Assignment of phycocyanobilin in HMPT using triple resonance experiments

A complete assignment of all resonances of a small organic molecule is a prerequisite for a structure determination using NMR spectroscopy. This is conventionally obtained using a well‐established strategy based on COSY, HMQC and HMBC spectra. In case of phycocyanobilin (PCB) in HMPT this strategy was unsuccessful due to the symmetry of the molecule and extreme signal overlap. Since ¹³C and ¹⁵N labeled material was available, an alternative strategy for resonance assignment was used. Triple resonance experiments derived from experiments conventionally performed for proteins are sensitive and easy to analyze. Their application led to a complete and unambiguous assignment using three types of experiments. Copyright © 2011 John Wiley & Sons, Ltd.