New aminocyclitols as modulators of glucosylceramide metabolism

A series of 13 aminocyclitol derivatives belonging to two different families is described. Their configuration is governed by the regio- and stereocontrolled epoxide opening of a suitably protected conduritol-B epoxide. Studies on several glycosyl processing enzymes indicate that some of them are good inhibitors of glucosylceramide hydrolase. A rationale to account for preliminary structure-activity relationships is provided.     

Protective hybrid sol-gel coatings containing bioactive particles on surgical grade stainless steel: Surface characterization

Metallic materials are the most used materials as orthopaedic or dental implants for their excellent mechanical properties. However, they are not able to create a natural bonding with the mineralized bone and they could release metallic particles that could finally end in the removal of the implant. One way to avoid these effects is to protect the metallic implant with a biocompatible coating. In this work there are analyzed two kinds of protective organic-inorganic sol-gel made coatings with the adding of glass-ceramic particles with the aim of generating bioactivity. The samples are surface characterized by SEM, XRD and XPS. Amorphous hydroxyapatite (aHAp) deposited on the samples after 30 days of immersion in simulated body fluid (SBF) is detected on the samples and its presence is considered as a first signal of bioactivity.     

Sampling and determination of gas phase divalent mercury in the air using a KCl coated denuder

KCl coated denuders were employed for the measurement of divalent mercury (Hg²⁺) species in the air. Laboratory tests show that gaseous Hg²⁺ can be collected by the denuder with an average efficiency of 98% and elemental Hg will pass through it freely. Hg²⁺ trapped in the denuder can be quantitatively extracted by 1 mol/L HCl and analyzed by the method of SnCl₂ reduction-CVAFS determination. Hg²⁺ concentrations of 0.04–0.15 ng m^–3 corresponding to about 2–9% of the total gaseous mercury in the ambient air were determined at several sampling locations.     

Synthesis of cyclopropene analogues of ceramide and their effect on dihydroceramide desaturase

The synthesis of several analogues of the N-[(1R,2S)-2-hydroxy-1-hydroxymethyl-2-(2-tridecyl-1-cyclopropenyl)ethyl]octanamide (GT11), the first reported inhibitor of dihydroceramide desaturase, as well as their effects on this enzyme, are described. Modifications of the parent structure include variations on the cyclopropene ring, the N-acyl chain length, the configuration of the stereocenters, and the hydroxyl group at C1. The key intermediates for the synthesis are the products resulting from the addition of suitable organolithium compounds to either Garner's aldehyde or its enantiomer. The final products are obtained by TMSTf-induced cleavage of the protecting groups and N-acylation, both under specific conditions. An alternative method for N-Boc deprotection is also reported that allows us to obtain the cyclopropene analogue of sphingosine 12a, which can be transformed into GT11 upon acylation. The procedure consists of the conversion of the Garner aldehyde addition products into the bicyclic dihydrooxazolo[3,4,0]oxazol-3-ones 19 by transesterification in basic medium of the tert-butyl group with the hydroxyl function at C3. Mild cleavage of the N,O-isopropylidene cyclic acetal present in 19 affords the oxazolidin-2-one 20, which gives 12a upon saponification. Furthermore, compound 20 is also the key intermediate in the synthesis of the terminal deoxy, methoxy, and fluoro derivatives 9, 10, and 11, respectively. Determination of dihydroceramide desaturase activity in vitro showed that GT11 was a competitive inhibitor (Ki = 6 microM) and that its analogues with N-hexanoyl (6) and N-decanoyl (7) moieties inhibited the enzyme with similar potencies (IC50 = 13 and 31 microM, respectively). No decrease in dihydroceramide desaturase activity was observed with any of the other compounds tested.     

One-and two-photon ionization of aqueous tryptophan by the harmonics of the Nd laser

Study of the photoionization of aqueous tryptophan by the 265 nm harmonic of the Nd-glass laser at different laser pulse durations and energies established that this reaction is due to one-photon as well as two-photon absorption, the latter occurring mainly via the excited singlet slate Addition of the 353, or, alternatively, the 530 nm harmonic increased the photoelectron yield appreciably Double-pulse experiments (lower harmonic delayed with respect to the 265 nm pulse) were used to determine the relative importance of the excited singlet and triplet states in the two-photon processes responsible for this increase.