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Selected ion monitoring (SIM) is an acquisition mass spectrometry (MS) scan mode used for monitoring one or a restricted number of ions. Unlike full scan acquisition, the MS analyzer during the SIM acquisition can spend more time for the selected ion, avoiding to acquire other ions that are not of interest for the analyst. This article takes into account the advantages and disadvantage of the SIM MS technique, considering that its use is generally coupled with separation techniques such as gas chromatography or high-performance liquid chromatography. An overview about sample introduction, ionization sources, and mass analyzers (both at low- and high-resolution) used during SIM experiments is here given. However, the increasing request of tandem mass spectrometry instrumentation is supplanting little by little the use of SIM acquisition in place of selected reaction monitoring (SRM), which is the evolution of SIM acquisition with tandem MS. A comparison between high-resolution SIM MS and SRM MS acquisition is also taken into account. At last, new trends of HR MS acquisitions are considered, in which generally the potentiality of data independent acquisition and of retrospective analysis can be utilized at the expense of the use of SIM experiments.

Photoautotrophic growth of Synechocystis sp. PCC 6803 in a flat-panel photobioreactor, run in turbidostat mode under increasing intensities of orange-red light (636 nm), showed a maximal growth rate (0.12 h−1) at 300 μmolphotons m−2 s−1, whereas first signs of photoinhibition were detected above 800 μmolphotons m−2 s−1. To investigate the dynamic modulation of the thylakoid proteome in response to photoinhibitory light intensities, quantitative proteomics analyses by SWATH mass spectrometry were performed by comparing thylakoid membranes extracted from Synechocystis grown under low-intensity illumination (i.e. 50 μmolphotons m−2 s−1) with samples isolated from cells subjected to photoinhibitory light regimes (800, 950 and 1460 μmolphotons m−2 s−1). We identified and quantified 126 proteins with altered abundance in all three photoinhibitory illumination regimes.These data reveal the strategies by which Synechocystis responds to photoinibitory growth irradiances of orange-red light. The accumulation of core proteins of Photosystem II and reduction of oxygen-evolving-complex subunits in photoinhibited cells revealed a different turnover and repair rates of the integral and extrinsic Photosystem II subunits with variation of light intensity. Furthermore, Synechocystis displayed a differentiated response to photoinhibitory regimes also regarding Photosystem I: the amount of PsaD, PsaE, PsaJ and PsaM subunits decreased, while there was an increased abundance of the PsaA, PsaB, Psak2 and PsaL proteins. Photoinhibition with 636 nm light also elicited an increased capacity for cyclic electron transport, a lowering of the amount of phycobilisomes and an increase of the orange carotenoid protein content, all presumably as a photoprotective mechanism against the generation of reactive oxygen species.

To address the growing interest of consumers for information on the provenance of foodstuffs, the production chain of world renowned Moscato d’Asti white wine has been studied using the distribution of lanthanides as chemical markers. From soil to must, upon every stage of the chain, samples have been taken and analysed with ICP-MS in order to verify whether the original fingerprint of soil is maintained or not along the chain. Results of this traceability study show clearly that lanthanides fingerprint is kept unaltered in the passage soil-grapes-must, while fractionation occurs upon wine clarifying with bentonites. The second part of the work involves a study on 102 samples of Moscato d’Asti musts in order to verify how they reflect the features of the different geographical zones where they come from, and to build a basis to be able to identify possible adulterations performed by addition of foreign musts.

Marengo, E. and Todeschini, R., 1993. Linear discriminant hierarchical clustering: a modeling and cross-validable divisive clustering method. Chemometrics and Intelligent Laboratory Systems, 19: 43–51. A simple modification of the linear discriminant classification tree (LDCT) (R. Todeschini and E. Marengo, Linear discriminant classification trees, Chemometrics and Intelligent Laboratory Systems, 16 (1992) 25-35) method is used to deal with clustering problems in the framework of a divisive hierarchical strategy. The method produces a mathematical model which allows the validation of the obtained clusters by using a cross-validation technique; simple parameters can then be estimated to assess the significance of the clusters. The performance of linear discriminant hierarchical clustering has been tested on seven data sets where the class assignments are known.

A new algorithm for optimal, distance based, experimental design is presented. The proposed approach, in contrast to other optimality criteria, does not require any preliminary hypothesis about a regression model. The best set of experiments is defined through a fast exchange algorithm where, in each cycle, a substitution is selected to provide the maximum increase of the minimum distance between the currently selected experiments. Such an algorithm provides a final uniform distribution of the experiments selected from the set of allowed candidates.

Leardi, R., Marengo, E. and Todeschini, R., 1991. A new procedure for the visual inspection of multivariate data of different geographic origins. Chemometrics and Intelligent Laboratory Systems , 12: 181–187. A new display method to be used for data of different geographic origin is presented. A geographic map of the region is shown, the zone corresponding to each sample being in a colour which is derived from the sum of the fundamental colours which have been associated with the variables (original or transformed). Three real examples show that the interpretation of the resulting plots is much easier compared to dealing with classical loading and score plots, both concerning the differences between the objects as well as the relative importance of the variables.