Tyrosine phosphorylation of cortactin by the FAK-Src complex at focal adhesions regulates cell motility.

BackgroundCell migration plays an important role in many physiological and pathological processes, including immune cell chemotaxis and cancer metastasis. It is a coordinated process that involves dynamic changes in the actin cytoskeleton and its interplay with focal adhesions. At the leading edge of a migrating cell, it is the re-arrangement of actin and its attachment to focal adhesions that generates the driving force necessary for movement. However, the mechanisms involved in the attachment of actin filaments to focal adhesions are still not fully understood.ResultsSignaling by the FAK-Src complex plays a crucial role in regulating the formation of protein complexes at focal adhesions to which the actin filaments are attached. Cortactin, an F-actin associated protein and a substrate of Src kinase, was found to interact with FAK through its SH3 domain and the C-terminal proline-rich regions of FAK. We found that the autophosphorylation of Tyr(397) in FAK, which is necessary for FAK activation, was not required for the interaction with cortactin, but was essential for the tyrosine phosphorylation of the associated cortactin. At focal adhesions, cortactin was phosphorylated at tyrosine residues known to be phosphorylated by Src. The tyrosine phosphorylation of cortactin and its ability to associate with the actin cytoskeleton were required in tandem for the regulation of cell motility. Cell motility could be inhibited by truncating the N-terminal F-actin binding domains of cortactin or by blocking tyrosine phosphorylation (Y421/466/475/482F mutation). In addition, the mutant cortactin phosphorylation mimic (Y421/466/475/482E) had a reduced ability to interact with FAK and promoted cell motility. The promotion of cell motility by the cortactin phosphorylation mimic could also be inhibited by truncating its N-terminal F-actin binding domains.ConclusionsOur results suggest that cortactin acts as a bridging molecule between actin filaments and focal adhesions. The cortactin N-terminus associates with F-actin, while its C-terminus interacts with focal adhesions. The tyrosine phosphorylation of cortactin by the FAK-Src complex modulates its interaction with FAK and increases its turnover at focal adhesions to promote cell motility

A visual analysis of the usage efficiency of library books

The monographic collections in academic libraries have undergone a period of tremendous growth in volume, in subject diversity, and in formats during the recent several decades. Readers may find it difficult to prioritize which book(s) should be borrowed for a specific purpose. The log data of book loan record may serve as a visible indicator for the more sought-after books by the readers. This paper describes our experimental efforts in works in a university library setting. The visual analysis is thought to provide an effective way to extract the book usage information, which may yield new insights into a host of other related technical as well as user behavior issues. Initial experiment has demonstrated that the proposed approach as articulated in this article can actually benefit end-users as well as library collection development personnel in their endeavor of book selections with effective measure.</p

Triply heavy tetraquark states with the QQQˉqˉQQ\bar{Q}\bar{q} configuration

In the framework of the color-magnetic interaction, we systematically investigate the mass splittings of the $QQ\bar{Q}\bar{q}$ tetraquark states and estimated their rough masses in this work. These systems include the explicitly exotic states $cc\bar{b}\bar{q}$ and $bb\bar{c}\bar{q}$ and the hidden exotic states $cc\bar{c}\bar{q}$, $cb\bar{b}\bar{q}$, $bc\bar{c}\bar{q}$, and $bb\bar{b}\bar{q}$. If a state around the estimated mass region could be observed, its nature as a genuine tetraquark is favored. The strong decay patterns shown here will be helpful to the experimental search for these exotic states.Comment: 14 pages, 3 figures and 9 tables. Accepted by Eur. Phys. J.

Heat transfer measurement in oil-based nanofluids.

Nanoparticles are a class of materials that exhibit unique physical and chemical properties compared to those of the same material at the bulk scale. One method of enhancing the thermal conductivity, and hence the heat transfer coefficient, of a fluid is to add nanoparticles to the fluid creating a so called nanofluid. The term nanofluids was coined by researchers at Argonne National Laboratory and refers to a two-phase mixture composed of a continuous liquid phase and dispersed nanoparticles in suspension. Nowadays, nanofluids are considered to be the next-generation heat transfer fluids as they offer exciting new possibilities to enhance heat transfer performance compared to pure liquids. Heat transfer coefficient of a fluid is the proportionality coefficient between the heat flux that is a heat flow per unit area and the thermodynamic driving force for the flow of heat. It shows how effective heat can be transferred within a system and can be passively enhanced by changing flow geometry, boundary conditions, or by enhancing thermal conductivity of the fluid. In most existing systems, since the first two of these are set by design, the only method to enhance heat transfer is to enhance heat transfer properties of the fluid. In this study, we used three sizes of Cu nanoparticles with different particle loadings and dispersed them into PAO formulated motor oil to create nanofluids. Measurements of heat transfer coefficients and other fluid properties were performed. Both base and nanofluids appeared to behave like Newtonian fluids and an up to 25% enhancement of the heat transfer coefficient was observed in the laminar flow regime. The heat transfer coefficient is shown to increase with increasing Reynolds number. However, as fluid temperature increases, the heat transfer coefficient decreased. Various factors including Reynolds number, fluid temperature, nanoparticle size, and nanoparticle loadings are all capable of impacting the enhancement ratio. A consistent downward trend of enhancement ratio with respect to Reynolds number was observed for the nanofluids discussed in this work. Future studies in the turbulent flow regime are needed to confirm this trend. Finally, a theoretical model to predict the heat transfer coefficient of nanofluids is developed based on previously published correlations the results of which are in excellent agreement with the experimental data

Production of alcohols via syngas fermentation using Alkalibaculum bacchi monoculture and a mixed culture

Gasification-syngas fermentation is a hybrid conversion technology. In this process, feedstocks such as biomass or municipal solid waste are gasified to syngas (CO, H2 and CO2), which is then converted into biofuels and chemicals using biocatalysts. Recently isolated Alkalibaculum bacchi strains CP11T, CP13 and CP15 were found to convert CO and H2) into ethanol and acetic acid at initial pH 8.0. Bottle fermentations showed that CP15 was the most promising strain for ethanol production because of its higher growth and ethanol production rates and yield than CP11T and CP13. The cost of CP15 medium was reduced by 27% by removing TAPS buffer and replacing yeast extract (YE), minerals and vitamins with corn steep liquor (CSL). The use of CSL resulted in a twofold increase in ethanol production in bottle fermentations. Fermentations were scaled up to 3-L and 7-L fermentors in semi-continuous and continuous modes with and without cell recycle. Results of the continuous syngas fermentation with cell recycle showed a maximum of 5.5 g/L cell mass concentration at a dilution rate of 0.033 h-1 in the YE medium. Cell mass and ethanol concentrations were 2.2 g/L and 6.5 g/L, respectively, at a dilution rate of 0.011 h-1. When CSL medium was used in continuous syngas fermentation, the maximum produced concentrations of ethanol, n-propanol and n-butanol were 8 g/L, 6 g/L and 1 g/L, respectively. n-Propanol and n-butanol were not typical products of strain CP15. A 16S rRNA gene-based survey revealed a mixed culture in the fermentor dominated by A. bacchi strain CP15 (56%) and Clostridium propionicum (34%). The mixed culture presents an opportunity for higher alcohols production from syngas. Semi-continuous fermentations in a 3-L fermentor with the mixed culture and CSL medium resulted in a twofold more total alcohol production than in the YE medium. The synergy between strain CP15 and C. propionicum in the mixed culture in bottle fermentations resulted in 50% higher efficiency in converting propionic acid, butyric acid and hexanoic acid to their respective alcohol