J.M. Orea

trans-Resveratrol and Grape Disease Resistance. A Dynamical Study by High-Resolution Laser-Based Techniques

Two modern laser-based techniques were synchronously applied to study the dynamics of the trans-resveratrol activity in Botrytis cinerea-infected grapes. Direct analysis of trans-resveratrol in both infected and noninfected grapes (Vitis vinifera, Aledo variety) was performed by using an analytical technique incorporating laser desorption coupled with laser resonant ionization and time-of-flight mass spectrometry. On the other hand, one of the most sensitive on-line methods for trace gas detection, laser photoacoustic spectroscopy, was used to investigate the involvement of the plant hormone ethylene (C2H4) in theB. cinerea grapes interaction and its temporal relationship with the trans-resveratrol content upon infection. The trans-resveratrol content and the ethylene released by noninfected grapes showed an opposite behavior. In this case, a high trans-resveratrol content corresponds to a low ethylene emission. For the B. cinerea-infected grapes, ethylene emission rises up after 48 h when the analogous content of trans-resveratrol started to decrease irreversibly. Moreover, the activity of trans-resveratrol as natural pesticide has been investigated by exogenous application on grapes. A short submerge (5 s) of the grapes in 1.6 × 10−4 m solution of trans-resveratrol delays the increase of C2H4 emission with about 48 h and produces a decrease of the C2H4 concentration and its emission rate. The treatment has positive effects on fruit conservation during storage; it doubled the normal shelf-life of grapes at room temperature, maintaining their post-harvest quality within 10 d.

Reaction dynamics of the (R CH3, C2H5 and n-C3 H7) system: chemiluminescence, photon yield, electronic branching ratio and influence of the radical group

Abstract The Ca ( 1 D 2 , 3 P J ) + RI ( R  CH 3 , C 2 H 5 , n - C 3 H 7) → CaI ( A,B ) + R reaction system has been studied by measuring its chemiluminescence under beam gas conditions. Absolute values of the reaction cross-sections were determined at low collision energy E T ≤ 0.20 eV . In addition, the electronic branching ratio, photon yield and influence of the radical size group on the reaction cross-section have been estimated. The results are discussed in the light of different reaction mechanisms involving the attacking Ca atom into the Cz.sbnd;I bond.

Analysis of Carbendazim in Agricultural Samples by Laser Desorption and REMPI Time-of-Flight Mass Spectrometry.

A method has been developed for the analysis of carbendazim in agricultural samples. This has been accomplished by the combination of laser desorption with resonance-enhanced multi-photon ionization (REMPI) coupled to time-of-flight mass spectrometry detection. After the optimization of the experimental conditions and the location of the resonant wavelength of the substance, several samples of pepper extract enriched with carbendazim were analyzed, finding a detection limit of the same order of magnitude as that of current GC and HPLC techniques, but with higher sensitivity and faster sample preparation.

Reaction dynamics of the Ca(1D2, 3PJ) + CH3I → CaI + CH3 system: chemiluminescence, energy disposal and product polarization

Abstract The Ca ( 1 D 2 , 3 P J ) + CH 3 → CaI(A,B) + CH 3 reactions system has been studied by measuring its chemiluminescence under beam-gas conditions. Absolute values of the state-to-state reaction cross-sections were determined at low collision energy E T ⩽ 0.20 eV . In addition, the electronic branching ratio and product energy disposal have been determined for each metastable reaction. The major changed observed in the chemiluminescence when comparing the Ca(1D2) reaction versus that of Ca ( 3 P J ) is the total yield associated with the former reaction. To the best of our spectral resolution neither the electronic branching ratio e.g. CaI(A)/CaI(B) nor the internal CaI energy disposal change significantly as the metastable Ca ( 1 D 2 )/ Ca ( 3 P J ) ratio is varied. In spite of the fact that the Ca ( 3 P J ) reaction is less exoergic, the CaI product appears with a higher fraction of internal energy than that of Ca(1D2) reaction. Thus, the fraction of the total energy appearing in CaI internal energy amounts to 57.5% in the Ca ( 3 P J ) reaction while it is 19.3% only for the Ca(1D2) reaction. This difference is discussed in the light of a distinct mechanism associated with the attack of the excited Ca atom into the CI bond. No significant chemiluminescence yield was found for the energetically open CaCH∗3 channels. The product chemiluminescence polarization was also measured as a function of the metastable concentration. A significant degree of polarization was found depending upon the specific electronic excitation. The analysis of the polarization emission associated to the parallel CaI(X 2 Σ + ← B 2 Σ + ) emission led into a strong polarization of the product rotational angular momentum. The comparison of the product rotational alignment for the kinematically identical Ca ( 1 D 2 , 3 P J , 1 P 1 ) + CH 3 → CaI ∗ ( B 2 Σ + ) + CH 3 reaction system showed that the CaI rotational polarization diminishes in the 3 P J → 1 D 2 → 1 P 1 sequence, e.g. as the reaction exothermicity increases. In addition the degree of polarization associated with other emission bands as for example CaI(X 2 Σ + ← A 2 Π 1 2 ) indicates the presence of a parallel transition which was been interpreted as mixing of Hunds case (a) and (c) appropriate for this heavy CaI diatom produced with a high rotational excitation.

