High resolution electron impact

Pseudopterosin X (1) was isolated as a yellow colored gum. The UV spectrum of 1 showed maximum absorption at 280 nm due to the presence of a highly substituted benzene chromophore [10], Its IR spectmm displayed intense absorption bands at 3,470 (OH), 2,904 (CH), 1,705 (C = O), 1,595 (C = C) and 1,100 (C-0) cm . The high-resolution electron-impact mass spectmm (HREIMS) of 1 showed M+ at m/z 474.2622, and this mass provided molecular formula indicating the presence of nine double bond equivalents in 1. The C-NMR chemical shift assignments of 1 are shown around stracture 1. On the basis of the detailed NMR studies and comparison with the reported pseudopterosins in the literature and L-xylose [3-5], stmcture 1 was proposed for this new natural product. 

As a representative example of these compounds, the analysis of the high-resolution, electron-impact (e.i.) mass spectrum of the D-glucopyr-anose derivative 134 is shown in Fig. 4. 

High resolution electron impact mass spectral analyses were carried out at the Midwest Center for Mass Spectrometry, University of Nebraska, Lincoln, Nebraska. The samples were rapidly heated to about 450 C. 

HREI-MS high-resolution electron-impact mass spectrometry... 

Demethylsonodione (7), a p-quinonoid aporphine, was obtained as greenish prisms. Its molecular formula was determined as C19H17O5N by high-resolution electron impact mass spectrometry (HREIMS) at m/z 339.1098 [M]+ [24]. The UV spectrum with maxima at 219, 283, 336, and 642 nm was typical of a p-quinonoid aporphine skeleton [53]. In its IR spectrum, absorption bands at 3440 cm 1 (phenolic hydroxyl) and 1635 cm 1 (carbonyl) were apparent. The H-NMR spectrum indicated signals... 

HR-EI-MS = High Resolution-Electron Impact Ionization-Mass Spectrometry. 

HA-LAESI heat-assisted laser ablation electrospray ionization HR-EI high-resolution electron impact... 

Various mass spectral techniques have been used in characterizing various metal-containing macromolecules. The focus will be on two techniques. The first one is the most commonly employed mass spectrophotometer setup, called high-resolution electron impact mass spectrometry (HREl-MS). The second system is the matrix-assisted laser desorption ionization (MALDl) system. Illustrative examples of these two procedures are given for the products of Group IVB metallocene dichlorides and the antibacterial drug norfloxacin, scheme 8. 

High resolution electron impact mass spectra High resolution mass spectra Nuclear magnetic resonance relative to proton Infrared spectra... 

Acetone powder (2 g) of com seeds Zea mays L.) was prepared and extracted as described previously [3]. The cmde extract was immediately incubated with 32 KBq 9-hydroxy-16-hydroperoxy- 10(E), 12(2), I4( )-[ I- C]octadecatrienoic acid (1.3 MBq/mmol) at 22° C for 1 h. Substrate was prepared by incubation of potato (Solarium tuberosum L.) tuber homogenate with 74 KBq [l- " C]linolenic acid (1.3 MBq/mmol) as described before [4]. The products were extracted by ethyl acetate and analyzed by RP- and SP- HPLC as described previously [3]. Radioactivity in the eluate was detected by HPLC radioisotope detector Beckman 171 (Beckman, USA). Ultraviolet spectra (190-370 nm) were recorded in line during HPLC analysis using RSD 2140 diode-array detector (LKB, Bromma, Sweden). High-resolution electron-impact mass... 

Azonazine is an unusual hexaqrdic dipeptide that includes a diketopiperazine moiety that was isolated from the Hawaiian marine sediment-derived fungus Aspergillus insulicola The absolute configuration was established by extensive nuclear magnetic resonance (NMR), high-resolution electron impact mass spectrometry (HREIMS) and circular dichroism (CD) analysis. 

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