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Rationale: As a powerful ambient ion source, atmospheric pressure (AP) matrix‐assisted laser desorption/ionization (MALDI) enables direct analysis at atmospheric pressure/temperature and minimal sample preparation. With the increasing usage of AP‐MALDI sources with Orbitrap instruments, systematic characterization of the extent of ion suppression effect (ISE) in AP‐MALDI‐Orbitrap mass spectrometry imaging (MSI) is desirable. Recently, a new low‐pressure MALDI platform has been introduced that reportedly provided better sensitivity. While extensive research efforts have been devoted to improving spatial resolution, fewer studies focused on the characterization and sensitivity improvement of these MALDI platforms that, coupled with high‐resolution Orbitraps, provide powerful strategy for MSI. Methods: We compared the analytical performance of AP and low‐pressure (subatmospheric) MALDI sources to study the effect of pressure control in the ion source. Using a model peptide/protein mixture, we systematically evaluated the factors influencing ISE. Furthermore, the effect of laser spot size was evaluated through tissue imaging analysis of lipids and neuropeptides. The effects of ion suppression and laser spot size have also been examined by comparing the number of identified molecular species during MSI analysis. Results: Several key operating parameters including source pressure, laser energy, laser repetition rate, and microscopic slide coating materials were optimized to minimize the ISE. Under the optimal conditions, the subatmospheric AP‐MALDI‐Orbitrap platform with high spatial and mass spectral resolution enabled significantly improved coverage of several lipid and neuropeptide families in the MS analysis of mouse brain tissue sections. Conclusions: The new SubAP‐MALDI source coupled with an Orbitrap mass spectrometer was established as a viable platform for in situ endogenous biomolecular analysis with increased sensitivity compared with conventional AP‐MALDI sources as evidenced by the confident identification of neuropeptides from mouse brain imaging analyses. The alleviated ISE was key to substantial performance improvement due to optimized intermediate pressure conditions and better ion collection by the ion funnel. [ABSTRACT FROM AUTHOR]

The advent of foundation models, which are pre-trained on vast datasets, has ushered in a new era of computer vision, characterized by their robustness and remarkable zero-shot generalization capabilities. Mirroring the transformative impact of foundation models like large language models in natural language processing, visual foundation models (VFMs) have become a catalyst for groundbreaking developments in computer vision. This review paper delineates the pivotal trajectories of VFMs, emphasizing their scalability and proficiency in generative tasks such as text-to-image synthesis, as well as their adeptness in discriminative tasks including image segmentation. While generative and discriminative models have historically charted distinct paths, we undertake a comprehensive examination of the recent strides made by VFMs in both domains, elucidating their origins, seminal breakthroughs, and pivotal methodologies. Additionally, we collate and discuss the extensive resources that facilitate the development of VFMs and address the challenges that pave the way for future research endeavors. A crucial direction for forthcoming innovation is the amalgamation of generative and discriminative paradigms. The nascent application of generative models within discriminative contexts signifies the early stages of this confluence. This survey aspires to be a contemporary compendium for scholars and practitioners alike, charting the course of VFMs and illuminating their multifaceted landscape. [ABSTRACT FROM AUTHOR]

Abstract: We report herein the facile surface-functionalization of one type of biocompatible, oligomeric nanoparticles 1-NPs with NIR-emitting CdTe/CdS QDs and folate for tumor-targeted imaging in vivo. The –NH2 and –SH groups of cysteine residues on the 1-NPs were utilized to covalently conjugate CdTe/CdS QDs and Mal-FA to prepare the hybrid nanoparticles 1-NPs-QDs-FA. As-prepared 1-NPs-QDs-FA showed NIR-fluorescence emission at 734 nm, selective uptake by FR-overexpressing tumor cells in vitro, and selective FR-overexpressing tumor-targeted imaging in vivo. This first example of oligomeric/inorganic hybrid nanoparticles provides people with new type of biomaterials for tumor-targeted imaging with high selectivity. [Copyright &y& Elsevier]

Abstract: A water-soluble, biocompatible, and fluorescent chemosensor (1) for label-free, simple, and fast detection of mercury ions (Hg2+) in aqueous solutions and in HepG2 cells with high selectivity is reported herein. Chelation of 1 with Hg2+ results in the disappearance of its fluorescence emission at 350nm and the appearance of a new emission at 405nm. Selectivity and interference studies indicated that 1 could be selectively chelated by Hg2+ without interference from other metal ions. Insight into the mechanisms responsible for its fluorescence effect was gained from ultrafast transient absorption spectroscopy. With these properties, 1 was successfully applied for imaging Hg2+ in living cells and for removing Hg2+ from river water. Moreover, we also constructed a simple device for fast and effective removal of Hg2+ from contaminated liquid samples. [Copyright &y& Elsevier]

Previously, we have reported the stabilization effect of Hofmeister salts for multiprotein complexes (MPC) in the absence of bulk solvent (J. Am. Chem. Soc. 2011, 133 (29), 11,358–11367; Angew. Chem. Int. Ed. 2012, 51 (23), 5692–5695; Angew. Chem. Int. Ed. 2013 , 52 (32), 8329–8332.). Our efforts sought to bridge the gap between gas-phase protein structures and those found in solution. To reveal more detailed MPC topology information, native ion mobility-mass spectrometry (IM-MS) measurements are often combined with gas-phase activation methods. Conventional activation methods, including collision induced dissociation/unfolding (CID/CIU), however, primarily report information focused on monomeric subunits within the MPC, limiting the topological information obtained. Herein, we describe a simple buffer-doping method that promotes an alternative MPC CID pathway which readily produces product ions that correspond to larger sub-complexes from within some parent assemblies. Interestingly, tetramers exhibiting a dimer of dimers quaternary structure (e.g. hemoglobin and concanavalin A) produce dimeric product ions upon collisional activation following ionization from bicarbonate buffer, in contrast to the commonly observed monomer-ejection CID pathway. In order to both further investigate and validate our native IM-MS, we performed bottom-up proteomics experiments on MPCs housed in bicarbonate buffer. Our efforts revealed evidence of bicarbonate-mediated disulfide bond formation in proximal Cystine residues. We close by discussing the applications for these observations in the context of MPC structure determination by native IM-MS. [Display omitted] • Adding ammonium bicarbonate to samples prior to native MS promotes the formation of large sub-complexes during CID. • Bicarbonate buffers can catalyze the formation of disuflide bonds and other chemical cross-links within protein complexes. • Bicarbonate buffer additives could enable future protein-protein contact mapping efforts. [ABSTRACT FROM AUTHOR]