I am preparing a modified lectin based immuno assay. I am oxidizing my monoclonal anti-PSA antibodies (Abs) to avoid non-specific lectin attachment to the carbohydrated present of the Abs. I am following the following approach for oxidation.
1) Removal of sodium azide from Abs using desalting (spin filteration)
2) Reconstitution of Abs in PBS buffer.
3) Addition of sodium periodate solution for oxidation (20mM sodium iodate, 100mM sodium acetate, 150mM of NaCl - solution made in DI-water). Add equal amount of the solution to the Ab solution, at 4C in dark and keep it for 2 hours.
4) Removal of oxidized antibodies and reconstitution in sodium bicarbonate buffer (pH9.6). This avoids self conjugation of the Abs with themselves from the amine side.
5) Conjugation of NHS-PEG-PC-biotin linker using the generic biotinylation protocol.
6) Removal of excess biotin and blocking of excess aldehyde sites with 1M ethanolamine solution.
7) Removal of excess solution and extracting biotinylated Abs.
I want to block the oxidized Abs and want to know whether my approach will be fine ? I want to conjugate the biotin linker from the amine side using the NHS chemistry. I have seen oxidized Ab blocking with MPBH + Cys-Gly dipeptides. I am not sure whether this blocking mechanism will affect my biotinylation ?
Please advise.
4) Schiff bases will be potentially produced once you oxidized antibody. High pH favors this reaction.
You can use ethanolamine to block aldehyde groups.
If MPBH is:
(4-(4-N-maleimidophenyl)butyric acid hydrazide)
then they are using it to attach the dipeptide to the oxidize carbohydrate.
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