I have no experience of Qtof, but I see from an ASMS poster which Micromass
sent me that they claim to do precursor ions scans. I copy the intro to the
poster below. Anyone wanting a copy (pdf) may email me and I'll send one
(884K).
Len
Protein bound carbohydrate plays an important role in both the
structure and function of glycoproteins and it is estimated that
over 70% of eukaryotic proteins may be glycosylated.
N-linked carbohydrates can be classified into three main types:
high mannose, complex and hybrid.
Using ESI-MS/MS these different types can be classified
according to their characteristic fragment ions and their
sequences deduced.
The unique characteristics of the precursor-scanning mode of
the Q-Tof allow the individual glycans, cleaved from
glycoproteins, to be rapidly characterised (e.g. glycan type,
extent of sialylation and/or fucosylation and number of branches
on the reducing end) in a single experiment and without prior
separation.
Additional structural information is deduced by MS/MS analysis
of individual glycans.
Identifying proteins, separated by gel electrophoresis, using mass
spectrometry has become a routine technique in many laboratories
today. This, however, is often only the first step in the
characterisation of protein and defining the extent and type of post
translational modification is key in understanding the structure and
function of the protein. Up to 70% of eukaryotic proteins may be
glycosylated and techniques for rapidly classifying the glycan
structures will be useful in unravelling this complex field. N-linked
glycans can be classified into three main types; high mannose,
complex and hybrid. Whilst their structures can vary enormously, the
core reducing end of two N-acetylglucosamines (GlcNAc) and three
mannose residues is common to all. Mass spectrometry has played a
crucial role in the structural analysis of oligosaccharides. In their
native form they are relatively difficult to ionise and derivatisation by
permethylation, peracetylation or reductive amination is often
employed.
In this study we have used 2-aminoacridone (2-AMAC) to derivatise,
via reductive amination, glycan mixtures released from standard
glycoproteins namely; ovomucoid, and porcine thyroglobulin.
Precursor scanning tandem mass spectrometry is an established
technique for producing a spectrum of all precursor ions that
dissociate to give a common fragment ion and in this way may be
used to characterise mixtures or detect compounds of a specific type
in a mixture. A unique aspect of the Q-Tof lies in its ability to perform
multiple precursor scans simultaneously in a single experiment.
Using the Micromass Q-Tof hybrid tandem mass spectrometer, these
mixtures were rapidly characterised in terms of glycan type, extent of
sialylation and/or fucosylation and number of branches on the non-reducing
end of the carbohydrate.
*********************************************************************
Dr Len C. Packman
Assistant Director of Research
Protein and Nucleic Acid Chemistry Facility
Department of Biochemistry
University of Cambridge
80 Tennis Court Road
Old Addenbrookes Site
Cambridge, CB2 1GA, UK
Tel: +44 (1223) 333639
FAX: +44 (1223) 766002
e-mail: lcp2@mole.bio.cam.ac.uk
Visit my WWW page at http://www.bio.cam.ac.uk/proj/adr/PNAC/pnac.html