Proper Attribution (was Re: Hydrophobic Peptide: Fragment detection

John A. Newitt newitt at nih.gov
Mon Jul 31 13:18:37 EST 1995


Folks could you please make sure to structure your attributions properly
such that they reflect who actually wrote which text.  I replied to a
message posted in this group like this:

---begin pasted text-------------------------------------------------------
In article <3v14s8$33e at newsbf02.news.aol.com>, a999999361 at aol.com
(A999999361) wrote:

> We are working with a 25 amino acid peptide ... extremely hydrophobic ...
> which was synthesized solid phase using Fmoc chemistry. After HPLC
> (reverse phase), Mass Spec indicated the presence of fragments. Further
> Mass Spec experiments indicate that laser desorption will cause these same
> fragments, but do not rule out the presence of the fragments *prior* to
> Mass Spec. The components differ by  approximately 500 MW.
> 
> Question: What is the best (and preferably quickest) method to determine
> the presence of fragments, assuming the sample is supposed to contain only
> pure peptide?

If you have access to a good protein chemistry facility, an N-terminus
analysis might tell you something.  If you get two or more distinct
N-terminal residues, your peptide definitely isn't pure.  A result that
only a single N-terminus exists, does NOT rule out the presence of
multiple peptides, however.

Regards,

John A. Newitt, Ph.D.           |   <newitt at nih.gov>
-snip-
---end pasted text--------------------------------------------------------

Rick Neubig <RNeubig at umich.edu> replied by email AND posting to me, NOT to
a999999361 at aol.com (whoever that is) like this:

---begin pasted text------------------------------------------------------
newitt at ncifcrf.gov (John A. Newitt) wrote:

>> We are working with a 25 amino acid peptide ... extremely hydrophobic ...
>> which was synthesized solid phase using Fmoc chemistry. After HPLC
>> (reverse phase), Mass Spec indicated the presence of fragments. Further
>> Mass Spec experiments indicate that laser desorption will cause these same
>> fragments, but do not rule out the presence of the fragments *prior* to
>> Mass Spec. The components differ by  approximately 500 MW.
>> 
>> Question: What is the best (and preferably quickest) method to determine
>> the presence of fragments, assuming the sample is supposed to contain only
>> pure peptide?


You could try an analytical HPLC to see if there are multiple
peaks. As with the N terminal analysis, negative results aren't
definitive but would make you feel more comfortable about
the integrity of your sample.

_________________________________________________________
Rick Neubig                             RNeubig at umich.edu
-snip-
---end pasted text----------------------------------------------------------

Rick appears to attribute the initial question to me (the double brackets
suggest otherwise, but not all people use the same quoting indicator). 
Now this was harmless and, I'm sure, unintentional, but I don't want to be
held responsible for what other people say.  So please make sure you're
attributions clearly reflect who said what.  Also, if you are going to
send email in addition to posting, it doesn't help the person with the
problem if you send mail to someone who was replying with a
suggestion--send it to the initial person who posted the question.

Just a pet peeve.  Thanks for letting me vent.

Regards,

John A. Newitt, Ph.D.           |   <newitt at nih.gov>
National Institutes of Health   |   FAX: 301-402-0387
Bethesda, Maryland  USA         |   <this space for rent>



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