Modulation of amyloid-β aggregation by metal complexes with a dual binding mode and their delivery across the blood–brain barrier using focused ultrasound

One of the key hallmarks of Alzheimer''s disease is the aggregation of the amyloid-β peptide to form fibrils. Consequently, there has been great interest in studying molecules that can disrupt amyloid-β aggregation. While a handful of molecules have been shown to inhibit amyloid-β aggregation in vitro, there remains a lack of in vivo data reported due to their inability to cross the blood–brain barrier. Here, we investigate a series of new metal complexes for their ability to inhibit amyloid-β aggregation in vitro. We demonstrate that octahedral cobalt complexes with polyaromatic ligands have high inhibitory activity thanks to their dual binding mode involving π–π stacking and metal coordination to amyloid-β (confirmed via a range of spectroscopic and biophysical techniques). In addition to their high activity, these complexes are not cytotoxic to human neuroblastoma cells. Finally, we report for the first time that these metal complexes can be safely delivered across the blood–brain barrier to specific locations in the brains of mice using focused ultrasound.

We report a series of non-toxic cobalt(iii) complexes which inhibit Aβ peptide aggregation in vitro; these complexes can be safely delivered across the blood–brain barrier in mice using focused ultrasound.     

A multiresidual method based on ion-exchange chromatography with conductivity detection for the determination of biogenic amines in food and beverages

In the present work a sensitive and accurate method by ion chromatography and conductimetric detection has been developed for the determination of biogenic amines in food samples at microgram per kilogram levels. The optimized extraction procedure of trimethylamine, triethylamine, putrescine, cadaverine, histamine, agmatine, spermidine, and spermine from real samples, as well as the separation conditions based on a multilinear gradient elution with methanesulfonic acid and the use of a weak ionic exchange column, have provided excellent results in terms of resolution and separation efficiency. Extended calibration curves (up to 200 mg/kg, r?>?0.9995) were obtained for all the analyzed compounds. The method gave detection limits in the range 23–65 μg/kg and quantification limits in spiked blank real samples in the range 65–198 μg/kg. Recovery values ranged from 82 to 103 %, and for all amines, a good repeatability was obtained with precision levels in the range 0.03–0.32 % (n?=?4). The feasibility and potential of the method were tested by the analysis of real samples, such as tinned tuna fish, anchovies, cheese, wine, olives, and salami.

Determination of the amino acid tryptophan and the biogenic amine tryptamine in foods by the heavy atom induced-room temperature phosphorescence methodology

Very simple and selective methods are presented to determine the amino acid tryptophan (Trp) and the biogenic amine tryptamine (Tryp), both compounds with an indole-type molecular structure by the methodology named Heavy Atom Induced-Room Temperature Phosphorescence (HAI-RTP) which constitutes the first time that HAI-RTP has been used to detect compounds with non-naphthalenic structures in their molecules. Different variables affecting the phosphorescence signal (heavy atom perturber and sodium sulfite concentration) were carefully studied. The analytical curves give a linear dynamic range of 15-100 ng ml(-1) and a detection limit of 4 ng ml(-1) for Trp and 94-400 ng ml(-1) and 28 ng ml(-1) for Tryp. The methods have been successfully applied to the analysis of complex food matrices such as the presence of tryptophan in yoghurt and tryptamine in bottled beer. A single alkaline hydrolysis to release Trp from yoghurt proteins and two methods for extracting Tryp from beer samples are proposed and optimised. A total Trp content of 374 mg of Trp per kg of yoghurt was quantified by the standard addition method of calibration and a recovery of 90% was obtained for 250 ng ml(-1) of Tryp in spiked non-alcoholic beer samples.     

