MS And MALDI-TOF Flashcards
Mass spectrometer is able to
Measure atomic and molecular weights of charged species
Analyse low levels of compound
Analyse mixtures
Defn mass spectrometry
Process of weighing molecules based on ratio of mass and charge
How to impart charge in MS
Electron impact/ ionization
Form radical cation (molecular ion)
Defn isotope
Atom of the same element with different number of neutrons. More mass same charge
How to calculate mass accuracy needed
Half (dif between molecular weights/ mol weight of highest)
Defn mass resolution
Ability to differentiate two ion signals from one another in mass spectrum
Three basic components of mass spectrometer
Ion source
Mass analyzer
Ion detector
Two ways to ionize sample
Matrix assisted laser desorption ionization
Electro spray ionization ( [] dependent)
Types of mass analyses
TOF
Quadrupoles
Quadrupole in trap
Ion cyclotron resonance
What is adv of reflector TOF MS
Higher resolution as tube effectively twice as long and ion mirror is penetrated to varying degrees depending on kinetic energy
How does quadrupole work
Four poles. Opposites have like charges. Cause molecules to oscillate. If oscillation to large ion is lost. Therefore only particular molecules can pass at given setting/interval
Ion with …. M/z have … cyclotron frequencies
Lower - higher
Higher - lower
B ions contain …
Y ions contain …
N terminus
C terminus
How does one identify proteins in MS
Digest product with trypsin (cleaves after K or R) collide peptide with high energy inert gas. Measure mass spectra of fragments. Difference between peaks correspond to aa sequence.
