Perspectives in science最新文献

Modern tools for enzyme discovery combined with the development of increasingly reliable strategies for protein engineering have greatly expanded the range of enzymes with suitable properties for practical applications. This situation presents enormous opportunities for the design of sustainable biocatalytic strategies for the production of high-value chemicals. Here, we highlight recent contributions from our laboratory concerning ω-transaminases and monoamine oxidases, two enzyme classes that have been exploited for the industrial scale production of active pharmaceutical ingredients or key chiral intermediates. Firstly, we describe the development of novel ‘smart’ amine donors which overcome inherent challenges associated with controlling the equilibrium position of ω-TA catalyzed processes. Subsequently, we demonstrate how engineered variants of monoamine oxidase developed in our laboratory have been applied as biocatalysts for the synthesis of a diverse range of active pharmaceutical ingredients and alkaloid natural products. Through these illustrative examples, we hope to promote the wider application of enzymes within the synthetic community.

Upon completing 100 years since it was published, the work Die Kinetik der Invertinwirkung by Michaelis and Menten (MM) was celebrated during the 6th Beilstein ESCEC Symposium 2013. As the 7th Beilstein ESCEC Symposium 2015 debates enzymology in the context of complex biological systems, a post-MM approach is required to address cell-like conditions that are well beyond the steady-state limitations. The present contribution specifically addresses two hitherto ambiguous constants whose interest was, however, intuited in the original MM paper: (i) the characteristic time constant τ_∞, which can be determined using the late stages of any progress curve independently of the substrate concentration adopted; and (ii) the dissociation constant K_S, which is indicative of the enzyme–substrate affinity and completes the kinetic portrayal of the Briggs–Haldane reaction scheme. The rationale behind τ_∞ and K_S prompted us to revise widespread concepts of enzyme's efficiency, defined by the specificity constant k_cat/K_M, and of the Michaelis constant K_M seen as the substrate concentration yielding half-maximal rates. The alternative definitions here presented should help recovering the wealth of published k_cat/K_M and K_M data from the criticism that they are subjected. Finally, a practical method is envisaged for objectively determining enzyme's activity, efficiency and affinity – (EA)² – from single progress curves. The (EA)² assay can be conveniently applied even when the concentrations of substrate and enzyme are not accurately known.

Experiential science learning based on the in-built sensors of handheld devices such as smartphones, tablet computer and game consoles has seen quite a strong development in recent years. In particular, such devices with internal acceleration sensors offer an innovative approach to kinematics learning in classroom physics, a notoriously difficult topic for pupils. In view of research and teaching in this domain, the practical advantages and disadvantages of two such devices, the Nintendo WiiMote and the Apple iPod touch, are discussed.

Beyond the specific examples, this comparison of the advantages and disadvantages of two different “philosophies” of instructional technology with regard to their use in science learning experiments provides arguments for discussions and decisions related to such technology in other and future settings, which can be of interest to both researchers and practitioners in the field.

Polycyclic aromatic hydrocarbons (PAHs) are highly toxic, pervasive environmental pollutants with mutagenic, teratogenic, and carcinogenic properties. There is interest in exploiting the nutritional capabilities of microbes to remove PAHs from various environments including those impacted by improper disposal or spills. Although there is a considerable body of literature on PAH degradation, the substrates and products for many of the enzymes have never been identified and many proposed activities have never been confirmed. This is particularly true for high molecular weight PAHs (e.g., phenanthrene, fluoranthene, and pyrene). As a result, pathways for the degradation of these compounds are proposed to follow one elucidated for naphthalene with limited experimental verification. In this pathway, ring fission produces a species that can undergo a non-enzymatic cyclization reaction. An isomerase opens the ring and catalyzes a cis to trans double bond isomerization. The resulting product is the substrate for a hydratase-aldolase, which catalyzes the addition of water to the double bond of an α,β-unsaturated ketone, followed by a retro-aldol cleavage. Initial kinetic and mechanistic studies of the hydratase-aldolase in the naphthalene pathway (designated NahE) and two hydratase-aldolases in the phenanthrene pathway (PhdG and PhdJ) have been completed. Crystallographic work on two of the enzymes (NahE and PhdJ) provides a rudimentary picture of the mechanism and a platform for future work to identify the structural basis for catalysis and the individual specificities of these hydratase-aldolases.

This paper presents a technique that aimed to accomplish an efficient balance between video compression using H.265 protocol and retention of 8K resolution. The study implements multi-level of optimization in the encoding process using H.265 where JPEG2000 standards play a crucial role. The study also applies a novel concept of orthogonal projection that manages pixels metadata required in every frame transition followed by motion compensation. By using multiple file formats of 30 video datasets, the outcome of the study is found to be accomplishing approximately 49% of enhancement in data quality and around 59% of improvement in video compression in comparison to the existing techniques of HEVC-based video compression.

In this study, an attempt has been made to study the performance characteristics of diagrid structures using nonlinear static pushover analysis. The models studied are circular in plan with aspect ratio H/B (where H is total height and B is the base width of structure) varying from 2.67 to 4.26. The three different angles of external brace considered are 59°, 71° and 78° (Kim et al., 2010). The width of the base is kept constant at 12 m and height of the structure is varied accordingly. The nonlinear behaviour of the elements is modelled using plastic hinges based on moment–curvature relationship as described in FEMA 356 guidelines. Seismic response of structure in terms of base shear and roof displacement corresponding to performance point were evaluated using nonlinear static analysis and the results are compared. For 71° brace angle model base shear at performance shows an increase in all the aspect ratio considered in the study. The performance of the structure is influenced by brace angle and aspect ratio.

The paper demonstrates about melioration of integer order and fractional order model of heating furnace. Both models are being placed in closed loop along with the proportional integral derivative (PID) controller and fractional order proportional integral derivative (FOPID) controller so that the various time domain performance characteristics of the heating furnace can be meliorated. The tuning parameters (K_p, K_i and K_d) of the controllers has been found using the Astrom-Hagglund tuning technique and the differ-integrals (λ and μ) are found using the Nelder-Mead optimisation technique.

This paper evaluates the change in metabolic energy required to maintain the signalling activity of neurons in the presence of an external electric field. We have analysed the Hodgkin–Huxley type conductance based fast spiking neuron model as electrical circuit by changing the frequency and amplitude of the applied electric field. The study has shown that, the presence of electric field increases the membrane potential, electrical energy supply and metabolic energy consumption. As the amplitude of applied electric field increases by keeping a constant frequency, the membrane potential increases and consequently the electrical energy supply and metabolic energy consumption increases. On increasing the frequency of the applied field, the peak value of membrane potential after depolarization gradually decreases as a result electrical energy supply decreases which results in a lower rate of hydrolysis of ATP molecules.

The thermal performance of open earth pan furnace used conventionally for preparing jaggery (gur) is very low. Dry bagasse is used as a fuel to produce heat in a combustion process in the open earth furnace. The energy loss due to inefficient combustion process, the energy loss through exhaust gases and other losses due to furnace wall, convection and radiation bring the thermal efficiency of open earth pan furnace to a low value. Certain quantity of energy produced in combustion process is used to sensibly heat the sugarcane juice to its evaporation temperature. Solar collectors can supply the sensible heat required to raise the sugarcane juice temperature up to its boiling point, thereby reducing the total quantity of heat required in preparing the jaggery. Solar drier can be used to supply hot air required for the combustion process to burn the bagasse in more efficient manner. This paper presents analytical calculations done to study the performance improvement of the jaggery making unit using solar collector and solar drier.