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Newer and safer agrochemicals are always in demand to meet the increasing needs of a growing population for affordable food. Spatial chemical monitoring of the active mobility of an agrochemical is essential to this agrochemical development process and mass spectrometry imaging (MSI) is proposed as a safer, easier alternative to the existing standard of autoradiography for the same. With desorption electrospray ionisation mass spectrometry imaging (DESI MSI) using leaf imprints, we were able to visualize the active agrochemical mobility of a commercial fungicide formulation with the active ingredient Azoxystrobin in whole tomato leaves. The leaf-imprinting method was optimized with precise control over the pressure conditions and time of imprinting to yield highly consistent samples for imaging. The reproducibility of this method was tested with the Azoxystrobin formulation applied to tomato leaves and was compared to the mobility of the unformulated Azoxystrobin standard in similar application conditions. The xylem mobility and the lateral-leaf lamina spreading of the fungicide were visualized with mass spectrometry imaging and validated using complementary LC-MS studies. The necessity and importance of the agrochemical application as a formulation were re-iterated by the limited mobility observed in Azoxystrobin standard studies compared to the Azoxystrobin formulation. This mass spectrometry imprint-imaging method could be translated for the visualization of any xenobiotic in further foliar systems particularly with soft leaves. [ABSTRACT FROM AUTHOR]

Neuroinflammation is a complex biological process related to a variety of pathologies, often requiring better understanding in order to develop new, targeted therapeutic interventions. Within this context, multimodal Mass Spectrometry Imaging (MSI) has been used to characterise molecular changes in neuroinflammation for biomarker discovery not possible to other techniques. In this study, molecules including bioactive lipids were detected across inflamed regions of the brain in rats treated with lipopolysaccharide (LPS). The detected lipids may be acting as inflammatory mediators of the immune response. We identified that N-acyl-phosphatidylethanolamine (NAPE) species accumulated in the inflamed area. The presence of these lipids could be related to the endocannabinoid (eCB) signalling system, mediating an anti-inflammatory response from microglial cells at the site of injury to balance pro-inflammation and support neuronal protection. In addition, polyunsaturated fatty acids (PUFAs), specifically n-3 and n-6 species, were observed to accumulate in the area where LPS was injected. PUFAs are directly linked to anti-inflammatory mediators resolving inflammation. Finally, acylcarnitine species accumulated around the inflammation region. Accumulation of these molecules could be due to a deficient β-oxidation cycle. [ABSTRACT FROM AUTHOR]

Although the benefits of decreased sample temperature for the molecular profiling of organic materials with time-of-flight secondary ion mass spectrometry (TOF-SIMS) have been established, the mechanism behind spectral changes observed at low temperature, particularly increased protonated molecular ion [(M + H).sup.+] yields, have not been examined in detail. We have developed a procedure to investigate these effects by monitoring secondary ion yields under sustained primary ion bombardment as the sample temperature is cooled from room temperature down to 80 K. Examination of biomaterlals such as an amino acid (arginine), a polypeptide (Gly-Gly-Tyr-Arg), a lipid (1,2 dipalmitoyl-sn-glycero-3 phosphatidylcholine), and a drug molecule (cyclosporine A) each provide evidence of ion yield enhancement at 80 K under either 20 keV [C.sub.60.sup.+] or 20 keV [Au.sub.3.sup.+] bombardment. For example, arginine shows a 2-fold increase in the steady-state intensity for the [(M + H).sup.+] ion at 80 K compared to the steady state at 300 K. It is shown that there is a correlation between the yield enhancement and a reduction in the damage cross section, which for arginine under 20 keV [Au.sub.3.sup.+] bombardment decreases from 5.0 [+ or -]0.4 x [10.sup.-14] [cm.sup.2] at 300 K to 2.0 [+ or -] 0.3 x [10.sup.-14] [cm.sup.2] at 80 K. The role of water as the facilitator for this reduction is explored through the use of [H.sub.2]O and [D.sub.2]O dosing experiments at 80 K. 10.1021/ac101746h

