I 13C 14N, and I 12C 15N, has been recorded in the range from 4200 to 4400 cm −1 with a resolution of 0.02 cm −1 using a Fourier transform infrared spectrometer. The following band origins have been determined from the analysis of the spectra: ν 0 (I 12C 14N)=4332.8368 cm −1, ν 0 (I 13C 14N)=4235.7355 cm −1, and ν 0 (I 12C 15N)=4274.2851 cm −1. This allowed us to achieve complete knowledge of the energies for all levels of ICN corresponding to double vibrational excitation. An improved evaluation of the quartic force field of cyanogen iodide has been performed using the new data obtained together with those already known from previous works.

Hydrogen cyanide: theory and experiment

The results of large-scale ab initio calculations for hydrogen cyanide are compared with available experimental data. The equilibrium bond lengths of the electronic ground state are obtained with an accuracy of ≈ 0.0005 Å and the wavenumbers of the fundamental vibrational transitions have errors of 2.1 cm −1 ( ν 1), 1.3 cm −1 ( ν 2) and 5.8 cm −1 ( ν 3). An accurate three-dimensional CCSD(T) electric dipole moment is reported and, by combination of experiment and theory, the equilibrium dipole moment is determined as being μ e = − 3.0146(5) D. The calculated transition dipole moments of the ν 3 bands of HCN isotopomers agree with experiment, and the intensity anomaly found experimentally for H 12C 14N and H 12C 15N is reproduced by theory for the first time. Accurate equilibrium geometries are reported for the two lowest electronic states of HCN + (X̃ 2Π and A ̃ 2Σ + ). By combination of experimental and theoretical data, the equilibrium excitation energy of the first excited singlet state (Ã 1 A″) is obtained as T e = 53 266 ± 30 cm −1. The equilibrium geometry of the lowest triplet state (ã 3A′) is r e = 1.100 A ̊ , R e = 1.288 A ̊ and α e = 120.9 °. Its T e value is recommended as being 38 500 ± 500 cm −1.

14N and 15N imaging by SIMS microscopy in soybean leaves

The distribution of 15N and 14N compounds in cryofixed and resin embedded sections of soybean ( Glycine max L) leaves was studied by SIMS microscopy. The results indicate that, with a mass resolution M/Δ M higher than 6000, images of the nitrogen distribution can be obtained from the mapping of the two secondary cluster ions 12C 14N − and 12C 15N −, in samples of both control and 15N-labeled leaves. The ionic images were clearly related to the histological structure of the organ, and allow the detection of 14N and 15N at the subcellular level. Furthermore, relative measurements of the 12C 14N − and 12C 15N − beams made possible the quantification of the 15N atom% in the various tissues of the leaf.

Stable multi-line CW vibration laser near 5 μm based on F H(CN −) centers in CsBr

Stable cw laser operation has been obtained from F center/CN - defect pairs, “F H(CH -) centers”, in CsBr crystals. Pumped with the 676 nm krypton laser line in one of their electronic absorption transitions in the visible, the F H(CN -) centers perform (e-v) energy transfer into higher vibrational (v) levels of the CN - molecule and lase on their v=3→2 CN - vibrational transition near 5 μm up to a crystal temperature limit of ≈30 K. Using F H(CN -) defects with 12C 14N, 12C 15N, 13C 14N and 13 C 15N isotopes in the same crystal, we could obtain simultaneous four-line laser operation at 2010, 1980, 1970 and 1940 cm −1.

Fourier transform spectra of overtone bands of HCN from 5400 to 15100 cm −1

The absolute intensities and vibration-rotation constants of 26 overtone and combination bands of HCN are reported. The dynamic range for the absolute intensity measurements is nearly one million to one. Absorption spectra of HCN from 5400 to 15100 cm −1 were obtained using the Fourier transform spectrometer at the Kitt Peak National Solar Observatory with optical path lengths up to 432 m. The frequencies of 1346 assigned HCN lines were used to derive vibration-rotation constants for 23 bands (14 Σ-Σ, 4 Π-Π, 4 Π-Σ, and 1 Σ-Π) of H 12C 14N, 3 bands (Σ-Σ) of H 13C 14N, and 2 bands (Σ-Σ) of H 12C 15N. These new band origin and rotational constant data have been combined with existing data given in the literature to derive an improved set of vibrational (ω, x, and y) constants and rovibrational (α and γ) constants for HCN. The vibrational dependence of the centrifugal distortion constants has also been examined. One thousand thirtysix derived line areas were used to determine absolute intensities for all 28 bands. Four weak stretch-only bands were observed for the first time: the (300)-(000), the (201)-(000), the (301)-(000) and the (202)-(000). Such data should be an important aid in accurately determining the CN contribution to the potential and dipole moment functions. Finally, we present a comparison of 13 of the measured absolute overtone intensities (stretching states only) with recent ab initio results.

