Forensic application of the luminol reaction as a presumptive test for latent blood detection

The forensic application of the luminol chemiluminescence reaction is reviewed. Luminol has been effectively employed for more than 40 years for the presumptive detection of bloodstains which are hidden from the naked eye at crime scenes and, for this reason, has been considered one of the most important and well-known assays in the field of forensic sciences. This review provides an historical overview of the forensic use of luminol, and the current understanding of the reaction mechanism with particular reference to the catalysis by blood. Operational use of the luminol reaction, including issues with interferences and the effect of the luminol reaction on subsequent serological and DNA testing is also discussed.     

A combined computational and experimental study of polynuclear Ru-TPPZ complexes: insight into the electronic and optical properties of coordination polymers

We report a combined experimental and computational study of polynuclear [Ru(n)(TPPZ)(n)(+1)](2)(n)(+) complexes, of interest in the field of photoactive polymers. The complexes with n = 1, 2, 3 and n > 5 have been synthesized and spectroscopically characterized. A red-shift of the visible band maximum from 2.59 to 2.03 eV is observed going from the monomer to the longer oligomeric species (n > 5). To characterize the geometries, electronic structure, and excited states of these complexes, density functional theory (DFT) and time-dependent DFT calculations on the [Ru(n)(TPPZ)(n)(+1)](2)(n)(+) series with n = 1-4 in solution have been performed. The agreement between experimental and calculated spectra is good, both in terms of absorption maximum energies and relative intensities for different values of n. For all the investigated complexes, we assign the main band in the visible region as a metal-to-metal plus ligand charge transfer (MMLCT) transition. The resulting excited states are delocalized throughout the entire complexes, as they originate from a superposition of pi(TPPZ)-t(2g)(Ru) states. The low-energy shoulder of the main visible absorption band, present in the experimental spectra for n > 1, is proposed to arise from spin-forbidden singlet-triplet transitions of similar MMLCT character, consistent with the observed enhancement of this feature in the spectra of the corresponding Os oligomers.     

Effects of inhibitors of Delta24(25)-sterol methyl transferase on the ultrastructure of epimastigotes of Trypanosoma cruzi.

Trypanosoma cruzi is the ethiological agent of Chagas disease. New compounds are being developed based on the biosynthesis and function of sterols, because T. cruzi has a requirement for specific endogenous sterols for growth and survival. Sterol biosynthesis inhibitors (SBIs) are drugs commonly used against fungal diseases. These drugs act by depleting essential and specific membrane components and/or inducing the accumulation of toxic intermediary or lateral products of the biosynthetic pathway. In this work we present the effects of WSP488, WSP501, and WSP561, specific inhibitors of Delta24(25)-sterol methyl transferase, on the ultrastructure of T. cruzi epimastigotes. All three drugs inhibited parasite multiplication at low concentrations, with IC50 values of 0.48, 0.44, and 0.48 muM, respectively, and induced marked morphological changes including (a) blockage of cell division; (b) swelling of the mitochondrion, with several projections and depressions; (c) swelling of the perinuclear space; (d) presence of autophagosomes and myelin-like figures; (e) enlargement of the flagellar pocket and of a cytoplasmic vacuole located in close association with the flagellar pocket; (f) detachment of the membrane of the cell body; and (g) formation of a vesicle at the surface of the parasite between the flagellar pocket and the cytostome. Our results show that these drugs are potent in vitro inhibitors of growth of T. cruzi.     

Theoretical analysis of fluorine addition to single-walled carbon nanotubes: functionalization routes and addition patterns

We present a theoretical investigation on the chemical addition patterns governing the fluorination of single wall carbon nanotubes. Monte Carlo calculations based on a Hückel model suggest that fluorination is stabilized in a bandlike pattern due to electronic confinement effects on the tube bond network topology. Ab initio analysis of the fluorination of small nanotubes show that fluorine addition along the nanotube axis direction is favored by a mechanism of carbon framework distortion. The experimentally observed formation of fluorine bands may be thus explained in terms of multiple axial C(2)F rows expanding by contiguous axial addition.     

Deep eutectic solvents and their applications as green solvents

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Structural effects upon competitive decomposition pathways of Thiosulfoxide intermediates

Mixtures of sulfides and disulfides are obtained upon reaction of boron trisulfide with a series of allyl aryl suit oxides, with the product distributions dependent upon the structures of the intermediate thiosulfoxides.     

