Long-lived metallized tips for nanoliter electrospray mass spectrometry

Sheathless electrospray at nL/min flow rates combined with Fourier-transform mass spectrometry has made possible high resolving power (> 50,000) mass spectra of subattomole samples of > 8 kDa proteins separated by capillary electrophoresis (Valaskovic, G. A.; Kelleher, N. L.; McLafferty, F. W. Science, 1996, 273, 1199–1202). However, for this new method the mechanical stability of the thin (35 to 100 nm) gold film electrodes has limited tip lifetime to 15 to 30 min. A technique for SiOx coating of the gold is described that provides a steady ion current (± 10 pA) for 1 to 2 h, even with arcs or interruptions of the electrospray voltage

Fourier-transform electrospray instrumentation for tandem high-resolution mass spectrometry of large molecules

AbstractMass spectrometry instrumentation providing unit resolution and 10-ppm mass accuracy for molecules larger than 10 kDa was first reported in 1991. This instrumentation has now been improved with a 6.2-T magnet replacing that of 2.8 T, a more efficient vacuum system, ion injection with controlled ion kinetic energies, accumulated ion trapping with an open-cylindrical ion cell, acquisition of 2M data points, and updated electrospray apparatus. The resulting capabilities include resolving power of 5 × 105 for a 29-kDa protein, less than 1-ppm mass measuring error, and dissociation of protein molecular ions to produce dozens of fragment ions whose exact masses can be identified from their mass-to-charge ratio values and isotopic peak spacing

Interpretation of mass spectra

XVII+371hlm.;24c

A Conversation with Fred W. McLafferty

Sponsored by the Oral History Project of the Department of Chemistry and Chemical Biology at Cornell University, led by Charles Wilcox and Kelly Strickland, this presents an extended interview with a senior member of the faculty, Fred McLafferty, in which he shares his life's journey, professional interests and reflections about the distinctive character of his department and its nurturing environment. Topics [m:s]: Biography [13:37]; Cornell Faculty [6:26]; Department Changes [19:54]; Industry Changes [4:48]; McLafferty Rearrangement [6:46]; Long View [10:51]; Fourier Transform [9:21]; Next Frontiers [10:46]; Concluding Remarks [3:59] Short biographies of interviewee and interviewer [Hector Abruna] are included, in addition to a photo gallery and list of publications of the interviewee. Video Total Run Time: 1 hr and 31 minutes The streaming video is openly accessible at: http://ifup.cit.cornell.edu. The DVD was produced by J. Robert Cooke.1_n4r9fbm

Automated de novo sequencing of proteins by tandem high-resolution mass spectrometry

A de novo sequencing program for proteins is described that uses tandem MS data from electron capture dissociation and collisionally activated dissociation of electrosprayed protein ions. Computer automation is used to convert the fragment ion mass values derived from these spectra into the most probable protein sequence, without distinguishing Leu/Ile. Minimum human input is necessary for the data reduction and interpretation. No extra chemistry is necessary to distinguish N- and C-terminal fragments in the mass spectra, as this is determined from the electron capture dissociation data. With parts-per-million mass accuracy (now available by using higher field Fourier transform MS instruments), the complete sequences of ubiquitin (8.6 kDa) and melittin (2.8 kDa) were predicted correctly by the program. The data available also provided 91% of the cytochrome c (12.4 kDa) sequence (essentially complete except for the tandem MS-resistant region K(13)–V(20) that contains the cyclic heme). Uncorrected mass values from a 6-T instrument still gave 86% of the sequence for ubiquitin, except for distinguishing Gln/Lys. Extensive sequencing of larger proteins should be possible by applying the algorithm to pieces of ≈10-kDa size, such as products of limited proteolysis