Temperature,Hydrostatic Pressure,and Osmolyte Effects on Liquid–Liquid Phase Separation in Protein Condensates: Physical Chemistry and Biological Implications

Liquid–liquid phase separation (LLPS) of proteins and other biomolecules play a critical role in the organization of extracellular materials and membrane-less compartmentalization of intra-organismal spaces through the formation of condensates. Structural properties of such mesoscopic droplet-like states were studied by spectroscopy, microscopy, and other biophysical techniques. The temperature dependence of biomolecular LLPS has been studied extensively, indicating that phase-separated condensed states of proteins can be stabilized or destabilized by increasing temperature. In contrast, the physical and biological significance of hydrostatic pressure on LLPS is less appreciated. Summarized here are recent investigations of protein LLPS under pressures up to the kbar-regime. Strikingly, for the cases studied thus far, LLPSs of both globular proteins and intrinsically disordered proteins/regions are typically more sensitive to pressure than the folding of proteins, suggesting that organisms inhabiting the deep sea and sub-seafloor sediments, under pressures up to 1 kbar and beyond, have to mitigate this pressure-sensitivity to avoid unwanted destabilization of their functional biomolecular condensates. Interestingly, we found that trimethylamine-N-oxide (TMAO), an osmolyte upregulated in deep-sea fish, can significantly stabilize protein droplets under pressure, pointing to another adaptive advantage for increased TMAO concentrations in deep-sea organisms besides the osmolyte's stabilizing effect against protein unfolding. As life on Earth might have originated in the deep sea, pressure-dependent LLPS is pertinent to questions regarding prebiotic proto-cells. Herein, we offer a conceptual framework for rationalizing the recent experimental findings and present an outline of the basic thermodynamics of temperature-, pressure-, and osmolyte-dependent LLPS as well as a molecular-level statistical mechanics picture in terms of solvent-mediated interactions and void volumes.     

FT-IR,FT-Raman,NMR spectra and DFT calculations on 4-chloro-N-methylaniline

In this work, the vibrational spectral analysis was carried out by using FT-IR and FT-Raman spectroscopy in the range 400–4000 and 50–3500 cm^?1 respectively, for the title molecule. The structural and spectroscopic data of the molecule in the ground state were calculated by using density functional method using 6-311++G(d,p) basis set. The vibrational frequencies were calculated and scaled values were compared with experimental FT-IR and FT-Raman spectra. The observed and calculated frequencies are found to be in good agreement. The complete assignments of all the vibrational mode were performed on the basis of the total energy distributions (TED). ¹³C and ¹H NMR chemical shifts results were given and are in agreement with the corresponding experimental values. The theoretically constructed FT-IR and FT-Raman spectra exactly coincides with experimental one.     

Synthesis and evaluation of new phosphonic acid‐functionalized acrylamides with potential biomedical applications

Phosphorus‐containing acidic monomers are able to interact with the inorganic phase of mineralized tissues such as enamel, dentin, and bone. From this perspective, three phosphonic acid‐containing acrylamide monomers with different lengths of alkyl chains were synthesized to be used for both self‐etching dental adhesives and mineralized hydrogel scaffolds. Monomers were synthesized by the reaction of α‐aminophosphonates (diethyl aminomethylphosphonate, diethyl 2‐aminobutan‐2‐ylphosphonate, and diethyl 2‐aminooctan‐2‐ylphosphonate) with acryloyl chloride followed by the hydrolysis of phosphonate groups by using trimethylsilyl bromide. The properties such as pH in the range of mild self‐etching adhesives, hydrolytic stability, high rate of copolymerizations with 2‐hydroxyethyl methacrylate (HEMA) and HEMA/glycerol dimethacrylate, giving high‐molecular‐weight polymers on thermal polymerization, and strong decalcification ability of hydroxyapatite make these monomers good candidates for self‐etching adhesives, although no appreciable effect of the number and size of the α‐substituents was observed. Hydrogel scaffolds containing phosphonic acid groups were fabricated, characterized, and mineralized. Altogether, the results suggest that these phosphonic acid‐containing monomers have suitable properties to be used in fabrication of biomaterials for both dental and bone tissue engineering applications. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2755–2767     

