Search

In a previous study, we demonstrated that spectral counts-based label-free proteomic quantitation could be improved by distributing peptides shared between multiple proteins. Here, we compare four quantitative proteomic approaches, namely, the normalized spectral abundance factor (NSAF), the normalized area abundance factor (NAAF), normalized parent ion intensity abundance factor (NIAF), and the normalized fragment ion intensity abundance factor (NFAF). We demonstrate that label-free proteomic quantitation methods based on chromatographic peak area (NAAF), parent ion intensity in MS1 (NIAF), and fragment ion intensity (NFAF) are also improved when shared peptides are distributed on the basis of peptides unique to each isoform. To stabilize the variance inherent to label-free proteomic quantitation data sets, we use cyclic-locally weighted scatter plot smoothing (LOWESS) and linear regression normalization (LRN). Again, all four methods are improved when cyclic-LOWESS and LRN are applied to reduce variation. Finally, we demonstrate that absolute quantitative values may be derived from label-free parameters such as spectral counts, chromatographic peak area, and ion intensity when using spiked-in proteins of known amounts to generate standard curves.

The characterization of protein modifications is essential for the study of protein function using functional genomic and proteomic approaches. However, current techniques are not efficient in determining protein modifications. We report an approach for sequencing proteins and determining modifications with high speed, sensitivity and specificity. We discovered that a protein could be readily acid-hydrolyzed within 1 min by exposure to microwave irradiation to form, predominantly, two series of polypeptide ladders containing either the N- or C-terminal amino acid of the protein, respectively. Mass spectrometric analysis of the hydrolysate produced a simple mass spectrum consisting of peaks exclusively from these polypeptide ladders, allowing direct reading of amino acid sequence and modifications of the protein. As examples, we applied this technique to determine protein phosphorylation sites as well as the sequences and several previously unknown modifications of 28 small proteins isolated from Escherichia coli K12 cells. This technique can potentially be automated for large-scale protein annotation.

With the expanding wind power scale by each year, the traditional method for optimizing spinning reserve (SR) capacity is no longer applicable. Due attention has to be paid on this added wind uncertainty when setting the SR requirement. For obtaining the more optimal and reasonable results, a technique that SR determination can be dealt should be researched in wind power integration system. Therefore, with involving wind farm output variables, the fresh and upgrade Robust Linear Optimization (RLO) which proposed by Seong-Cheol Kang is firstly introduced into constructing the model of minimum generating the cost of conventional generators (CGs) and SR cost and its optimal capacity in this paper. The wind farm output was described as its minimum, maximum and mean values in the model through the SCK robust linear optimization theory. The reliability for optimal SR capacity and total cost can be preliminarily calculated under a variety of wind power fluctuation in this model. The validity of the proposed method will be verified by the test results of the IEEE-30 bus system. The relationships of wind uncertainties and required SRs can also be confirmed.

Thermal management faces a challenge in high power and density packaging. Microchannel is a promising technique for heat transfer in minimized devices. However, the high power chip has a flat structure to need a microgap for heat transfer in efficiency. This paper studied the heat transfer with non-boiling in microgap with gas-water two-phase flow based on the phenomenological theory. The input heat flux was fixed and the volume flow rates of nitrogen and DI water had a widely values. Six spots of wall temperature had been monitored, and it was found the outlet areas had higher wall temperature than those at inlet areas. The wall temperature decreased with the increasing of volume flow rate of DI water, or with the increasing of volume flow rate. The phenomenological equation had been established for the wall temperature including two components, which were a negative power exponent function and a negative logarithm function governed by the volume flow rates of DI water and nitrogen, respectively. Compared with the liquid component, the gas component has a stronger effect on the wall temperature equation, and it was attributed to the gas fraction playing a more important role in heat transfer with gas-water two-phase flow. Q N2 =512 sccm and Q water =128 sccm were the best parameters for heat transfer in microgap in experiments.

The development of affinity purification technologies combined with mass spectrometric analysis of purified protein mixtures has been used both to identify new protein–protein interactions and to define the subunit composition of protein complexes. Transcription factor protein interactions, however, have not been systematically analyzed using these approaches. Here, we investigated whether ectopic expression of an affinity tagged transcription factor as bait in affinity purification mass spectrometry experiments perturbs gene expression in cells, resulting in the false positive identification of bait-associated proteins when typical experimental controls are used. Using quantitative proteomics and RNA sequencing, we determined that the increase in the abundance of a set of proteins caused by overexpression of the transcription factor RelA is not sufficient for these proteins to then co-purify non-specifically and be misidentified as bait-associated proteins. Therefore, typical controls should be sufficient, and a number of different baits can be compared with a common set of controls. This is of practical interest when identifying bait interactors from a large number of different baits. As expected, we found several known RelA interactors enriched in our RelA purifications (NFκB1, NFκB2, Rel, RelB, IκBα, IκBβ, and IκBe). We also found several proteins not previously described in association with RelA, including the small mitochondrial chaperone Tim13. Using a variety of biochemical approaches, we further investigated the nature of the association between Tim13 and NFκB family transcription factors. This work therefore provides a conceptual and experimental framework for analyzing transcription factor protein interactions.

