Bright two-photon fluorescent probes are highly desirable to be able to optically probe biological activities deep inside living organisms with larger imaging depth, minor autofluorescence background, and less photodamage. In this study, we report the biocompatible nitrogen-doped graphene quantum dots (N-GQDs) as efficient two-photon fluorescent probes for cellular and deep-tissue imaging. The N-GQD was prepared by a facile solvothermal method using dimethylformamide as a solvent and nitrogen source. The two-photon absorption cross-section of N-GQD reaches 48,000 Göppert-Mayer units, which far surpasses that of the organic dyes and is comparable to that of the high performance semiconductor QDs, achieving the highest value ever reported for carbon-based nanomaterials. More importantly, a study of penetration depth in tissue phantom demonstrates that the N-GQD can achieve a large imaging depth of 1800 μm, significantly extending the fundamental two-photon imaging depth limit. In addition, the N-GQD is nontoxic to living cells and exhibits super photostability under repeated laser irradiation. The high two-photon absorption cross-section, large imaging depth, good biocompatibility, and extraordinary photostability render the N-GQD an attractive alternative probe for efficient two-photon imaging in biological and biomedical applications.

Nonsteroidal anti‐inflammatory drugs interfere with the metabolism of arachidonic acid to proinflammatory prostaglandins and leukotrienes by targeting cyclooxygenases (COXs), 5‐lipoxygenase (LOX), or the 5‐LOX–activating protein (FLAP). These and related enzymes act in conjunction with marked crosstalk within a complex lipid mediator (LM) network where also specialized proresolving LMs (SPMs) are formed. Here, we present how prominent LM pathways can be differentially modulated in human proinflammatory M1 and proresolving M2 macrophage phenotypes that, upon exposure to Escherichia coli, produce either abundant prostaglandins and leukotrienes (M1) or SPMs (M2). Targeted liquid chromatography–tandem mass spectrometry–based metabololipidomics was applied to analyze and quantify the specific LM profiles. Besides expected on‐target actions, we found that: 1) COX or 15‐LOX‐1 inhibitors elevate inflammatory leukotriene levels, 2) FLAP and 5‐LOX inhibitors reduce leukotrienes in M1 but less so in M2 macrophages, 3) zileuton blocks resolution‐initiating SPM biosynthesis, whereas FLAP inhibition increases SPM levels, and 4) that the 15‐LOX‐1 inhibitor 3887 suppresses SPM formation in M2 macrophages. Conclusively, interference with discrete LM biosynthetic enzymes in different macrophage phenotypes considerably affects the LM metabolomes with potential consequences for inflammation‐resolution pharmacotherapy. Our data may allow better appraisal of the therapeutic potential of these drugs to intervene with inflammatory disorders.—Werner, M., Jordan, P. M., Romp, E., Czapka, A., Rao, Z., Kretzer, C., Koeberle, A., Garscha, U., Pace, S., Claesson, H.‐E., Serhan, C. N., Werz, O., Gerstmeier, J. Targeting biosynthetic networks of the proinflammatory and proresolving lipid metabolome. FASEB J. 33, 6140–6153 (2019). http://www.fasebj.org

Highlights d S. aureus causes SPM formation in human M2 macrophages by a-hemolysin d a-hemolysin elicits SPM biosynthesis by activation of 15lipoxygenase-1 in M2 d Inhibition of ADAM10 or 15-lipoxygenase-1 knockdown reverts a-hemolysin actions d a-hemolysin elevates SPM levels in mouse peritoneum devoid of leukocyte influx

A B S T R A C TNatural organic matter (NOM) is a complex and non-uniform mixture of organic compounds which plays an important role in environmental processes. Due to the complexity, it is challenging to obtain fully detailed structural information about NOM. Although Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) has been demonstrated to be a powerful tool for providing molecular information about NOM, multiple ionization methods are needed for comprehensive characterization of NOM at the molecular level considering the ionizing selectivity of different ionization methods. This paper reports the first use of matrix assisted laser desorption/ionization (MALDI) method coupled with FT-ICR-MS for molecular characterization of NOM within a mass range of 200-800 Da. The mass spectral data obtained by MALDI were systematically compared with data generated by electrospray ionization (ESI). It showed that complementary molecular information about NOM which could not be detected by ESI, were provided by MALDI. More unsaturated and aromatic constituents of NOM with lower O/C ratio (O/C ratio < 0.5) were preferentially ionized in MALDI negative mode, whereas more polar constituents of NOM with higher O/C ratio were preferentially ionized in ESI negative mode. Molecular anions of NOM appearing at even m/z in MALDI negative ion mode were detected. The results show that NOM molecules with aromatic structures, moderate O/C ratio (0.7 > O/C ratio > 0.25) and lower H/C ratio were liable to form molecular anions at even m/z, whereas those with higher H/C ratio are more likely to form deprotonated ions at odd m/z. It is speculated that almost half of the NOM molecules identified by MALDI may be aromatic or condensed aromatic compounds with