Modeling of copper(II) and lead(II) adsorption on kaolinite-based clay minerals individually and in the presence of humic acid

The aim of this study is to explain how clay minerals adsorb heavy metals individually and in the presence of humic acid, and to model heavy metal adsorption specifically based on surface-metal binary and surface-metal-ligand ternary complexation. The adsorption of Cu(II) and Pb(II) on kaolinite-based clay minerals has been modeled by the aid of the FITEQL3.2 computer program using single- and double-site binding models of the Langmuir approach. Potentiometric titrations and adsorption capacity experiments were carried out in solutions containing different concentrations of the inert electrolyte NaClO4; however, the modeling of binary and ternary surface complexation was deliberately done at high ionic strength (0.1 M electrolyte) for eliminating adsorption onto the permanent negatively charged sites of kaolinite. A "two-site, two pKa" model was adapted, and as for the two surface sites responsible for adsorption, it may be arbitrarily assigned that [triple bond]S1OH sites represent silanol and organic functional groups such as carboxyl having pKa values close to that of silanol, and [triple bond]S2OH sites represent aluminol and organic functional groups such as phenolics whose pKa values are close to that of aluminol, as all the studied clays contained organic carbon. Copper(II) showed a higher adsorption capacity and higher binding constants, while lead(II), being a softer cation (in respect to HSAB theory) preferred the softer basic sites with aluminol-phenol functional groups. Heavy metal cations are assumed to bind to the clay surface as the sole (unhydrolyzed) M(II) ion and form monodentate surface complexes. Cu(II) and Pb(II) adsorption in the presence of humic acid was modeled using a double-site binding model by the aid of FITEQL3.2, and then the whole system including binary surface-metal and surface-ligand and ternary surface-metal-ligand complexes was resolved with respect to species distributions and relevant stability constants. Electrostatic effects were accounted for using a diffuse layer model (DLM) requiring minimum number of adjustable parameters. Metal adsorption onto clay at low pH increased in the presence of humic acid, and the metal adsorption vs pH curves of metal-kaolinite-humic acid suspensions were much steeper (and distinctly S shaped) compared to the wider pH-gradient curves observed in binary clay-metal systems. The clay mineral in the presence of humic acid probably behaved more like a chelating ion-exchanger sorbent for heavy metals rather than being a simple inorganic ion exchanger.     

Muscle skin temperature responses for hamstring and quadriceps to aerobic and anaerobic test conditions in Turkish Olympic Sailing Athletes

Olympic class sailing is a competitive sport and requires several abilities. An understanding of the responses to aerobic and anaerobic loading will be useful for assessing the training programs, protective strategies and possibility of injuries. Therefore, the aim of this study is to determine lower extremity main muscles skin temperature responses to aerobic and anaerobic test conditions in Turkish Olympic Sailing Athletes. Eighteen sailing athletes were assessed during preseasonal assessment period. Temperatures of quadriceps and hamstring muscle groups were evaluated bilaterally during rest and after Wingate Treadmill tests. Wingate test was accepted as an indicator of anaerobic performance and Treadmill test as an aerobic performance. Infrared thermography was performed to assess the skin temperature at anterior and posterior parts of thigh for both legs. In the triplicate comparison, the temperature changes between the rest, aerobic test and anaerobic test conditions were significant (p?<?0.05). In the analysis to determine the difference between the compared groups; for both muscle groups, temperature change after anaerobic performance was not significant; in contrast to this result the change in muscle temperature after aerobic performance was significant (p?<?0.05). Energetic—metabolic activity of major muscle groups of lower extremities during aerobic and anaerobic performance are important for injury prevention, treatment, rehabilitation and return to play. Present study shows that aerobic performance or activities requires higher energetic-metabolic activity.

