Linear ion trap mass analyzer could improve analytical performance compared to the traditional three-dimensional ion trap. In this study, a systematic investigation of the effect of octopole field on ...the performance of linear quadrupole ion trap was studied by both theoretical simulations and experiments. An asymmetric semi-circular linear ion trap (AsC-LIT) analyzer was designed and tested based on the theoretical results. The AsC-LIT consists of one pair of larger semi-circular rods with radius
R
y
and one pair of smaller semi-circular rods with radius
R
x
(
R
y
>
R
x
) in the cross section for introducing the quantitative octopole field. The analytical performances of these simplified AsC-LITs with different amounts of octopole fields were carefully investigated using both theoretical simulations and experimental validation. Experimental results showed that it could have a mass resolution of 1645 at
m
/
z
175 (arginine); furthermore, the low mass cutoff and CID efficiency can be significantly improved when some positive octopole is added. The simulative results indicated that 2.56% octopole component was the best choice for achieving higher analytical performances. The theoretical and experimental studies of this work could certainly enrich the knowledge of a higher order electric field effect on the linear ion trap, furthermore, the simple geometric design and performance characteristics of this new AsC-LIT make it particularly attractive in the development of miniaturized mass spectrometers.
A linear ion trap mass analyzer could improve analytical performance compared to the traditional three-dimensional ion trap, giving rise to higher analytical performance.
A guanidine-functionalized (GF) covalent organic framework (COF) nanocomposite has been developed by a post-synthetic approach for specific capture and separation of phosphopeptides and exosomes. The ...abundant binding sites on COF can immobilize a large number of gold nanoparticles (AuNPs), which can be used to react with amino groups to graft polyethyleneimine (PEI). Finally, Fe
3
O
4
@COF@Au@PEI-GF is obtained through the reaction of PEI and guanidyl group for phosphopeptides and exosomes detection. This composite shows a low detection limit (0.02 fmol), size exclusion effect (β-casein digests:Albumin from bovine serum protein = 1:10,000), good reusability (10 cycles), and high selectivity (β-casein digests:Albumin from bovine serum digests = 1:10,000). For complex biological sample, 4 phosphopeptides can be successfully identified from human serum. Furthermore, for the first time, we used guanidyl-functionalized probe to capture exosomes in human serum, providing a new method for enriching exosomes. The above experiments showed that Fe
3
O
4
@COF@Au@PEI-GF not only effectively enrich phosphopeptides and remove macromolecular proteins, but also successfully separate and capture exosomes. This demonstrates the great potential of this composite for the specific enrichment of phosphopeptides and isolation of exosomes.
Graphical abstract
A strategy for effectively enriching global phosphopeptides was successfully developed by using ammonia methyl phosphate (APA) as a novel chelating ligand and Ti
4+
and Nb
5+
as double functional ...ions (referred to as Fe
3
O
4
@mSiO
2
@APA@Ti
4+
/Nb
5+
). With the advantage of large specific surface area (151.1 m
2
/g), preeminent immobilized ability for metal ions (about 8% of total atoms), and unbiased enrichment towards phosphopeptides, Fe
3
O
4
@mSiO
2
@APA@Ti
4+
/Nb
5+
displays high selectivity (maximum mass ratio β-casein to BSA is 1:1500), low limit of detection (LOD, as low as 0.05 fmol), good relative standard deviation (RSD, lower than 7%), recovery rate of 87% (
18
O isotope labeling method), outstanding phosphopeptide loading capacity (330 μg/mg), and at least five times re-use abilities. In the examination of the actual sample, 24 phosphopeptides were successfully detected in saliva and 4 phosphopeptides were also selectively extracted from human serum. All experiments have shown that Fe
3
O
4
@mSiO
2
@APA@Ti
4+
/Nb
5+
exhibits exciting potential in view of the challenge of low abundance of phosphopeptides.