Rs-Type coordinates in weakly-bound dimers: application to linear dimers B⋯HCN, where BCO, N 2 and HCN

An expression is derived for r s-type coordinates z i of the atoms i in weakly-bound linear dimers under the assumption that the monomer geometries survive dimer formation. The zero-point motion is modelled by angular oscillations θ and φ of the subunits pivoted at their respective mass centres. The coordinate z i is the distance from the dimer centre of mass to the centre of the ring described by the nucleus of atom i during such zero-point oscillations. The z i have been determined for the heavy atoms in B⋯HCN, where BOC, N 2 and HCN. In order to do so, the rotational constant B 0 has been measured experimentally for the isotopic species H 13C 15N⋯H 12C 15N and H 12C 15N⋯H 13C 15N. The values are B 0 = 1642.2596 MHz and 1669.3139 MHz, respectively. The r s-type distances r(B⋯C) between the carbon atom of the HCN donor subunit and the acceptor atom of B are compared with their r 0 analogues.

Haem-rotational disorder in monomeric allosteric cyano-Met insect haemoglobins monitored by resonance Raman spectroscopy

The haem-rotational disorder (insertion of haem into globin rotated about the α, γ-meso axis by 180 °) has been investigated in the cyano-Met form of the monomeric allosteric insect haemoglobins, CTT III and CTT IV, by resonance Raman spectroscopy. The effect of haem disorder on the resonance Raman spectra has been observed in proto-IX, deutero-IX, and meso-IX CTTs. Most importantly, in the absence of overlapping vinyl vibrations, we have identified two Fe C N bending vibrations at 401 cm −1 and 422cm −1 (pH 9.5) for 57Fe deutero-IX CTT IV ligated with 13C 15N −, which are attributed to the two haem-rotational components. One Fe G N bending mode at 422cm −1 shows a pH-induced shift to 424 cm −1 (pH 5.5) indicating the t → r conformational transition, whereas the other bending mode is pH-insensitive, representing a non-allosteric component. By replacing the unsymmetrical porphyrins with the “symmetrical” protoporphyrin-III we eliminate the haem disorder. Then, sharpening of the Fe N ɛ(His) (at 313 cm −1) and Fe-CN (at 453 cm −1) stretching modes is observed and a single Fe C N bending mode (at 412 cm −1) appears. In cyano-Met proto-IX CTT III two vinyl bending vibrations at 412 cm −1 and 591 cm −1 assigned by deuteration of the vinyl groups also reflect the haem disorder. The 412 cm −1 vinyl vibration is intensity-enhanced via through-space coupling with one of the Fe C N bending modes (at 412 cm −1). In the cyano-Met form of proto-III CTT III this vinyl vibration is shifted to 430 cm −1 resulting in a dramatic drop in intensity. It is most likely that the specific vinyl-protein interaction at position 4 in one of the haem-rotational components is the origin of the coupling between the Fe C N and vinyl bending modes. The Fe-N ɛ(proximal His) and the Fe-CN stretching vibrations as well as the Fe-C-N bending vibration have been identified by 54Fe 57Fe and 13C 15N/ 12C 15N/ 13C 14N/ 12C 14N isotope exchange.

The rotational a-type sepctra of 15N-labeled diazirine, H 2CN 2

The rotational a-type spectra of isotopically enriched diazirine isotopomers, H 2 12C 14N 15N and H 2 12C 15N 2, have been recorded in the region between 8 and 300 GHZ; the latter isotopomer has been observed for the first time. Using Watson's A-reduced Hamiltonian, the rotational constants and the quartic and some sextic centrifugal distortion constants have been determined for the ground vibrational states.

Classical chaos and quantum simplicity: Highly excited vibrational states of HCN

Direct overtone spectra of H 12C 14N, H 13C 14N, and H 12C 15N have been measured between 15 000 and 18 500 cm−1 with a precision of 0.001 cm−1. These were obtained using intracavity photoacoustic spectroscopy, with a fully automated laser system. The spectra are unperturbed. The transition energies and rotational constants are in good agreement with predictions of first order anharmonic constants. Classical trajectories for HCN have been computed on the best experimentally parameterized potential, and found to be stochastic 12 990 cm−1 above the ground state. Quantal density of states were computed for HCN and show that if extensive vibrational coupling occurs, the observed states would be highly perturbed. The simplicity of the observed states is shown to be expected given a Franck–Condon type limitation on significantly perturbing states. The results show the inapplicability of classical dynamics for predicting the dynamics of molecular vibrations.

