______________________________ Reply Separator _________________________________
Subject: Re: mass units
Author: Ioannis Papayannopoulos <iap@tp.net> at Internet
Date: 7/9/98 12:25 PM
Katheryn,
I (following the example of others) use Da when I refer to a molecular mass
outside the context of a mass spectrometric measurement (e.g. "myoglobin is
a 17 kDa protein", but "the molecular weight of myoglobin is 16950.5" [this
number is from memory, so it may be wrong]). I don't seem to be able to
find much occasion to use u unless I am referring to (measured) mass
diferences (e.g. "the fragment ion at m/z 300.3, corresponding to a
difference of 147 u from the ion at m/z 447.3, indicates the presence of
Phe...". I suppose the fraze "the ion 18 u below the mass of the
protonated molecule indicates the loss of water" could very well be "the
ion 9 u below the m/z of the doubly protonated molecule indicates the loss
of water", but, somehow, the latter does not sound quite right.
Ioannis Papayannopoulos
At 01:24 PM 7/9/98 +0000, Katheryn Resing wrote:
>With regard to u, how does one refer to this when speaking or writing. It
>bothers me to refer to both m and m/z with units of u and I certainly think
>the some peopel would prefer Daltons, rather than units, as the word unit
>has another, more general usage in science.
>
>
>Katheryn Resing
>
>
>