Improved survival of cardiac cells on surface modified electrospun nanofibers

Polycaprolactone (PCL) is a popular synthetic polymer used in the field of cardiac tissue engineering (CTE) due to its non-toxic degraded by products and low cost manufacturing method. However, hydrophobic nature of this material limits its wide spread application in different cell interaction processes. Therefore, current study aims to chemically modify PCL made random and aligned nanofibers with collagen coating mimicking the oriented matrix of the cardiac cells. Morphological and chemical properties of the electrospun PCL nanofibers were evaluated by SEM, FTIR, XRD and water contact angle measurement. Results indicated that the anisotropic characteristics of aligned nanofibers promoted cell attachment and alignment, which closely match the requirements of native cardiac cells. Thus, aligned nanofibers could be preferred for cardiac tissue regeneration and defects over random nanofibers.     

Enantioselective Copper‐Catalyzed Quinoline Alkynylation

A highly enantioselective copper‐catalyzed alkynylation of quinolinium salts is reported. The reaction employs StackPhos, a newly developed imidazole‐based chiral biaryl P,N ligand, and copper bromide to effect a three‐component reaction between a quinoline, a terminal alkyne, and ethyl chloroformate. Under the reaction conditions, the desired products are delivered in high yields with ee values of up to 98 %. The transformation tolerates a wide range of functional groups with respect to both the alkyne and the quinoline starting materials and the products are easily transformed into useful synthons. Efficient, enantioselective syntheses of the tetrahydroquinoline alkaloids (+)‐galipinine, (+)‐angustureine, and (?)‐cuspareine are reported.     

Enantioselective Total Synthesis of (−)‐Martinellic Acid

An enantioselective total synthesis of martinellic acid is described. The pyrroloquinoline alkaloid core is efficiently prepared from a quinoline, employing a method which relies on a newly developed Cu‐catalyzed enantioselective alkynylation using the chiral imidazole‐based biaryl P,N ligand StackPhos to establish the absolute stereochemistry. The remaining carbon atoms are then installed by means of a diastereoselective Pd‐catalyzed decarboxylative allylation and the synthesis is completed after straightforward functional‐group manipulation. This new synthetic method enables the most concise enantioselective synthesis of this important class of molecules to date.     

Lanthanide-ion-assisted structural collapse of layered GaOOH lattice

GaOOH nanorods were prepared by hydrolysis of Ga(NO(3))(3)·xH(2)O by urea at ~100 °C in the presence of different amounts of lanthanide ions like Eu(3+), Tb(3+), and Dy(3+). On the basis of X-ray diffraction and vibrational studies, it is confirmed that layered structure of GaOOH collapses even when very small amounts of lanthanide ions (1 atom % and more) are present in the reaction medium during the synthesis of GaOOH nanorods. The incorporation of lanthanide ions at the interlayer spacing of the GaOOH lattice, followed by its reaction with OH groups that connect the layers containing edge-shared GaO(6) in GaOOH, is the reason for the collapse of the layered structure and associated amorphization. This leads to the formation of finely mixed hydroxides of lanthanide and gallium ions. These results are further confirmed by steady-state luminescence and excited-state lifetime measurements carried out on the samples. The morphology of the nanorods is maintained upon heat treatment at high temperatures like 500 and 900 °C, and during this process, the finely mixed lanthanide and gallium hydroxides facilitate diffusion of lanthanide ions into the Ga(2)O(3) lattice, as revealed by the existence of strong energy transfer with an efficiency of more than 90% between the host and lanthanide ions.     

