Well it was a sort of sarcasm about many researches in which nature of
the peptides used doesn't count.
Vladimir
On 01/08/2000, fperini@unmc.edu wrote:
> I always look forward at your replies.And,just for this,I did some
> major editing to my original reply.I was having some vision problems,
> but this is not a good excuse for the errors.It should be more
> understandable.You correct that in most cases it does not matter if there
> is any of the D-form,except if you want to use the compound in enzymatic
> assays.Enzymes are very specific for L-amino acids.
> Vladimir Titov <vmtitov@aha.ru>@aecom.yu.edu> on 08/01/2000 08:08:03 AM
> Please respond to Vladimir Titov <vmtitov@aha.ru>
> Sent by: Association of Biomolecular Resource Facilities
> <abrf-request@aecom.yu.edu>
> To: Recipients of ABRF List <abrf@aecom.yu.edu>
> cc: Recipients of ABRF List <abrf@aecom.yu.edu>
> Subject: Re[2]: Racemization/polarimeters
> High resolution NMR detects diastereomers, but you need an expert to
> interprete the spectra. HPLC often works, but not always. Polarimetry
> is not the method for peptides, because optical rotation depends on
> concentration of peptide in the sample which is subject to another
> analysis. Threrefore, the errors from the two analyses would be
> multiplied. I have heard about AAA on chiral phases but have never
> seen anyone who used it. In my cinical opinion, for most research
> there is no difference which substance is used at all, so it's better
> to forget about racemization and present HPLC and mass spec. If you
> are producing a pharmaceutical compound, it makes a difference but you
> would have resources to study the compound and develop analytical
> methods.
> On 31/07/2000, fperini@unmc.edu wrote:
>> I have been spending a good deal of time trying to get an universal
>> procedure,and I
>> found out that no matter which method I tried,it does not work all the
>> time.
>> If the peptide is relatively small,and I will not be pinned down on
> size,a
>> reverse phase HPLC separation will do the job.If you can get the same
>> column,conditions,etc.as the initial
>> run,it should work when combined with amino acid analysis.Once,I got a
>> peptide which gave
>> baseline resolution of two peaks of identical size.I found out that the
>> researcher
>> synthesized the derivatives,using the D,L-amino acid,but it was only
> five residues in length..
>> To get the percentage of D-amino acid is not so easy.I have seen
>> publications,which took advantage of the chiral properties,and I tried
>> the procedures.They work for only a few amino acids.Probably,the best
>> method is that of
>> N.Nimura and T.Kinoshita,J.Chromat.,vol.352,169-177(1986).It relies on
> the
>> reaction of
>> primary amino acids with o-phtaldehyde(OPA),in presence of a sulfur
> compound
>> which is usually in
>> the L-form.A ternary complex is formed,and it is possible to separate the
>> one with the
>> L-amino acid from D-amino acid,by the fact that there is a L-L and D-L
>> form.The authors and
>> I have been using N-acetyl-L-cysteine,although other sulfur compounds
> have
>> been used.
>> It is a precolumn derivatization and detection is fluorometric.I do not
>> think that any
>> other physico-chemical method will work.
> Vladimir Titov
> Bokiron Ltd., Moscow, Russia
Vladimir Titov
Bokiron Ltd., Moscow, Russia
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