MALDI and Virtual 2D

Mitchell Isaacs misaacs at spam_me_not.student.usyd.edu.au
Fri Jan 11 22:24:19 EST 2002


"Simon" <cristoni at itba.mi.cnr.it> wrote in message
news:a1hg0n$anl$1 at sun250.unimi.it...

> In this paper the second dimension of classical 2D-GEL has been sobstitued
> with the MALDI technique. My questions are: 1) In the paper it is
specified
> that the MALDI (PerSeptive-Vestec Voyager Elite and PerSeptive) use the
> LINEAR MODE in order to perform the analysis on the first dimension of the
> GEL. Do you know what does LINEAR MODE means? 2) Do you know some
laboratory
> that are able to use this technique? I am strongly interested in
> collaboration with this groups.
Linear mode just means that you use the MALDI with the reflectron switched
off - so your flight path is shorter.

If you have been analysing peptides then you should have been using
reflectron mode - basically, the peptides go one way up the flight tube,
then get reflected back down the tube by the reflectron. This means that the
flight path is doubled, and the resolution is improved. However, proteins
and large peptides aren't terribly stable over this long path after being
reflected, and tend to fragment. So you turn off the reflectron to analyse
them, in linear mode.

While this means that the proteins and larger peptides won't fragment so
much, your resolution will be worse. Also, you will definitely need to spike
with several internal calibrants - linear mode accuracy is notoriously bad.

If you have been using MALDI to analyse peptides, then it is not too
difficult to change to linear mode for protein analysis.

Cheers,
Mitchell





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