Order Mass Spectrometry Assignment

Order Mass Spectrometry Assignment
6.1 Modern mass spectrometers allow us to combine electrospray ionization
with a time-of-flight analyser. Discuss the potential advantages of such an
arrangement.
6.2 a. In a MALDI-TOF experiment ions are detected 250 μs after laser
irradiation. What is the mass of one mole of the investigated molecules
Figure 6.14 Peptide ladder sequencing. The differences between the mass peaks correspond
to the masses of amino acid subunits. The amino acid sequence of the original peptide corresponds to the sequence of mass differences in the spectrum.
164 6 Mass Spectrometry
when no ions can be detected at other times? The tube is 2 m long and
the acceleration voltage is 5 kV. Is the sample a peptide or a protein?
b. At what time after the laser irradiation would you expect the ions of a
fluorescent label of molecular weight 100 g mol1
Order Mass Spectrometry Assignment
6.3 You want to analyse a mixture of different biomolecules by MALDI mass
spectroscopy. You are not sure if the mixture contains exclusively proteins
or also oligonucleotides. What compound would you select for the matrix
preparation?
6.4 The natural abundance of 13C is ∼1.11%. Calculate the intensity distribution of the isotope peaks in the MALDI mass spectra of a singly charged
1 kDa peptide and a singly charged 10 kDa protein. Assume that no other
elements than carbon occur in different isotopes in the biomolecules and
that carbon accounts for ∼80% of the total mass of the biomolecules.
6.5 A quadrupole mass analyser is adjusted in such a way that only proteins
corresponding to a very narrow distribution of mass-to-charge ratio values
can pass the analyser. What instrumental parameters do you have to
change, and in what way, if you want to use the analyser to select proteins
corresponding to a larger range of mass-to-charge ratio values?
6.6 Ion traps can be used to store biomolecule ions of a distinct sample and
eject and analyse biomolecule ions of distinct mass-to-charge ratio one
after another. In what situation is such a procedure especially useful?
6.7 Sketch the mass spectrum you would expect in a peptide ladder sequencing of the peptide Pro-Lys-Gly-Cys-Trp-His-Gly. Consider the convention
that the primary sequence of peptides or proteins starts at the N-terminus.
6.8 You are not sure whether a distinct protein occurs as a trimer or a tetramer. How could you distinguish between these two possibilities?