Malaria detection by laser desorption mass spectrometry

4 MALARIA DETECTION BY LASER DESORPTION MASS SPECTROMETRY 

The fragment ions at m/z 571,557,526,512,498, and 484 correspond to consecutive cleavages of 45 (COOIF), 59 (CHT OOIF) or 73 (CH2CH2COOH ) from M+ that are directly correlated with the heme structure. Hemin, synthetic (l-hematin (heme crystals), and parasite-derived heme crystals yield 

In the first LDMS-based detection of malaria in human subjects (unpublished), lOOpl P. falciparum or P. v/vax-infected blood samples, grouped into three different parasitemia ranges—low (10-150 parasites/pl), mid (2 x 103 parasites/pl), and high (25 x 103-60 x 103 parasites/pl)—have been examined using both sample preparation protocols. Parasitemia levels in these samples were previously determined independently for each sample by optical microscopy examination of blood smears. The LDMS data clearly indicate that 

2 Choline Phosphate—Another Unique LDMS Biomarker for Malaria Detection 

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Demirev, P. A. Feldman, A. B. Kongkasuriyachai, D. Scholl, P. Sullivan, D. J. Kumar, N. Detection of malaria parasites by laser desorption mass spectrometry. 

In early mass spectrometry applications of lasers, the sample was irradiated directly by a laser beam to desorb intact sample-related ions [27]. In this direct mode, termed laser desorption/ionization (LDI), the extent of energy transfer is, however, difficult to control and often leads to excessive thermal degradation. Also, not all compounds absorb radiation at the laser wavelength and thus are not amenable to LDI. Only those compounds that have mass below 1000 Da can be analyzed by LDI. Analytical sensitivity is also poor. A key contribution of LDI experiments is the observation that the desorption efficiency of amino acids and peptides that absorb the laser fight beam is greater than those without the chromophore [28]. IR lasers (e.g., an Nd YAG laser at 1.06 p m and a pulsed CO2 laser at 10.6 pm) and UV lasers (frequency-quadrapled Nd YAG laser at 266 nm) have aU been used. The detection of malaria parasites in blood by LDI with an N2 laser has been demonstrated [29]. 

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