Abstract
st1\:*{behavior:url(#ieooui) } /* Style Definitions */ table.MsoNormalTable {mso-style-name:Table Normal; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:Times New Roman; mso-ansi-language:#0400; mso-fareast-language:#0400; mso-bidi-language:#0400;} A matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometer has been constructed at the Department of Physics, University of Colombo, Sri Lanka. In this mass spectrometer, a solid sample which contains analyte molecules embedded in a suitable matrix compound in excess is exposed to a UV pulsed nitrogen laser source (λ = 337 nm). The desorbed secondary ions from the sample are mass analyzed using the time-of-flight technique. The first MALDI-TOF mass spectra of two peptides namely [tyr 8 ]-bradykinin (1076.2 u) and porcine N-acetyl renin substrate tetradecapeptide (1801.1 u) with the matrix 2,5 di-hydro benzoic acid (154.1 u) have been obtained. Each peptide produced a MH + peak corresponding to its intact molecular ion with m/q values of 1089 ± 6 and 1794 ± 8 respectively. doi:10.4038/sljp.v1i0.168 Sri Lankan Journal of Physics, Vol.1,(2000) 33-42
Highlights
The stop detector is made of two micro channel plates (MCP) coupled in tandem
The laser trigger signal peak was observed in all MALDI mass spectra
MALDI-TOF spectra were taken by setting a 2 μs delay in the oscilloscope in order to check for any pre-laser events
Summary
PD-MS was the only technique that could be used at that time for the mass analysis of large bio-molecules that are nonvolatile and thermally labile. In 1987, Karas and Hillenkamp showed that by using a low concentration of analyte molecules embedded in a relatively larger amount of suitable matrix of low molecular weight, it was possible to desorb and ionize very large bio-molecules[6]. This technique was called matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). The higher sensitivity that the MALDI technique has over the PD technique in detecting molecular ions in crude samples[10] and in mixtures[11] is considered as a distinct advantage in local natural product analysis
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