Comparison of UV derivative-spectrophotometry and partial least-squares (PLS-1) calibration for determination of methotrexate and leucovorin in biological fluids

Binary mixtures of methotrexate (MTX) and leucovorin (LV) have been resolved by application of first-derivative spectrophotometry and partial least squares calibration (PLS-1). By measuring the first-derivative signals of MTX and LV at 354 and 300 nm, respectively, simultaneous determination was possible. The mean recoveries for urine samples were 91 and 96% for MTX and LV, respectively. Partial least squares (PLS-1) multivariate calibration has been applied to the determination of these compounds in serum and in urine without pretreatment of the samples. The absorption spectra of serum or urine samples spiked with methotrexate and/or leucovorin, were used to optimize the calibration matrixes by the PLS-1 method. The sensitivity and selectivity of the proposed procedures were calculated. Mean recoveries were 101 and 97% for MTX and LV, respectively, for serum samples, and 101 and 98% for MTX and LV, respectively, for urine samples.     

Kinetic-fluorimetric determination of cerium with 1-amino-4-hydroxyanthraquinone

A simple, sensitive, and selective method for the kinetic—fluorimetric determination of cerium (0.1–0.9 ppm), based on the oxidative reaction between cerium(IV) and 1-amino-4-hydroxyanthraquinone, has been developed. The reaction is followed by the measurement of the rate of appearance of yellow fluorescence (λ_ex = 480 nm, λ_em = 575 nm). About 20 cations and anions show negligible interference effects, even when present in large amounts. Only V(V) interferes at similar concentrations to those of Ce(IV) to be determined.     

Extractive-spectrophotometric determination of molybdenum as an ion-association complex with thiocyanate and adogen

A selective and sensitive method is described for the determination of trace amounts of molybdenum, based on its reaction with thiocyanate and its extraction (into toluene) as an ion-association complex formed with adogen (methyltrioctylammonium chloride). The molar absorptivity is 2.13 x 10(4) l.mole(-1).cm(-1) at lambda(max) 467 nm. The method has been applied to molybdenum determination in steels.     

Kinetic spectrophotometric determination of nanogram levels of manganese by use of the salicylaldehyde guanylhydrazone-hydrogen peroxide system

A kinetic method is described for determining trace amounts of manganese(II), based on its catalytic effect on the oxidation of salicylaldehyde guanylhydrazone by hydrogen peroxide. The reaction is followed spectrophotometrically by measuring the rate of change of absorbance at 505 nm. The calibration graph is linear in the range 8-80 mug/l. with a relative error of +/- 1%. The method has been applied to the determination of manganese in various samples.     

The application of homotopy analysis method to solve nonlinear differential equation governing Jeffery–Hamel flow

In this paper Jeffery–Hamel flow has been studied and its nonlinear ordinary differential equation has been solved through homotopy analysis method (HAM). The obtained solution in comparison with the numerical ones represents a remarkable accuracy. The results also indicate that HAM can provide us with a convenient way to control and adjust the convergence region.     

Metamagnetic model in a field of arbitrary direction

The free energy of a metamagnetic model, in a magnetic field making an angle θ with the direction of uniaxial anisotropy, is calculated in the context of the mean-field approximation. The tricritical temperature decreases as θ increases, and finally vanishes for θ larger than a certain critical angle. In the (H_∥, H_⊥, T) space there is a line of tricritical points which separates two smoothly joining surfaces of first and of second order phase transitions.     

Neuromodulation by soy diets or equol: Anti-depressive &; anti-obesity-like influences,age- &; hormone-dependent effects

Background  

Soy-derived isoflavones potentially protect against obesity and depression. In five different studies we examined the influence of soy-containing diets or equol injections on depression, serotonin levels, body weight gain (BW) and white adipose tissue (WAT) deposition in female Long-Evans rats at various stages of life [rats were intact, ovariectomized or experienced natural ovarian failure (NOF)].     

Molecular [(fe(3))-(fe(3))] and [(fe(4))-(fe(4))] coordination cluster pairs as single or composite arrays

The synthesis of molecular cluster pairs is a challenge for coordination chemists due to the potential applications of these species in molecular spintronics or quantum computing. The ligand H(4)L, 1,3-bis-(3-oxo-3-(2-hydroxyphenyl)-propionyl)-2-methoxybenzene, has been successfully used to obtain a series of such complexes using the basic Fe(III) trinuclear carboxylates as starting materials. Synthetic control has allowed the isolation of the two molecular cluster pairs that form the composite [Fe(4)O(2)(PhCO(2))(6)(H(2)L)(pz)](2)[Fe(3)O(PhCO(2))(5)(py)(H(2)L)](2) (1). The dimers of trinuclear units, [Fe(3)O(PhCO(2))(5)(H(2)O)(H(2)L)](2) (2) and [Fe(3)O(o-MePhCO(2))(5)(H(2)L)(py)](2) (3), and the dimers of tetranuclear units, [Fe(4)O(2)(PhCO(2))(6)(H(2)L)(pz)](2) (4) and [Fe(4)O(2)(o-MePhCO(2))(6)(H(2)L)(pz)](2) (5), are presented here. The magnetic properties of the reported aggregates show that they are pairs of semi-independent clusters weakly interacting magnetically as required for two-qubit quantum gates.     

Polarography and artificial neural network for the simultaneous determination of nalidixic acid and its main metabolite (7-hydroxymethylnalidixic acid)

Nalidixic acid (NA) and its main metabolite, 7-hydroxymethylnalidixic acid (OH-NA), are simultaneously determined by applying artificial neural networks (ANNs), to their square wave voltammetric signals. The scores of a PCR model, built with the voltammetric data of a set of standard samples, recorded between −0.70 and −1.0 V, are used as training set for the net for each compound. The trained nets (ANNs) are used for the simultaneous determination of NA and OH-NA in urine. The recovery values are comprised between 91 and 109% for NA and between 82 and 112% for OH-NA, being these results better than the results obtained by application of partial least squares (PLS) multivariate calibration.     

Inhibition of cyclin-dependent kinases, GSK-3beta and CK1 by hymenialdisine, a marine sponge constituent

BACKGROUND: Over 2000 protein kinases regulate cellular functions. Screening for inhibitors of some of these kinases has already yielded some potent and selective compounds with promising potential for the treatment of human diseases. RESULTS: The marine sponge constituent hymenialdisine is a potent inhibitor of cyclin-dependent kinases, glycogen synthase kinase-3beta and casein kinase 1. Hymenialdisine competes with ATP for binding to these kinases. A CDK2-hymenialdisine complex crystal structure shows that three hydrogen bonds link hymenialdisine to the Glu81 and Leu83 residues of CDK2, as observed with other inhibitors. Hymenialdisine inhibits CDK5/p35 in vivo as demonstrated by the lack of phosphorylation/down-regulation of Pak1 kinase in E18 rat cortical neurons, and also inhibits GSK-3 in vivo as shown by the inhibition of MAP-1B phosphorylation. Hymenialdisine also blocks the in vivo phosphorylation of the microtubule-binding protein tau at sites that are hyperphosphorylated by GSK-3 and CDK5/p35 in Alzheimer's disease (cross-reacting with Alzheimer's-specific AT100 antibodies). CONCLUSIONS: The natural product hymenialdisine is a new kinase inhibitor with promising potential applications for treating neurodegenerative disorders.