I'm studying the reaction mechanism of polymerization (condensation), specifically from several amino acids (glycine) into a polypeptide. What is are the steps in this reaction mechanism?

*I've tried searching everywhere for it without luck.

Question

I'm studying the reaction mechanism of polymerization (condensation), specifically from several amino acids (glycine) into a polypeptide. What is are the steps in this reaction mechanism? 

*I've tried searching everywhere for it without luck.

aaronq · Answer

biosynthesis or chemical transformations?

anonymous · Answer

Chemical transformations I think. Basically curly arrows and the transformation of electrons between atoms.

aaronq · Answer

so you're using coupling reagents like DCC and NHS?

I can help you figure out the mechanism, i just need to know what reagents you're using.

anonymous · Answer

I'm not sure what the catalysts/conditions are, just the fact that several amino acids bond to form a polypeptide because of the attraction between the lone pair on nitrogen of one, and the slightly positive carbon atom on the other.

aaronq · Answer

hmm okay, so this (attached) is the mechanism. I assumed this was biosynthesis (i.e. done by a ribosome, so i used tRNA to hold the amino acid, but you can replace it with another leaving group like NHS http://en.wikipedia.org/wiki/N-Hydroxysuccinimide) you can also show the last step (proton transfer) by the negative O on the tRNA taking the proton from the $-NH^+_2-$.

anonymous · Answer

How does the tRNA come in? I noticed in the diagram that it's drawn attached to one of the amino acids, but I'm slightly confused on where it came from and how it catalyzes the reaction

aaronq · Answer

we'll the catalysis would occur via the ribosome tRNA are mediator molecules for amino acids are to be recognized. i can redraw it using other reagents but i thought this would be less complicated.

anonymous · Answer

I understand that part, just not why the tRNA is already bonded to the amino acid :/

aaronq · Answer

because that's how amino acids are brought to a ribosome during translation (you know, anticodon-codon recognition?).

anonymous · Answer

Oh, we haven't learned that yet but I think I can work with the diagram. thanks!

aaronq · Answer

no problem, i hope thats sufficient. If you have doubts or want the mechanism with the other reagents, just ask.