I think false positive is due another reactive handle present in Substrate like
-OH or other amino group either we can protect them,
1. Resin is old and expired
2. You add the 3 solutions in different order. You need to add them in specific order as in literature. Also, renew the solutions if they are old.
3. You have other amine groups exposed. Try acetylation before moving ahead.
If these are not the cases, please be more specific and clarify what you mean false positive results.
Ninhydrin can react ammonium ions. Therefore, you should wash your gels by water.
Thank you all for your kind inputs.
@Kou Hayakawa But my peptides would also get partially washed away if I do so. Isn't it?
Can you please clarify why you think that the positive result is false?
@Zoltan Dekan Even after coupling an amino acid several times with varying conditions, the KT showing positive results. Therefore, had a thought about possibility of false results in KT.If it is the case, I would like to know possible reasons for that.
Surely, peptide is bound to polystylene (Merrifield’s resin) gel via ester bond, which is labile to water.
I have bound peptides to aminopropylated-silica gel using 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) via amido bond, which seems stable. About 60 cycles of Edman degradation has been possible (please see file; HepG2 fucoidan).
Then, development of SPPS by using silica gel seems to be better.
You may have a difficult (aggregating) sequence. What is the calculated coupling yield?
It would also be helpful to know the peptide sequence, the type of chemistry you are using, the type of resin, the amino acid that you are trying to couple and its position in the sequence.
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