Mass spectrometry validation of fluorescently labeled chemokines.

aMolecular weight of the adduct (dye and the phosphopantetheinyl arm of coenzyme A) in Daltons as determined by mass spectrometry following the PPTase reaction, assuming the formation of the appropriate number of disulfide bonds for the given chemokine.bTheoretical molecular weight of the adduct based on the published structure of the dye.cCXCL12 mutant with CXCR4 antagonist properties developed in our laboratory (manuscript in preparation).Abbreviations: PPTase, phosphopantetheinyl transferase. NA, not available. ND, not determined. CPM, 7-diethylamino-3-(4′-maleimidylphenyl)-4-methylcoumarin. NPM, N-(1-pyrenyl)maleimide. GAG, glycosaminoglycan. vMIP-II, viral macrophage inflammatory protein-II.