Protein Biophosphors: Biodegradable,Multifunctional, Protein‐Based Hydrogel for White Emission,Sensing, and pH Detection

A highly efficient, multifunctional, bioderived white‐emitting hydrogel (biophosphor) consisting of crosslinked bovine serum albumin and three fluorescent dyes, Coumarin 460, fluorescein, and 5(6)‐carboxy‐x‐rhodamine, is reported here. White emission is obtained upon excitation of the biophosphor at 365 nm with appropriate mole ratios of the above dyes. The CIE 1931 chromaticity coordinates of white emission with 365 nm excitation are (0.36, 0.37), and the correlated color temperature is 5300 K. Multifunctional nature of the biophosphor is also demonstrated. A UV‐light‐emitting‐diode (361 nm) coated with this biophosphor, for example, indicates white emission (CIE 0.28, 0.31) with a half‐life of 106 (±5) h. The white emission is also highly sensitive to pH over a broad range (pH 1–11). Incorporation of glucose oxidase and peroxidase in the biophosphor allows for the detection of glucose over a physiologically relevant range of 1.8–288 mg dL^?1. This is a unique, advanced biophosphor with LED and sensing applications, and it is the first example of a multifunctional, proteinaceous white emitter.     

Catalytic activity of copper(II)complexes of immobilized ‘polystyrene-bound 4-(N,N-dimethylamino)pyridine’ for the oxidative coupling of 2,6-disubstituted phenols

‘Polystyrene-bound 4-(N,N-dimethylamino)pyridine’-copper (PS-DMAP-Cu(ii)) catalysts for the oxidation of 2,6-disubstituted phenols were immobilized by grafting or by partial adsorption on silica and by crosslinking with 2% divinylbenzene. The most active immobilized catalyst is the most flexible, i.e. the grafted one, which however is still six times less active than unbound linear PS-DMAP-Cu(II). The less extended conformation of the adsorbed polymeric catalyst exhibits a significantly lower activity. For the crosslinked catalyst, indications were obtained that diffusional limitations occur. Application of all three types of immobilized PS-DMAP based catalysts in a continuous stirred tank (CST) reactor was unsuccessful. The phenol conversion drastically decreased in time. This loss of activity could be explained by the destructive effect of water: interaction of reaction water with the very basic DMAP ligands may result in the production of an excess of hydroxide which, according to our earlier work, deactivates the catalyst. A catalyst based on the less basic poly(styrene-co-4-vinylpyridine) adsorbed onto silica exhibited an invariable phenol conversion in the CST reactor for at least 230 h.     

Association of stereoregular poly(methyl methacrylates): 2. Formation of stereocomplex in bulk

Blends of isotactic and syndiotactic poly(methyl methacrylate) (i- and s-PMMA) are obtained by precipitation from chloroform and acetone solutions. By differential scanning calorimetry and dynamicmechanical measurements the formation of stereocomplexes from i- and s-PMMA in bulk is demonstrated. After annealing of the blends at 130–160°C a melting endotherm is detected and it is established by X-ray analysis that this endotherm is caused by formation of crystalline stereocomplex. The rate of complex formation is maximal at 140°C and the extent of complex formation is maximal at an isotactic-rich composition. It appears that the difference in solvent history can be removed by heating to 240°C. The subsequent S-shaped course of glass transition temperature, T_g, with composition is explained by the occurrence of some complex formation during cooling from 240°C. Asymmetry and shift of the dynamic-mechanical damping curves after annealing are also explained by the formation of complexes. A mechanism is proposed with helical isotactic chains acting as nuclei for a fringed micelle type of complex formation.     

Crystallization and melt behaviour of isotactic poly(2-vinylpyridine)

The crystallization and melting behaviour of highly isotactic poly(2-vinylpyridine) (it-P2VP) with $\text{M}\text{?}{}_{\mathrm{<mtext>v</mtext>}}\text{= 4 × 10}{}^5$ has been studied by microscopy and d.s.c.. The maximum spherulitic growth rate was found to be 250 × 10^?3μm/min at a crystallization temperature T_c of 165°C. Experimental data could be described by the growth rate theory for small supercooling, by taking the appropriate value of 75 for the constant c₂ of the WLF equation. The chain-folded surface free energy σ_e, was estimated at 39.5 × 10^?3 J m^?2. The melting curves showed 1,2 or 3 melting endotherms. At large supercooling, crystallization from the melt produced a small melting endotherm just above T_c. This peak may originate from secondary crystallization of melt trapped within the spherulites. The next melting endotherm is related to the normal primary crystallization process. Its peak temperature increased linearly with T_c, yielding an extrapolated value for the equilibrium melting temperature T°_m of 212.5°C. At the normal values of T_c and heating rate a third endotherm appeared with a peak temperature that was independent of T_c, but rose with decreasing heating rate. From the effects of heating rate and partial scanning on the ratio of peak areas, it is concluded that this peak arises from secondary crystallization by continuous melting and recrystallization during the scan. This crystallization and melting behaviour of it-P2VP is very similar to that of isotactic polystyrene.     

