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XCMS Online

XCMS Online is a computer science 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 XCMS Online rather than just read about it. In short: XCMS Online is a cloud version of the original eXtensible Computational Mass Spectrometry (XCMS) technology (a bioinformatics software designed for statistical analysis of mass spectrometry data), created by the Siuzdak Lab at Scripps Research. XCMS introduced the concept of nonlinear retention time alignment that allowed for the statistical assessment of the detected peaks across LCMS and GCMS datasets.

XCMS Online — main illustration
XCMS Online — illustration

Key takeaways

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

Reference excerpt

XCMS Online is a cloud version of the original eXtensible Computational Mass Spectrometry (XCMS) technology (a bioinformatics software designed for statistical analysis of mass spectrometry data), created by the Siuzdak Lab at Scripps Research. XCMS introduced the concept of nonlinear retention time alignment that allowed for the statistical assessment of the detected peaks across LCMS and GCMS datasets. XCMS Online was designed to facilitate XCMS analyses through a cloud portal and as a more straightforward (non command driven) way to analyze, visualize and share untargeted metabolomic data. Further to this, the combination of XCMS and METLIN with 960,000 authentic standards, allows for the identification of known molecules using METLIN's tandem mass spectrometry data, and enables the identification of unknown (uncharacterized molecules) via similarity searching of tandem mass spectrometry data. XCMS Online has also become a systems biology tool for integrating different omic data sets. As of January 2021, the XCMSOnline - METLIN platform has over 44,000 registered users. XCMS - METLIN was recognized in 2023 as the year's top analytical innovation. XCMS Online works by comparing groups of raw or preprocessed metabolomic data to discover metabolites using methods such as nonlinear retention time alignment and feature detection & matching. Once analysis is complete the data can be viewed several different ways including via bubble plots, heat maps, chromatograms, and box plots. In addition, XCMS Online is integrated with METLIN, a large metabolite database. The following file formats are supported for direct upload to the site.

History In 2005, the Siuzdak Lab created an open-source tool named XCMS in the programming language R. Noticing the need for a more accessible, graphical data processing tool they created the cloud-based XCMS Online in 2012. The ability for users to stream data directly from instruments while being acquired was added in 2014. Also in that year a commercial version named XCMS Plus (owned by Mass Consortium Corporation) was released and, in 2015, SCIEX became a reseller. In 2017 it was shown that XCMS Online could be used in a systems biology workflow. One year later, in the absence of a publicly available alternative, a version of XCMS Online and METLIN-MRM was released with the ability to perform multiple reaction monitoring (MRM) and generate MRMs. In 2026, a new version of METLIN-MRM was introduced that enabled a more refined means of generating MRM isotope removal, in-source fragment removal and spline-fitting at multiple collision energies. The accuracy of uMRM was demonstrated on over 300 molecular standards as compared to traditional approaches.

References

External links XCMS Online

Illustrations

XCMS Online: XCMS nonlinear alignment of liquid chromatography mass spectrometry data sets
XCMS nonlinear alignment of liquid chromatography mass spectrometry data sets

Worked examples

Example 1 — a first encounter with XCMS Online

Start with the simplest possible case. Write down what XCMS Online claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, 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 XCMS Online 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 XCMS Online 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 XCMS Online

In research
XCMS Online appears in computer science 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 XCMS Online 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
XCMS Online is common in secondary-school and first-year university syllabi. It links to neighbouring topics Bioinformatics software, Mass spectrometry software, so understanding it makes those chapters shorter.
In everyday life
Look for XCMS Online 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 XCMS Online in 20 minutes

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

Frequently asked questions

What is XCMS Online in simple terms?

XCMS Online is a cloud version of the original eXtensible Computational Mass Spectrometry (XCMS) technology (a bioinformatics software designed for statistical analysis of mass spectrometry data), created by the Siuzdak Lab at Scripps Research. XCMS introduced the concept of nonlinear retention tim…

Why does XCMS Online matter?

Because it connects several computer science 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 XCMS Online?

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 XCMS Online.

Tags

  • Bioinformatics software
  • Mass spectrometry software

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