Effects of fungal laccase immobilization procedures for the development of a biosensor for phenol compounds

Fungal laccase was immobilized on carbon-fiber electrodes using classical methods: physical adsorption, glutaraldehyde, carbodiimide and carbodiimide/glutaraldehyde. The highest biosensor response was obtained using carbodiimide/glutaraldehyde for coupling laccase to carboxyl groups on the carbon fibers. In this method, different percentages of glutaraldehyde had important effects on the sensitivity of the biosensor, the best percentage of glutaraldehyde being 10% (m/v). The behavior of the obtained biosensor was investigated in terms of sensitivity, operational range, pH and applied potential. The developed biosensor showed an optimum response at pH 5.0 and at an applied potential of -100 mV. The immobilized laccase retained a good activity for over 2 months.     

Uniqueness for the harmonic map flow from surfaces to general targets

LetM be a two-dimensional compact Riemannian manifold with smooth (possibly empty) boundary,N an arbitrary compact manifold. Ifu andv are weak solutions of the harmonic map flow inH ¹(Mx[0,T]; N) whose energy is non-increasing in time and having the same initial datau ₀∈H¹(M, N) (and same boundary values if ?M≠Ø) thenu=v. Combined with a result of M. Struwe, this shows any suchu is smooth in the complement of a finite subset ofM×(0,T)c.     

Reaction of 5α, and 5β,3-keto-steroids with potassium superoxide

A regiospecific behaviour is observed in the reaction of 5α and 5β-keto-steroids with potassium superoxide; so the 5α- cholestan-3-one (I) gave the lactol II and the 3-keto-smilagenin (VII) gave the keto-acid VIIIa and a small amount of the diacid IXa. The 3-keto-dihydrolanosterol (V) afforded the lactol VI.     

On the use of ligand field parameters in the study of coordinated water molecules in Eu3+ complexes

A new methodology is proposed by which the number of coordinated water molecules, n, can be estimated in Eu(3+) complexes. It is based on a comparison between the theoretical and experimental Stark levels, the former being calculated by assuming that n varies from 0 to 4 and predicting the so-called ligand field parameters, . The methodology, initially developed in the study of the Eu(pya)(3).nH(2)O complex, has been applied successfully to beta-diketonate complexes of Eu(3+), for which crystallographic and luminescence data are available.     

Synthesis, modeling of the structure and kinetic study of the thermal decomposition of La(III) and Nd(III) complexes with 3-hydroxypicolinic acid

Synthesis, spectroscopic studies, prediction of the structure and thermal decomposition of the La(3-OHpic)₃ · 3H₂O and Nd(3-OHpic)₃ · 3H₂O (3-OHpic = 3-hydroxypicolinic acid) complexes are described. Elemental analysis and the IR vibrational data are consistent with the complex formulae. The absorption spectra in ethanol of the La(3-OHpic)₃ · 3H₂O and Nd(3-OHpic)₃ · 3H₂O show maximum absorptions at 214 and 211 nm, respectively, which are shifted to 225 nm in the free ligand. The ab initio method RHF/STO-3G/ECP(MWB52) was used to optimize the geometry and the INDO/S-CI model for calculating the electronic spectra of these complexes. A good agreement between theoretical and experimental UV absorption spectra has been obtained. The thermal decomposition was studied by non-isothermal thermogravimetry. Thermal decomposition reactions of the complexes La(3-OHpic)₃ · 3H₂O and Nd(3-OHpic)₃ · 3H₂O are best described by R2 and R3 kinetic models.     

Palladium-catalyzed C–H alkenylation of quinoxaline N-oxide enabled by a mono-N-protected amino acid

The efficient alkenylation of quinoxaline N-oxide was achieved via Pd-catalyzed C–H activation, using the assistance of a mono-N-protected amino acid. Further deoxygenation of the 2-styrylquinoxaline-N-oxides yielded the corresponding styrylquinoxaline derivatives.     

AM1 Sparkle modeling of Er(III) and Ce(III) coordination compounds

The recently defined Sparkle/AM1 model is now extended to Er(III) and Ce(III), using the same parameterization scheme. Thus, a set of fifteen complexes for each lanthanide ion, with various representative ligands of high crystallographic quality (R factor < 0.05 Å), and which possess oxygen and/or nitrogen as coordinating atoms, was used as the training set. In the validation procedure we used a set of twenty-two more complex structures for the Ce(III) ion and twenty-four more for the Er(III) ion, all of high crystallographic quality. For the thirty-seven cerium(III) complexes and thirty-nine erbium(III) complexes considered, the Sparkle/AM1 unsigned mean error, for all interatomic distances between the Ln(III) ion and the ligand atoms of the first sphere of coordination, is 0.08 and 0.06 Å, a level of accuracy comparable to present day ab initio/ECP geometries, while being hundreds of times faster. The Sparkle/AM1 model may thus prove useful for luminescent complex design.     

Dimensional crossover and finite-size scaling belowT c

Using the formalism developed in earlier work, dimensional crossover on ad-dimensional layered Ising-type system satisfying periodic boundary conditions and of sizeL is considered belowT _c (L), T _c (L) being the critical temperature of the finite-size system. Effective critical exponents _eff and _eff are shown explicitly to crossover between theird- and (d–1)-dimensional values for _L in the limitsL/ _L andL/ _L 0, respectively, _L , being the correlation length in the layers. Using anL-dependent renormalization group, the effective exponents are shown to satisfy natural generalizations of the standard scaling laws. In addition,L-dependent global scaling fields which span the entire crossover are defined and a scaling form of the equation of state in terms of them derived. All the above assertions are verified explicitly to one loop in perturbation theory, in particular effective exponents and a universal crossover equation of state are obtained and shown in the above asymptotic limits to be in good agreement with known results.