chemoleo - 10-5-2005 at 08:07
Here's a work related question:
I need to modify a doublebond R1R2C=CHR where R = CR3 with an unknown compound so that an adduct is formed. Preferably a large molecule, so that I can
use HPLC to purify this adduct away from the rest that doesn't contain double bonds.
Specifically, these are peptides - so they contain NH2, guanidine groups, phenylgroups, OH, COOH. But the good peptide contains NO
double bonds, and the bad peptide does contain them. And these I want to get rid of.
Does anyone know reagents that *specifically* react with double bonds to form large adducts? Like dyes etc?
azaleaemerson - 10-5-2005 at 09:35
How about aromatic substitution with polystyrene? A friedel-crafts reaction could cause the double bond to react with dissolved coffee cups. All my
books are still at my ex's, so that's the best suggestion I can make for now.
chemoleo - 10-5-2005 at 09:56
Lol, please understand -
these are expensive peptides, made in a proper lab. No coffee cups this time - I need a specific reagent preferably of a high molecular mass that
reacts with the double bond and nothing else.
azaleaemerson - 10-5-2005 at 10:11
Fancy, eh? Ok, then how about a commercial support of a diene that will do diels alder with the double bond. Check out this paper:
http://www.arkat-usa.org/ark/journal/2004/I02_Zwanenburg/BZ-...
That's all for now before I get caught wasting company time.
chemoleo - 10-5-2005 at 10:32
Thanks but it's not quite what I am after.
It's cyclopentadiene, undergoing adducts which uses both double bonds, to form dicyclic derivatives.
Ok, imagine the formula/sequence is this:
R-CO-NH-C(=HCCH3)-CO-NH-R
I am trying to react something with THIS double bond only, and specifically. either forming a complete split of the two, or an adduct that has a
larger mass/distinct properties on the HPLC.
There got to be some specific analytical dye based tests out there... are there analysis in organic chemistry-type books out there / on the Ftp?
Marvin - 11-5-2005 at 07:48
Biochem is not my strongpoint but, is it important that you can get the peptide back from the adduct and what sort of mw of peptide are we talking
about?
I'm wondering at the moment if it might be possible to cleave the bond instead and look for the fragments.
chemoleo - 11-5-2005 at 08:02
No, the double bonded one can be modified/destroyed by any means. I don't need it. In fact, I want to get rid of it, in a batch that contains
both the correct peptide and the double bonded one.
In other words, I need a dye or something that reacts / forms adducts with double bonds specifically.
Essentially in analytical organic chemistry there must be ways that describe the photometric detection of double bonds?
mw: 5-7000 Da.
Magpie - 11-5-2005 at 08:07
I am not an expert in organic chemistry and know very little about biochemistry. I don't have a proven recipe. But it seems like you should be
able to brominate the double bond with HBr. Once you have formed this halide you should be able to react it with a sodium alkoxide to form an ether.
This alkoxide could hopefully be of high enough molecular weight that it would provide a separable compound.
Caveat: I don't know how delicate these peptides are. So from my viewpoint the above is strictly experimental.
chemoleo - 11-5-2005 at 08:20
Yeh , of course there are those addition reacitons, but I don't think the peptide bonds would take kindly to such conditions.
There are of course the KMnO4/OsO4 esters, that, when hydrolysed, form the diol, but I wouldn't want to subject a peptide to such conditions.
Having searched more in the meantime (it appears dehydroalanine is a good search term), it appears that R-CH2-SH reacts with those doublebonds. I
suppose I could use a large molecule containing this group. Hmm.
[Edited on 11-5-2005 by chemoleo]
unionised - 13-5-2005 at 06:45
IIRC Chromatography using Ag+ on some inert substrate will selectively absorb/ retain unsaturated materials. Not sure how well it would work with all
those polar peptide bonds there though.