Hi everyone,
I am trying to conjugate primary amine of chitosan with NHS-PEG-MAL. Chitosan is in a solution. In literature, some people directly add NHS-PEG-MAL powder to chitosan solution while others use some different solvents like water, dmso and others for NHS-PEG-MAL.
Normally, this reaction efficiently takes place at pH 8. However, chitosan has pH limitation, it precipitates at neutral and basic pH. So people in literature use pH around 6. Efficiency is low but still enough.
All in all, i want to know difference between using solvent for such reaction in terms of mechanism of reaction. Can you suggest me any reading to understand these concepts?
Thank you all
The choice of solvent has to do with the hydrolysis of the NHS group. Once in aqueous solution two reactions can happen, the one you want to modify the amino groups from chitosan and the hydrolysis of the NHS group. If you want to reduce hydrolysis use DMSO to dissolve the NHS-containing molecule. Since you have the restriction of pH given the solubility of chitosan, the best thing is to run the reaction at pH 6 in the presence of DMSO.
Tons of literature are available about the reaction mechanism of NHS-ester and amine.
Give a search in google with:
'nhs ester amine reaction mechanism' and get them. Finding the right literature is an important skill.
Here are the first two results, which popped up in google:
https://www.thermofisher.com/us/en/home/life-science/protein-biology/protein-biology-learning-center/protein-biology-resource-library/pierce-protein-methods/amine-reactive-crosslinker-chemistry.html
https://www.lumiprobe.com/protocols/nhs-ester-labeling
read and learn.
Dear Sengupta,
I have already checked these two. There are no answers to my questions.
Please kindly read the questions again. Thanks.
This might help
http://mhhe.com/physsci/chemistry/carey/student/olc/ch20reactionsesters.html
http://chemistry2.csudh.edu/rpendarvis/aminrxn.html
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