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Contents : Lecture 2 Mass Analyzers for Protein Analysis Nancy Allbritton M.D. Ph.D. Department of Physiology & Biophysics 824-9137 (office) nlallbri@uci.edu Office- Rm D349 Medical Science D Bldg. Mass Analyzers- Measure m/z Properties of Analyzers: 1. Upper Mass Limit (Mass Range)- highest measurable m/z 2. Ion Transmission (Sensitivity)- ratio of ions reaching detector to that produced at the source 3. Mass Accuracy- difference between theoretical & measured mass mass accuracy (mreal mmeasured)/mreal express as ppm Ex: measured mass 1000.2 real mass 1000 m 0.2 mass accuracy 0.2/1000 200/1 000 000 200 ppm R 6500 Mass Analyzers Total Peptide Charge 3+ Properties of Analyzers: 4. Mass Resolutionability to resolve 2 ions with a small mass difference R 500 Resolution R m/ m m mass difference of 2 nearby masses m & (m+ m) with a signal overlap of 10% Mass Analyzers for Proteins/Peptides Types of Analyzers: 1. Quadrupole Analyzer- R 3000 m/z 2000 mass accuracy 400 ppm poor sensitivity 2. Ion Trap- R 5000 m/z 2000 mass accuracy 200 ppm excellent sensitivity 3. Time of Flight (TOF)- R 10 000 m/z 500 000 mass accuracy 10 ppm very good sensitivity 4. Fourier-Transform Ion Cyclotron Resonance (FTICR) R 1 000 000 mass accuracy 1 ppm Very expensive (limited availability) Ions are confined in a high B field B field is created by a superconducting magnet Circling frequency of ions z/m Time of Flight (TOF) Analyzer Principle: For a constant kinetic energy different masses move at different v. 1. Accelerate a bolus of ions with a potential VsEnergykinetic mv2/2 qVs for m mass v velocity q charge z e 2. Ions then enter a field-free region of length d 3. Measure the time t for the ions to cover the distance d v d/t Solve for tt2 (m/z)(d2/2Vse) MALDI-TOF

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