Collection of selected reaction monitoring and full scan data on a time scale suitable for target compound quantitative analysis by liquid chromatography/tandem mass spectrometry

A hybrid linear ion trap/triple quadrupole mass spectrometer was used to demonstrate the value of collecting full scan qualitative data during quantitative analysis of target compounds. We present examples of the additional information that can be obtained from plasma samples analyzed primarily for target compound concentrations. This information includes detection of circulating metabolites, dosing vehicle, interfering matrix components, and potential interfering drug conjugates. Additionally, the quantitative results from selected reaction monitoring (SRM) analysis and from combined full scan and SRM analysis (SRM/EMS) were compared. The quantitative data in both scan modes are acceptable in terms of sensitivity, accuracy and precision. One can conclude from this work that the hybrid linear ion trap/triple quadrupole mass analyzer can provide in a single analysis both useful qualitative data, and accurate and precise quantitative data from the samples routinely prepared and analyzed for target drug concentrations.     

Short stereocontrolled synthesis of trans and cis-tetrahydro-pyrazinoisoquinolinediones

Addition of aldehyde dimethyl acetals (here acetaldehyde) to unisolated O-trimethylsilyl derivatives of 1-acetyl-3-arylmethylpiperazine-2,5-diones (here 2,5-dimethoxyphenyl), in the presence of TMSOTf as the catalyst, gave nearly quantitatively the corresponding N-methoxyalkyl derivatives which, under acidic treatment, gave in very good yield through a Pictet-Spengler-type reaction involving N-acyliminium cations (6S*,11aR*)-2-acetyl-6-alkyl-3,6,11,11a-tetrahydro-2H-pyrazino[1,2-b]isoquinoline-1,4-diones. Epimerization of the 11a-stereocentre was accomplished by radical bromination, spontaneous hydrobromide elimination and catalytic hydrogenation, to give the (6S*,11aS*)-isomers. We propose these compounds as precursors of tetrahydroisoquinoline antitumour antibiotics.     

Planar Chromatographic and Electrophoretic Study of Thermally Induced Conformational Modifications of Protein Structure

JPC – Journal of Planar Chromatography – Modern TLC -     

On the generation of novel anticancer drugs by recombinant DNA technology: the use of combinatorial biosynthesis to produce novel drugs

Chemotherapeutic drugs for cancer treatment have been traditionally originated by the isolation of natural products from different environmental niches, by chemical synthesis or by a combination of both approaches thus generating semisynthetic drugs. In the last years, a number of gene clusters from several antitumor biosynthetic pathways, mainly produced by actinomycetes and belonging to the polyketides family, are being characterized. Genetic manipulation of these antitumor biosynthetic pathways will offer in the near future an alternative for the generation of novel antitumor derivatives and thus complementing current methods for obtaining novel anticancer drugs. Novel antitumor derivatives have been produced by targetted gene disruption and heterologous expression of single (or a few) gene(s) in another hosts or by combining genes from different, but structurally related, biosynthetic pathways ("combinatorial biosynthesis"). These strategies take advantage from the "relaxed substrate specificity" that characterize secondary metabolism enzymes.     

Investigation of thermal stability, spectral, magnetic, and antimicrobial behavior for new complexes of Ni(II), Cu(II), and Zn(II) with a bismacrocyclic ligand

Novel complexes of type M₂LCl₄·nH₂O (M: Ni, n = 4; M: Cu, n = 2.5 and M: Zn, n = 1.5; L: ligand resulted from 1,3-phenylenediamine, 3,6-diazaoctane-1,8-diamine, and formaldehyde one-pot condensation) were synthesized and characterized. The ligand was also isolated and characterized. The complexes features have been assigned from microanalytical, electrospray ionization tandem mass spectrometry, IR, UV–vis, ¹H NMR, and EPR spectra as well as magnetic data at room temperature. Simultaneous thermogravimetric/dynamic scanning calorimetry/evolved gas analysis measurements were performed to evidence the nature of the gaseous products formed in each step. Processes as water elimination, fragmentation, and oxidative degradation of the organic ligand as well as chloride elimination were observed during the thermal decomposition. The final product of decomposition was metal(II) oxide except for copper complex where CuCl remained also in the oxide network. The complexes exhibited an improved antibacterial activity in comparison with the ligand concerning both planktonic as well as biofilm-embedded cells.