The global convergence of the BFGS method with a modified WWP line search for nonconvex functions

Numerical Algorithms - The BFGS method, which has great numerical stability, is one of the quasi-Newton line search methods. However, the global convergence of the BFGS method with a Wolfe line...     

In-tip nanoreactors for cancer cells proteome profiling

Mass spectrometry (MS)-based proteome profiling is essential for molecular diagnostics in modern biomedical study. To date, sample preparation including protein extraction and proteolysis is still very challenging and lack of efficiency. Recently tips-based sample preparation protocols exhibit strong potentials to achieve the goal of “a proteome in an hour”. However, in-tip proteolysis is still rarely reported and far from ideal for dealing with complex bio-samples. In this work, nanoreactors encapsulated micropipette tips were demonstrated as high performance devices for fast (∼minutes) and multiplexing proteolysis to assist the profiling of cancer cells proteome. Nanoporous silica materials with controlled pore size and surface chemistry were prepared as nanoreactors and encapsulated in micropipette tips for efficient in situ proteolysis. The as-constructed device showed desirable sensitivity (LOD of 0.204 ± 0.008 ng/μL and LOQ of 0.937 ± 0.055 ng/μL), selectivity, stability (two months under −20 °C), reusability (at least 10 times), and little memory effect in MS based bottom-up proteomic analysis. It was used for comprehensive protein mapping from cancer cell lines. The number of identified proteins was increased by 18%, 22%, 52%, and 52% dealing with HepG2, F56, MCF7, and HCCLM3 cancer cells, compared to traditional in-solution proteolysis based bottom-up proteomic strategy. With the enhanced performance, our work built a novel, efficient and miniaturized platform for facile proteomic sample preparation, which is promising for advanced biomarkers discovery in biomedical study.     

Immobilization of Antibodies on Magnetic Carbonaceous Microspheres for Selective Enrichment of Lysine‐acetylated Proteins and Peptides

Lysine acetylation is a dynamic and reversible modification, which has been proved to be a key posttranslational modification in cellular regulation. However, the low amounts of the acetylated proteins could hardly be detected before enrichment. In this study, for the first time, antibody‐immobilized magnetic carbonaceous microspheres were developed for selective enrichment of acetylated proteins and peptides. At first, standard proteins composed of acetylated bovine serum albumin, myoglobin, α‐casein and ovalbumin were used as model proteins to verify the enrichment efficiency. Then, the synthesized peptide was employed to confirm the selectivity of the method. Besides, the antibody‐immobilized magnetic particles were successfully applied to analyze mouse mitochondrial proteins. After database search, 29 acetylated sites in 26 proteins were identi?ed.     

Preferential Formation of Mono‐Metallofullerenes Governed by the Encapsulation Energy of the Metal Elements: A Case Study on Eu@C2n (2n=74–84) Revealing a General Rule

Encapsulating one to three metal atoms or a metallic cluster inside fullerene cages affords endohedral metallofullerenes (EMFs) classified as mono‐, di‐, tri‐, and cluster‐EMFs, respectively. Although the coexistence of various EMF species in soot is common for rare‐earth metals, we herein report that europium tends to prefer the formation of mono‐EMFs. Mass spectroscopy reveals that mono‐EMFs (Eu@C_2n) prevail in the Eu‐containing soot. Theoretical calculations demonstrate that the encapsulation energy of the endohedral metal accounts for the selective formation of mono‐EMFs and rationalize similar observations for EMFs containing other metals like Ca, Sr, Ba, or Yb. Consistently, all isolated Eu‐EMFs are mono‐EMFs, including Eu@D_3h(1)‐C₇₄, Eu@C_2v(19138)‐C₇₆, Eu@C_2v(3)‐C₇₈, Eu@C_2v(3)‐C₈₀, and Eu@D_3d(19)‐C₈₄, which are identified by crystallography. Remarkably, Eu@C_2v(19138)‐C₇₆ represents the first Eu‐containing EMF with a cage that violates the isolated‐pentagon‐rule, and Eu@C_2v(3)‐C₇₈ is the first C₇₈‐based EMF stabilized by merely one metal atom.     

基质辅助激光解吸电离质谱和电喷雾电离质谱在辣根过氧化物酶糖肽结构分析中的应用

糖链结构的质谱解析是今后糖蛋白分析中的重要研究内容,其中完整糖肽的分析,由于可以同时获得糖基化位点和对应糖链的结构信息,更具有重要意义和研究前景。本工作对质谱软电离技术在完整糖肽分析中的应用进行了研究,其中包括了基质辅助激光解吸电离(matrix-assisted laser desorption ionization, MALDI)和电喷雾电离(electrospray ionization, ESI)技术。通过平行使用两种串联质谱(tandem mass spectrometry, MS/MS)分析策略: MALDI-MS/MS和ESI-MS/MS对目标糖蛋白——辣根过氧化物酶进行分析,并讨论了其互补性。结果表明,MALDI和ESI技术各有优劣,结合串联质谱分析,可获得糖肽的糖链结构信息;两条路线互补使用,在揭示蛋白质糖基化修饰(位点和结构)的研究中十分必要。     