Single-Step Purification and Characterization of Recombinant Aspartase of Aeromonas media NFB-5

Aspartase (L-aspartate ammonia-lyase; EC 4.3.1.1) catalyzes the reversible amination of fumaric acid to produce L-aspartic acid. Aspartase coding gene (aspA) of Aeromonas media NFB-5 was cloned, sequenced, and expressed with His tag using pET-21b(+) expression vector in Escherichia coli BL21. Higher expression was obtained with IPTG (1.5?mM) induction for 5?h at 37?°C in LB medium supplemented with 0.3% K₂HPO₄ and 0.3% KH₂PO₄. Recombinant His tagged aspartase was purified using Ni?CNTA affinity chromatography and characterized for various biochemical and kinetic parameters. The purified aspartase showed optimal activity at pH?8.5 and 8.0 in the presence and absence of magnesium ions, respectively. The optimum temperature was determined to be 35?°C. The enzyme showed apparent K _m and V _max values for L-aspartate as 2.01?mM and 114?U/mg, respectively. The enzyme was stable in pH range of 6.5?C9.5 and temperature up to 45?°C. Divalent metal ion requirement of enzyme was efficiently fulfilled by Mg²⁺, Mn²⁺, and Ca²⁺ ions. The cloned gene (aspA) product showed molecular weight of approximately 51?kDa by SDS-PAGE, which is in agreement with the molecular weight calculated from putative amino acid sequence. This is the first report on expression and characterization of recombinant aspartase from A. media.     

Mechanically Robust,Electrically Conductive Biocomposite Films Using Antimicrobial Chitosan‐Functionalized Graphenes

An effective way of covalently functionalizing graphene with a chitosan polymer via a nitrene chemistry is demonstrated. The biofunctionalized graphene is prepared by the chemical reduction of graphene oxide using a nitrene chemistry, and then covalently grafting chitosan to the graphene surface. The effectiveness of the biofunctionalized graphene as a reinforcing filler (4 wt%) in a chitosan polymer matrix is verified by the dramatic enhancement of the mechanical properties (breaking stress = 330%, Young's modulus = 243%) and the electrical conductivity (0.3 S m^?1) without much loss in the elongation‐at‐break. The reinforcing effect can be explained by both the homogeneous dispersion of graphene within the matrix and the strong bond arising from the intrinsically intimate contact between the graphene and the matrix. The high antimicrobial activity of the biofunctionalized graphene compared with graphene oxide and chemically reduced graphene may be because of the presence of chitosan polymer on the edges of the graphene. The strong, antimicrobial graphene‐filled composite film can be used for food packaging and for coating various biomedical devices, where bacterial surface colonization is undesirable.     

Orientational disorder and geometrical isomeric effect on nonlinear optical properties of poly bis(glycine)cadmium chloride

Poly bis(glycine)cadmium chloride (BGCC) crystals of both undoped and doped with thiourea (Tu) were grown from saturated solutions by a slow evaporation technique. The geometrical isomerism of the octahedral BGCC molecule is investigated using single crystal XRD, powder XRD and FT-IR. The significant difference between the two isomers namely facial (fac) and meridional (mer), is explained in terms of the different point group symmetries of C₃ and C₁, respectively. The loss of point group symmetry from C₃ to C₁ is attributed for the observed powder second-harmonic generation (SHG). Semi-empirical calculations from the optimized geometrical parameters also supported non-linear optical properties of the material.     

Parameter-robust numerical method for a system of singularly perturbed initial value problems

In this work we study a system of M( ≥ 2) first-order singularly perturbed ordinary differential equations with given initial conditions. The leading term of each equation is multiplied by a distinct small positive parameter, which induces overlapping layers. A maximum principle does not, in general, hold for this system. It is discretized using backward Euler difference scheme for which a general convergence result is derived that allows to establish nodal convergence of O(N ^− 1ln N) on the Shishkin mesh and O(N ^− 1) on the Bakhvalov mesh, where N is the number of mesh intervals and the convergence is robust in all of the parameters. Numerical experiments are performed to support the theoretical results.     

High order robust approximations for singularly perturbed semilinear systems

In this paper, a system of M (?2) singularly perturbed semilinear reaction–diffusion equations is considered. To obtain a high order approximation to the solution of this system, we propose a hybrid numerical method that employs a generalized Shishkin mesh with the Numerov discretization in the boundary layer regions and either a non-equidistant generalization of the Numerov discretization or classical central differences in the outer region. It is proved that the method is almost fourth order convergent in the maximum norm uniformly with respect to the perturbation parameter. Numerical experiments support the theoretical results and demonstrate the effectiveness of the method.