Graphene catalyzes the reversible formation of a C-C bond between two molecules

Carbon deposits are well-known inhibitors of transition metal catalysts. In contrast to this undesirable behavior, here we show that epitaxial graphene grown on Ru(0001) promotes the reversible formation of a C-C bond between -CH₂CN and 7,7,8,8-tetracyano-p-quinodimethane (TCNQ). The catalytic role of graphene is multifaceted: First, it allows for an efficient charge transfer between the surface and the reactants, thus favoring changes in carbon hybridization; second, it holds the reactants in place and makes them reactive. The reaction is fully reversible by injecting electrons with an STM tip on the empty molecular orbitals of the product. The making and breaking of the C-C bond is accompanied by the switching off and on of a Kondo resonance, so that the system can be viewed as a reversible magnetic switch controlled by a chemical reaction.

Dielectrophoretic assembly of liquid-phase-exfoliated TiS3 nanoribbons for photodetecting applications

Liquid-phase exfoliation produces colloidal two-dimensional materials that can be assembled by dielectrophoresis to fabricate optoelectronic devices.

[L-2-hydroxyglutaric aciduria: clinical, biochemical and neuroradiological findings in two Venezuelan patients]

INTRODUCTION

L-2-hydroxyglutaric aciduria is a rare inborn error of metabolism, autosomal recessive, identified in about 50 patients. The primary defect is still unknown. The clinical phenotype is variable. Affected individuals show slowly progressive neurodegenerative disorder with cerebellar ataxia and mental retardation. Pyramidal, and extrapyramidal signs, seizures and macrocephaly have been reported. All patients previously described show a pattern of subcortical leukoencephalopathy with nearly empty gyral cores and cerebellar atrophy in neuroimaging studies. The diagnosis is established by detection of increased levels of L-2-hydroxyglutaric acid in urine, plasma and cerebrospinal fluid.

CASE REPORTS

We here describe two patients 7 and 9 years old, who presented psychomotor retardation, seizures, progressive cognitive deterioration, and pyramidal, extrapyramidal and cerebellar signs. Magnetic resonance scanning of the brain demonstrated a bilateral subcortical leukoencephalopathy pattern and areas of increased T2-weighted signal in the basal ganglia and cerebellar dentate nuclei. The analysis of organic acids in urine by gas chromatography/mass spectrometry showed elevated 2-hydroxyglutaric acid, 100% of it in the form of L enantiomer.

CONCLUSION

The diagnostic consideration is based on clinical findings and typical neuroimaging pattern and is established by detection of L-2-hydroxyglutaric acid in body fluids. Subcortical white matter loss is an important clue to diagnosis.

Development and validation of an enzyme-linked immunosorbent assay (ELISA) for recombinant human gamma interferon

A one-site ELISA for the quantification of recombinant human gamma interferon (rh-IFN-gamma) was developed and validated. A single monoclonal antibody (Mab) was used as a "catching" antibody and as a horseradish peroxidase (HRP)-labeled conjugate. Detection limit and quantification limit of this assay were estimated to be 1.26 and 15 ng/mL, respectively, and the coefficient of variation was below 15%. The ELISA was specific for rh-IFN-gamma, showing no cross reactivity to other related molecules in the range of the concentrations studied. The results correlated well with those obtained by a bioassay method. By using this assay, it was demonstrated that 0.01-1% (v/v) Tween 80 protected rh-IFN-gamma during freezing and thawing.

Chemical Constituents of the Lichen Ramalina hierrensis

The following compounds have been isolated from the lichen RAMALINA HIERRENSIS, collected on savin, and endemic to the Canary Islands: ursolic acid, iso-arborinol acetate, beta-sitosterol, ergosterol peroxide, cerevisterol, (-)-sandaracopimaric acid, parietin, (+)-usnic acid, (+)-iso-usnic acid, divaricatic acid, atranorin, stictic acid, gangaleodin, variolaric acid, montagnetol, and hierridin. The structures of all compounds were elucidated by physical, spectral, and chemical methods.