In Situ Analysis of Plant Tissue Underivatized Carbohydrates and On-Probe Enzymatic

YOUSEF GHOLIPOUR; HIROSHI NONAMI; ERRA BALSELLS, ROSA

ANALYTICAL BIOCHEMISTRY

Elsevier

Lugar: Amsterdam; Año: 2008 vol. 383 p. 159 - 167

0003-2697

Underivatized carbohydrates of tulip bulb and leaf tissues were characterized in situ by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) by using carbon nanotubes (CNTs) as matrix. Two sample preparation methods including (i) deposition of CNTs on the fresh tissue slices placed on the probe, and (ii) locating semi-transparent tissues on a dried layer of CNTs on the probe, were examined. Furthermore, practicability of in situ starch analysis by MALDI-TOF MS was examined by detection of glucose originated from on-probe amyloglucosidase-catalyzed degradation of starch on the tissue surface. Besides, CNTs could efficiently desorb/ionize natural mono-, di-, and oligosaccharides extracted from tulip bulb tissues as well as glucose resulted by starch enzymatic degradation in vitro. These results were compared with those obtained by in situ MALDI-TOF MS analysis of similar tissues. Positive ion mode showed superior signal reproducibility. CNTs deposited under semi-transparent tissue could also desorb/ionize neutral carbohydrates leaded to almost complete elimination of matrix cluster signals but with increase in tissue-originated signals. Furthermore, several experiments were carried out to compare the efficiency of 2,5-dihydroxybenzoic acid, nor-harmane, á-cyano-4-hydroxycinnamic acid and CNTs as matrices for MALDI of neutral carbohydrates from the intact plant tissue surface and for enzymatic tissue starch degradation; these results are discussed in brief. Among matrices studied, the lowest laser power was needed to acquire carbohydrate signals with high signal-to-noise ratio and resolution when CNTs were used.