Mass spectrometry and the search for moonlighting proteins

Mass spectrometry has become one of the most important techniques in proteomics because of its use to identify the proteins found in different cell types, organelles, and multiprotein complexes. This information about protein location and binding partners can provide valuable clues to infer a protein's function. However, more and more proteins are found that "moonlight," or have more than one function, and the presence of moonlighting proteins can make more difficult the identification of protein function in those studies. This review discusses examples of moonlighting proteins and how their presence can affect the results of mass spectrometry studies that identify the locations, levels, and changes in protein expression. Although the presence of moonlighting proteins can complicate the results of those studies, mass spectrometry-derived protein-expression profiles potentially provides a very powerful method to find additional moonlighting proteins because they do not require a prior hypothesis of the protein's function.     

Atomic-scale investigation of ε and θ precipitates in bainite in 100Cr6 bearing steel by atom probe tomography and ab initio calculations

Carbide precipitation during upper and lower bainite formation in high-carbon bearing steel 100Cr6 is characterized using transmission electron microscopy and atom probe tomography. The results reveal that both ε and θ carbides precipitate in lower bainite isothermally held at 260 °C and only θ precipitates form in upper bainite isothermally held at 500 °C. ε and θ precipitate under paraequilibrium condition at 260 °C in lower bainite and θ precipitates under negligible partitioning local equilibrium condition in upper bainite at 500 °C. In order to theoretically study ε and θ precipitation and the ε → θ transition in bainite, thermodynamic calculations have been carried out using ab initio techniques. We find that ε and θ carbides in ferrite have almost identical thermodynamic stability, and hence have similar formation probability. In austenite, however, cementite formation is clearly preferred: it is favored by 5 kJ mol^?1 at room temperature and still by 4 kJ mol^?1 at 500 °C. Hence, the thermodynamic predictions agree well with the atom probe tomography results.     

Thermodynamics of carbon solubility in ferrite and vacancy formation in cementite in strained pearlite

In order to investigate the thermodynamic driving force for the experimentally observed accumulation of C in ferritic layers of severely plastically deformed pearlitic wires, the stabilities of C interstitials in ferrite and of C vacancies in cementite are investigated as a function of uniaxial stain, using density-functional theory. In the presence of an applied strain along [1 1 0] or [1 1 1], the C interstitial in ferrite is significantly stabilized, while the C vacancy in cementite is moderately destabilized by the corresponding strain states in cementite [1 0 0] and ([0 1 0]). The enhanced stabilization of the C interstitial gives rise to an increase in the C concentration within the ferritic layers by up to two orders of magnitude. Our results thus suggest that in addition to the generally assumed non-equilibrium, dislocation-based mechanism, there is also a strain-induced thermodynamic driving force for the experimentally observed accumulation of C in ferrite.     

Oil-palm and Rainforest Phytoliths Dissolve at Different Rates - with Implications for Silicon Cycling After Transformation of Rainforest Into Oil-palm Plantation

Silicon - Phytoliths make up the predominant fraction of biogenic silica in plant litter and soils. Thus, they represent a major source of dissolved silicon (Si) in soil-plant systems. Dissolution...     

Heat transfer in metal foams and designed porous media

We present the characterization of heat transfer in commercial metal foam filled tubular reactors in comparison to a designed laser sintered device. The investigations are performed at empty tube Reynolds numbers ranging from 600 to 7600. Volumetric heat transfer performances up to 4.5 MW/(m³ K) were estimated by means of a simple calorimetric measurement setup, which is 3 orders of magnitude higher compared to conventional batch reactors. The heat transfer was found to increase with the ligament diameter ascribed to the enhanced turbulent kinetic energy induced. The fixed wall connection of the fully sintered device, realized by the applied manufacturing method, leads to 30% improvement of the heat transfer compared to no connection. Selective laser sintering was found to be an efficient tool for the design of continuous heat exchanger reactors covering a wide range of applications by simply adapting the geometry.     

Highly Efficient Platinum-Catalyzed Enantioselective Hydrogenation of Trifluoroacetoacetates in Acidic Solvents

The hydrogenation of methyl-, ethyl- and isopropyl-4,4,4-trifluoroacetoacetates to the corresponding chiral trifluoromethyl alcohols has been investigated over Pt/A1₂O₃ modified by O-methyl-cinchonidine. Up to 96% ee and 1850 h^-1 average TOF have been achieved in the synthesis of this important chiral building block. The special role of reaction medium and particularly the impact of water and acids on enantiodiscrimination are discussed.     

