A few days ago, my colleague Dr. John Stenson previewed the upcoming launch of the OMNISEC software’s newest feature: compositional analysis!  Amidst your excitement at the great content headed your way, you might be wondering, “what can compositional analysis do for me and my samples?” 

In this post, I’ll offer examples of applications that benefit from compositional analysis so that you can answer that question for yourself.  And even if compositional analysis won’t work for you right now, think about what it could unlock for your future analyses!


Firstly, let’s start with the hot application in gene therapy and vaccine development: AAVs.  Compositional analysis is the perfect method for characterizing your capsids and determining the filled percentage.  The different UV absorptions of the capsid protein and the polynucleotide payload allow the calculation of full and empty titer values.  The OMNISEC software is set up to report the relevant numbers, including total, full, and empty capsid titer, % full AAV, and cp/vg ratio.  That’s in addition to standard GPC/SEC data such as molecular weight, molecular size, and concentration!

Protein conjugates

Secondly, an appended PEG or polysaccharide can play a critical role in a protein’s effective size, structure, solubility, and stability, which can lead to improvements in the compound’s efficiency and safety.  These benefits can depend on getting the degree of PEGylation or glycosylation just right.  Compositional analysis is ideally suited to characterize your bioconjugates, as your protein will be UV active while the PEG or polysaccharide component will generally not produce a UV response.  In addition, you can determine your protein’s oligomeric state, the molecular weight of the appended polymer, and concentration of each.  That’s a lot from one injection!

Membrane proteins

By using detergents to maintain their solubility, membrane proteins can be studied by SEC as membrane protein-detergent complexes.  As you probably guessed by now, compositional analysis is a natural fit here since the protein is UV active and the detergent complex usually isn’t.  Using this method, you can calculate the concentration and absolute molecular weight of the protein – all while it remains in the detergent complex!

Drug-delivery conjugates

These bioconjugates use antibodies or other biopolymers as a molecular Trojan Horse to deliver cytotoxic drugs, primarily to tumor cells.  A specific amount of cytotoxic agent is attached to each macromolecular vehicle.  Determining the number of cytotoxic passengers on each macromolecular vehicle is crucial to ensure your drug-delivery conjugate has the potential to act as intended.  Once again, you can use compositional analysis to quantify and characterize each component.

Polymer blends

A mixture of two individual polymers can create an entirely new material with unique properties.  As you might expect, the ratio of the polymeric components can directly affect the behavior of the blend.  And like a broken record…compositional analysis can work well for this purpose.  Just remember, like the example below, at least one of your components needs to be UV active!


Last, but certainly not least, are copolymers.  These are similar to polymer blends except the “mixing” is done on a molecular level.  But the great thing about compositional analysis is that it works either way!  The method measures the concentration of each component within a sample, regardless if the connection is covalent, supramolecular, or non-existent.

Final thoughts

In conclusion, the addition of compositional analysis could take your GPC/SEC analyses to another level.  So register here to join us on April 22nd for the launch event to learn more!  Furthermore, if you have any questions please don’t hesitate to contact us or email me directly at kyle.williams@malvernpanalytical.com

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