Rotational spectra of excited vibrational states of F 12C 15N. Equilibrium structure of cyanogen fluoride

The rotational spectra of F 12C 15N have been observed in the ground state and in the (01' 0), (02° 0), (10° 0), (20° 0) and (00° 1) excited vibrational states. From analysis of the spectroscopic data available for F 12C 14N, F 12C 15N and F 13C 14N the equilibrium structure of cyanogen fluoride has been evaluated.

Laser Stark spectroscopy of DCN and DC 15N

Using a CO laser, laser Stark resonance spectra were measured for the CN stretching fundamentals (the 00 01-00 00 bands) of D 12C 14N and D 12C 15N near 1925 cm −1. Laser Stark resonances were also measured for the hot band 01 11-01 10 of D 12C 14N. In addition to accurately determining the band centers, dipole moments are given for the different vibrational states involved.

Infrared spectrum of H 12C 14N and H 12C 15N

The high-resolution spectrum of H 12C 14N has been measured near 4870 and 6060 cm −1. The following bands have been identified and analyzed: 01 12-00 00, 02 02-01 10, 02 22-01 10, 04 01-00 00, 11 11-00 00, 12 01-01 10, and 12 21-01 10. The CN stretching fundamental ( ν 3) of H 12C 15N has also been measured near 2100 cm −1. This fundamental is found to be 3 cm −1 higher than previously reported. Other bands that have been identified in the H 12C 16N spectrum are 03 10-00 00, 04 00-01 10, 04 20-01 10, and 01 11-01 10.

Analysis of the microwave rotation spectrum of silyl cyanide, SiH 3CN, in its ground and vibrationally excited states

The rotational spectrum of silyl cyanide, SiH 3CN, has been studied by microwave spectroscopy. A detailed analysis of the transitions in the excited states of the ν 3, ν 4, ν 7, and ν 8 modes has been carried out. In particular the v 8 = 1, 2, 3, and 4 vibrational satellites have been subjected to a complete vibration-rotation analysis. Ground state transitions of 28SiH 3 12C 14N, 29SiH 3 12C 14N, 30SiH 3 12C 14N, 28SiH 3 13C 14N, and 28SiH 3 12C 15N have all been studied in natural abundance. The overall study has yielded a large amount of detailed vibration-rotation data. The effects of quadrupole interactions have been taken into account. To confirm the analysis, computer simulated spectra have been compared with those observed.

Force field of cyanogen from vibrational spectra of isotopic species

The Raman spectra of ( 12C 14N) 2, ( 13C 14N) 2, and ( 12C 15N) 2 in the vapor phase have been studied. From the isotope shifts of several levels the Fermi resonance constant, W 01000-0002 00 = 41 cm −1, has been determined. The observed data, together with earlier infrared data, allow a determination of all the first order anharmonic corrections and thus of the fundamental harmonic frequencies. From these results, force constants and compliance constants of a general quadratic force field are calculated and discussed.

The molecular Zeeman effect in F 12C 15N

The molecular rotational Zeeman effect has been observed at high magnetic fields in F 12C 15N. The magnetic susceptibility anisotropy is χ ⊥ − χ | = (7.2 ± 0.8) × 10 −6 erg/G 2 mole, the molecular g value is −0.0504 ± 0.0008, and the molecular quadrupole moment is (−3.7 ± 1.0) × 10 −26 esu. The results are compared with HCN, FCCH, and HCCH. A new synthesis for FCN is described and an interpretation of the electronic structure is given.

Infrared bands of H 12C 15N, D 12C 15N and H 13C 15N

Infrared spectra of some of the isotopic varieties of the hydrogen cyanide molecule have been measured employing high precision vacuum grating spectrographs. Several bands of H 12C 15N, D 12C 15N and H 13C 15N occurring in the 2–7μ region have been reported for the first time. Molecular constants were derived from these data.

HCN rotational-vibrational energy levels and intensity anomalies determined from infrared measurements

New measurements have been made on the infrared transitions 11 10-00 00, 04 00-00 00, 12 00-01 10, 12 20-01 10, 05 10-01 10, 13 30-02 20, 13 10-02 00, 12 20-00 00, and 20 00-00 00 for HCN and on the 11 10-00 00 transitions for both H 13C 14N and H 12C 15N. Wherever possible those measurements were combined with laser measurements to obtain the best set of constants for describing the energy levels. Unusual intensity distributions were observed and attributed to intensity mixing through ℓ-type resonance. Several P-branch lines of a Δ-Σ (12 20-00 00) transition were also observed although the intensity was somewhat less than predicted from ℓ-type resonance effects.