Combining UV Absorbance and Diagnostic CID Fragment Ions to Identify and Distinguish Isobaric Chromophores on Phycobiliproteins
Abstract:
Certain cyanobacteria change the tetrapyrrole pigments attached to phycoerythrin inresponse to the color of light available. These tetrapyrrole pigments consist ofphycoerythrobilin (PEB) and phycourobilin (PUB) which are structural isomers PEB andPUB differ in the position of one double bond and are therefore isobaric but have differentUV-absorbance spectra. Each phycobiliprotein may have several bilin pigments attached tovarious cysteine residues. Researchers purify microgram amounts of protein to performHPLC-UV-VIS experiments to identify the pigments utilized by the organism. The pigmentsattached to phycoerythrins produced in green vs blue light in Synechococcus RS 9916 havenot been determined. This work utilizes the CID fragmentation patterns of differentbilipeptides in conjunction with UV-absorbance to facilitate pigment attachment siteidentifications.
