What is MALDI-TOF mass spectrometry and its use in microbial identification?

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The other day, someone in our lab asked how exactly MALDI-TOF identifies microbes, and it got me curious again. I’d read a paper on it before, and this explanation really made it click. It outlines how MALDI-TOF mass spectrometry works step-by-step, from sample prep to ionization, and why it’s such a reliable method in microbiology labs.

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Anttilampinen 2025-06-10T10:12:04+00:00 1 Answer 8 views
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  1. fleming
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    2025-06-10T10:12:55+00:00
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    How MALDI-TOF MS Works for Microbial ID:

    1. Sample Preparation (The “Matrix” Part):

    • A small amount of microbial colony (bacteria or yeast) grown on an agar plate is smeared directly onto a target plate (usually metal).
    • A chemical solution called a matrix (typically a small organic acid like α-cyano-4-hydroxycinnamic acid, CHCA) is overlaid onto the microbial sample and allowed to co-crystallize as it dries.

    2. Ionization (The “MALDI” Part):

    • The target plate is inserted into the mass spectrometer under vacuum.
    • A pulsed laser beam (usually UV) is fired at the sample spot.
    • The matrix absorbs the laser energy efficiently, vaporizing rapidly along with the microbial analytes embedded within it.
    • During this rapid desorption process, the microbial analytes (primarily abundant proteins like ribosomal proteins) become ionized, typically gaining a single positive charge (protonation).
    • MALDI is a…

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