changes in protein profiles in bortezomib applied multiple myeloma ...
changes in protein profiles in bortezomib applied multiple myeloma ...
changes in protein profiles in bortezomib applied multiple myeloma ...
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2.1.4.5.2.1. Time-of-Flight Mass Analyzer (TOF)<br />
A time-of-flight (TOF) mass analyzer was firstly <strong>in</strong>troduced by Stephens <strong>in</strong><br />
1946 (Stephens, 1946). It is one of the simplest <strong>in</strong>strument <strong>in</strong> terms of its work<strong>in</strong>g<br />
pr<strong>in</strong>ciple.<br />
Chiefly, TOF analysis is based on accelerat<strong>in</strong>g a set of ions to a dedector with<br />
the same amount of k<strong>in</strong>etic energy. All the ions are exposed to high voltage to create an<br />
electric field that allows the ions to be accelerated. After acceleration, the ions go to a<br />
field-free region where they fly at a velocity that is <strong>in</strong>versely proportional to their m/z. It<br />
means that, the smaller ions reach the dedector first because of their greater velocity and<br />
the larger ions take longer. Because the ions have the same energy, yet a different mass,<br />
the ions reach the dedector at different times. Thus the analyzer is called time-of-flight<br />
because the m/z is determ<strong>in</strong>e from the ions time of arrival. F<strong>in</strong>ally, required time is<br />
measured for the travel of the ion through the length of the field-free region.<br />
The resolution is a very important parameter <strong>in</strong> proteomics studies. In a TOF<br />
mass analyzer, both the length of the flight tube and the accelerat<strong>in</strong>g the voltage affect<br />
the resolution. So, <strong>in</strong> order to improve the sensitivity and to <strong>in</strong>crease the resolution, both<br />
acceleration voltages can be lowered and reflectron modes which <strong>in</strong>crease the length of<br />
the flight tube can be placed at the end of the drift zone (Figure 2.8). In summary, us<strong>in</strong>g<br />
a long flight tube is the only way to have both high resolution and high sensitivity.<br />
Figure 2.8. Schematic Representation of Reflectron Time-of-Flight Mass Analyzer<br />
(Source: The University of Bristol, 2007)<br />
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