Blackbody infrared radiative dissociation of larger (42 kDa) multiply charged proteins

Blackbody infrared radiative dissociation (BIRD), demonstrated originally w ith ions as large as 17 kDa, has been applied to larger proteins in a 6 T F ourier-transform mass spectrometer. For carbonic anhydrase (29 kDa), ThiF ( 27 kDa), and thiazole kinase (29 kDa), ion cell temperatures of 60-110 degr eesC give mostly uninformative H2O loss, but 145 degreesC gives extensive b ackbone dissociation. For carbonic anhydrase ions at 70 degreesC, H2O loss continues for > 240 s; thermalizing ions for similar to 30 s reduces H2O lo ss eightfold. For thiaminase I (42 kDa), H2O loss is not observed, with bac kbone dissociation occurring above 150 degreesC. For these proteins, BIRD h as effected cleavages of 34, 41, 23, and 28, respectively, backbone bonds. Although most are the same as those cleaved by infrared multiphoton dissoci ation and collisionally activated dissociation, some BIRD cleavages do prov ide additional and complementary sequence information. Carbonic anhydrase a lso shows extensive H2O loss from its fragment ions that compromises their validity for sequencing. (C) 2001 Elsevier Science B.V.