Figure 1

ESI spectrum of a recombinant intersectin SH3 domain-containing protein (Yvonne Grömping Group, Dep. of Biomolecular Mechanisms). The protein exhibits multiple peaks, with charges from +5 to +9 and thus a range of mass/charge (m/z) values. The experimentally determined mass of the intact protein is 7204.6 Da, which is in good agreement with the calculated average mass of 7205.4 Da.

Figure 2

Maldi TOF analysis of a partially purified recombinant protein yielded the expected m/z value (left) and a number of lower m/z contaminants (right). Peptide ladder analysis generated the sequence shown (in one letter code), identifying the contaminants as breakdown products of the full-lenght protein.

Figure 3

One example of such an analysis is Figure 3. Certain crystallization screen conditions result in the formation of a massive shower of rod-like crystals from a recombinant chaperone protein (Jochen Reinstein Group / Ilme Schlichting Group, Dep. Biomolecular Mechanisms). Individual crystals can be teased out and washed (Figure 3B). After transfer to the Maldi plate, the crystal is dissolved and analyzed (Figure 3C). Anylyses of the starting protein solution, the wash solutions and the dissolved crystal show that, in this case, the protein molecules in the crystal have m/z values identical to that of the starting material. In those quite common situations where this is not the case, PMF mass spectrometry has proven indispensable in identifying the missing amino acids, which can be invaluable for (re)interpretation of electron density maps and/or for new cloning/protein experiments. Maldi TOF analysis of a single protein crystal. A crystallization reaction of a recombinant molecular chaperone protein prduces a shower of crystals (A), from which a single crystal was isolated (B) and subsequently washed. Maldi TOF analysis demonstrated that the protein in the crystal was identical to that in the starting solution.

Figure 4

The XPSPECTRA microspectrophotometer installed at the protein crystallography X10SA beamline at the Swiss Light Source (SLS) at the Paul Scherrer Institute, Villigen, Switzerland. The optical axis and the synchrotron beam axis intersect within a 20 μm spot on which the crystal is centered.

Figure 5

A crystal of a BLUF domain protein in various positions on the microspectrophotometer and its UV-VIS spectrum (left). Maldi TOF analysis of the same crystal (right) demonstrates that this protein contains bound FAD and not FMN.

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