DYOR
Bead assisted mass spectromery
Mass spectrometry (MS) is an analytical technique that measures the mass-to-charge ratio of ions.
Large molecules such as proteins can be fragmented into smaller molecules. Each fragment causes a different peak in the spectra. A mass spectrum is a plot of the ion signal as a function of the mass-to-charge ratio (how much of a fragment is present). These spectra are used to determine the elemental or isotopic signature of a sample, the masses of particles and of molecules, and to elucidate the chemical identity or structure of molecules and other chemical compounds.
In order to make sure a clean signal is generated a purification step is required. Traditionaly lab intense techniques such as gas or liquid chromatography have been used - these use the phusical properies of molecules to separate them (remember filter paper and ink at school?)
https://en.wikipedia.org/wiki/Chromatography
This is where BAMS comes in
By coating beads in affimers that bind protein X the target protein can be "pulled" out of a solution. Everything else passes on with the beads retaining the protein that is being looked for. By them eluting (washing) the beads an enriched sample of the target protein is obtained. Previously Adeptrix the company behind BAMS used antibodies as the binding reagent.
By having different beads in a tray of wells it is possible to extract more than one target (multiplex). Alternatively each well could be a different sample generating high throughput ( > 2000 samples per hour - reference needed)
A good example of how this is applied (albeit with Abs) is
Ref : Affinity-Bead Assisted Mass Spectrometry (Affi-BAMS): A Multiplexed Microarray Platform for Targeted Proteomics : GM Hamza et al
https://www.mdpi.com/1422-0067/21/6/2016
NOTE : The involvement of AZ
9th June
Avacta Group announced that a BAMSTM diagnostic test for the COVID-19 infection, being developed with its partner Adeptrix (Beverly MA, USA), has reached prototype stage
The bead-assisted mass spectrometry (“BAMS”) assay is able to identify fragments of the spike protein using mass spectrometry, at concentrations in the range found in patient samples generated from standard throat swabs.
The combination of the selectivity of the Affimer reagents used to capture the virus spike protein with the precision and accuracy of mass spectrometry detection provides for a very high degree of specificity in the assay.
The next step in the development of the final product to run on the installed base of mass spectrometers in clinical laboratories around the world is to evaluate and optimise the BAMS assay using patient samples at laboratory sites in the UK and US which will be done imminently before moving to manufacturing, clinical validation to quantify the sensitivity and specificity and CE/FDA approval for professional use in the summer.
MALDI-TOF
In mass spectrometry, matrix-assisted laser desorption/ionization (MALDI) is an ionization technique that uses a laser energy to create ions from large molecules with minimal fragmentation.
] It has been applied with molecules which tend to be fragile and fragment when ionized by more conventional methods.
MALDI methodology is a three-step process.
1. The sample is mixed with a suitable matrix material and applied to a metal plate.
2. A pulsed laser irradiates the sample, triggering ablation and desorption of the sample and matrix material.
3. The analyte molecules are ionized in the hot plume of ablated gases, and then they can be accelerated into a mass spectrometer is used to
Image from Adeptix website Ref Hamza et al