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The spatial resolution of microdissection‐based analytical methods to detect ocular lens glucose uptake, transport and metabolism are poor, whereas the multiplexing capability of fluorescence microscopy‐based approaches to simultaneously detect multiple glucose metabolites is limited in comparison with mass spectrometry‐based methods. To better understand lens glucose transport and metabolism, a more highly spatially resolved technique that maintains the fragile ocular lens tissue is required. In this study, a sample preparation method for matrix‐assisted laser desorption/ionisation imaging mass spectrometry (MALDI IMS) analysis of ocular lens glucose uptake and metabolism has been evaluated and optimised. Matrix choice, tissue preparation and normalisation strategy were determined using negative ion mode MALDI‐Fourier transform‐ion cyclotron resonance MS of bovine lens tissue and validation performed using gas chromatography‐MS. An internal standard was applied concurrently with N‐(1‐naphthyl)ethylenediamine dihydrochloride (NEDC) matrix to limit cracking of the fresh frozen lens tissue sections. MALDI IMS data were collected at a variety of spatial resolutions to detect both endogenous lens metabolites and stable isotopically labelled glucose introduced by ex vivo lens culture. Using this approach, initial steps in important metabolic processes that are linked to diabetic cataract formation were spatially mapped in the bovine lens. In the future, this method can be applied to study the dynamics of glucose uptake, transport and metabolic flux to aid in the study of diabetic lens cataract pathophysiology. [ABSTRACT FROM AUTHOR]

The eye is an elegant organ consisting of a number of tissues and fluids with specialised functions that together allow it to effectively transmit and transduce light input to the brain for visual perception. One key determinant of this integrated function is the spatial relationship of ocular tissues. Biomolecular distributions within the main ocular tissues cornea, lens, and retina have been studied extensively in isolation, yet the potential for metabolic communication between ocular tissues via the ocular humours has been difficult to visualise. To address this limitation, the current study presents a method to map spatial distributions of metabolites and small molecules in whole eyes, including ocular humours. Using a tape‐transfer system and freeze‐drying, the spatial distribution of ocular small molecules was investigated in mouse, rat, fish (black bream), and rabbit eyes using negative ion mode MALDI imaging mass spectrometry. Full‐scan imaging was used for discovery experiments, while MS/MS imaging for identification and localisation was also demonstrated. In all eyes, metabolites such as glutathione and phospholipids were localised in the main ocular tissues. In addition, in rodent eyes, major metabolites were distributed relatively uniformly in ocular humours. In contrast, both uniform and spatially defined ocular metabolite distributions were observed in the black bream eye. Tissue and ocular humour distributions were reproducible, as demonstrated by the three‐dimensional analysis of a mouse eye, and able to be captured with high spatial resolution analysis. The presented method could be used to further investigate the role of inter‐tissue metabolism in ocular health, and to support the development of therapeutics to treat major ocular diseases. [ABSTRACT FROM AUTHOR]

We have studied the gas-phase reactionsof CF+with24 neutral species. Reaction rate constants and product branchingfractions are measured at 298 K using a flowing afterglow-selectedion flow tube. Experimental work is supported by computational chemistrycalculations to provide insight into the reactivity of classes ofneutral molecules. Reactions of CF+with small triatomicspecies and oxygen-containing organic molecules produce the stablemolecule CO. The product branching fractions are discussed, and thepotential energy surfaces for a few representative reactions are examined.CF+is highly reactive with complex molecules and willlikely be destroyed in dense environments in the interstellar medium.However, the lack of reactivity with small diatomic molecules willlikely enable its survival in diffuse regions. [ABSTRACT FROM AUTHOR]

The chemistry of HCNH + in Titan’s atmosphere is not completely understood despite previous experimental and theoretical studies. In response to recent suggestions in the literature, we have searched for specific products of the reactions of HCNH + with H 2, CH 4, C 2H 2, and C 2H 4 using the flowing afterglow-selected ion flow tube technique. We have probed for an association mechanism for reaction with H 2, and associative-H 2 loss for the reactions involving CH 4, C 2H 2, and C 2H 4. In all cases, these reaction mechanisms were found to be inefficient pathways for the depletion of HCNH +. Our ab initio computational studies characterize the structures and energies for these mechanisms and indicate that the proposed pathways are endothermic or possess reaction barriers. We compare our studies to previous experimental and computational work, and we suggest other ion-neutral reactions with HCNH + that have not been included in previous models of Titan’s ionosphere. [ABSTRACT FROM AUTHOR]