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Molecular Composition of Leaves and Stems of Genetically Modified Bt and Near-Isogenic Non-Bt Maize—Characterization of Lignin Patterns

^a UFZ-Center for Environmental Research Leipzig-Halle Ltd., D-04318 Leipzig, Germany
^b RWTH Aachen, Institute of Environmental Research (Biology V), Chair of Ecology, Ecotoxicology, Ecochemistry, D-52076 Aachen, Germany
^c Leibniz-Center for Agricultural Landscape and Land Use Research, D-15374 Muncheberg, Germany
^d Department of Chemistry, University of Waterloo, Waterloo, ON, N2L 3G1 Canada

View larger version (15K): [in a new window]   Fig. 1. Structures of analytes released after tetramethylammonium hydroxide (TMAH)-induced thermochemolysis of lignin (P-type: R1 = H, R2 = H; G-type: R1 = OCH3, R2 = H, S-type: R1 = OCH3, R2 = OCH3); modified from del Rio et al. (1998).

View larger version (43K): [in a new window]   Fig. 2. Total ion chromatogram (TIC) of lignin breakdown products after tetramethylammonium hydroxide (TMAH) thermochemolysis. Sample: non-Bt maize stem (Prelude). Thermochemolysis: on-line, 500°C, 25% TMAH solution in methanol, capacitive discharge heating (see text). Stationary phase: DB-624 (GC conditions: see text). Peak labels: see Fig. 1 (molecular mass in Dalton in parentheses).

View larger version (14K): [in a new window]   Fig. 3. Lignin markers P18 and G18 in stems of maize of the transgenic Bt line (Novelis T, top) and the near-isogenic non-Bt line (Nobilis, bottom) obtained by thermochemolysis. Stationary phase: DB-5ms. The chromatograms (shown in mirror representation, time in min) present the sum of extracted ions acquired in full scan mode: molecular ion m/z = 192 amu for P18, molecular ion m/z = 222 amu for G18 and molecular ion m/z = 188 amu for phenanthrene-d10 (internal standard, IST). Peak areas of the target analytes normalized to the peak areas of the internal standard for better comparison.

View larger version (23K): [in a new window]   Fig. 4. Lignin markers obtained on CuO oxidation. Top: stem of Bt line Novelis T, bottom: stem of near-isogenic non-Bt line Nobilis. Data in parentheses: molecular mass of the free phenol (in Dalton). Peaks referred to identical internal standard (IST) (deuterated dimethylphenol; target molecular mass ion: m/z = 125 amu). GC–MS: free fatty acid phase (FFAP) stationary phase. Data presentation: Extracted ions (full scan data acquisition mode).

View larger version (23K): [in a new window]   Fig. 5. Lignin markers obtained by CuO oxidation; sample subjected to BF3/methanol methylation (see Materials and Methods). Top: Novelis T, Bt stem; bottom: Nobilis, non-Bt stem. Acids S6 and G18 (see Fig. 1) in methylated form. Presentation as superposition of three ion traces. GC–MS conditions: see caption to Fig. 4.