     

Dynamical investigation of effects of variable damper settings induced brake pressure oscillations on axle and wheel oscillations during ABS-braking based on experimental study

In this study, the effects of variable damping setting induced brake pressure oscillations on axle and wheel oscillations have been experimentally explored. For this, antilock brake system (ABS) tests are conducted on wet and slippery rough roads with hard, medium-hard and soft shock absorbers. In ABS tests, the axle height, the longitudinal and vertical axle accelerations have been measured. The results are discussed for time and frequency responses of axle vibrations in vertical and longitudinal direction. The time responses are separately considered for high and low piston velocities of damper. Also, in order to occur the effects of changes in ABS-brake pressure on axle vibrations, novel rules are designed. These rules are based on the integration of suspension dynamics into braking dynamics. The results show that the brake pressure is distinctly changed by variable damping settings. In time responses, these differences are determined by changes in time period and magnitude of brake pressure during build-up and reduction process. In frequency responses, the brake pressure differences are occurred by the different change frequencies of brake pressure causing resonance at axle vibrations. Also, the changes in magnitude of resonance peaks have determined the effects of brake pressure changes on axle vibrations. As a result, it is possible to damp the oscillations by changing the magnitude and frequency of brake pressure by means of the damper settings during ABS-braking.     

Testing Platform and Delay Compensation Methods for Distributed Real-Time Hybrid Simulation

Experimental Techniques - Real-time hybrid simulation (RTHS) plays an essential role in understanding the time-dependent behavior of structures when subject to extreme hazard loadings in civil...     

Multinomial tau-leaping method for stochastic kinetic simulations

We introduce the multinomial tau-leaping (MtauL) method for general reaction networks with multichannel reactant dependencies. The MtauL method is an extension of the binomial tau-leaping method where efficiency is improved in several ways. First, tau-leaping steps are determined simply and efficiently using a priori information and Poisson distribution-based estimates of expectation values for reaction numbers over a tentative tau-leaping step. Second, networks are partitioned into closed groups of reactions and corresponding reactants in which no group reactant set is found in any other group. Third, product formation is factored into upper-bound estimation of the number of times a particular reaction occurs. Together, these features allow larger time steps where the numbers of reactions occurring simultaneously in a multichannel manner are estimated accurately using a multinomial distribution. Furthermore, we develop a simple procedure that places a specific upper bound on the total reaction number to ensure non-negativity of species populations over a single multiple-reaction step. Using two disparate test case problems involving cellular processes--epidermal growth factor receptor signaling and a lactose operon model--we show that the tau-leaping based methods such as the MtauL algorithm can significantly reduce the number of simulation steps thus increasing the numerical efficiency over the exact stochastic simulation algorithm by orders of magnitude.     

On dynamical behavior for optical solitons sustained by the perturbed Chen–Lee–Liu model

This study investigates the perturbed Chen–Lee–Liu model that represents the propagation of an optical pulse in plasma and optical fiber. The generalized exponential rational function method is used for this purpose. As a result, we obtain some non-trivial solutions such as the optical singular, periodic, hyperbolic, exponential, trigonometric soliton solutions. We aim to express the pulse propagation of the generated solutions, by taking specific values for the free parameters existed in the obtained solutions. The obtained results show that the generalized exponential rational function technique is applicable, simple and effective to get the solutions of nonlinear engineering and physical problems. Moreover, the acquired solutions display rich dynamical evolutions that are important in practical applications.     

Impact of Capillary Pressure, Salinity and In situ Conditions on CO2 Injection into Saline Aquifers

This article presents a numerical investigation of the combined effects of capillary pressure, salinity and in situ thermodynamic conditions on CO₂-brine-rock interactions in a saline aquifer. We demonstrate that the interrelations between capillary pressure, salinity, dissolution and drying-out affect CO₂ injectivity and storage capacity of a saline aquifer. High capillary forces require a high injection pressure for a given injection rate. Depending on salinity, the increase in injection pressure due to capillary forces can be offset by the dissolution of CO₂ in formation water and its compressibility. Higher capillary forces also reduce gravity segregation, and this gives a more homogeneous CO₂ plume which improves the dissolution of CO₂. The solubility of CO₂ in formation water decreases with increasing salinity which requires an increased injection pressure. Higher salinity and capillary pressure can even block the pores, causing an increased salt precipitation. Simulations with various pressure-temperature conditions and modified salinity and capillary pressure curves demonstrate that, with the injection pressures similar for both cold and warm basins at a given injection rate, CO₂ dissolves about 10% more in the warm basin water than in the cold basin. The increase in dissolution lowers the injection pressure compensating the disadvantage of low CO₂ density and compressibility for storage in warm basins.