Imaging of cholesterol and other metabolites simultaneously by ambient mass spectrometry will greatly benefit biological studies, however, it still remains challenging. Herein, by adding acid into the desorption electrospray ionization (DESI) spray solvent, we achieved simultaneous mass spectrometry imaging of cholesterol and other metabolites directly from mouse brain sections. The introduction of acid increased the signal intensity of cholesterol in mouse brain tissues by approximately 21-fold. Additionally, the present strategy provided increased signal intensities for other metabolites up to 62-fold, as well as identification of seven more metabolites (23 vs 16 for acid-enhanced DESI vs DESI). Moreover, increased corelationships for alanine as well as putrescine and spermidine with cholesterol were discovered under acid-enhanced DESI. The potential of the present strategy in the fields of biological and medical research was demonstrated by investigating the level change for cholesterol, alanine, putrescine, and spermidine in Alzheimer's disease (AD) mouse brain.

No abstract

A charge tag is introduced in living cells via a biocompatible click reaction, which greatly increases the sensitivity for single cell mass spectrometry.

Ruthenium-arene complexesa re au nique class of organometallic compounds that have been shown to have prominent therapeutic potencies.H ere, we have investigated the interactions of Ru-cymene complexes with az incfinger protein NCp7, aiming to understand the effects of various ligandso nt he reaction. Five different binding modes were observed on selected Ru-complexes. Ru-cymene complex can bind to proteins through either noncovalent binding aloneo rt hrough ac ombinationo fc ovalent and nonco-valentb inding modes. Moreover,t he noncovalent interaction can promote the coordination of Ru II to NCp7, resulting synergistic effects of the different ligands. The binding of Ru(Cym) complexes leads to dysfunction of NCp7 through zinc-ejection and structural perturbation. These results indicate that the reactivityo fR u-complexes can be modulated by ligands through differenta pproaches, which could be closely correlated to their different therapeutic effects.

Native electrospray ionization was known to preserve the protein structure in solution, which overcame the uncontrollable acidification of droplets during transfer from solution into the gas phase in conventional electrospray ionization. However, detailed experimental studies on when and how could native electrospray ionization minimize structural perturbations remain quite unclear. Herein, we conducted molecular dynamics simulations to investigate the protein structure evolution during electrospray ionization. At a neutral droplet pH, the protein structure in solution could be retained after evaporation, which was in accordance with previous reports. As the droplet pH deviated from neutral, we have found that the compact protein structure would not unfold until the last 10 ns prior to the final desolvation, which demonstrated that the role of native electrospray ionization in preserving the protein structure was mainly reflected on the final evaporation stages. The present study might provide new insights into studying the microscopic biomolecular events occurring during the liquid–gas interface transition and their influence on solution–structure retention.

Nucleocapsid protein 7 (NCp7) is an attractive target for anti‐HIV drug development. Here we found that ruthenium complexes are reactive to NCp7 and various Ru‐agents exhibit significantly different reactivity. Interestingly, the zinc‐finger domains of NCp7 also demonstrate different affinity to Ru‐complexes; the C‐terminal domain is much more reactive than the N‐terminal domain. Each zinc‐finger domain of NCp7 binds up to three Ru‐motifs, and the ruthenium binding causes zinc‐ejection from NCp7 and disrupts the protein folding. Therefore, ruthenium complexes interfere with the DNA binding of NCp7 and interrupt the protein function. The different reactivity of Ru‐agents suggests a feasible strategy for improving the targeting of NCp7 by ligand design. This work provides an insight into the mechanism of ruthenium complex with NCp7, and suggests more potential application of ruthenium drugs.

The unique thermodynamic and kinetic coordination chemistry of ruthenium allows it to modulate key adverse aggregation and membrane interactions of α‐synuclein (α‐syn) associated with Parkinson's disease. We show that the low‐toxic RuIII complex trans‐[ImH][RuCl4(Me2SO)(Im)] (NAMI‐A) has dual inhibitory effects on both aggregation and membrane interactions of α‐syn with submicromolar affinity, and disassembles pre‐formed fibrils. NAMI‐A abolishes the cytotoxicity of α‐syn towards neuronal cells and mitigates neurodegeneration and motor impairments in a rat model of Parkinson's. Multinuclear NMR and MS analyses show that NAMI‐A binds to residues involved in protein aggregation and membrane binding. NMR studies reveal the key steps in pro‐drug activation and the effect of activated NAMI‐A species on protein folding. Our findings provide a new basis for designing ruthenium complexes which could mitigate α‐syn‐induced Parkinson's pathology differently from organic agents.

The registration of the mass spectrometry imaging (MSI) data with mouse brain tissue slices from the atlases could perform automatic anatomical interpretation, and the comparison of MSI data in particular brain regions from different mice could be accelerated. However, the current registration of MSI data with mouse brain tissue slices is mainly focused on the coronal. Although the sagittal plane is able to provide more information about brain regions on a single histological slice than the coronal, it is difficult to directly register the complete sagittal brain slices of a mouse as a result of the more significant individualized differences and more positional shifts of brain regions. Herein, by adding the auxiliary line on the two brain regions of central canal (CC) and cerebral peduncle (CP), the registration accuracy of the MSI data with sagittal brain slices has been improved (∼2–5-folds for different brain regions). Moreover, the histological sections with different degrees deformation and different dyeing effects have been used to verify that this pipeline has a certain universality. Our method facilitates the rapid comparison of sagittal plane MSI data from different animals and accelerates the application in the discovery of disease markers.