A method for calibration and validation subset partitioning

This paper proposes a new method to divide a pool of samples into calibration and validation subsets for multivariate modelling. The proposed method is of value for analytical applications involving complex matrices, in which the composition variability of real samples cannot be easily reproduced by optimized experimental designs. A stepwise procedure is employed to select samples according to their differences in both x (instrumental responses) and y (predicted parameter) spaces. The proposed technique is illustrated in a case study involving the prediction of three quality parameters (specific mass and distillation temperatures at which 10 and 90% of the sample has evaporated) of diesel by NIR spectrometry and PLS modelling. For comparison, PLS models are also constructed by full cross-validation, as well as by using the Kennard-Stone and random sampling methods for calibration and validation subset partitioning. The obtained models are compared in terms of prediction performance by employing an independent set of samples not used for calibration or validation. The results of F-tests at 95% confidence level reveal that the proposed technique may be an advantageous alternative to the other three strategies.     

Development of the analytical methods and reference materials program for dietary supplements at the National Institutes of Health

The need for validated analytical methods and reference materials to identify and measure constituents in dietary supplements is essential. Such methods allow for the documentation that products meet manufacturer's specifications and contain what their labels declare. In March 2003, the U.S. Food and Drug Administration issued a proposed rule that would establish specific current good manufacturing practices for dietary supplements. This proposed rule requires that companies create a quality control unit to set specifications and ensure compliance with these specifications using scientifically valid procedures. This report provides insights and lessons learned from 3 meetings the Office of Dietary Supplements (ODS) at the National Institutes of Health helped organize. These meetings were structured to (1) educate individuals about the importance and need for validated analytical methods and reference materials to identify and quantify constituents of dietary supplements; (2) identify resources required to fulfill this need; and (3) serve as a platform to obtain input from interested parties to help frame the research agenda for the Dietary Supplements Methods and Reference Materials Program within ODS. Stakeholder's opinions and views expressed at these 3 meetings are outlined in this report.     

The dynamics of gallamine: A potent neuromuscular blocker. A determination by quantum mechanics and molecular dynamics (i) in vacuo studies

The potent neuromuscular blocker, gallamine, possesses three chemically equivalent, flexible side chains, the motion of which has been proposed as important in its mode of action on the acetylcholine receptor in vivo. The flexibility of the side chains has been investigated in the present initial study by a combination of quantum mechanics and molecular dynamics on the isolated, unsolvated molecule. Net atomic charges for the gallamine molecule have been calculated using the semiempirical program MOPAC for use in the molecular dynamics simulation. The flexibility of the side chains has been shown to correlate with the range of fluctuations in torsion angles observed in the crystal structure of gallamine.     

Spectra of semi-regular polytopes

We compute the spectra of the adjacency matrices of the semi-regular polytopes. A few different techniques are employed: the most sophisticated, which relates the 1-skeleton of the polytope to a Cayley graph, is based on methods akin to those of Lovász and Babai ([L], [B]). It turns out that the algebraic degree of the eigenvalues is at most 5, achieved at two 3-dimensional solids.Dedicated to the memory of R. MañéResearch supported by MCT and CNPq, Brazil.     

SERS as a valuable tool for detection and treatment follow‐up of fungal infection in mice lungs: use of Amphotericin B and its nanoencapsulation onto magnetic nanoparticles

This study reports on the use of surface‐enhanced Raman scattering (SERS) detection and follow‐up treatment of Paracoccidioides brasiliensis (Pb) infection in lung's mice. We also reports on the introduction of a new drug carrier system [nanoparticle‐Amphotericin B (NP‐AmB)], comprising magnetic NP surface functionalized with AmB, and its use in the treatment of infected and non‐infected mice. SERS was successfully used to monitor the efficacy of the mice's treatment using the new NP‐AmB, while free AmB (F‐AmB), considering the current drug of choice for treatment of Pb infection, was also used and taken as reference for the treatment. We found SERS provides a robust platform to discriminate infected lung tissues from non‐infected ones based on fingerprints assessed via SERS spectra and focused on the redox state of heme groups present in the collected biological material. Finally, SERS data reported in this study indicated that the new NP‐AmB formulation provides similar clinical response as the F‐AmB, although incorporating 40% lower content of AmB and administered in a time interval schedule (every 72 h) three times longer than F‐AmB (every 24 h). Copyright © 2013 John Wiley & Sons, Ltd.     

Study of Electrochemical Oxidation of Xanthohumol by Ultra-Performance Liquid Chromatography Coupled to High Resolution Tandem Mass Spectrometry and Ion Mobility Mass Spectrometry

Electrochemically assisted oxidation off-line combined with UPLC/ESI–MS and ion mobility mass spectrometry enabled us to gain insight into the oxidation mechanisms of xanthohumol. Several types of monomeric oxidation products were identified, i.e., monohydroxylated and dehydrogenated derivatives and related quinones. Besides, high contents of dimers were observed. The structures of four main oxidative condensation products of two xanthohumol molecules were proposed based on combination of retention time, exact mass measurement, fragmentation pattern, data from on-line ion mobility mass spectrometric experiments and with the support of independent electrochemical experiments. To the best of our knowledge, this is the first evidence on formation of xanthohumol dimers. The effect of the pH on the generation of oxidation products was further investigated. The monomeric and dimeric oxidation products are favored at pH of 5.5 and 4.5, respectively.