On the electronic energy disposal of calcium excited atom reactions with halogen-containing compounds: Electronic branching ratio and spin–orbit state populations

Abstract This paper reports on the electronic energy disposal of the Ca( 1 D 2 )+RX → CaX ∗ +R reaction system in which R=CH3, H and X=Cl, Br and I. The chemiluminescence yield was collected from either beam–gas or beam–beam reactions resolving the A and B electronically excited CaX states as well as the 2 Π 3/2, 1/2 spin–orbit states. The experimentally observed branching ratio, i.e. Γ(A/B) deviates significantly from the statistical value of 2 and hardly changes with collision energy. This deviation has been attributed to an increased role of Σ→Π transitions, i.e. the lack of orbital following as the impact parameter increases. In relation to the spin–orbit state population the overall behaviour is a nearly equally state population which, in principle, seems to be due to strong state mixing in these excited alkaline-earth halide reaction products. These findings are discussed in light of dynamical models currently used to interpret the reaction dynamics of excited species.

On the Use of the Own Plant's Defence Compounds to Maintain the Post- Harvest Fruit Quality

This work demonstrates that the own plant defence compounds, like resveratrol in grapes, can be used as a natural and ecological alternative to chemical pesticides. An extract from vine leaves was used to maintain the quality of post-harvested grapes. Specifically, an extract (95% water and 5% ethanol) of such leaves was prepared and, subse- quently, different bunches of grapes were immersed in it. The same number of bunches received either water or ethanol (5%) treatment, being both used as blank. Remarkably, on the 14th day after the beginning of the treatment the extract treated grapes, always maintained at room temperature, showed no sign of physical deterioration. In contrast, the two blank samples, i.e.: the water or ethanol treated bunches appeared dehydrated, infected and deteriorated. Furthermore, the external application of the leafs extract does not modify sensorial, biochemical and nutritional properties of the fruits. The beneficial effects of trans-resveratrol, such as anticancer, antiviral, neuroprotective, antiaging and anti-inflamatory support further the use of this natural compound instead of hazardous synthetic pesticides. Therefore, this study represents a step towards the development of new protocols to maintain the post-harvest fruit quality without resorting to chemical pesti- cides.

Spectroscopy of carbendazim in the UV region by resonant multiphoton ionisation

Abstract The spectroscopic characterisation of carbendazim (methyl 2-benzimidazolecarbamate) has been carried out by combining laser desorption (LD) with resonance-enhanced multiphoton ionization (REMPI) followed by time-of-flight mass spectrometry (TOFMS) detection. After optimization of the experimental conditions, the REMPI spectrum of carbendazim was obtained in the region between 280 and 283 nm, with the (0,0) band and Δ v =0 sequence structure at 281.1±0.2 nm. The spectrum exhibits a sequence of peaks separated by approximately 69 cm −1 , consistent with the presence of a low-energy vibration in the ground electronic state. This result is of value in facilitating the development of a direct and sensitive analytical method for the determination of carbendazim in a given sample by LD–REMPI–TOFMS.

On the determination of D00 (CaCl) from translational energy threshold measurements

By using the crossed‐beam technique the translational energy threshold for the Ca(3PJ)+HCl→CaCl (A 2Π)+H chemiluminescent reaction was found to be E0=350±60 meV. By means of energy balance relations, a value of D00 (CaCl)=4.2±0.09 eV was obtained. The potentiality of the present method, based on translational energy measurements, to determine dissociation energies is addressed.

STUDY OF AGRICULTURAL SAMPLES BY LASER DESORPTION COUPLED WITH RESONANCE-ENHANCED MULTIPHOTON IONIZATION AND TIME-OF-FLIGHT MASS SPECTROMETRY: APPLICATION TO CARBENDAZIM ANALYSIS IN PEPPER

A method for the analysis of carbendazim in peper has been developed using Supercritical Fluid Extraction (SFE) for the sample preparation and the combination of Laser Desorption (LD) with Resonance Enhanced Multi-Photon Ionization (REMPI) coupled to Time-of-Flight Mass Spectrometry (TOF-MS) for the detection. The method allows the analysis of carbendazim in pepper reducing the sample preparation step and avoiding the matrix effects present in classical GC and HPLC techniques, as well as the problems related to the labile properties of carbendazim. The detection limit obtained is of the same order of magnitude as the generally employed HPLC technique, but with higher sensitivity and easier sample preparation.

Research Activity Using Molecular Beam and Laser Techniques: A Progress Report

We shall briefly describe the main research areas, now in progress in our molecular beam and laser group. The current activity includes our traditional molecular beam work as well as other experiments carried out in the new labs of our Institute. Essentially we present here the current progress on Crossed-beam and Beam-gas Chemilumine scence, Laser-induced Beam Surface Reaction, Laser Analytical Chemistry, Laser-initiated Reactions Studies by Chemiluminescence and Laser-induced Fluorescence, Spectroscopy and Structure of van der Waals molecules. For each section recent results are presented. Due to the basic scope of the present progress report the emphasis is made on the new experimental developments as well as on the capabilities of both basic and applied research techniques now operative in our group.