Greetings!
> The Journal of Biological Chemistry allows the use of
> "Molecular mass (symbol m) is expressed in daltons (Da); one dalton is 1/12
> of the mass of carbon 12. Molecular weight (Mr, relative molecular mass) is
> the ratio of the mass of a molecule to 1/12 of the mass of carbon 12 and is
> I am trying to put a "style page" together for the Journal of Biomolecular
> Techniques and am scratching my head a bit about how to represent mass.
After one lecture on MALDI on our department seminary I have a
discussion with our senior professor Sommer about how to express the molar
weight units, because he is quite unsatisfied with using Da (dalton) as AU
(absorbance units). Finally I have found that the most correct will be
"a.m.u." (atomic mass unit), defined in the same way the Dalton above.
So we use symbol "Mr" for the molecular weight and "a.m.u." for its
units.
> There is no mention of the term "m/z" although I am used to seeing this in
> a whole host of mass spectrometric output.
We describe in reports and publication the "m/z" as a mass to
charge parameter, detected by the instrumentation, from which may be the
Mr calculated (you should know the charge).
Its unit is a bit unclear: the m/z parameter is, in the terms of SI
units: a.m.u. to coulomb. But we do use for the electron charge
(1.602E-19 C) nameless unit, we always say: `it has one pozitive charge'
instead of `it has charge /1.602E-19/ C'.
So we are always trying to keep "m/z" appart from "Mr" in describing the
mass spectra. These two are different in what is to say.
Hojudijaca onale hijemor,
Farewell, I hope to meet you again,
Lakantunok atrojum hijor Gods will be on your side
ce atrojumhi taxmele only if you go in their direction
ge pelije ragin ifrab. and thereto wisdom is needed.
Jan Havlis, Ph.D.
MALDI TOF Mass Spectrometry Laboratory
Department of Analytical Chemistry
Faculty of Natural Sciences
Masaryk University
Kotlarska 2, CS-611 37 BRNO
Czech Republic
tel.: 420-5-41129495
fax.: 420-5-41211214
jdqh@chemi.muni.cz
http://www.chemi.muni.cz/~jdqh/index.html