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.


At ph=4, what is the charge of the peptide GET?

At ph=4, what is the charge of the peptide GET? - Peptide Forum

At ph=4, what is the charge of the peptide GET? - 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 01-31-2013, 03:16 AM
Pipette Filler
Points: 1,018, Level: 18 Points: 1,018, Level: 18 Points: 1,018, Level: 18
Activity: 0% Activity: 0% Activity: 0%
 
Join Date: Aug 2007
Posts: 3
Thanks: 0
Thanked 0 Times in 0 Posts
Default At ph=4, what is the charge of the peptide GET?



At ph=4, what is the charge of the peptide GET
Reply With Quote
  #2  
Old 01-31-2013, 04:15 AM
Pipette Filler
Points: 2, Level: 1 Points: 2, Level: 1 Points: 2, Level: 1
Activity: 0% Activity: 0% Activity: 0%
 
Join Date: Jul 2009
Posts: 9
Thanks: 0
Thanked 0 Times in 0 Posts
Default

The N-terminal amino group will have a charge of +1 because its pKa is around 9 or so. Likewise, the C-terminal carboxyl group will have a charge of -1 because its pKa is around 2.1 or so. Now, the only side chain that can be ionized is the carboxyl group of glutamic acid (E). Its pKa is about 4.25. Since this is slightly above 4, more of the glu carboxyl groups will be un-ionized, and the molecule will still have a slight negative charge. If the pH was exactly equal to the pKa of the glu carboxyl, you could say that the molecule would have a net charge of -1/2. Since you are at a pH a little below the pKa, the net charge will be less than -1/2, but it won't be 0.

You could actually use the Henderson-Hasselbalch equation to calculate the fraction of side chains that are ionized and calculate a specific charge, but that's probably not what they want you to do.
Reply With Quote
Reply

Tags
charge , peptide , ph4


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
PLEASE! - Need HELP with finding the net charge of this peptide at pH 9? molly Peptide Forum 1 10-11-2012 04:06 AM
Finding net charge on a peptide? Hermione Granger Peptide Forum 1 10-08-2012 03:44 AM
net charge of a peptide? yahman Peptide Forum 2 09-20-2012 06:44 AM
disulfide cleavage dpar Peptide Forum 5 08-20-2010 01:09 PM
Nobel Prize for David Thomson?! caltechdude Physics Forum 428 01-21-2005 10:39 PM


All times are GMT. The time now is 09:02 PM.


Powered by vBulletin® Version 3.8.4
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Copyright 2005 - 2012 Molecular Station | All Rights Reserved
Page generated in 0.12074 seconds with 16 queries