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I am a high school senior and decided to do a project on the essential amino acid composition of varying vegan protein mixtures. I have run into a problem concerning protein purification. One of the vegan protein powder mixtures I have chosen contains 1% fat (it does not really specify on the label but I assume it comes from the hemp seed protein; here is the link to the nutritional label: https://tinyurl.com/4fkymstf). My method of analysis is ion exchange chromatography and then light absorbance as seen here: https://tinyurl.com/4n3ukwa2. Can I just ignore the fat and continue to hydrolyze the proteins in 6.0 M HCl or does it actually matter? If it does matter I am going to cry because my only method of extraction is solubility-based (rice protein and hemp seed protein are insoluble in water compared to pea protein so I would have to do some alkaline solution BS to make them all soluble and then extract any residue left over from the alkaline additive which makes me sad). Note that I already found a way to extract the sodium on the label.

TLDR: For ion exchange chromatography in regards to amino acid analysis will a small amount of fat contaminant skew results to a significant degree/do I need a 100% pure protein sample?

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Ideally, one should do chromatography after the crude product (hydrolyzed proteins in yours case) have been pre-cleaned. Fats do not dissolve in water, so I assume, you will carefully filter your sample before loading the ion-exchange resin. Also you can you do a solvent extraction in a separatory funnel with an appropriate solvent (ask your teacher) to remove fats before loading the ion-exchange resin. One good news is that sulfonated ion exchange resins will only retain positively charged compounds, the rest of the junk will just wash off if you are washing the resin with water after sample loading. However, resins are organic compounds, they can non-selectively bind tenacious/sticky molecules.

In short, you can continue your hydrolysis experiment as planned and then do fat extraction before loading the ion-exchange column. Alternatively, if you have not already satrted, you can do fat exraction by solvent exrtaction before the hydrolysis and then you will be assured that there no fats in your sample. The latter is preferrable.

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