Go Back   Science Forums Biology Forum Molecular Biology Forum Physics Chemistry Forum > Molecular Research Topics Forum > Proteomics Forum > Peptide Forum
Register Search Today's Posts Mark Forums Read

Peptide Forum Peptide Forum. Ask and discuss questions on peptide protocols, custom peptide synthesis, peptide identification and peptide sequencing.


Where does the H come from in peptide bonds?

Where does the H come from in peptide bonds? - Peptide Forum

Where does the H come from in peptide bonds? - Peptide Forum. Ask and discuss questions on peptide protocols, custom peptide synthesis, peptide identification and peptide sequencing.


Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 12-16-2009, 01:17 PM
Pipette Filler
Points: 5, Level: 1 Points: 5, Level: 1 Points: 5, Level: 1
Activity: 0% Activity: 0% Activity: 0%
 
Join Date: Dec 2009
Posts: 2
Thanks: 0
Thanked 0 Times in 0 Posts
Default Where does the H come from in peptide bonds?



Please can you clarify this for me, it drives me nuts ;-P
Forget about side chains and the H and just look at the amino group and carboxylgroup of AAs
H2N and COOH. Because one is a weak base and the other a weak acid, they act at physiolocal pH at proton acceptor/donor making it H3N+ and COO-, the usual zwitterionic form of AAs
( Hope I got it right so far)
Now in peptide bonds ( lets just look at the bonds and forget about the rest) the COOH forms with the next NH2 (of the next AA) a CONH +H2O bond
But you write a peptide bond starting with H3N.......
but where does the extra H come from? It could come from its own ( in zwitterionic form) , but then peptide bonds are not possible because the H from the COOH would be missing
Or do peptide bonds only happen well below pI?
Sorry if I ask such a basic question, but I look and search and cant find an answer.
Thanks
Reply With Quote
  #2  
Old 12-17-2009, 06:11 AM
Kunal Pandya's Avatar
Graduate Student
Points: 3,203, Level: 37 Points: 3,203, Level: 37 Points: 3,203, Level: 37
Activity: 0% Activity: 0% Activity: 0%
 
Join Date: Dec 2009
Location: India
Posts: 141
Thanks: 0
Thanked 6 Times in 6 Posts
Default Re: Where does the H come from in peptide bonds?

Hi

During making of peptide we use two amino acid. In which one having Protected amino part while other one having protected carboxyl group so you can proceed to go for desire reaction.

Example

Boc-Gly-COOH + NH2-Gly-COOMe + Coupling reagent

So what you get is
Boc-Gly-CO-NH-Gly-COOMe (i.e. OH from Carboxyl part while H is from Amino part gives H2O)

Thus to form peptide bond you must have to break zwitter ion other wise it not participate in reaction.It break during protection of Amino or carboxyl part. So buring deprotection of Boc with TFA we get protonated amino site .while if we use any other group cleaved under basic condition then you get just free amino site.

Regards
Kunal Pandya
__________________
Kunal Pandya

Last edited by Kunal Pandya; 12-17-2009 at 06:16 AM. Reason: Not special
Reply With Quote
Reply

Tags
bonds , peptide


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
The peptide bonds that link amino acids in a protein are? blueg Peptide Forum 2 11-11-2010 03:07 AM
disulfide cleavage dpar Peptide Forum 5 08-20-2010 01:09 PM
Peptide bonds and zwitterions? I_am_not_bad Peptide Forum 1 12-17-2009 06:18 AM
peptide bonds hold together what kinds of molecules? Bre Peptide Forum 2 09-26-2009 02:20 AM
What are ionic, covalent, and peptide bonds? imad Peptide Forum 0 08-25-2009 09:17 PM


All times are GMT. The time now is 10:32 AM.


Powered by vBulletin® Version 3.8.4
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Copyright 2005 - 2012 Molecular Station | All Rights Reserved
Page generated in 0.11786 seconds with 16 queries