Maldi tof mass spectrometry ppt

MALDI stands for Matrix-Assisted Laser Desorption Ionization.
TOF stands for Time of Flight.
By Jwala Jayadeep
KUFOS

1. MALDI - TOF MASS SPECTROMETRY BY JWALA 1 st MSc MARINE MICROBIOLOGY

2. INTRODUCTION MALDI is a soft ionization technique that strikes large molecules with laser energy into minimal ion fragments . MALDI  stands for  M atrix- A ssisted  L aser  D esorption  I onization. TOF  stands for  T ime  o f  F light. This technology generates characteristic mass spectral fingerprints which are compared with large library of mass spectra. As the spectral fingerprints are unique signatures for each microorganism, accurate microbial identification at the genus and species levels is done using bioinformatics pattern profiling.

3. MALDI-TOF MASS SPECTROMETER

4. WORKING PRINCIPLE FOR MALDI-TOF SPECTROMETRY The MALDI-TOF process is a two-phase procedure; Ionization Phase Time of flight phase The second phase is the time-of-flight mass spectrometry phase . It has two modes:- linear mode and reflector mode.

5. METHODOLOGY First, the analyte should be dissolved in a solvent making up to 0.1mg /ml and the matrix should be dissolved with a saturated or concentrated solution of about 10mg /ml. Both the solution is then mixed together in 1000:1 to 100,000:1 ratio. The mixture is placed on a metal target plate which crystallizes on drying and forms a solid deposit. Then the mixture is transferred into the MALDI – TOF instrument for analysis .

6. Sublimation and ionization separate the ions depending upon the size and charge ratio through a TOF analyzer which is operated on the MS software. To increase the ability in identifying gram-positive and sugar non fermenting bacterial species, formic acid is used with the preparatory extraction of microbes whereas gram-negative bacteria can be identified using direct cell profiling.

7. The process of mass spectrometry

8. Target plate

9. APPLICATIONS OF MALDI-TOF MASS SPECTROMETRY Biochemistry Peptide mass fingerprinting ( PMF ) Clinical and environmetal bacteriology Detection of viruses Organic chemistry Medicine

10. ADVANTAGES Significantly decreases the turnaround time. Processing time is similar to rapid bio-chemicals.  The sample preparation is simple and the sample requirement is minimal.  A single colony is sufficient in order to generate spectra of sufficient quality Cost effective-low consumable costs

11. Automated , robust, inter-laboratory reproducibility Broad applicability (all types of bacteria including anaerobes, fungi) Adaptable-open system, expandable by user.

12. DISADVANTAGES Identification of new isolates is possible only if the spectral database contains peptide mass fingerprints of the type strains of specific genera/species/subspecies/strains No susceptibility information is provided  Not useful for direct testing of clinical specimens (except urine)

13. Some organisms require repeat analysis and additional processing (extraction) The acceptable score cut-offs vary between studies and some closely related organisms are not differentiated. Some organisms currently cannot be reliably identified by this method, such as  Shigella   spp and  Streptococcus  pneumoniae .

14. REFERENCES en.wikipedia.org/wiki/Matrix- assisted_laser_desorption /ionization Modern Experimental Biochemistry. Rodney F Boyer. Benjamin/Cummings publishing company Inc. Redwoodcity , California. thesciencenotes.com/maldi-tof-mass-spectrometry-principle-methodology-and-applications/