nnan Li

Direct Analysis in Real Time Mass Spectrometry: a Powerful Tool for Fast Analysis

Direct analysis in real time mass spectrometry (DART-MS) is one of the variants of ambient mass spectrometry. The ionization process of DART-MS is in open environment and only takes few seconds, so it is suitable for fast analysis. Actually, since its introduction in 2005, more and more attentions have been drawn to its various applications due to its excellent proper- ties, e.g., fast analysis, and no or less sample preparation, high salt tolerance and so on. This review summarized the promising features of DART-MS, including its ionization mechanism, equipment modification, wide applications, coupling techniques and extraction strategies before analysis.

Study on the interaction of uranyl with sulfated beta-cyclodextrin by affinity capillary electrophoresis and molecular dynamics simulation.

The study on sulfated beta‐cyclodextrin binding to uranyl ion helps to get a better understanding of uranyl compounds’ intermolecular interaction mechanism and facilitates the structure‐based design of uranyl binding molecules. Here we investigated the electromigration of the inclusion complex by using affinity capillary electrophoresis in acidic solution. The binding constant was determined to be logK = 2.96 ± 0.02 (R2 = 0.996) through nonlinear regression approach. The possible configurations and structural features of the inclusion complex were further studied by molecular dynamics simulation. The results suggest the distinctions of coordination environment and hydration compared with bare uranyl ion in aqueous solution. Thus, two water oxygen atoms coordinated with uranyl in the first hydration shell at 2.55 angstrom instead of five in the same distance range. The binding free energy was calculated as –12.10 ± 1.46 kcal/mol by means of thermodynamic perturbation method. The negative value indicates that the process of S‐β‐CD capture uranyl ion in the aqueous media is spontaneous.

Lipidomic analysis of plasma in patients with lacunar infarction using normal-phase/reversed-phase two-dimensional liquid chromatography-quadrupole time-of-flight mass spectrometry

AbstractStroke is a major cause of mortality and long-term disability worldwide. The study of biomarkers and pathogenesis is vital for early diagnosis and treatment of stroke. In the present study, a continuous-flow normal-phase/reversed-phase two-dimensional liquid chromatography–quadrupole time-of-flight mass spectrometry (NP/RP 2D LC-QToF/MS) method was employed to measure lipid species in human plasma, including healthy controls and lacunar infarction (LI) patients. As a result, 13 lipid species were demonstrated with significant difference between the two groups, and a “plasma biomarker model” including glucosylceramide (38:2), phosphatidylethanolamine (35:2), free fatty acid (16:1), and triacylglycerol (56:5) was finally established. This model was evaluated as an effective tool in that area under the receiver operating characteristic curve reached 1.000 in the discovery set and 0.947 in the validation set for diagnosing LI patients from healthy controls. Besides, the sensitivity and specificity of disease diagnosis in validation set were 93.3% and 96.6% at the best cutoff value, respectively. This study demonstrates the promising potential of NP/RP 2D LC-QToF/MS-based lipidomics approach in finding bio-markers for disease diagnosis and providing special insights into the metabolism of stroke induced by small vessel disease. Graphical abstractFlow-chart of the plasma biomarker model establishment through biomarker screening and validation

A plasma lipidomics strategy reveals perturbed lipid metabolic pathways and potential lipid biomarkers of human colorectal cancer

To explore underlying molecular mechanisms and identify novel lipid biomarkers promising for colorectal cancer (CRC) diagnosis, a continuous-flow two dimensional liquid chromatography-quadrupole time-of-flight mass spectrometry (2D LC-QToF/MS) method was employed to comprehensively measure lipid species in human plasma of CRC patients and healthy controls. With a total of 427 annotated lipid species, we identified 64 lipid species with corrected p value less than 0.05 and fold change more than 1.5. These significantly altered lipid species were mainly involved in glycerolipids and glycerophospholipids metabolism and sphingolipids metabolism. After the diagnosis ability evaluation based on the receiver operating characteristic (ROC) curve, phosphatidylglycerol (34:0), sphingomyelin (42:2), ceramide (44:5), lysophosphatidylcholine (18:3), lysophosphatidylcholine (18:2), phosphatidylethanolamine (O-36:3), phosphatidylethanolamine (O-38:3) and sphingomyelin (38:8) were finally proposed as the potential biomarkers with the area under the curve (AUC) more than 0.900. These results suggest that this 2D LC-QToF/MS-based lipidomics profiling has great potential as a noninvasive diagnostic method in detecting CRC and hopefully provide new clues to understand its underlying mechanism.

