FTMS Structure Elucidation of Natural Products:  Application to Muraymycin Antibiotics Using ESI Multi-CHEF SORI-CID FTMSⁿ, the Top-Down/Bottom-Up Approach, and HPLC ESI Capillary-Skimmer CID FTMS

Abstract

The molecular formulas for the structures and substructures of muraymycin antibiotics A1 (C52H90N14O19, MW 1214) and B1 (C49H83N11O18, MW 1113) were determined using electrospray ionization (ESI) Fourier transform mass spectrometry (FTMS). The muraymycin A1 and B1 structures were elucidated by utilizing capillary-skimmer fragmentation with up to five stages of mass spectrometry (MS5). Multi-CHEF, a multiple ion isolation method, was used at each stage of MS(n) to isolate a parent ion and up to four reference ions, for exact-mass calibration. The parent ions were fragmented by SORI-CID and the product ions internally calibrated with average absolute mass errors less than 1 ppm at each stage in the fragmentation processes. Using the top-down/bottom-up approach, the molecular formulas for the antibiotics were determined by summing the elemental formulas of the neutral losses, obtained by measuring the mass differences (<500 Da) between the genetically related sequential parent ion masses in the MS(n) spectra, with the unique elemental formula of the lowest parent ion mass (<500 Da). The structures of 12 additional compounds in the muraymycin complex were elucidated using HPLC ESI capillary-skimmer CID FTMS by correlating their fragmentation patterns with those of muraymycins A1 and B1. Sequential neutral losses of an aminosugar, a valine, a uridine, and an ester fatty acid from the muraymycin parent ions provided diagnostic fragments for characterization.

Differentiating Fragmentation Pathways of Cholesterol by Two-Dimensional Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

“…Furthermore, with quadrupole isolation, increasing the resolution in precursor selection goes hand in hand with a decrease in signal intensity, which is not an issue in the 2D FT-ICR experiment [38]. Other isolation methods, such as SWIFT [39,40] or CHEF [39,[41][42][43][44][45], are available for high-resolution isolation windows within the ICR cell. Other ion trapping devices, like linear or quadrupolar ion traps [46], can select ions with a narrow isolation window (1 Da or better) using tailored waveforms.…”

Microbial paclitaxel: advances and perspectives

“…80 Accurate quantitative HPLC analysis depends on complete resolution of paclitaxel from other taxanes with similar physicochemical properties; that is, separation can not be considered trivial as some taxanes have similar retention times. Figure 2 (a) HPLC-ESI-MS chromatogram of taxane standard (Hauser Inc., Boulder, CO, USA) containing 10-deacetylbaccatin III (1), baccatin III (2), 10-deacetyl-7-xylosyltaxol B (3), 10-deacetyl-7-xylosyltaxol (4), taxinine M (5), 10-deacetyl-7-xylosyltaxol C (6), 10-deacetyl-taxol (7), 7-xylosyltaxol (8), cephalomannine (9), 10-deacetyl-7-epitaxol (10), taxol (11), taxol C (12) and 7-epitaxol (13 82 NMR, although more convincing than the techniques cited above, requires relatively large amounts of purified paclitaxel, difficult to obtain in microbial cultures. Many fungi and some bacteria have been reported in the literature as paclitaxel producers with concentrations ranging from 0.024 to 800 ng ml À1 (Table 1).…”

Modern mass spectrometry for synthetic biology and structure-based discovery of natural products

“…44 MS 2 data have also been used to automatically narrow down potential chemical formulae. 53-55 In fact, this method can be paired with matching isotope patterns for de novo chemical formula determination, which is particularly helpful when dealing with an unknown compound and beginning a full structure determination. 56,57 …”