AN ELECTROSPRAY-IONIZATION MASS-SPECTROMETRIC STUDY OF THE EXTRACELLULAR HEMOGLOBINS FROM CHIRONOMUS-THUMMI-THUMMI

The aquatic larvae of the dipteran Chironomus thummi thummi contain ex tracellular hemoglobins which exhibit stage-specific expression. We ha ve used maximum entropy-based deconvolution of the complex, multiply c harged electrospray ionization mass spectra, to demonstrate the presen ce of more than 20 components, ranging in mass from 14,417.3 Da to 17, 356.5 Da in the 4th instar larvae. Of the 15 major peaks with intensit ies > 10 relative to 100 for the 14,417.3 Da-component (CTT-IV), only the 15,528.2-Da peak does not correspond to a known amino acid sequenc e. Since the number of C. thummi thummi globin genes now stands at 27, including one cDNA and not counting three that must encode known glob ins, our results suggest that only a limited number of the globin gene s are expressed in the 4th instar larvae. (C) 1998 Elsevier Science B. V.