How curcumin works preferentially with water soluble antioxidants.

In this study we investigated physicochemical characteristics of the curcumin radical by pulse radiolysis and laser flash photolysis. Two methylated curcumin derivatives, methylcurcumin and trimethylcurcumin, were synthesized to explore the role of phenol hydroxy and beta-diketone moieties in the free radical chemistry of curcumin. Our results show that the initially generated beta-oxo-alkyl transforms rapidly, probably via an intramolecular H-atom shift, into the phenoxyl-type curcumin radical. This phenoxyl does not react with oxygen, k < 10(5) M(-1) s(-1), and can be repaired by any water-soluble antioxidant with appropriate redox potential, E(6) < 0.83 V, for example, with vitamin C, k = (6 +/- 1) x 10(6) M(-1) s(-1). A molecular mechanism of cancer chemoprevention by curcumin is proposed, with special emphasis on the synergism with water-soluble antioxidants.     

A short range many-body potential for modelling bcc metals

The problem considered is the fitting of a many-body interaction potential to bulk crystal data. A parameterisation of the potential is assumed which is based on physical considerations. The free parameters are determined by using global optimization to perform a least squares fit, to a large number of crystal properties. This has been achieved for body centered cubic (bcc) materials. The approach adopted here fits the bcc crystal structure, as the preferred minimum energy configuration for tungsten, and also fits the dimer energetics and the elastic properties of crystalline tungsten.     

Alcaloides steroidiques—LII Alcaloides du buxus balearica Willd.: Cycloprotobuxine-D, buxamine-E, buxaminol-E, N-isobutyryl-baleabuxidine-F, N-benzoyl-baleabuxidine-F, baleabuxoxazine-C, N-isobutyryl-baleabuxidienine-F, N-benzoyl-baleabuxidienine-F, N-isobutyryl-baleabuxaline-F

The following alkaloides have been extracted from the leaves of Buxus balearica Willd.: cyclomicrophylline-B, cycloprotobuxines A, C and D, baleabuxine (N-isobutyryl-baleabuxine-F), buxamine-E and buxaminol-E (already reported), N-isobutyryl- and N-benzoyl-baleabuxidine-F, baleabuxoxazine-C, N-isobutyryl- and N-benzoyl-baleabuxidienine-F, N-isobutyryl-baleabuxaline-F, the structures of which are proposed. The stereochemistry of baleabuxidines and baleabuxoxazines is established on the base of chemical correlations between these two groups and cyclomicrophyllines.     

Role of the ubiquitin proteasome system in Parkinson's disease

Parkinson's disease (PD) is the most common neurodegenerative movement disorder. Although a subject of intense research, the etiology of PD remains poorly understood. Recently, several lines of evidence have implicated an intimate link between aberrations in the ubiquitin proteasome system (UPS) and PD pathogenesis. Derangements of the UPS, which normally functions as a type of protein degradation machinery, lead to alterations in protein homeostasis that could conceivably promote the toxic accumulation of proteins detrimental to neuronal survival. Not surprisingly, various cellular and animal models of PD that are based on direct disruption of UPS function reproduce the most prominent features of PD. Although persuasive, new developments in the past few years have in fact raised serious questions about the link between the UPS and PD. Here I review current thoughts and controversies about their relationship and discuss whether strategies aimed at mitigating UPS dysfunction could represent rational ways to intervene in the disease. Publication history: Republished from Current BioData's Targeted Proteins database (TPdb; http://www.targetedproteinsdb.com).     

Adsorption of nicotine from aqueous solution onto hydrophobic zeolite type USY

The isothermal adsorption of nicotine from an aqueous solution onto zeolite type USY was investigated. The adsorption isotherms of nicotine onto the zeolite at different temperatures ranging from 298 to 322 K were determined. It was found that the adsorption isotherms can be described by the model of Freundlich adsorption isotherm. Based on the adsorption isotherms the changes of adsorption heat, free energy and entropy with adsorption degree were determined. The determined decrease of adsorption heat with adsorption degree can be explained by the presence of the adsorption centers of different energy and concentration on interface of zeolite-nicotine solution. It was found that the probability function of density distribution of the heat of adsorption (DDF) has exponential form. It was concluded that the possibility of fitting the adsorption isotherms of nicotine onto the zeolite by Freundlich adsorption isotherm was a direct consequence of that. The determined increase in entropy with the increase in adsorption degree can be explained with the change of phase state of adsorbed nicotine.     

Pulse chirp effects in ultrafast laser-induced breakdown spectroscopy

When compared to many other sensitive methods for material detection, such as inductively coupled mass spectroscopy and thermal ionization mass spectroscopy, laser-induced breakdown spectroscopy (LIBS) typically exhibits a lower signal-to-noise ratio (SNR), resulting in higher detection limits. Increasing the SNR of LIBS would improve the ability to characterize the sample composition with increased accuracy and speed and reduce the amount of material needed to perform analysis. We have been investigating the effect of simple ultrashort laser pulse shaping on the SNR of LIBS. Our goal is to control the dynamics of the ionization and recombination processes in the laser-produced plasma to favorably affect the SNR associated with the line emission from the plasma. Pulse shaping is performed using an acousto-optic programmable dispersive filter. An adaptive learning algorithm is being developed to automate the pulse shape optimization process for maximization of LIBS SNR in nuclear security-relevant material characterization scenarios. We report a 27 % increase of the SNR for non-gated LIBS measurements of uranium by utilizing simple pulse shaping limited exclusively to excess quadratic spectral phase of the laser pulse.     

One-pot synthesis and structure of 10-heteroarylphenothiazines

Novel 10-heteroarylphenothiazine compounds were prepared in high yields by Ullmann coupling of the appropriate iodoheterocycle, prepared in situ, with a series of phenothiazines. The ¹³C nmr analysis of titled compounds predicts geometries which are in excellent agreement with available x-ray crystal structure data. The results also indicate significant π-interaction between the electron-rich phenothiazine ring and the π-deficient heterocycles.     

Bioorthogonal chemical tagging of protein cholesterylation in living cells

We report the first chemical probe for bioorthogonal chemical tagging of post-translationally cholesterylated proteins with an azide in living cells. This enables rapid multiplexed fluorescence detection and affinity labelling of protein cholesterylation, as exemplified by Sonic hedgehog protein, opening up new approaches for the de novo identification of cholesterylated proteins.