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The UNC PEP-MX core has a Refeyn One Mass Photometry instrument that’s now available for use. The Mass Photometer measures minute perturbations in the refractive index of a solution as biomolecules tumble within. Sophisticated software then calculates the masses of the particles that produced those optical differences (Figure 1).


Figure 1. Recent experimental data acquired by the mass photometer on a joint project between the laboratories of Dr N Brown and Dr J Schisler (UNC Pharmacology). The sample was composed of the ubiquitin ligase known as CHIP (C-terminus of Hsc70-interacting protein). CHIP is known to exhibit successive oligomeric states, clearly identifiable in the histogram.


The mass photometer has a range of 40 kDa – 5 MDa with an accuracy ~5-10% of known. Sample needs are roughly 100 ul at 100 nM (~5 ug/ml) or less, and the instrument can accommodate proteins, DNAs, RNAs, and virtually any assemblies thereof. The instrument can assess sample quality, oligomeric states, complex formation, and more. Contact the core ( to schedule training and instrument time!