Novel Ag ion-selective electrodes based on two new mixed azathioether crowns containing a 1,10-phenanthroline sub-unit

Novel polymeric membrane (PME) and coated graphite (CGE) silver-selective electrodes based on two recently synthesized mixed azathioether crowns containing a 1,10-phenanthroline sub-unit were prepared. The electrodes reveal a Nernstian behavior over quite wide Ag⁺ ion concentration ranges with a very low limits of detection (LOD) (i.e. down to 1.0×10⁻⁸ M for CGEs and 8.0×10⁻⁷ M for PMEs). The potentiometric responses are independent of the pH of the test solution in the pH range 3.0-7.0. The electrodes possess advantages of low resistance, very fast response time, relatively long lifetimes and, especially, good selectivities relative to a wide variety of other cations. The electrodes were used, as indicator electrodes, in the potentiometric titration of silver ion and in the determination of Ag⁺ in waste water, photographic emulsion and radiographic and photographic films.     

Comparison of solid-phase extraction and micro-solid-phase extraction for liquid chromatography/mass spectrometry analysis of pesticides in water samples

Our recent on-line solid-phase extraction (SPE) device for micro-liquid chromatography, known as micro-solid-phase extraction (microSPE), was compared with traditional SPE for the analysis, from aqueous samples, of 4 pesticides belonging to different classes. Two different kinds of adsorbents, C18 and graphitized carbon black, were tested. A 2-stage ion trap mass spectrometer, equipped with homemade microflow electrospray ion (ESI) source, was used. Detection limits with a signal-to-noise ratio of 3:1 for both extraction methods were in the range of 0.1 microg/L for all compounds. However, better recoveries were obtained when microSPE traps were used.     

Synthetic approach to substituted cyclopropanes based on the coupling reaction of lithiated chloroalkyloxazolines with Fischer carbene complexes

Regioselective addition of lithiated oxazoline 2a, easily available from 2-(1-chloroethyl)-4,4-dimethyl-2-oxazoline 1a (LDA, THF, -98 degrees C), to alpha,beta-unsaturated Fischer carbene complexes 3 afforded cyclopropylcarbene complexes 4 as sole diastereoisomers. Exposure of carbene complexes 4a-c (M = Cr) to air and sunlight gave cyclopropane carboxylate derivatives 5a-c. A plausible mechanistic explanation is proposed. Moreover, when lithiated oxazoline 2b was generated from 1b in the presence of the carbene complex 3a,b, the oxazolinylcyclopropane carboxylates 6a,b formed as a 1:1 mixture of diastereoisomers. Chiral lithiated oxazoline 2c added regioselectively and diastereoselectively to chromium complexes 3a,b and to tungsten complexes 3d,e, leading, after oxidation of the metal fragment, to esters 7a,b with good diastereoselectivity (dr = 4:1). The reaction of lithiated oxazoline 2d with chromium complex 3b and tungsten complex 3e proceeded less diastereoselectively, furnishing, in both cases, after oxidation, the ester 7c as a 3:2 diastereoselective mixture.     

The migratory insertion of carbon monoxide and methyl isocyanide into zirconium–carbon and titanium–carbon bonds anchored to a calix[4]arene moiety: a dynamical density functional study

The energetics and reaction mechanism of the migratory insertion of carbon monoxide and methyl isocyanide into the zirconium–carbon and titanium–carbon bonds in [calix[4](OMe)₂(O)₂–M–Me₂], (M=Zr, Ti), have been investigated by combining static and dynamic density functional calculations. Two steps have been characterized: the coordination of the incoming nucleophilic moiety leading to relatively stable facial adducts; its subsequent insertion into the M–C bond, leading to ²-bound acyl or iminoacyl complexes, providing a rationale for the different behavior of CO and MeNC towards both insertion and deinsertion reactions. Our results indicate that the rate-determining step for the overall MeNC insertion into the M–C bond is its coordination to the electron-deficient metal center, with the titanium system featuring a higher energy barrier (12.7 versus 5.5 kcal mol^–1). Ab initio molecular dynamics simulations have been performed on the Zr system by means of the Car–Parrinello method, to study the hitherto inaccessible mechanistic features of the insertion reactions.Contribution to the Björn Roos Honorary Issue