Graphical abstract
A Ti
4+
-functionalized magnetic covalent organic framework material with flexible branched polymers (mCOF@ -PL@THBA-Ti
4+
) built
via
an immobilized metal ion affinity chromatography (IMAC) ...enrichment strategy was proposed through post-synthesis modification. Hydrophilic -poly-
l
-lysine ( -PL) rich in amino active groups was first introduced in the fabrication of the phosphopeptide enrichment material to increase the hydrophilicity while providing more functional modification pathways of the material. 2,3,4-Trihydroxy-benzaldehyde (THBA) provides abundant binding sites for the immobilization of numerous Ti
4+
, which is advantageous for the subsequent efficient phosphopeptide enrichment. The magnetic nanocomposite exhibited outstanding performance of phosphopeptide enrichment with good selectivity (1 : 5000), a low detection limit (2 fmol), and relatively high loading capacity (66.7 mg g
−1
). What's more, after treatment with mCOF@ -PL@THBA-Ti
4+
, 16 endogenous phosphopeptides from fresh saliva of healthy people were recognized by MALDI-TOF MS, and 50 phosphopeptides belonging to 35 phosphoproteins from the serum of uremia patients were detected by nano-LC-MS/MS. Proteomics data analysis for the differential protein selection between uremia and normal controls was conducted using R software, and four down-regulated and three up-regulated proteins were obtained. The results suggested that the prepared material has potential applications in biomarker discovery.
A Ti
4+
-functionalized magnetic covalent organic framework material with flexible branched polymers (mCOF@ -PL@THBA-Ti
4+
) was proposed through post-synthesis modification.
Rationale
The conformation of a protein largely depends on the interactions between peptides. Specific and intrinsic sequence peptide patterns, such as DNA double helix backbones, may be present in ...proteins. A computational statistical deep learning method has supported this assumption, but it has not been experimentally proven. Mass spectrometry, as a fast and accurate experimental method, could be used to evaluate the interaction of biomolecules. The results would be of great value for further study of the mechanism of protein folding.
Methods
Several potential intrinsic peptides were chosen by the deep learning method, including seven groups of pentapeptides and five groups of nonapeptides. The noncovalent interactions between mixed polypeptides were investigated by electrospray ionization mass spectrometry (ESI‐MS) in full‐scan and collision‐induced dissociation (CID) modes. Molecular dynamics and molecular mechanics Poisson–Boltzmann surface area (MD‐MM/PBSA) analyses were also performed to support the results.
Results
The ESI‐MS spectra showed that 11 of the 12 groups of mixed polypeptides formed binary and ternary complexes with relatively high stability. The binding between nonapeptide groups was stronger than that between pentapeptide groups according to the relative intensity. The binding energies calculated by the MM/PBSA binding energy tool also provided strong evidence for the combination of the complexes. Electrostatic interactions, hydrophobic interactions, and van der Waals forces were thought to stabilize the complexes according to the binding models.
Conclusions
The results implied the formation of stable complexes between polypeptides and identified their noncovalent interactions, proving that specific sequences and combinations with relatively strong binding ability exist in potential intrinsic sequences of peptides in protein structures.
During the constant-voltage welding machine employed welding process, a common phenomenon of arc attachment point moving from the bottom of the narrow gap to the sidewalls occurs, and metal transfer ...behavior appears greatly different. A mechanism that the arc inherent-self regulation combines the minimum arc voltage principle was proposed to elaborate the arc climbing up process along the sidewalls. The arc shape was approximately classified into three patterns by the change of arc conductive path, and the amount of the arc conductive path and its distributive symmetry determine the action of the electromagnetic force on the droplet as well as the metal transfer mode. As the number of the arc conductive paths increases, and the conductive paths distribute symmetrically, the necking process of the droplet detachment occurs more easily, and the metal transfer from globular mode to spray mode becomes more smoothly. Simulation results match the experiments and verify the mechanism proposed. In a constant-current welding power source adopted condition, the arc climbing up phenomenon cannot be observed, and a stable welding process is obtained.
