Raman Spectroscopic study of valinomycin-metal complexes

Liddle, W.Kevin; Willis, T. W.; Tu, Anthony T.; Sankaram, M. B.; Devarajan, S.; Easwaran, K. R. K.

doi:10.1016/0009-3084(85)90037-4

Cited by 6 publications

(6 citation statements)

References 10 publications

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“…For smaller dipeptides, the conformer populations obtained by ROA were shown to be equivalent to those obtained by NMR spectroscopy. 14 The valinomycin structure including its complexes was also studied by other methods, including, for example, unpolarized Raman spectroscopy, [15][16][17] infrared absorption (IR), 18 optical rotatory dispersion (ORD), 7 and electronic and vibrational circular dichroism (ECD, VCD). 3,19 In particular, the VCD technique provides important knowledge about the peptide backbone, but the side chain VCD signal is too weak.…”

Section: Introductionmentioning

confidence: 99%

Formation and structure of the potassium complex of valinomycin in solution studied by Raman optical activity spectroscopy

Yamamoto

Straka

Watarai

et al. 2010

Phys. Chem. Chem. Phys.

100

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The formation and structure of the potassium complex with valinomycin in solution were studied by means of Raman and Raman optical activity (ROA) spectroscopy. The complexation caused significant spectral changes, particularly in the region 1200-1400 cm(-1). The experimental spectra were interpreted using first principles computations. A complete computational conformational search combined with the spectral analysis revealed the arrangement of the isopropyl side chains in the complex. From a total of 6579 unique conformers two predominant ones were confirmed in the solution by ROA. A third one was predicted theoretically, but its population in the experiment could be estimated only roughly. The most populated conformer does not exhibit C(3) symmetry, and is different from that present in the crystal and the NMR-derived structure. Molecular dynamics techniques were used to estimate the molecular flexibility and its effect on the spectra. Density functional computations and Cartesian coordinate transfer (CCT) techniques provided the ROA and Raman spectral shapes and intensities well comparable with the experiment. The polar solvent (methanol) environment modeled with a polarizable continuum model (PCM) leads to rather minor changes in the conformer populations and vibrational properties as compared to vacuum computations, due to the hydrophobic character of the complex. Additional computational experiments suggest that the vibrational interactions determining the ROA spectra are quite local, which contributes to the good spatial resolution of the method. A reduction of the noise in the experimental spectra as well as increased precision of the simulations is desirable for the further exploration of the potential of the ROA spectroscopy for biomolecular studies in the future.

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Section: Introductionmentioning

confidence: 99%

Formation and structure of the potassium complex of valinomycin in solution studied by Raman optical activity spectroscopy

Yamamoto

Straka

Watarai

et al. 2010

Phys. Chem. Chem. Phys.

100

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“…It is distinguished by the unique ability to transport potassium cations across natural and artificial membranes selectively (42). The conformation of valinomycin has been verified by several spectroscopic studies (43)(44)(45). Positive identification of this molecule can be obtained quite easily by SFC/MS.…”

Section: Resultsmentioning

confidence: 79%

Direct heated interface probe for capillary supercritical fluid chromatography/double focusing mass spectrometry

Huang¹,

Jackson²,

Markides³

et al. 1988

Anal. Chem.

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A capillary supercritical fluid chromatograph was coupled to a double focusing mass spectrometer with a direct heated probe Interface. The Interface contained a fused silica transfer capillary containing a frit restrictor at the end which was heated to a temperature of 300-350 °C by resistance heating. The total column effluent was transferred Into the mass spectrometer Ion source. This Interface not only preserved the chromatographic efficiency but also provided for mass spectral detection and Identification of various high molecular weight, thermally labile, and polar compounds. Electron-Impact and chemical Ionization mass spectra of selected natural products and pharmaceuticals were obtained at the low nanogram level.

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“…Although no significant differences were seen in this study for spectra of pesticides, herbicides, and explosives using the two different reagent gas mixtures, CO, + CH4 and CO, + NH,, a biologically important cyclic peptide, valinomycin, yielded different fragmentation patterns when these reagent gas mixtures were used. logical membranes (29). Figure 7 shows total ion chromatograms of this polypeptide under CO, + CH, and CO, + NH, negative ion MS conditions.…”

Section: Resultsmentioning

confidence: 98%

Application of capillary supercritical fluid chromatography–double focusing mass spectrometry under negative ion chemical ionization conditions

Huang

Jackson

Markides

et al. 1990

J Microcolumn Separations

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Abstract. The application of mass spectrometry in the negative ion mode with capillary column supercritical fluid chromatography is described. The supercritical fluid chromatography mobile phase (CO,) was used as the primary reagent gas to generate thermalized electrons and reagent anions (such as 0-and CO;). When trace amounts of CH4 or NH, gas were also introduced into the chemical ionization source, the mass spectrometer sensitivity was increased. Detection limits ( S / N = 5 ) for heptachlor were determined to be 20 pg and 200 fg for full scan and selected ion monitoring modes, respectively. Mass spectra of a cyclic peptide, valinornycin, obtained with these mixed reagents (CH, + CO, and NH, + CO,) gave the molecular anion at m/z 11 10 as the most abundant ion and additional fragment ions that yielded peptide sequence information.

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Raman Spectroscopic study of valinomycin-metal complexes

Cited by 6 publications

References 10 publications

Formation and structure of the potassium complex of valinomycin in solution studied by Raman optical activity spectroscopy

Formation and structure of the potassium complex of valinomycin in solution studied by Raman optical activity spectroscopy

Direct heated interface probe for capillary supercritical fluid chromatography/double focusing mass spectrometry

Application of capillary supercritical fluid chromatography–double focusing mass spectrometry under negative ion chemical ionization conditions

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