Discussion-2-Jan 10, 2025

What is the key difference between b-ions and y-ions?

• b-ions retain charge on the C-terminal, y-ions on the N-terminal.

• b-ions retain charge on the N-terminal, y-ions on the C-terminal.

• Both b-ions and y-ions retain charge on the N-terminal.

• Both b-ions and y-ions retain charge on the C-terminal.

Why is the y-ion series often more intense than the b-ion series in tandem MS?

• Peptides fragment more readily at the N-terminal.

• y-ions are detected at higher resolution than b-ions.

• b-ions are unstable during collision-induced fragmentation.

• Tryptic peptides have Lys/Arg at the C-terminus, which retains the positive charge.

What is the goal of tandem mass spectrometry (MS/MS)?

• Determine the 3D structure of proteins.

• Measure the abundance of neutral molecules.

• Obtain peptide sequence information.

• Quantify lipids in a sample.

How is the monoisotopic mass of a protein defined?

• The sum of masses for all isotopes of each element.

• The sum of abundance-weighted masses of all stable isotopes.

• The sum of masses for the most abundant isotope of each element.

• The average molecular mass of the protein.

Why can neutral molecules not be analyzed in a mass spectrometer?

• They cannot generate adducts.

• They cannot be focused or accelerated by ion optics.

• They have unstable isotopes.

• They lack a measurable mass.