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. Author manuscript; available in PMC: 2012 May 17.
Published in final edited form as: Biochemistry. 2011 Apr 22;50(19):3891–3902. doi: 10.1021/bi1017039

Figure 4.

Figure 4

Direct MALDI MS quantification of lipids relative to phospholipid internal standards (i.s.) in the unextracted isolated membranes (mem.) from R. sphaeroides strains under different growth conditions as described in Materials and Methods: WT/ P+, CL−/ P+, WT/ P− and CL−/ P−. (A) positive ion mode, (B) negative ion mode m/z 600–1000, and (C) negative ion mode m/z 1200–1600. The highlighted peaks emphasize internal standards and lipids of interest. In (A) under P− conditions loss of PC (m/z 286, 824, 838) and gain of DGTS (m/z 802) is seen, while in (B) under P− conditions, there is relative loss of PG (m/z 773) and retention of SQDG (m/z 819,821,845, 847 849). In (C) under P− conditions, loss of CL (m/z 1455.8, 1429.8) is seen relative to CL internal standard (m/z 1239.5). The negative ion mode peaks at m/z 1495.9, 1497.9, 1533.8 and 1535.8 were determined by MS/MS and MSn not to be CL or CL derivatives.