Deuterated plant extracts

Figure 7. An example of the use of deuterated GA s as internal standards for the quantitation of GA s in plant extracts. [2a-zH1]GAts was added to an extract of young pea seeds in order to quantitate GA29 (cf. 25). Ions in the region of the molecular ion were scanned. The acidic fraction from the pea seed extract was run as the Me TMS derivative on a MS 30 coupled to a Pye 104 GC via a single-stage silicone membrane separator (34).

GC-MS with or without SIM is the most reliable identification tool of BRs.739 Prior to GC-MS analysis, vicinal hydroxyls in BRs are derivatized to methaneboronates, while isolated hydroxyl groups are converted to trimethylsilyl ethers (Figure 31). Fragment ions derived from the side chains have been used as diagnostic ions for mass spectrometric detection of BRs (Figure 31). Mass spectrometric data on methaneboronate derivatives of BRs have been reviewed.754 For quantitation of the endogenous levels of BRs, deuterated BRs have been frequently used as internal standards by adding to plant extracts.739... 

Plant material is homogenized in acetone followed by addition of water. The filtered extract is diluted with acetone-water (2 1 v/v) and filtered through a syringe filter. The sample extract is diluted 1 1 with a deuterated azinphos-methyl internal standard and analyzed using LC/MS/MS in the positive-ion selected reaction monitoring (-I-SRM) mode. 

DFI Kohl and PM Wood (1969) On the molecular identity of ESR signal II observed in photosynthetic systems The effect of heptane extraction and reconstitution with plastoquinone and deuterated plastoquinone. Plant Physiology 44 1439-1445... 

Fig. 2. (A) K-band ESP-EPR spectra of the CPI complex (top) and Rb sphaeroides R26 reaction-center complex (bottom) in the charge-separated states [P700 -A,4 and [P870 Q4, respectively (B) X-band ESP-EPR spectra of spinach PS-I particles extracted with a hexane-MeOH mixture (a), reconstituted with protonated (b) and deuterated (c) vitamin Ki (C) ESP-EPR spectra of spinach PS-I particle in glycine buffer at pH 10.8 and untreated (a), reduced with 50 mM dithionite and 0,5 mM methyl viologen and dark-incubated (b), and the reduced sample dialyzed overnight against glycine buffer and reconcentrated (c). Figure source (A) Petersen, Stehlik, Gast and Thurnauer (1987) Comparison of the electron spin polarized spectrum found in plant photosystem I and in iron-depleted bacterial reaction centers with time-resolved K-band EPR evidence that the photosystem I acceptor is a quinone. Photosynthesis Res 14 22 (B) and (C) Snyder and Thurnauer (1993) Electron spin polarization in photosynthetic reaction centers. In J Deisenhofer and JR Norris (eds) The Photosynthetic Reaction Center, Vol 11 313,315.

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