Encapsulation of Mithramycin in Liposomes in Response to a Transmembrane Gradient of Calcium Ions

The recent discovery that mithramycin(MTR) in aqueous solution forms a high affinity[Ca(MTR)4]2- complex led us to the idea thatCa2+-loaded liposomes might be able to accumulateMTR in their aqueous internal compartment. Wetherefore investigated the uptake of MTR into largeunilamellar vesicles (LUV) containing NaCl orCaCl2. Our data show that MTR was efficientlyaccumulated within LUV made fromdipalmitoylphosphatidylcholine and cholesterol, onlywhen the liposomes contained Ca2+ and wereresuspended in a Ca2+-free medium. A drugencapsulation efficiency as high as 60% was achieved,at a drug to lipid molar ratio of 1/18. The circulardichroism and fluorescence excitation spectra ofliposome-encapsulated MTR (LMTR) displayed strongsimilarities with those of the [Ca(MTR)4]2-complex. LMTR was found to be stable, when submittedto conditions that destabilized the[Ca(MTR)4]2- complex. Upon dilution andincubation for 24 h at 37 °C, MTR-containingliposomes did not release a significant amount of MTR.These properties were attributed to the formation ofa high affinity complex between MTR and Ca2+inthe aqueous compartment of liposomes.     

Application of liquid chromatography quadrupole time-of-flight mass spectrometry to the identification of acetamiprid transformation products generated under oxidative processes in different water matrices

This work allowed the identification of major transformation products (TPs) of acetamiprid (ACTM) during Fenton process. Acetamiprid is a chloronicotinoid insecticide widely used around the world for its characteristics (high insecticidal activity, good systemic properties, suitable field stability, etc.). The degradation of the parent molecule and the identification of the main TPs were evaluated in different water matrices (demineralized water and real agro-food industrial wastewater). TPs of acetamiprid generated by Fenton experiments were monitored and identified by liquid chromatography quadrupole time-of-flight tandem mass spectrometry (LC–QTOF–MS/MS). Up to 14 TPs were characterized based on the accurate mass of the molecular ion and fragment ions obtained in both full-scan and MS/MS modes. Most of them were eliminated after 75 min of treatment time in demineralized water. However, in real agro-food industrial wastewater, most of them were eliminated at 90 min of treatment time, demonstrating the influence of the matrix composition on the studied compound degradation.     

Finite element analysis of axisymmetric systems without ignoring shear strain effects

Summary The finite element method is used to calculate the elastic displacements and internal forces in shells with axisymmetric geometry and load; the shell is assumed to be strainable by shear as well as by bending and normal forces. It is assumed that the finite elements have a simple curvature whose displacement function is analytically expressed by power polynomials of the meridian coordinate; the chosen parameters are the displacement components of the nodes; their number may be smaller than that of the polynomial terms, whose dependence is therefore uniquely defined by the minimum total potential energy condition. By this means it is possible to obtain an accurate numeric solution even with a few elements as long as they are sufficient to represent the shell geometry and follow the load distribution. The exposition is completed by the block diagram of the numeric computing program and the results in some examples.

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Sommario Col metodo degli elementi finiti viene impostato il calcolo degli spostamenti elastici e delle azioni interne in lastre assialsimmetriche per geometria e per carico; si suppone la lastra deformabile oltre che alle azioni flettenti e normali anche all'azione di taglio.Si assumono elementi finiti a semplice curvatura con funzione spostamento analiticamente espressa da polinomi di potenze della coordinata meridiana; si scelgono quali parametri le componenti di spostamento dei nodi; il loro numero può essere inferiore a quello dei coefficienti polinomiali considerati la cui dipendenza viene pertanto univocamente definita con la condizione di minima energia potenziale totale.Seguendo questa via è possibile ottenere una soluzione numerica accurata anche con pochi elementi finiti purchè sufficienti a rappresentare convenientemente la geometria della lastra e a seguire la distribuzione dei carichi.L'esposizione è completata dallo schema a blocchi del programma di calcolo numerico per l'elaborazione elettronica e dai risultati ottenuti in alcuni casi esemplificativi.

     

Synthesis of novel simplified eleutheside analogues with potent microtubule-stabilizing activity, using ring-closing metathesis as the key-step

The synthesis of a number of novel simplified eleutheside analogues with potent tubulin-assembling and microtubule-stabilizing properties is described, using ring-closing metathesis as the key-step for obtaining the 6-10 fused bicyclic ring system.