White‐Emitting Protein Nanoparticles for Cell‐Entry and pH Sensing

Facile synthesis of white‐emitting, protein‐based, metal‐free, stable, nontoxic, and pH sensitive, advanced functional nanoparticles (GlowDots), as alternatives to quantum dots, is reported here. Controlled cross‐linking of bovine serum albumin resulted in facile formation of spherical nanoparticles of 35 nm in diameter with a sharp size distribution (±10 nm), which were then conjugated with specific dyes to produce white‐emitting particles with tunable excitation wavelengths. Chemical novelty is that the particle size, size distribution, stability, surface chemistry, and emission properties are under full chemical control where the size and absorption/emission properties are independently tuned. Up to 100 dye molecules were attached to each particle, on an average, and hence, particles acquired strong absorption cross‐sections as well as high brightness. White fluorescence of GlowDots is strongly sensitive to pH over a range of pH 2–11, and pH‐induced emission changes are fully reversible. The particles readily entered HeLa cells and emission color depended on particle location in the live cells, which is most likely due to the local environment surrounding the particles. These are the very first reports of white‐emitting advanced functional nanoparticles that are biodegradable, sensitive to pH, and amenable for live cell imaging to probe the subcellular compartments.     

Dye doped sulphamic acid crystals: a potential material for optoelectronic applications

Journal of Materials Science: Materials in Electronics - This is the first study to look at how organic dyes Reactive Orange 16 (RO 16) and Safranin affects the optical and thermal characteristics...     

Enzyme-inorganic nanoporous materials: Stabilization of proteins intercalated in α-zirconium(IV) phosphate by a denaturant

Improving the stability of proteins and enzymes at solid–liquid interfaces is challenging and it has important implications in biocatalysis and biosensors. Here, we report that moderate concentrations of urea stabilize heme proteins, such as met-hemoglobin (Hb) or met-myoglobin (Mb) bound to α-zirconium phosphate (α-ZrP). The half-life of Hb intercalated in the galleries of α-ZrP, for example, increased from 127 h (no urea) to >235 h (2 M urea). The peroxidase-like activity of Hb intercalated in α-ZrP was also improved by the addition of urea, and the product yields increased from 44% (no urea) to 79% (2 M urea). These improvements are not limited to Hb, and similar results also observed with Mb. Urea also inhibited the dithionite reduction of the ferric form of the intercalated heme proteins to their corresponding ferrous forms but not the oxidation of the ferric form to the corresponding high valent iron-oxo species. These observations open new possibilities to control the properties of immobilized proteins.     

Pulsating hydromagnetic flow of Casson fluid in a vertical channel filled with non-Darcian porous medium

This paper analyzes the Joule heating, Dufour number, and Soret number effects on hydromagnetic pulsatile flow of a Casson fluid in a vertical channel filled with a non-Darcian porous medium. The governing partial differential equations (PDEs) of the Casson fluid flow are transformed to ordinary differential equations (ODEs) using perturbation technique and solved by employing shooting method with Runge–Kutta (R–K) fourth-order technique using MATHEMATICA function NDSolve. The influence of Forchheimer number, Casson fluid parameter, Dufour number, radiation parameter, and Soret number on flow variables has been studied and the numerical results obtained are presented. The results reveal that the velocity rises with the rise of Darcy number, whereas it decreases for a given rise in the Forchheimer number. Furthermore, the temperature distribution enhances by increasing the Dufour number.     

Performance evaluation of fuel cell fed electric vehicle system with reconfigured quadratic boost converter

The performance evaluation of 1.26 kW fuel cell fed electric vehicle system with reconfigured Quadratic Boost Converter along with the neural network based maximum power point tracking algorithm is presented in this paper. The acceptance of EV in modern society is relevant for the creation of pollution free environment. The main reason for creation of excessive pollution is transportation by the mode of roadways, with the own internal combustion engines by using crude oil as primary energy source. In this paper, a 1.26 kW Proton Exchange Membrane Fuel Cell (PEMFC) fed electric vehicle is designed in MATLAB/Simulink environment. To integrate PEMFC to brushless DC (BLDC) motor are configured Quadratic Boost Converter is designed for high static converter voltage gain. The performance of the proposed EV system is analysed with perturb and observer method and neural network based MPPT control techniques and obtained results are compared at different fuel cell input temperature conditions with respect to different time periods.