# Molecular weight information derived from cryo-em micrographs?

**URL:** <https://forum.scilifelab.se/t/molecular-weight-information-derived-from-cryo-em-micrographs/291>\
**Category:** Cryo-EM\
**Created:** [18 July 2023 07:35 UTC](https://forum.scilifelab.se/t/molecular-weight-information-derived-from-cryo-em-micrographs/291 "2023-07-18T07:35:51Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![kohyou92](https://avatars.discourse-cdn.com/v4/letter/k/49beb7/32.png) [@kohyou92](https://forum.scilifelab.se/u/kohyou92)\
**Post date:** [18 July 2023 07:35 UTC](https://forum.scilifelab.se/t/molecular-weight-information-derived-from-cryo-em-micrographs/291/1 "2023-07-18T07:35:52Z")

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Nowadays there are mass photometry techniques that use TIRF-like microscopy technique to measure molecular weight of particles. I wonder if we can derive/deduce molecular weight information directly from cryo-em micrographs as well.

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**Author:** ![Guillaume](https://dub1.discourse-cdn.com/flex013/user_avatar/forum.scilifelab.se/guillaume/32/162_2.png) [@Guillaume](https://forum.scilifelab.se/u/Guillaume)\
**Post date:** [30 October 2023 08:18 UTC](https://forum.scilifelab.se/t/molecular-weight-information-derived-from-cryo-em-micrographs/291/2 "2023-10-30T08:18:11Z")

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Hello,

The only thing mass photometry and single-particle cryoEM have in common is that they are single-molecule techniques. They don’t measure the same properties of the molecules.

The best way I can think of to “derive/deduce molecular weight” from cryoEM micrographs is far from direct: obtain a 3D reconstruction of sufficient quality to build a complete atomic model (preferably with an unbiased and automatic method, like [ModelAngelo](https://doi.org/10.1101/2023.05.16.541002)), then from this atomic model you can deduce the sequence and molecular weight. But this is only going to work with ideally-behaved particles, because if you can’t resolve some regions in the 3D reconstruction, you will obtain an incomplete atomic model and will therefore underestimate the molecular weight.

I think these two techniques are best used together. Especially for heterogeneous mixtures, it can be extremely helpful to have a mass photometry measurement: it will tell you how many different species to expect and their relative abundance, which both help a lot to analyze your cryoEM data.

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**Author:** ![Lawatson](https://dub1.discourse-cdn.com/flex013/user_avatar/forum.scilifelab.se/lawatson/32/183_2.png) [@Lawatson](https://forum.scilifelab.se/u/Lawatson)\
**Post date:** [11 June 2024 11:06 UTC](https://forum.scilifelab.se/t/molecular-weight-information-derived-from-cryo-em-micrographs/291/3 "2024-06-11T11:06:11Z")

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Is this discussion is still carrying on?