01Understand the kind of size being reported

NIST’s DLS guidance defines hydrodynamic diameter through an equivalent sphere that diffuses at the same rate as the measured object. The conversion depends on the liquid and measurement conditions, including viscosity and temperature.NIST SP 1200-6 — Measuring the Size of Nanoparticles in Aqueous Media Using Batch-Mode Dynamic Light Scattering (opens in a new tab)

For a non-spherical peptide assembly, the reported diameter therefore should not be read automatically as its physical length or width. A microscopy image and a DLS value can describe different aspects of the same sample.

Check whether the output is radius or diameter before comparing numbers. A radius of 20 nm and a diameter of 40 nm are numerically different descriptions of the same spherical size.

The liquid used in the calculation matters. A result processed with an inappropriate medium description should not be rescued by simply adding more decimal places to the size estimate.

02Read the weighting and analysis method

NIST distinguishes the cumulant z-average and polydispersity information from a reconstructed size distribution. Cumulant analysis does not itself produce a full distribution of individual particle sizes.NIST SP 1200-6 — Measuring the Size of Nanoparticles in Aqueous Media Using Batch-Mode Dynamic Light Scattering (opens in a new tab)

A peak representing 10% of measured intensity should not be relabelled as 10% of particles. The denominator has changed, and the conversion requires more than copying the percentage.

Keep the software analysis and relevant assumptions available with the displayed plot. Two attractive graphs can disagree because their outputs use different definitions rather than because the sample changed.

03Recognise the importance of reporting choices

Farkas and Kramar’s 2021 experimental and metrological study examined DLS distributions across nanoparticle sizes and dispersities. They found that commonly reported central values could differ substantially depending on analysis and weighting choices.Farkas and Kramar — Dynamic light scattering distributions by any means (2021) (opens in a new tab)

The paper argues for more careful interpretation of distribution means and questions the reliability of some dispersity descriptors. Its findings concern the tested nanoparticle datasets, rather than a universal numerical correction for peptide assemblies.Farkas and Kramar — Dynamic light scattering distributions by any means (2021) (opens in a new tab)

For a peptide study, this makes the reporting definition part of the result. Selecting whichever average agrees best with an expected answer is not a defensible substitute for explaining the analysis.

04Make comparisons at the appropriate level

Compare samples using consistent definitions and documented conditions. If concentration, liquid composition or sample processing differs, state those differences before attributing a size shift to a molecular mechanism.

An additional structural or chemical method can test an explanation that DLS leaves open. The choice depends on whether the unresolved question concerns shape, composition, amount or another property.

A useful summary reports the hydrodynamic-size result, its analysis basis and the main limits of interpretation. It avoids turning one size plot into a complete inventory of the sample’s molecular and particulate contents.