Buckmlnsterfullerene ([C.sub.60) as a primary ion for secondary ion mass spectrometry (SIMS) has shown many benefits over classical SIMS sources in the analysis of large organic molecules including many of biological significance. One constraint has been the limited focusing capabilities of the [C.sub.60] beam. Although this could be circumvented by using beam size limiting apertures at the cost of beam current, high-resolution imaging using conventional time-of-flight (TOF) instruments has been challenging and time-consuming. We present a method in which we combine the use of an unfocused [C.sub.60.sup.+] beam with an ion optical microscope. A delay line detector is used to obtain fully resolved hyperspectral data sets that contain both the full mass spectral and the localization information. The obtained image resolving power is 4[micro]m at a pixel size of 250 nm. Microscope mode [C.sub.60.sup.+] imaging was shown to resolve micrometer-scale features in a combined polymer-tissue sample. Our new approach demonstrates high-quality SIMS imaging using the full [C.sub.60.sup.+] beam current. This results in equal or better resolving power at reduced acquisition speed. 10.1021/ac902587g

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) has unique capabilities in the area of high-resolution mass spectrometric imaging of biological samples. The technique offers parallel detection of native and nonnative molecules at physiological concentrations with potentially submicrometer spatial resolution. Recent advances in SIMS technology have been focused on generating new ion sources that can in turn be used to eject more intact molecular and biological characteristic species from a sample. The introduction of polyatomic ion beams, particularly C~0, for TOF-SIMS analysis has created a whole new application of molecular depth profiling and 3D molecular imaging. However, such analyses, particularly at high lateral resolution, are severely hampered by the accompanying mass spectrometry associated with current TOF-SIMS instruments. Hence, we have developed an instrument that overcomes many of the drawbacks of current TOF-SIMS spectrometers by removing the need to pulse the primary ion beam. The instrument samples the secondary ions using a buncher that feeds into a specially designed time-of-flight analyzer. We have validated this new instrumental concept by analyzing a number of biological samples generating 2D and 3D images showing molecular localization on a subcellular scale, over a practical time frame, while maintaining high mass resolution. We also demonstrate large area mapping and the MS/MS capability of the instrument.

In this paper, the effect of prolonged [C.sub.60.sup.+] primary ion bombardment on the chemical information available from a section of rat brain is discussed. Initial attempts demonstrate the rapid loss of molecular signal from the bombarded area with both [C.sub.60.sup.+] and [Au.sup.+] used as a monatomic comparison. However, the nature of this signal disappearance is shown to be different. Analysis of the [C.sub.60.sup.+] data indicates a correlation between signal loss and the appearance of sodium and potassium adducts of phosphate and protein fragments; this is supported by model systems. By using an ammonium formate wash to reduce the salt levels within the tissue this effect is removed, allowing the chemistry of the tissue section to be better probed. Results collected from multiple sections suggest that at room temperature under vacuum conditions there is a migration of lipids to the surface of the tissue. Three-dimensional (3D) imaging is used to demonstrate that once these lipids are removed other species, such as proteins, are uncovered. By depth profiling the sample in a frozen state, the degree and importance of lipid migration to the observed localization of native compounds is assessed. This investigation into the behavior of biological tissue under high [C.sub.60.sup.+] fluxes not only allows an evaluation of the potential accuracy of 3D SIMS mapping of important biological molecules but also demonstrates the possibility of using ion doses beyond the traditional 'static limit' to provide higher secondary ion yields that could lead to greater detection limits and smaller useful lateral resolution within such analyses.

Imaging using time-of-flight secondary ion mass spectrometry (TOF-SIMS) with buckministerfullerene ([C.sub.60]) primary ions offers the possibility of mapping the chemical distribution of molecular species from biological surfaces. Here we demonstrate the capability of the technique to provide biomolecular information from the cell surface as well as from within the surface, as illustrated with the distribution of two antibiotics in Streptomyces coelicolor (a mycelial bacterium). Differential production of the two pigmented antibiotics under salt-stressed and normal conditions in submerged cultivations could be detected from the TOF-SIMS spectra of the bacteria, demonstrating the potential of the technique in studying microbial physiology. Although both the antibiotics were detected on the cell surface, sputter etching with [C.sub.60+] revealed the spectral features of only one of the antibiotics within the cells. Exploratory analysis of the images using principal component analysis assisted in analyzing the spectral information with respect to peak contributions and their spatial distributions. The technique allows the study of not only lateral but also the depthwise distribution of biomolecules, uniquely enabling exploration of the processes within biological systems with minimal system intervention and with little a priori biochemical knowledge of relevance.