The direct electron transfer reaction of glucose oxidase (GOx) at a bare silver electrode is verified. The electron transfer number n = 2, electron transfer coefficient α = 0.45 and rate constant of the electrochemical reaction Ks = 0.1 s−1 are obtained. This communication presents a multimolecular adsorption model to explain the properties of the direct electron reaction between GOx and bare silver electrodes. The residual valence force may be an important factor to ensure a direct electron transfer reaction on the bare electrode. On the basis of the experimental fact that only biologically active GOx exhibits electrochemical activity in solution, a facile analytical method for analyzing the active GOx concentration is developed. The results determined correspond very well to that of a spectrometric method.

A new type of disposable electrochemical sensor, which consists of a piece of Nafion membrane and a microdisk electrode, is developed. The Nafion membrane, which is butted by the electrode to actualize the electrochemical reaction, acts as the immobilization bed for mediator (anthraquinone) and enzyme (glucose oxidase). The sensor is not vulnerable to being broken or contaminated. By replacing the immobilization beds with different mediators and different enzymes in series, the sensor may be employed for the rapid analysis of a multi-component sample. The sensor exhibits a rapid, stable response to glucose. A consecutive calibration test shows that the original tip has an active period greater than 24 hours and the storage life time longer than 3 weeks. The linear range and the sensitivity of the original sensor are 6 mM and 0.52 nA/mM, respectively.

Several methods to obtain low-ppm mass accuracy have been described. In particular, online or offline lock mass approaches can use background ions, produced by electrospray under ambient conditions, as calibrants. However, background ions such as protonated and ammoniated polydimethylcyclosiloxane ions have relatively weak and fluctuating intensity. To address this issue, we implemented dynamic offline lock mass (DOLM). Within every MS1 survey spectrum, DOLM dynamically selected the strongest n background ions for statistical treatments and m/z recalibration. We systematically optimized the mass profile abstraction method to find one single m/z value to represent an ion and the number of calibrants. To assess the influence of the intensity of the analyte ions, we used tandem mass spectroscopy (MS/MS) datasets obtained from MudPIT analyses of two protein samples with different dynamic ranges. DOLM outperformed both external mass calibration and offline lock mass that used predetermined calibrant ions, especially in the low-ppm range. The unique dynamic feature of DOLM was able to adapt to wide variations in calibrant intensities, leading to averaged mass error center at 0.03 ± 0.50 ppm for precursor ions. Such consistently tight mass accuracies meant that a precursor mass tolerance as low as 1.5 ppm could be used to search or filter post-search DOLM-recalibrated MS/MS datasets.

The market multiplication theory includes the multiplication of market, time and benefit, and the direct marketing is based on this theory. Health food industry can adopt the mode of direct marketing, because the industry possesses characters of low production cost, high circulation cost and lots of users. The marketing mode, product promoting method and employee salary system of Amway Company which manages businesses including the health food production can be references for the direct marketing enterprises in the health food industry.

To gain insight into the nuclear proteome of Saccharomyces cerevisiae, nuclei were isolated and fractionated via sucrose gradient sedimentation. The resulting fractions were analyzed using multidimensional protein identification technology and the detected proteins were quantified using normalized spectral counts. A large number of low abundance proteins, many of which are involved in transcriptional regulation, were recovered. Sucrose gradient elution profiles of known protein complex components demonstrated that this approach may provide insight into the question of what percentage of the total population of a protein is in one complex, versus another protein complex, or exists as a free protein.

A new type of water-dispersive anticorrosive paint was prepared by using marine cobalt-rich crusts tailings which are the residue of cobalt-rich manganese crusts after the extraction of Co, Ni, Cu, Zn, Mn by acid leach. The first step making the paint is preparing the colored slurry by mixing the tailings (54.65%, mass) with water (40.78%) and some auxiliary materials (4.57%). The second step is mixing the colored slurry (40%) with a styrene-acrylate copolymer (40%), water (11.9%) and some auxiliary materials (8.1%). Test results indicate that the resistance to impact of the coating film is equal to or more than 490 Nmiddotcm, the resistance to saline water is more than 24 days. The tailings can provide both physical and chemical corrosion protection. With their fine particle size the tailings can be dispersed into the styrene-acrylate copolymer to form a uniform coating film with relatively high bonding strength on surfaces to be protected. With a high Fe2O3 content the tailings provide physical cladding. With a high content of Sr and other trace elements the tailings can react with corroded ferrite or with other corrosive materials, such as S04 2-, to form unreactive oxides or inert compounds. In this way, the tailings serve as chemical preservation agents. P2O5 contained within the tailings may combine with metallic elements or may react with polar groups in the styrene-acrylate copolymer to form stable complex compounds to keep corrosion from developing. Oxidizing and reducing properties of rare earth elements may accelerate the formation of a polymer network of coating molecules and shorten both the solidifying and film-forming times for the coating. The tailings also likely enhance the strength and water resistance of the resultant coatings.