Metabolomic Analysis of Mouse Embryonic Fibroblast Cells in Response to Autophagy Induced by Acute Starvation

Autophagy-related protein 7 (Atg7) is essential in the formation of the autophagophore and is indispensable for autophagy induction. Autophagy will exist in lower level or even be blocked in cells without Atg7. Even though the possible signaling pathways of Atg7 have been proposed, the metabolomic responses under acute starvation in cells with and without Atg7 have not been elucidated. This study therefore was designed and aimed to reveal the metabolomics of Atg7-dependent autophagy through metabolomic analysis of Atg7−/− mouse embryonic fibroblast cells (MEFs) and wild-type MEFs along with the starvation time. 30 significantly altered metabolites were identified in response to nutrient stress, which were mainly associated with amino acid, energy, carbohydrate, and lipid metabolism. For the wild-type MEFs, the induction of autophagy protected cell survival with some up-regulated lipids during the first two hours’ starvation, while the subsequent apoptosis resulted in the decrease of cell viability after four hours’ starvation. For the Atg7−/− MEFs, apoptosis perhaps led to the deactivation of tricarboxylic acid (TCA) cycle due to the lack of autophagy, which resulted in the immediate drop of cellular viability under starvation. These results contributed to the metabolomic study and provided new insights into the mechanism associated with Atg7-dependent autophagy.

Binding constant determination of uranyl-citrate complex by ACE using a multi-injection method.

The binding constant determination of uranyl with small‐molecule ligands such as citric acid could provide fundamental knowledge for a better understanding of the study of uranyl complexation, which is of considerable importance for multiple purposes. In this work, the binding constant of uranyl–citrate complex was determined by ACE. Besides the common single‐injection method, a multi‐injection method to measure the electrophoretic mobility was also applied. The BGEs used contained HClO4 and NaClO4, with a pH of 1.98 ± 0.02 and ionic strength of 0.050 mol/L, then citric acid was added to reach different concentrations. The electrophoretic mobilities of the uranyl–citrate complex measured by both of the two methods were consistent, and then the binding constant was calculated by nonlinear fitting assuming that the reaction had a 1:1 stoichiometry and the complex was [(UO2)(Cit)]−. The binding constant obtained by the multi‐injection method was log K = 9.68 ± 0.07, and that obtained by the single‐injection method was log K = 9.73 ± 0.02. The results provided additional knowledge of the uranyl–citrate system, and they demonstrated that compared with other methods, ACE using the multi‐injection method could be an efficient, fast, and simple way to determine electrophoretic mobilities and to calculate binding constants.

Lipid metabolism in mouse embryonic fibroblast cells in response to autophagy induced by nutrient stress

Autophagy is of great significance in maintaining cellular homeostasis. Aberrant autophagy has been reported to contribute to the disease aetiology of metabolic syndrome, especially several key lysosomal storage disorders. However, the molecular mechanisms and the correlation between autophagy and lipid metabolism remains unclear. This study was designed and aimed to reveal the alteration of lipid metabolism in response to the autophagy induced by nutrient stress to give new insights into the molecular mechanisms between autophagy and lipid metabolism. An online normal-phase/reversed-phase two-dimensional liquid chromatography-mass spectrometry (NP/RP 2D LC-MS) method was developed to perform the lipidomics analysis of Atg7-/- mouse embryonic fibroblast cells (MEFs) and wild-type MEFs under nutrient stress. 48 and 35 lipid species in wild-type and Atg7-/- MEFs respectively finally meet the screening criteria with p-value less than 0.05 and fold change more than 1.5 in response to nutrient stress. Their alterations indicated that autophagy participated lipid metabolism to generate energy and form autophagosomes with significantly increased free fatty acids and glycerophospholipids, which protected wild-type MEFs from serious damages and delayed cell death. However, in Atg7-/- MEFs, due to the inhibition of autophagy, lipids were continuously consumed and cells suffered from damages even death. These results illustrated the close relationship between autophagy and lipid metabolism comprehensively and revealed diverse lipid targets for the investigation of autophagy.

Metal–organic frameworks induce autophagy in mouse embryonic fibroblast cells

Autophagy is the lysosomal-dependent degradation process of intracellular substances in adaptation to environmental or developmental changes. It plays an essential role in maintaining cellular homeostasis while its dysfunction is involved in various human diseases. The regulation of autophagy has attracted more and more attention with the promise for improving treatment of diseases as a potential therapeutic target. Metal-organic frameworks (MOFs), as emerging biomaterials, have been investigated in the biological and biomedical fields in recent years. Therefore, it is interesting and significant to study the effects of MOFs on living cells from safety aspects as well as the therapeutic viewpoint, especially their effects on autophagy which have not been reported yet. In this study, the effects of Fe-MIL-101_NH2 on mouse embryonic fibroblasts (MEFs) were investigated and the potential applications of these nanoparticles in the regulation of autophagy were explored. Our results demonstrated that Fe-MIL-101_NH2 induced cytoprotective autophagy in MEFs instead of cytotoxicity. The activation of autophagy kept reactive oxygen species from accumulating, which protected MEFs from apoptosis. Further exploration of the possible mechanisms of MOF-induced autophagy revealed that the inhibition of mTOR pathway as well as the enhancement of Becline1 and Atg5 contributed to autophagy induction. Our study uncovered the autophagic effects and mechanistic insights of MOFs, which will be beneficial and meaningful to the safety evaluation and the reasonable and effective usage of MOFs.