DynaPro NanoStar manual - Department of Physiology and Biophysics

Correlation FunctionSample vs. SolventNot all samples can be measured, nor are all samples properly suited formeasurement by DynaPro instruments, and therefore not all samplesproduce valid correlation functions. Without a valid correlation function, itis not possible to determine a valid size distribution.A valid correlation function is generally smooth and continuous, exponentiallydecaying from a maximum value of 2 to a value of 1.The following figure shows a valid correlation function. Visually, weobserve one decay in the function.The function contains random values centered around 1, asymptoticallyreaching 1. Randomness represents the result from measuring puresolvent: solution containing zero analyte or analyte below the limits ofdetection. The size distribution analysis attempts to find a result for thesefunctions. These must be marked and removed from the analysis. It is generallya good idea to measure the solvent to confirm its purity. If youunexpectedly see a function characteristic of a solvent, increase the laserpower, measure the sample unfiltered (to avoid potential binding to themembrane) or uncentrifuged, and/or increase the concentration of theanalyte.DYNAMICS User’s Guide (M1400 Rev. K) 8-13