Screening Method for Five Commonly Used Amphetamines in Urine by NMR Spectroscopy

In the recent years the so-called designer drugs have been diffused dramatically worldwide. Amphetamine psychostimulants are one of the major classes of illicit drugs consumed for recreational purposes in the world. The detection of the illegal substances is important both in the management of their misuse and in the forensic field. Urine matrix is a reliable biological matrix for verifying amphetamines intake in the short and medium term because the excretion of these drugs mainly occurs in urine, where substantial amounts of unchanged drug are present. In response to a growing demand for reliable evidence of amphetamine use, a method for identification and quantitation of amphetamine, methamphetamine, 3,4-methylenedioxy-N-methylamphetamine, 3,4-methylenedioxyamphetamine, 3,4-methylenedioxy-N-ethylamphetamine in urine has been developed by nuclear magnetic resonance spectroscopy, using electronic reference to access in vivo concentration method. The method showed good linearity. The limits of detection and quantitation of amphetamines analyzed ranging from 1.9–7.9 to 5.8–23.8 μg mL^?1, respectively. These data demonstrate that the present method is suitable for detection of these drugs in urine samples, allowing to quantitate the target analytes without any purification step of the matrix.     

On Small Complete Arcs and Transitive ‐Invariant Arcs in the Projective Plane

Let q be an odd prime power such that q is a power of 5 or (mod 10). In this case, the projective plane admits a collineation group G isomorphic to the alternating group A₅. Transitive G‐invariant 30‐arcs are shown to exist for every . The completeness is also investigated, and complete 30‐arcs are found for . Surprisingly, they are the smallest known complete arcs in the planes , and . Moreover, computational results are presented for the cases and . New upper bounds on the size of the smallest complete arc are obtained for .     

Pulse Radiolysis and Ultra‐High‐Performance Liquid Chromatography/High‐Resolution Mass Spectrometry Studies on the Reactions of the Carbonate Radical with Vitamin B12 Derivatives

The reactions of the carbonate radical anion (CO₃ ^{. ?}) with vitamin B₁₂ derivatives were studied by pulse radiolysis. The carbonate radical anion directly oxidizes the metal center of cob(II)alamin quantitively to give hydroxycobalamin, with a bimolecular rate constant of 2.0×10⁹ M ^?1 s^?1. The reaction of CO₃ ^{. ?} with hydroxycobalamin proceeds in two steps. The second‐order rate constant for the first reaction is 4.3×10⁸ M ^?1 s^?1. The rate of the second reaction is independent of the hydroxycobalamin concentration and is approximately 3.0×10³ s^?1. Evidence for formation of corrinoid complexes differing from cobalamin by the abstraction of two or four hydrogen atoms from the corrin macrocycle and lactone ring formation has been obtained by ultra‐high‐performance liquid chromatography/high‐resolution mass spectrometry (UHPLC/HRMS). A mechanism is proposed in which abstraction of a hydrogen atom by CO₃ ^{. ?} from a carbon atom not involved in the π conjugation system of the corrin occurs in the first step, resulting in formation of a Co^III C‐centered radical that undergoes rapid intramolecular electron transfer to form the corresponding Co^II carbocation complex for about 50 % of these complexes. Subsequent competing pathways lead to formation of corrinoid complexes with two fewer hydrogen atoms and lactone derivatives of B₁₂. Our results demonstrate the potential of UHPLC combined with HRMS in the separation and identification of tetrapyrrole macrocycles with minor modifications from their parent molecule.     

Atomistic simulation study on the crack growth stability of graphene under uniaxial tension and indentation

Meccanica - Combining a series of atomistic simulations with fracture mechanics theory, we systematically investigate the crack growth stability of graphene under tension and indentation, with a...     

Truly-Biocompatible Gold Catalysis Enables Vivo-Orthogonal Intra-CNS Release of Anxiolytics

Being recognized as the best-tolerated of all metals, the catalytic potential of gold (Au) has thus far been hindered by the ubiquitous presence of thiols in organisms. Herein we report the development of a truly-catalytic Au-polymer composite by assembling ultrasmall Au-nanoparticles at the protein-repelling outer layer of a co-polymer scaffold via electrostatic loading. Illustrating the in vivo-compatibility of the novel catalysts, we show their capacity to uncage the anxiolytic agent fluoxetine at the central nervous system (CNS) of developing zebrafish, influencing their swim pattern. This bioorthogonal strategy has enabled -for the first time- modification of cognitive activity by releasing a neuroactive agent directly in the brain of an animal.