MALDI-TOF Mass Spectrometry

This presentation is about matrix-assisted laser desorption/ionization. It explains the sampling for TOF and its instrumentation.

1. MALDI-TOF Mass Spectrometry

2. Introduction MALDI is the abbreviation for "Matrix Assisted Laser Desorption/Ionization.” MALDI is appropriate to analyze biomolecules like peptides, lipids, saccharides, or other organic macromolecules. TOF stands for “Time of Flight”. This generates characteristic mass spectral fingerprints which is compared with large library of mass spectra. A versatile analytical technique to detect and characterize mixtures of organic molecules.

3. Principle of MALDI Matrix absorbs the ultraviolet light (nitrogen laser light, wavelength 337 nm) and converts it to heat energy. The analyte is embedded on the Target Plate. After a laser pulse, the irradiated spot is rapidly heated and becomes vibrationally excited. Matrix molecules energetically ablated from the surface of the sample. During ablation, the analyte molecules are usually ionized by being protonated or deprotonated with the nearby matrix molecules.

4. Types of MALDI Variation Commonly Used Laser: ultraviolet (UV) lasers are by far the most important light sources. Time Of Flight: ideally suited to the MALDI ionization process since the pulsed laser takes individual 'shots' rather than working in continuous operation. Atmospheric Pressure: is an ionization technique (ion source) that operates at normal atmospheric environment.

5. TOF analyser The mass analyser used for MALDI is TOF analyser . It allows accurate mass determination for high molecular weight species It makes TOF ideal for biomolecules . The ions desorbed by the laser pulse for accelerated in an electric field to a kinetic energy of several KeV.

6. TOF Analyser Accelaration distance Field Free Drift D istance Electrode with grid Sample holder Detector

7. TOF Analyser Flight tube length and flight time At the end of the tube, ions hit the detector. And drift time is measured electronically. Lighter ions are accelerated more than the heavier ions and reach the detector first. 2 m nanoseconds

8. TOF analyser Kinetic energy of the drifting ions is defined as The velocity can be defined as Substituting the velocity in eq.  

9. Sample pre-treatment Sample excess matrix. co- crystallised Destruction Fragmentation Matrix function Matrix Properties Co-desorption of the analyte

10. sample treatment Dried droplet method Mix Dry

11. Sample treatment Fast evaporation method Dissolved matrix Dissolved sample

12. Apllications of Maldi Used for the analysis of proteins and peptides . changes in structure can also be identified. Vey low amount of sample . sample preparation is easy and spectra is simple. Very fast separation method

13. https://youtu.be/0jeFpXHZ8W0