2015
CH908, Homework #1.
1: How do you calculate the natural abundance theoretical isotope distribution of an
arbitrary elemental composition? How do the algorithms work?
2: Calculate the theoretical isotope distribution of:
a) Cs5I4+
b) a polychlorinated biphenyl, with 4 chlorines.
c) C60+
d) the peptide, substance P (look up the sequence online)
3: “Exact Mass” calculations refer to use of the mass, measured on a mass
spectrometer, to determine (or at least limit) the elemental composition of a molecule.
a) how do exact mass calculations work?
b) calculate the possible elemental compositions for molecules with the
masses (assume instrumental mass accuracy is 0.5 ppm, and state any
assumptions you make):
i) 158.00377
ii) 134.96426
iii) 289.92236
iv) 719.9994
c) “Exact Mass” calculations have an upper mass limit. Explain.
d) What is the upper mass limit for an “Exact Mass” calculation if the
instrument is capable of mass accuracy of:
i) 10 ppm
ii) 1 ppm
iii) 0.1 ppm
4: Estimate the elemental composition in the following isotopic distributions (hint:
use a ruler).
Unregistered
100
90
80
70
60
50
40
30
20
10
0
157
158
159
160
161
Unregistered
162
163
164
100
90
80
70
60
50
40
30
20
10
0
134
136
138
Unregistered
140
142
100
90
80
70
60
50
40
30
20
10
0
288
290
292
294
296
298
300
302