Shortly after having graduated in 1966 and just employed as a research assistant in
a protein chemistry laboratory, my very first contact with mass spectrometry happened
when I stumbled on a paper by Michael Barber, the later discoverer of fast
atom bombardment (FAB). Together with a French group he had determined the
covalent structure of an almost 1.4 kDa complex peptidolipid called fortuitine by
using mass spectrometry. Fascinated by this to me unknown technique, I felt that
MS would be a future key analytical method in protein studies. At that time, the
only ionization method available was electron ionization, which required a sample
to be in the gaseous state in the ion source. Therefore most mass spectrometric
analyses were dealing with small organic molecules – and peptides and proteins
were not volatile. Fortuitine was a very fortuitous sample, because it was naturally
derivatized with the consequence that it could be volatilized into the ion source.
Nevertheless, I went into mass spectrometry. My first mass spectrometer was installed
in our laboratory in 1968. Mass spectrometers at that time were complex
fully manually operated instruments most of them magnetic/electrostatic sector instruments,
and the operator needed to know the instrument well in order to avoid
catastrophes by opening wrong valves at the wrong moment. Spectra were recorded
on UV paper with a galvanometer recorder or on photographic plates and
mass assignment was performed manually. During the 1970s a number of new
ionization methods and mass analyzers became available. These included ionization
by chemical ionization and by field ionization/desorption as well as mass
analyses by quadrupoles and ion traps. Computers became available for data acquisition
and mass assignment. Life became easier but the requirement for volatile
samples was still there.
The 1980s revolutionized the possibilities for mass spectrometric analysis. In
the early half of the decade introduction of FAB and commercialization of the 10
years earlier developed plasma desorption mass spectrometry allowed for analyses
of nonvolatile samples such as peptides, proteins, and nucleic acids. The first
commercial fully automated mass spectrometer, the BioIon plasma desorption
mass spectrometer, became available and the time-of-flight analyzer, which had
unlimited mass range, was revived. Late in the decade the two new and now
dominating ionization methods electrospray ionization (ESI) and matrix-assisted
laser desorption ionization (MALDI) were introduced. These two ionization methods
opened a new era for mass spectrometry. Now all the large nonvolatile biological
molecules could be analyzed. Till then GC-MS had been extensively used
for analysis of complex mixtures in environmental and clinical sciences, but due
to its nature it was limited to small volatile molecules. ESI made coupling of LC
with MS possible allowing for entirely new applications of mass spectrometry.
Proteomics now became a big move forward with mass spectrometry as the key
analytical tool. Thousands of scientists took up mass spectrometric analysis and
the instrument manufacturers realized that a new market had emerged and that the
new generation of users were different from the previous technically skilled specialists.
The new generation of instruments therefore became computer controlled,
equipped with safety features to avoid any erroneous operation and with fully
computerized data acquisition. The requirement from the biological sciences for
high speed, sensitivity, and mass accuracy resulted in dramatic improvements of
the performance of the instruments. Hybrid instruments combining the wellknown
mass analyzers were constructed, the FT-ICR mass spectrometer, which till
then had only been available in highly specialized mass spectrometry laboratories,
moved into the biological laboratory. Lately, the orbitrap analyzer, also based on
Fourier transformation, has become standard in advanced biological research laboratories.
Biological mass spectrometry and especially analysis of proteins and proteomics
now dominate mass spectrometry conferences and mass spectrometry has
a strong position in biological conferences, where these subjects ten years earlier
were only marginally present.
What are the consequences of this development? For me, having tried to get
mass spectrometry into protein science for more than 40 years it is of course encouraging.
Mass spectrometry is without any doubt now the most versatile analytical
technique available. It is used in a wide variety of areas from inorganic, nuclear
chemistry, and geochemistry over organic chemistry, environmental
analyses, clinical chemistry, to molecular and cell biology. Online separation of
complex mixtures is possible using either GC-MS or LC-MS. Almost all commercial
instruments are highly automated. However, this development also rises serious
concerns. Many of the new users consider the mass spectrometer as a black
box where they put in the sample in one end and get a result from the computer in
the other end. They do not or only marginally understand the principles in their instrument
and rarely look at the raw data. They are satisfied with computer prints
with lists of identified compounds. Sample preparation often follows standard protocols
and the understanding of the need for optimized sample preparation for
each analytical task is often ignored. As a result, a considerable amount of the data
obtained are questionable either due to poor sample preparation, poor instrument
performance, or suboptimal use of the instruments. It is my wish that the new generation
of mass spectrometry users will spend time to understand their instruments
and the requirements for optimal preparation of the samples and it is my hope that
this book will be read by many of them so that they can use their techniques to the
best of the equipment’s potential.
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