Note: An Unusual Route to General Relativity Equation in Presence of Dust in Irrotational Motion

We show that the general relativity theory equation, in presence of pressureless matter (dust) in irrotational motion, can be recovered from a scalar-tensor like variational approach. In this approach, the kinetic energy, , of a dynamical scalar field , couples directly to gravity. The lagrangian, exempt of explicit matter term, is varied in the framework of the first order formalism, and a conformal transformation, restoring riemannian geometry, is made. In this approach, it turns out that a non-empty spacetime is necessarily four-dimensional.     

Stable (amino)(phosphino)carbenes: difunctional molecules

(Amino)(phosphino)carbenes are stable due to the donation of the nitrogen lone pair, the phosphino group remains strongly pyramidalized. Reactions can be performed selectively at the carbene center, but also at the phosphorus center leading to new stable carbenes. These difunctional molecules can be considered as hybrid ligands.     

Cryo-trapping/SPME/GC analysis of cheese aroma

The advantages of combined cold-trapping of cheese volatiles and solid-phase microextraction-GC are demonstrated. This method is simple, cheap, compatible with classic identification equipment, and allows in-situ sampling.     

THE INTERACTION OF 8-AZIDOETHIDIUM AND tRNA

Abstract Optical spectroscopy and proton nuclear magnetic resonance spectroscopy have been used to investigate the non-covalent and covalent binding of 8-azidoethidium (8-azido-3-amino-5-ethyl-6-phe-nyl-phenanthridium) with transfer RNA (tRNA) molecules. The nuclear magnetic resonance measurements demonstrate that ethidium and ethidium monoazide bind to the same unique binding site on tRNA molecules. However, the optical studies demonstrate that the photochemical reaction between ethidium monoazide and tRNA generates at least three different photoproducts. One of the covalent photoproducts has fluorescence properties which mimic those of intercalated, non-covalently bound ethidium, but it is produced only in about 10% yield. The major photoproduct(s) is(are) virtually non-fluorescent. The ethidium monoazide photochemistry with tRNA molecules is obviously complex and this may complicate its use as a photolabel of polynucleotides.     

Synthese stereoselective DU (±)-β-santalol

We describe here a new convergent and stereoselective synthesis of (±)-β-santalol. This synthesis involves in the last step an original deprotective method of methoxyethoxymethyl ether using pyridinium tosylate.     

CH,CD, CC and HH coupling constants in isotopically enriched cyclobutene

¹H, ²H and ¹³C NMR studies of cyclobutene and a series of isotopically enriched species have led to a determination of the ¹H? ¹H, ¹³C? ¹H, ¹³C? ²H and ¹³C? ¹³C coupling constants in these compounds. In agreement with general observations, ¹J(CH) is found to depend on the hybridization of the carbon atoms. Likewise, ²J(HH), ²J(CC), ³J(HH) and ³J(CH), but not ²J(CH), depend on the angles between the bonds connecting the coupled nuclei. When comparing cyclobutene with thiete 1,1-dioxide (thiete sulphone) an increase of almost 20 Hz is observed for ¹J(C-2, H-2) in the latter compound. All but one of the observed deuterium isotope effects on chemical shifts are negative. In the case of isotope effects upon the one-bond coupling constants, the obtained values support the results of the theoretical calculations of Sergeev and Solkan.