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Mono-, di-, tri-, and hexaporphyrin derivatives were synthesized and their sensorial ability toward Na+ , Li+ , Ca2+ , Cu2+ , Ni2+ , Co2+ , Fe3+ , Zn2+ , Cd2+ , Hg2+ , Ag+ , Cr3+ , Pb2+ , and Al3+ was explored by absorption and emission spectroscopy and 1 H NMR spectroscopy. For all of the studied porphyrin derivatives the most significant spectral changes were observed upon addition of Zn2+ , Cd2+ , Cu2+ , Co2+ , Pb2+ , Hg2+ , and Fe3+ , which resulted in a color change from red to green. When the remaining metal ions were tested, no significant changes were observed. The results reveal, as expected, the formation of mononuclear complexes for porphyrin 4, dinuclear complexes for diporphyrin 7, and trinuclear complexes for triporphyrins 9 and 10. In addition, complexes of type M6 L were determined for hexaporphyrin 8. The NMR spectroscopy studies suggest that the interaction with the metals occurs with the formation of sitting-atop complexes. This study also shows that the sensitivity increases with increasing number of coordination sites, with the most pronounced case observed for Hg2+ . The lowest value of detectable concentration of 0.05 μm for Hg2+ was achieved for hexaporphyrin 8.

RATIONALE There is a need in imaging mass spectrometry to use the acquired isotope distribution to unequivocally determine the identity of a peptide ion. A way of achieving unambiguous differentiation of ions from protonated peptides from other [M + H]+ ions in a tissue would be via the direct on-tissue incorporation of 18O into peptides. METHODS Tissues were first digested with trypsin for 3 h at 37 °C in a humidified chamber. For the 18O-labelling of digested peptides 1 μL of H218O/50 mM ammonium acetate (at pH 6.75) was added to the array of tryptic spots and incubated at room temperature for 20 min. α-Cyano-4-hydroxycinnamic acid was used as a matrix modifier. The mass spectral analysis of tissue sections was carried out using a matrix-assisted laser desorption/ionisation tandem time-of-flight (MALDI-TOF-TOF) instrument. RESULTS On-tissue incorporation of 18O into peptides cannot be carried out during the digestion step inside a humidified chamber. After tissue digestion for 3 h at 37 °C in an humidified chamber, 18O labelling was carried out for 20 min at room temperature (no humidified chamber). No trypsin was needed to enhance the labelling. CONCLUSIONS For first time the feasibility of 18O-labelling of peptides in situ for tissues has been demonstrated. The method decouples protein digestion from peptide labelling and is performed in sequential steps. Furthermore, we observed that 18O incorporation produces characteristic isotopic peptide distributions, thus making facile distinguishing peptides from other tissue molecular components that ionise in the MALDI ion source. Copyright © 2012 John Wiley & Sons, Ltd.

The Front Cover represents the use of nano‐ and fluorescent anisotropic materials as drug‐delivery and imaging tools (Fluorescein/rhodamine dyes) for applications in biomedicine and cell culture to help to detect diseases in early stages. The Red and Green colors reproduced in the flag are dedicated to Portugal, the land of great explorers who helped to open new avenues for the human kind in America, Africa, Asia, and Oceania. In their Review, E. Oliveira et al. focus on fluorescent dyes containing certain fluorophores and discuss the metal complexes and nanomaterials that contain these dyes. More information can be found in the Review by E. Oliveira et al. on page 9 in Issue 1, 2018 (DOI: 10.1002/open.201700135).

The method allows the synthesis of N-substituted imidazoles from Morita—Baylis—Hillman adducts without previous activation of the secondary hydroxyl group.