Application of the Taguchi Method in Analyzing the Impact of Modified Gemini Surfactants on TiO2 Nano-Suspension

Regarding the TiO₂ nano-suspension under different influencing parameters such as hydrophilic chain length of the modified gemini surfactant (dispersant), electrolyte concentration and dispersant concentration, this study applied the Taguchi Method to analyze the optimal parameters of the TiO₂ nano-suspension using an L9(3³) orthogonal array for making the experimental formulas with the average particle size of the suspension as the smaller-the-better indicator. The experimental results suggested that the dispersing particle size of the nano-suspension was affected in order by the dispersant concentration (64.11%), the hydrophilic group chain length of dispersant (11.16%) and the electrolyte concentration (3.04%). Then, by the confirmation experiments based on the optimal parameter combinations of Taguchi Method analysis, the TiO₂ nano-suspension of uniform and minimized particle size were obtained. The result was within the 95% confidence interval, indicating that the reproducibility of the parameter design was high.     

Effect of degree of crystallographic texture on ferro‐ and piezoelectric properties of Ba0.85Ca0.15TiO3 piezoceramics

Crystallographic texturing is a promising approach to reduce the performance gap between randomly oriented polycrystalline piezoelectrics and perfectly oriented single crystals. Here, the influence of the degree of crystallographic texture on the electromechanical properties and their temperature stability of the lead‐free perovskite ferroelectric Ba_0.85Ca_0.15TiO₃ is investigated. Samples with a broad range of (100),(001) crystallographic texture (Lotgering factor 26%‐83%) were prepared by the reactive templated grain growth method. Crystallographic and microstructural analysis have been carried out using X‐ray diffraction and scanning electron microscopy, while the temperature‐dependent electromechanical properties were characterized by dielectric, piezoelectric, polarization, and strain measurements. It was revealed that the total bipolar strain and the coercive field are linearly dependent on the Lotgering factor. The total bipolar strain increased by 80%, whereas the coercive field decreased by 18% due to crystallographic texturing. Likewise, the temperature stability of the electromechanical properties of the samples was found to be dependent on the degree of texture. A sample with a high degree of texture exhibited a Curie temperature of 117°C, which is 21% higher compared to a counterpart with a low degree of texture. This was related to chemical inhomogeneity and a modified internal mechanical stress state.     

Cholesterol-Dependent Energy Transfer between Fluorescent Proteins—Insights into Protein Proximity of APP and BACE1 in Different Membranes in Niemann-Pick Type C Disease Cells

Förster resonance energy transfer (FRET) -based techniques have recently been applied to study the interactions between β-site APP-cleaving enzyme-GFP (BACE1-GFP) and amyloid precursor protein-mRFP (APP-mRFP) in U373 glioblastoma cells. In this context, the role of APP-BACE1 proximity in Alzheimer’s disease (AD) pathogenesis has been discussed. FRET was found to depend on intracellular cholesterol levels and associated alterations in membrane stiffness. Here, NPC1 null cells (CHO-NPC1^−/−), exhibiting increased cholesterol levels and disturbed cholesterol transport similar to that observed in Niemann-Pick type C disease (NPC), were used to analyze the influence of altered cholesterol levels on APP-BACE1 proximity. Fluorescence lifetime measurements of whole CHO-wild type (WT) and CHO-NPC1^−/− cells (EPI-illumination microscopy), as well as their plasma membranes (total internal reflection fluorescence microscopy, TIRFM), were performed. Additionally, generalized polarization (GP) measurements of CHO-WT and CHO-NPC1^−/− cells incubated with the fluorescence marker laurdan were performed to determine membrane stiffness of plasma- and intracellular-membranes. CHO-NPC1^−/− cells showed higher membrane stiffness at intracellular- but not plasma-membranes, equivalent to cholesterol accumulation in late endosomes/lysosomes. Along with higher membrane stiffness, the FRET efficiency between BACE1-GFP and APP-mRFP was reduced at intracellular membranes, but not within the plasma membrane of CHO-NPC1^−/−. Our data show that FRET combined with TIRF is a powerful technique to determine protein proximity and membrane fluidity in cellular models of neurodegenerative diseases.     

The Clouding of an Anionic Surfactant in Acid Solution: Mechanistic and Analytical Implications

The clouding of sodium dodecyl sulfate (SDS) in strongly acidic solutions has seen analytical use, but its mechanism has generally been misinterpreted. In the present work it was found that as SDS slowly hydrolyzes to form dodecanol, the solution passes through a series of compositions at which the aggregation of surfactant is promoted by nucleation onto traces of insoluble dodecanol. This occurred at concentrations well below the critical micelle concentration of SDS and resulted in mixed aggregates that grew to macroscopic size, giving the solution a cloudy appearance. The increasing dodecanol content eventually caused coalescence into a coacervate phase which evolved into a solid layer of dehydrated dodecanol. The process, which continued over an extended period, depended on the temperature and the concentration and type of acid used. The early stages of SDS aggregation were monitored through the I ₁/I ₃ ratio of pyrene fluorescence, which confirmed the existence of micelle-like aggregates at low surfactant concentration. The mixed SDS/dodecanol systems formed in acid hydrolysis were mimicked in neutral solution by combining the appropriate amounts of SDS, dodecanol, and NaCl. Clouding and the formation of a coacervate phase generally proceeded in a similar manner in these solutions.