I am trying to aggregate particles functionalized with biotin using streptavidin. Is inter-particle aggregation still possible if the biotin is at the end of a peg polymer chain? (for example peg 2000)?
Generally, when using polymeric biotin, I am not seeing much aggregation so I am wondering if Peg-biotin chains from the same particle are taking up all the streptavidin active sites?
I think that PEG functionalized biotin may could form micelles in solution, which could be very stable in aqueous solution. You can check the size of PEG and/or its aggregation in the solution by dynamic light scattering. I think you can also check the activity of the protein after functionalized by PEG (I has no idea on how to do this due to that I'm in polymer science).
Rory, I have to agree with Ruigang Liu. With Biotin attached to the end of PEG2000, it's doubtful that you are going to see aggregation. You could try using smaller, linear, discrete length PEGs. I'd start with Biotin on a tetraethylene glycol linker or perhaps a dodecaethylene glycol linker rather than Biotin on a PEG2000 linker. I have added a link to my company website, where you can find those types of small, discrete PEG linkers.
http://www.quantabiodesign.com
The biotin-avidin interaction is commonly exploited to detect and/or purify proteins because of the high specificity. Yes inter-particle aggregation is possible if the biotin is at the end of a peg polymer chain. Try ligation on a tetraethylene glycol linker or dodecaethylene glycol linker rather than Biotin on a PEG2000 linker. Synthesize lysine-reactive homobifunctional cross-linkers with the biotin in the middle of the linker and use it.
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