[C.sub.84.sup.+] and coronene ([C.sub.24][H.sub.12.sup.+]) have been studied as primary ions for use in secondary ion mass spectrometry. A representative range of samples has been used to compare the effectiveness of each primary ion with the existing [C.sub.60.sup.+], [Au.sup.+], and [Au.sub.3.sup.+] primary ions. It was found that [C.sub.84] is the most effective primary ion providing higher secondary ion yields and a high molecular to fragment ion ratio. Coronene had a performance similar to [C.sub.60]. Coronene and [C.sub.60] primary ions were also used to extend a previous study of matrix suppression/enhancement effects. The [C.sub.60] was found to ameliorate this effect, possibly due to the increase in protonation in polyatomic sputtering, and coronene was found to further reduce suppression showing evidence of a chemical effect.

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) using buckminsterfullerene ([C.sub.60]) as the primary ion source has the ability to generate chemical images of surfaces with high sensitivities and minimal chemical damage. We studied the application of [C.sub.60.sup.+] to depth profile a biological cell surface in a controlled manner and to subsequently image the revealed subsurfaces, in order to generate three-dimensional molecular images of the biological system. Such an analytical tool not only enables the surface localization of molecular species to be mapped but also enables the biomolecular distribution as a function of depth to be investigated with minimal sample preparation/intervention. Here we demonstrate the technique with a freeze-dried Xenopus laevis oocyte, which is a single cell. A [C.sub.60.sup.+] ion beam was used with computer-controlled analyses and etch cycles. Mass spectra derived from the surface revealed peaks corresponding to cholesterol (m/z 369) and other lipids at m/z 540-570 and 800-1000, in the positive ion mode, and lipid fatty acid side chains (e.g., m/z 255) in the negative ion mode. To our knowledge, this is the first demonstration of the 3D biomolecular imaging within an actual biological system using TOF-SIMS.

[C.sub.60] has been shown to give increased sputter yields and, hence, secondary ions when used as a primary particle in SIMS analysis. In addition, for many samples, there is also a reduction in damage accumulation following continued bombardment with the ion beam. In this paper, we report a study of the impact energy (up to 120 keV) of [C.sub.60] on the secondary ion yield from a number of samples with consideration of any variation in yield response over mass ranges up to m/z 2000. Although increased impact energy is expected to produce a corresponding increase in sputter yield/rate, it is important to investigate any increase in sample damage with increasing energy and, hence, efficiency of the ion beams. On our test samples including a metal, along with organic samples, there is a general increase in secondary ion yield of high-mass species with increasing impact energy. A corresponding reduction in the formation of low-mass fragments is also observed. Depth profiling of organic samples demonstrates that when using [C.sub.60], there does not appear to be any increase in damage evident in the mass spectra as the impact energy is increased.

A buckminsterfullerene ([C.sub.60])-based primary ion beam system has been developed for routine application in TOF-SIMS analysis of organic materials. The ion beam system is described, and its performance is characterized. Nano-amp beam currents of [C.sub.60.sup.+] are obtainable in continuous current mode. [C.sub.60.sup.2+] can be obtained in pulsed mode. At 10 keV, the beam can be focused to less than 3 [micro]m with 0.1 nA currents. TOF-SIMS studies of a series of molecular solids and a number of polymer systems in monolayer and thick film forms are reported. Very significant enhancement of secondary ion yields, particularly at higher mass, were observed using 10-keV [C.sub.60.sup.+] for all samples other than PTFE, as compared to those observed from 10 kev [Ga.sup.+] primary ions. Three materials (PS2000, Irganox 1010, PET) were studied in detail to investigate primary ion-induced disappearance (damage) cross sections to determine the increase in secondary ion formation efficiency. The [C.sub.60] disappearance cross sections observed from monolayer film PS2000 and self-supporting PET film are close to those observed from [Ga.sup.+]. The resulting [C.sub.60] efficiencies are 30-100 times those observed from gallium. The cross sections observed from [C.sub.60] bombardment of multilayer molecular solids are ~ 100 times less, such that essentially zero damage sputtering is possible. The resulting efficiencies are > [10.sup.3] greater than from gallium. It is also shown that [C.sub.60] primary ions do not generate any more low-mass fragments than any other ion beam system does. [C.sub.60] is shown to be a very favorable ion beam system for TOF-SIMS, delivering high yield, close to 10% total yield, favoring high-mass ions, and on thick samples, offering the possibility of analysis well beyond the static limit.