Characterisation of uniformly 13C, 15N labelled bacteriochlorophyll a and bacteriopheophytin a in solution and in solid state: complete assignment of the 13C, 1H and 15N chemical shifts

In this investigation we report a complete assignment of C-13, H-1 and N-15 solution and solid state chemical shifts of two bacterial photosynthetic pigments, bacteriochlorophyll (BChl) a and bacteriopheophytin (BPheo) a. Uniform stable-isotope labelling strategies were developed and applied to biosynthetic preparation of photosynthetic pigments, namely uniformly C-13, N-15 labelled BChl a and BPheo a. Uniform stable-isotope labelling with C-13, N-15 allowed performing the assignment of the C-13, N-15 and H-1 resonances. The photosynthetic pigments were isolated from the biomass of photosynthetic bacteria Rhodopseudomonas palustris 17001 grown in uniformly C-13 (99%) and N-15 (98%) enriched medium. Both pigments were characterised by NMR in solution (acetone-d(6)) and by MAS NMR in solid state and their NMR resonances were recorded and assigned through standard liquid 2D C-13-C-13 COSY, H-1-C-13 HMQC, H-1-N-15 HMBC and solid 2D C-13-C-13 RFDR, H-1-C-13 FSLG HETCOR and H-1-N-15 HETCOR correlation techniques at 600 MHz and 750 MHz. The characterisation of pigments is of interest from biochemical to pharmaceutical industries, photosynthesis and food research. Copyright (C) 2008 John Wiley & Sons, Ltd.