chemistry

Mass spectrometric immunoassay

Mass spectrometric immunoassay is a chemistry topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Mass spectrometric immunoassay rather than just read about it. In short: Mass spectrometric immunoassay (MSIA) is a rapid method is used to detect and/ or quantify antigens and or antibody analytes. This method uses an analyte affinity (either through antigens or antibodies) isolation to extract targeted molecules and internal standards from biological fluid in preparation for matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF-MS).

Key takeaways

Mass spectrometric immunoassay belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Mass spectrometric immunoassay to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Mass spectrometric immunoassay from memory before moving on to harder problems.

Reference excerpt

Mass spectrometric immunoassay (MSIA) is a rapid method is used to detect and/ or quantify antigens and or antibody analytes. This method uses an analyte affinity (either through antigens or antibodies) isolation to extract targeted molecules and internal standards from biological fluid in preparation for matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF-MS). This method allows for "top down" and "bottom up" analysis. This sensitive method allows for a new and improved process for detecting multiple antigens and antibodies in a single assay. This assay is also capable of distinguishing mass shifted forms of the same molecule via a panantibody, as well as distinguish point mutations in proteins. Each specific form is detected uniquely based on their characteristic molecular mass. MSIA has dual specificity because of the antibody-antigen reaction coupled with the power of a mass spectrometer. There are various other immunoassy techniques that have been used previously such as radioimmunoassay (RIA) and enzyme immunoassay (EIA and ELISA). These techniques are extremely sensitive however, there are many limitations to these methods. For example, quantification for ELISA and EIA require several hours because the binding has to reach equilibrium. RIA's disadvantage is that you need radioactive particles which are universally known to be carcinogens. The creation of MSIA fulfilled the need to determine the presence of one or more antigens in a specimen as well as the quantification of those said species.

History This assay was patented in 2006 by Randall Nelson, Peter Williams and Jennifer Reeve Krone. The idea first came about with the development of ELISA and RIA. An earlier patent method suggested tagging antigens or antibodies with stable isotopes or long-lived radioactive elements. But limitations to both methods called for a better detection methods of a protein or proteins. The invention combines antigen-antibody binding with a mass spectrometer which aids in identifying qualitatively and quantifying analytes respectively.

An early MSIA experiment was done on a venom laced human blood sample for the Antigen myotoxin. The experiment was successful in that the mass spectrum resulting from the analysis showed a distinct response for myotoxin at the molecular weight corresponding to 4,822 Da (a). The m/z ratio at 5,242 Da (b) is the molecular weight of the modified variant H-myotoxina, used as an internal reference species. The figure of the mass spectrum is shown below.

Methodology An illustration of the MSIA procedure is depicted in the figure to the right. Analytes in a biological liquid sample are collected from solution by using a MSIA tip (also known as MSIA microcolumns) that contains a derivatized affinity frit. Biological samples contain various proteins that span a wide dynamic range so purification is needed to minimize the complex matrix and maximize mass spectrometry sensitivity. the MSIA tip serves as a place to purify these samples by immobilizing the analyte with high selectivity and specificity. Analytes are bound to the frit based on their affinities and all other nonspecific molecules are rinsed away. The specific targets are then eluted on to a mass spectrometer target plate with a MALDI matrix. However, proteins may be digested prior to ms analysis. A MALDI-TOF-MS later follows and targeted analytes are detected based on their m/z values. This method is qualitative, but the addition of mass shifted variants of the analyte for use as an internal standard makes this method useful for quantitative analysis. Pipetor tips, which have been termed MSIA tips or affinity pipette tips play a key role in the process of detecting analytes within biological samples. MSIA tips typically contain porous solid support which has derivatized antigens or antibodies covalently attached. Different analytes have different affinity for the tips so it is necessary to derivatize MSIA tips based on the analyte of interest. The main use of these tips are to flow samples through and the analytes affinity for the bound antigen/antibody allows for the capture of analyte. Non specifically bound compounds are rinsed out of the MSIA tips. The process can be simplified into 6 simple steps which Thermo termed the "work flow".

Gather Sample Load Affinity Ligand Purify Target Analyte Elute Target Analyte Pre-MS Sampling Process MS Analysis Many "work flows" are commercially available for purchase.

Applications MSIA is a method that can be used as an assay for a variety of different molecules such as proteins, hormones, drugs, toxins, and various pathogens found in biological fluids (Human and animal plasma, saliva, urine, tears etc.). MSIA has also been applied to clinical samples and have been proven to be a unique assay for clinically relevant proteins. Successfully assaying toxins, drugs and other pathogens are important to the environment as well as the human body. MSIA can be used for a range of biomedical and environmental applications.An important application of mass spectrometric immunoassy is that it can be used as a rapid, sensitive and accurate screening of apolipoproteins and mutations of them. Apolipoproteins represent a groups of proteins with many functions such as transport and clearance as well as enzyme activation. Recent studies have claimed that mutations in apopliproteins result in, or assist in the progression of various associated diseases including amyloidosis, amyloid cardiomyopathy, Alzheimer's disease, hypertriglyceridemic, lowered cholesterol, hyperlipidemia and atherosclerosis to name a few. Nelson and colleagues did a study using MSIA to characterize and isolate apolipoproteins species.

Benefits There are many benefits to using a mass spectrometric immunoassay. Most importantly, the assay is extremely fast and the data are reproducible, and automated. They are sensitive, precise and allows for absolute quantification. Analytes can be detected to low detection limits (as low as picomolar) and the assay covers a wide dynamic range.

See also Immunoassay Immunoscreening SISCAPA

References

Illustrations

Worked examples

Example 1 — a first encounter with Mass spectrometric immunoassay

Start with the simplest possible case. Write down what Mass spectrometric immunoassay claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Mass spectrometric immunoassay before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Mass spectrometric immunoassay ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Mass spectrometric immunoassay

In research: Mass spectrometric immunoassay appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Mass spectrometric immunoassay in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Mass spectrometric immunoassay is common in secondary-school and first-year university syllabi. It links to neighbouring topics Biochemistry methods, Immunologic tests, Mass spectrometry, so understanding it makes those chapters shorter.
In everyday life: Look for Mass spectrometric immunoassay outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Mass spectrometric immunoassay in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Mass spectrometric immunoassay means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Mass spectrometric immunoassay out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Mass spectrometric immunoassay in simple terms?

Why does Mass spectrometric immunoassay matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Mass spectrometric immunoassay?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Mass spectrometric immunoassay.