Question 1

Which combination of analytical techniques is most commonly used in tandem mass spectrometry (MS/MS) for protein sequencing?

Accepted Answer

Mass spectrometer with a mass spectrometer

Question 2

In tandem mass spectrometry, what is the primary advantage of using two mass spectrometers in sequence?

Accepted Answer

It enables filtering of unwanted ions to obtain a much cleaner and simpler mass spectrum.

Question 3

During tandem mass spectrometry, what is the role of the collision cell?

Accepted Answer

It fragments selected protein ions by collision with an inert gas.

Question 4

A protein fragment with a mass-to-charge ratio ($m/z$) of 1,169 passes into the second mass spectrometer and you find peaks at $m/z$ values of 1,137 and 1,082. What is the most likely explanation for these peaks?

Accepted Answer

They represent fragments formed by sequential loss of amino acid residues.

Question 5

If a peptide fragment has the following amino acid masses: D (115), G (57), L (113), and M (131), and the fragment mass is 1,268, which two amino acids are most likely at the N-terminal end if the first two residues sum to 246?

Accepted Answer

N and M

Question 6

Which of the following best describes the process of protein fragmentation in tandem mass spectrometry?

Accepted Answer

Proteins are fragmented by collision with an inert gas in a vacuum chamber.

Question 7

Why is tandem mass spectrometry considered the gold standard for sequencing proteins?

Accepted Answer

It can analyze purified proteins or a single protein in a mixture.

Question 8

In the context of tandem mass spectrometry, what does the term $m/z$ refer to?

Accepted Answer

The ratio of mass to charge of an ion.

Question 9

Which step in tandem mass spectrometry is responsible for selecting a specific peptide ion for fragmentation?

Accepted Answer

The first mass spectrometer (MS1)

Question 10

A researcher uses tandem mass spectrometry to analyze a protein mixture. What is the main reason for using this technique over single-stage mass spectrometry?

Accepted Answer

It enables sequencing of proteins even in complex mixtures.

Question 11

Which of the following is NOT a typical application of tandem mass spectrometry in biochemistry?

Accepted Answer

Measurement of protein concentration in solution

Question 12

In tandem mass spectrometry, what is the purpose of filtering unwanted ions before fragmentation?

Accepted Answer

To obtain a cleaner and more interpretable mass spectrum

Question 13

Which of the following statements about tandem mass spectrometry is TRUE?

Accepted Answer

It can analyze both purified proteins and proteins in mixtures.

Question 14

A scientist is analyzing a peptide using tandem mass spectrometry. After fragmentation, the mass spectrum shows peaks corresponding to $m/z$ values that decrease by approximately the mass of individual amino acids. What does this pattern indicate?

Accepted Answer

The peptide is undergoing sequential loss of amino acid residues.

Question 15

Which device in tandem mass spectrometry is responsible for measuring the $m/z$ of fragmented ions?

Accepted Answer

The second mass spectrometer (MS2)

Question 16

In a tandem mass spectrometry experiment, why is it important to use an inert gas in the collision cell?

Accepted Answer

To facilitate fragmentation of peptide ions without chemical modification.

Question 17

Which of the following best explains why tandem mass spectrometry can be used to sequence proteins in a mixture?

Accepted Answer

It can selectively fragment and analyze individual peptide ions from a complex mixture.

Question 18

A tandem mass spectrometry experiment produces a series of peaks at $m/z$ values corresponding to the loss of specific amino acids. How can this information be used to determine the sequence of the peptide?

Accepted Answer

By matching the mass differences between peaks to the known masses of amino acids.

Tandem Mass Spectrometry in Protein Analysis

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