ZF2001 contains a tandem-repeat dimeric receptor-binding domain of the SARS-CoV-2 spike protein with aluminum hydroxide adjuvant. In a phase 3 trial, 28,904 participants in five countries were ...randomly assigned to receive three doses of ZF2001 or placebo. After 6 months of follow-up, efficacy was 76% against infection, 87% against critical or severe disease, and 86% against death. Most side effects were local, low-grade, and transient.
In this work, the parametric quadrupole resonance caused by the phase modulation of waveform potential is studied. Based on analytical and numerical description of the ion motion in the quadrupole ...mass filter with the phase modulation, a stability island is found with good ion optical properties such as high ion transmission efficiency (16%), high mass resolution (peak width measured at 10% of peak height, R0.1 = 6000), the required separation time (100–150 radio frequency RF cycles), and good peak shape of trapezoid form. Furthermore, the analysis of the frequency spectrum of the applied potential and the quadrupole mass filter (QMF) acceptance are also presented; a resonance frequency is found from this spectrum. Finally, a suitable stability X‐islands with relative modulation frequency,
ν=2±β,β=1P,10≤P≤40, is established and studied in detail. Here, β is the imaginary part of the characteristic exponent of stable solutions to the Mathieu equation.
Abstract
Tracking and associating different views of the same target across moving cameras is challenging as its appearance, pose and scale may vary greatly. Moreover, with multiple targets a ...management module is needed for new targets entering and old targets exiting the field of view of each camera. To address these challenges, we propose DMMA, a Distributed Multi-camera Multi-target Association for real-time tracking that employs a target management module coupled with a local data-structure containing the information on the targets. The target management module shares appearance and label information for each known target for inter-camera association. DMMA is designed as a distributed target association that allows a camera to join at any time, does not require cross-camera calibration, and can deal with target appearance and disappearance. The various parts of DMMA are validated using benchmark datasets and evaluation criteria. Moreover, we introduce a new mobile-camera dataset comprising six different scenes with moving cameras and objects, where DMMA achieves 92% MCTA on average. Experimental results show that the proposed tracker achieves a good association accuracy and speed trade-off by working at 32 frames per second (fps) with high definition (HD) videos.
We previously demonstrated that mitochondrial bioenergetic deficits in the female brain accompanied reproductive senescence and was accompanied by a shift from an aerobic glycolytic to a ketogenic ...phenotype. Herein, we investigated the relationship between systems of fuel supply, transport and mitochondrial metabolic enzyme expression/activity during aging (3-15 months) in the hippocampus of nontransgenic (nonTg) background and 3xTgAD female mice. Results indicate that during female brain aging, both nonTg and 3xTgAD brains undergo significant decline in glucose transport, as detected by FDG-microPET, between 6-9 months of age just prior to the transition into reproductive senescence. The deficit in brain metabolism was sustained thereafter. Decline in glucose transport coincided with significant decline in neuronal glucose transporter expression and hexokinase activity with a concomitant rise in phosphorylated/inactivated pyruvate dehydrogenase. Lactate utilization declined in parallel to the decline in glucose transport suggesting lactate did not serve as an alternative fuel. An adaptive response in the nonTg hippocampus was a shift to transport and utilization of ketone bodies as an alternative fuel. In the 3xTgAD brain, utilization of ketone bodies as an alternative fuel was evident at the earliest age investigated and declined thereafter. The 3xTgAD adaptive response was to substantially increase monocarboxylate transporters in neurons while decreasing their expression at the BBB and in astrocytes. Collectively, these data indicate that the earliest change in the metabolic system of the aging female brain is the decline in neuronal glucose transport and metabolism followed by decline in mitochondrial function. The adaptive shift to the ketogenic system as an alternative fuel coincided with decline in mitochondrial function. Translationally, these data provide insights into the earliest events in bioenergetic aging of the female brain and provide potential targets for preventing shifts to less efficient bioenergetic fuels and transition to the ketogenic phenotype of the Alzheimer's brain.
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