新型离子液体基质用于MALDI-MS高效离子化寡糖/糖肽

本研究发展了四种基于三羟基苯乙酮(THAP)的新型离子液体基质, 即2',3',4'-THAP/二甲基苯胺(DMA)、2',4',6'-THAP/DMA、2',3',4'-THAP/吡啶(Py)及2',4',6'-THAP/Py, 用于提高寡糖/糖肽在MALDI-TOF MS中的离子化效率. 与传统的固体基质2,5-二羟基苯甲酸(DHB)和2',4',6'-三羟基苯乙酮(2',4',6'-THAP)相比, 新型离子液体体系分析不同类型的寡糖链, 均可获得更高的检测灵敏度. 可使葡聚糖(dextran 1000)和环状寡聚糖β-环糊精在MALDI质谱中的信噪比提高10倍以上, RNase B的复杂寡糖链也实现了高灵敏度的检测. 在糖肽分析中, 2',3',4'-THAP/DMA离子液体高灵敏度地检测到辣根过氧化酶的7条糖肽, 而2',3',4'-THAP作为基质时却无法检测到任何信号.     

Global Insight into N-Glycome and N-Glycoproteome of Three Most Abundant Snake Venoms in Asia

Snake venom is a complex cocktail including a variety of biological active proteins and proteinaceous components, which have considerable medical and pharmacological importance. N-Glycosylation is widely impli- cated as a common modification in numerous venom proteins and impacts the in vivo venomic functions. However, systematic survey of N-glycome and N-glycoproteome on snake venoms has not been undertaken. In this study, em- ploying combination of N-glycomics and N-glycoproteomics strategies, we explored the N-glycosylation including both N-glycoproteins and N-glyco-chains in three venoms from Agkistrodon blomhoffii, Naja naja atra Cantor and Vipera russelii siamensis Smith, respectively, which are amongst the most abundant venomous snakes in Asia. As a result, numbers of N-glycoproteins and N-glycans were identified. However, the overlaps of N-glycoproteins and N-glycans of the three venoms were small. Thus, the exploration results of N-glycome and N-glycoproteome indicate that N-glycosylation increases the complexity and variety of the three venoms. Our research provided some new horizons for the comprehensive understanding of venoms variation, which is helpful for the basic venom re- search as well as the management of snake envenomation.     

On-line electrolytic dissolution of solid metal samples and determination of copper in aluminium alloys by flame atomic absorption spectrometry

A flow-injection system was developed in which alloy metal samples are electrolytically dissolved and the dissolved samples are analysed by flame atomic absorption spectrometry (FAAS). The effects of electrolyte composition and electrolysis parameters on the dissolution of the sample were studied. The method was used for the determination of copper in aluminium alloys. Electrolyte solutions consisting of 0.2–1.0 M nitric acid are better than other electrolytes tested with regard to both alloy sample dissolution and determination of copper by FAAS. The peak height increases linearly with the electrolysis time or current within a certain range. The detection limit depends on the sensitivity of the detector used, and can be improved by increasing the electrolysis time or current. Generally, aluminium alloys containing 0.5–10% copper can give suitable signals for FAAS determination. The reproducibility of electrolysis and determination is about 4% for the same sampling points and 5% for different sampling points on the alloy sample.     

Facile synthesis of 4‐mercaptophenylboronic acid functionalized gold nanoparticles for selective enrichment of glycopeptides

In the work, 4‐mercaptophenylboronic acid (4‐MPBA)‐functionalized gold nanoparticles were synthesized via a facile approach. At first, gold nanoparticles (about 50 nm) were prepared by a simple and convenient hydrothermal method based on a polyol process. Then, gold nanoparticles were modified with 4‐MPBA by the well‐known reaction of Au with the thiol groups. The MPBA‐functionalized gold nanoparticles were characterized by Fourier transform infrared spectra and UV/Vis adsorption spectra. Due to the fact that the boronic acid group on the surface of 4‐MPBA‐modified gold particles can form tight yet reversible covalent bonds with glycopeptides containing cis‐1,2‐diols groups, the MPBA‐modified gold nanoparticles were successfully applied to selective enrichment of glycopeptides. Isolation and enrichment of glycopeptides in a standard protein (asialofetuin and horseradish peroxidase) digestion and a complex sample were performed using MPBA‐modified gold nanoparticles, followed by matrix‐assisted laser desorption/ionization quadruple ion trap time‐of‐flight (MALDI‐QIT‐TOF) mass spectrometric analysis. The experimental results demonstrated that MPBA‐modified gold nanoparticles synthesized by the facile approach have the powerful potential for selective enrichment of glyciopeptides, and can be an alternative tool in glycoproteomics. Copyright © 2009 John Wiley & Sons, Ltd.