Soft-Ionization Mass Spectrometry Techniques in Plant Science

ERRA BALSELLS, R., NONAMI, H.,

RIHGA Royal Hotel Sakai, Sakai,

Congreso; International SCJ-JSABE Joint Symposium: Monitoring of Plant Physiological Information and its Applications to Plant Growth Control (MPPIAPGC); 2007

SCJ (Science Council of Japan) and JSABE(Japanese Society of Agricultujapanral Biological and Environmental Engineers and Scientists),

Soft-Ionization Mass Spectrometry Techniques in Plant Sciences. ??Rosa Erra-Balsells (University of Buenos Aires) Keywords: (FAB; UV-MALDI; ESI; CG-MS; LC-MS) Abstract Mass spectrometry (MS) is an analytical technique that uses a device that determines the molecular weight of chemical compounds by separating molecular gas ions according to their mass-to-charge ratio (m/z). Once the molecular gas is formed the ions are generated by inducing either the loss or the gain of charge (e.g., electron ejection, protonation or deprotonation, sodiation, etc). Once the gas ions are formed they can be separated according to m/z and finally detected.     The result of volatilization, ionization, ion separation, and detection is a mass spectrum that can provide molecular weight and even molecular structure. Basically mass spectrometers are devices formed by two components: (1) the ion source or ionization chamber and (2) the analyzer. The volatilization/ionization method used by the former defines what sort of compounds (analytes) can be analyzed. Historically, the first commercial ionization method available was the called ?gelectron ionization?h or ?gelectron impact?h (EI). The EI technique is straightfoward. The sample must be delivered as a gas, from the probe to pass into an electron ionization region where it interacts with an electron beam for ionization. The volatilization process usually accomplished by heating makes impossible to use EI as volatilization/ionization method for thermolabile compounds.      In the past, mass spectrometry was confined to the realm of small no-polar molecules; in general polar molecules and large molecules did not survive to the volatilization/ionization by EI. More recently, as a matter of fact since the early ?f90 two new MS technologies related with the volatilization/ionization process have made the study of biomolecules routine:  Ultraviolet Matrix-assisted Laser Desorption ionization (UV-MALDI) and electrospray ionization (ESI). These technologies have allowed for the analysis of proteins (proteomics), carbohydrates (glycomics), oligonucleotides, lipids and glycolipids, drug metabolites and in general small and large thermo-unstable compounds and untreatable polymers, with detection capabilities ranging from picomole to femto and atomole level. In addition, these techniques can provide High Resolution (HRMS) molecular weight accuracy on the order of 0.01 to 0.001% and structural information as well by means of high resolution (HR) tandem MS (HRMS/MS or HR/MSn). These recent advances have resulted in commercially available and increasingly affordable instruments with the ability to analyze bio molecules of mass greater than 200,000 Da and even to monitor intracellular drug interaction directly and to map cell tissues in straight way.    In general this new developments signify another dimension in biomolecular characterization through a new level of sensitivity, accuracy, and mass range.     The development of ?esoft?f ionization techniques has increased also the potential for MS analysis of mixtures of thermolabil and involatil samples. These ?esoft?f MS techniques, especially in conjuction with liquid chromatography (LC), enable the analysis of complex plant extracts containing mixtures of substances. Although LC-MS technique for the strait analysis of thermolabile non volatile complex mixtures started with Fast Atom Bombardment (FAB) ionization method the current option more popular is LC-ESI. The great advantage of LC-ESI is that it does not demand for derivatization of polar thermolabile non volatile biomolecules and the efficiency of the volatilization/ionization process is very high. Thus, small amount of mixtures of polar thermolabile bio molecules can easily been analyzed from the qualitative and quantitative point of view. Now complex mixtures of polar plant molecules, can be identified without previous derivatization.