Collision-induced dissociation

Definition

Collision-induced dissociation (CID) is a process in mass spectrometry where ions are fragmented into smaller pieces by colliding with neutral gas molecules. This technique is essential for understanding the structure and composition of biomolecules, particularly proteins, by providing detailed information about their sequence and post-translational modifications.

5 Must Know Facts For Your Next Test

1. CID helps in determining the amino acid sequence of proteins by analyzing the fragmentation patterns generated during the collision process.
2. In CID, the energy from colliding ions with gas molecules can lead to the breaking of chemical bonds within the ion, creating smaller fragments that can be analyzed.
3. The efficiency of CID can be influenced by factors such as collision energy, the type of gas used, and the physical properties of the ions being studied.
4. CID is particularly useful for characterizing post-translational modifications because different modifications can affect how a protein fragments during the process.
5. The ability to perform CID in tandem mass spectrometry allows for more sensitive detection and quantification of proteins and their variants in complex biological samples.

Review Questions

• How does collision-induced dissociation contribute to determining the amino acid sequence of proteins?
  • Collision-induced dissociation provides crucial insights into amino acid sequences by breaking down protein ions into smaller fragments upon collision with neutral gas molecules. The resulting fragmentation patterns are then analyzed through tandem mass spectrometry, allowing researchers to deduce the original sequence based on the mass-to-charge ratios of the fragments. This process is essential for accurately sequencing proteins and understanding their structural features.
• What role does collision energy play in collision-induced dissociation, and how might varying this energy affect the results?
  • Collision energy is a critical parameter in collision-induced dissociation as it determines how much kinetic energy is transferred to the ions during collisions. If the energy is too low, insufficient fragmentation may occur, resulting in incomplete or inaccurate structural information. Conversely, excessive energy can lead to excessive fragmentation or loss of critical information about the parent ion. Therefore, optimizing collision energy is vital for achieving reliable and interpretable results in mass spectrometry analyses.
• Evaluate how collision-induced dissociation aids in the characterization of post-translational modifications in proteins.
  • Collision-induced dissociation is instrumental in characterizing post-translational modifications because it allows researchers to observe how different modifications affect ion fragmentation patterns. By comparing fragmentation profiles of modified versus unmodified forms of a protein, scientists can identify specific PTMs based on unique fragment ions generated during CID. This analysis not only reveals the presence of modifications but also helps in determining their location within the protein sequence, contributing to a deeper understanding of protein function and regulation.

Related terms

Tandem Mass Spectrometry: A mass spectrometry technique that involves multiple stages of mass analysis to isolate and fragment ions, enabling detailed analysis of complex mixtures.

Fragmentation Patterns: The specific ways in which ions break apart during CID, which can provide insights into the molecular structure and sequence of the original molecule.

Post-Translational Modifications (PTMs): Chemical modifications that occur to proteins after translation, which can influence their function, localization, and stability.