The figure shows the partial sequence of the α_A1 globin and the postulated sites and products of cleavages generated by CID in the gas phase. Below, portions of the CID electrospray ionization mass spectra of the zebrafish adult α globins are shown. Identities of the product ions generated from the α_A1 globin (upper panel) are based on correspondence between the measured and predicted m/z values for the series of y- and b-type ions observed in the spectrum. Tentative assignment of product ions observed in the spectra of α_A2 and α_A3 globins (middle and bottom panels, respectively) is based on the premise that all zebrafish α chains fragment in the gas phase as shown at the top of the figure. This assumption is reinforced by agreement between the molecular masses of the α_A2 and α_A3 globins measured for intact molecules (Fig 7) and calculated from the m/z values of the putative b- and y-fragment ions observed in the CID spectra. Ions marked with dots in the bottom panel are believed to be derived from the minor component of the α_A3 -globin fraction and might indicate the presence of an additional α-type globin in adult zebrafish blood. Consult legend to Fig 8 for nomenclature used for peak annotation in the CID spectra.