Width of the size distributions in DLS is a measure of polydispersity of the particles. I am measuring size distribution of large unilamellar vesicles using DLS.
Polydispersity
In light scattering, the term polydispersity and % polydispersity are
derived from the Polydispersity Index, a parameter calculated from
a Cumulants analysis of the DLS-measured intensity autocorrelation
function. In the Cumulants analysis, a single particle size mode is assumed
and a single exponential fi t is applied to the autocorrelation function
and the polydispersity describes the width of the assumed Gaussian
distribution. In terms of a protein analysis, a % polydispersity less than
20% indicates that the sample is monodisperse.
Polydispersity index(PDI)= Mw/Mn
Mw: weight number molecular weight
Mn: average number molecular weight
I also measuring unilamellar vesicles using DLS with ZETASIZER Nano ZS (Malvern Instruments). The given value from the program is als called PDI but has nothing to do with classic description, Sozan is talking in the end. As she mentioned it is a parameter calculated from a Cumulants analysis of the DLS-measured intensity autocorrelation function. Values near zero indication a very sharp distribution where as value around one a very broad distribution.
DLS is OK. However, it can be also directly obtained using Gel Permeation Chromatography coupled with Mass spectrometry using MALDI (Matrix Assisted Laser Desorption and Ionization) or ESI-MS/MS (Electrospray Ionization). It is known to be more accurate and informative than other methods in use.
Arun Chattopadhyay How can one know by using ESI-MS/MS (Electrospray ionization) the shape is unilamellar vesicles? Can you please provide a detailed explanation or quote the related articles?
When subjected to ESI-MS/MS analysis, unilamellar vesicles will produce a characteristic mass spectrum that reflects the molecular weight of the lipids and other components present in the sample. However, the shape of the vesicles can also be inferred from the mass spectrum.
In particular, the presence of ions with low charge states in the mass spectrum can indicate the presence of unilamellar vesicles. This is because the low charge state ions are more likely to come from large, intact vesicles, rather than smaller, fragmented vesicles or individual lipid molecules. Additionally, the presence of specific lipid species in the mass spectrum can provide further evidence for the presence of unilamellar vesicles.
Overall, while ESI-MS/MS alone may not provide conclusive evidence for the presence of unilamellar vesicles, it can provide important clues about their size and shape, which can be used in conjunction with other analytical techniques to confirm their presence.
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