CONICET | Buscador de Institutos y Recursos Humanos

Mass spectrometry surface monitoring of plant materials. ??Rosa Erra-Balsells (University of Buenos Aires) Keywords: (MALDI; SIMS; ESI; DESI; imaging mass spectrometry) Abstract Among the different ionization methods of use in mass spectrometry techniques, few of them can be used for imaging mass spectrometry (MS) of intact plant tissue (leaf, steam, roots, fruits, etc.). Classically, those that have been attempted are Desorption Ionizatioin (DI) methods such as Seconday Ion Mass Spectrometry (SIMS) and Ultraviolet Matrix Assited Laser Desorption Ionization (UV-MALDI), a ?esoft?f or ?emild?f ionization method the latter and a quite ?estrong?f or ?ehard?f one the former. DI methods requires the use of a direct insertion probe for sample introduction as solid or viscous no volatil liquid on its surface, and uses a high-energy beam to shot and sputter the sample from the probe surface. Thus, sample is sputted as a ion-gas (desortion/ionization process) without using heat. Once the ions are formed they can separated according to m/z (m=ion mass; z=ion charge) and finally detected. The result of ionization, ion separation, and detection is a ?emass spectrum?f that can provide molecular weight or even structural information. To get these information molecule ions mas be intact after the DI. Only ?esoft?f DI methods fulfill this condition, but in general are too ?esoft?f to induce DI of biomolecules by shotting intact plant tissues. Up to now, the ?esoft?f ultraviolet UV-MALDI-imaging mass spectrometry (MALDI-IMS) has been used with success for on-tissue identification of aminoacids and small polipeptides in spatial discrete regions of intact animal brain tissue, bacteria and virus. After in situ tryptic digestions identification of proteins directly from rat tissue has been recently described (J. Mass Spectrom., 42, 254-262 (2007)) as well as cardiolipin in organs sections of rats (J. Am .Soc. Mass Spectrom. 18, 567-577 (2007)). Since the ?f80, the ?estrong?f SIMS-IMS has been applied in plant science. Two specific areas of plant physiology in which SIMS-IMS is used, have made important advances: metal toxicity and plant nutrition. For example, penetration of Al across root tissue and into cells has been investigated in both root tips and more mature root regions. Also, the transport of Ca to the apical meristem has been investigated. In general, excising the plant tissue and frozen is required before the IMS analysis. These applications are based on the measure fo the realtive intensity ratio between the species: 41K+/ 27Al+/ 40Ca+/ 44Ca+. Although this MS method is also used for sputting biomolecules and its fragments for mapping tussues its practical application is quite minor. Several efforts have been described recently in the literature in order to apply ?esoft?f ionization methods for imaging in plant science. As a clever combination of the ionization processes that occur in MALDI-MS and in electrospray ionization (ESI), both the softest ionization methods used for MS analysis of thermo unstab;e no-volatil polar and no polar biomolecules, the Desortion Electro Spray Ionization (DESI) method has been developed. ESI UV-MALDI The DESI technology is a simple, sensitive, gentle, and versatile ionization method that allows for the direct sampling of surfaces without any sample preparation and under ambient temperature and pressure conditions. DESI DESI-MS applications in plant science will be showed as well as recent new combinations of UV-MALDI and ESI for surface tissue imaging (NALDI; MELDI; etc.).

enviar mensaje