The mass photometer

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For molecular mass measurements with unmatched sensitivity, speed and simplicity of use. Refeyn’s second-generation mass photometer, the TwoMP, offers wider mass range, and improved resolution and statistics.

High-fidelity measurements

With its high sensitivity, the TwoMP is ideally suited for measurements at physiological (i.e. low) concentrations. The high dynamic range intrinsic to single molecule counting techniques ensures low-abundance species are still captured accurately.

Intuitive & efficient

Refeyn’s software automatically controls the acquisition process and performs the mass analysis in minutes. You can intuitively interpret the mass distribution results without the need for any prior knowledge.

Minimal setup required 

A compact, bench-top instrument with minimal installation requirements. Measurements only require a few microliters of sample and clean, high-quality coverslips.

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Key advances of the



Incorporating customer feedback, the latest advances in optics technology and custom software developments, Refeyn has evolved mass photometry to a new level with the next-generation mass photometer, TwoMP.

Wider mass range

The Refeyn TwoMP enables measurement of molecular mass across a wide mass range, from 30 kDa up to 5 MDa. 


You can reliably measure molecular masses down to 30 kDa and better quantify molecules close to the detection limits.


Figure 1 shows mass photometry peak resolution on a 30 kDa protein. The mass photometry analysis with the TwoMP clearly distinguishes two peaks, corresponding to the monomers and dimers formed by the example protein in solution. 

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Figure 1 Mass photometry with the Refeyn TwoMP allows mass measurements down to 30 kDa and features improved peak resolution at the detection limits.

Improved resolution

The TwoMP also features improved resolution, especially at higher masses. This makes the TwoMP mass photometer an ideal tool for analysing large, multi-component complexes (Figure 2) and measuring the full/empty ratio of adeno-associated virus (AAV) particles (Figure 3).

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Figure 2 Mass photometry enables monitoring of ribosome subunit assembly. The TwoMP mass photometer offers better resolution at higher masses, making it an ideal tool to study the assembly of macromolecular complexes.

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Figure 3 Mass photometry enables analysis of the full/empty ratio of AAV particles. The improved resolution of the Refeyn TwoMP mass photometer makes it possible to better differentiate empty (~3.7 MDa) and DNA-loaded AAV capsids (~1 MDa mass increase). 

Better statistics and quantification

The TwoMP mass photometer's larger detection area and wider dynamic range yield more counts per experiment, resulting in better statistics on your data.

You can reliably quantify all sample species as well as measure complex high-affinity molecular interactions directly in solution.

Figure 4 shows how mass photometry can be used to quantify molecular interactions. By measuring the mass of the antibody trastuzumab and its target antigen, Her2, individually and in mixtures, the interactions between individual antibody molecules and target antigens could be quantified.

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Figure 4 The Refeyn TwoMP mass photometer was used to quantify molecular interactions between an antibody (trastuzumab) and its target antigen (Her2). 

Mass photometry in action

Mass photometry measures mass at the single molecule level, providing insights into the composition and function of even complex samples and molecular mechanisms. This unique technology can be used to detect and characterise proteins, nucleic acids, lipids and / or sugars, providing information on structure (oligomeric state, modification), homogeneity, and function (quantifying interactions) – all in a matter of minutes, and using tiny amounts of sample.