A projected subgradient method for solving generalized mixed variational inequalities

We consider the projected subgradient method for solving generalized mixed variational inequalities. In each step, we choose an ε_k-subgradient u^k of the function f and w^k in a set-valued mapping T, followed by an orthogonal projection onto the feasible set. We prove that the sequence is weakly convergent.     

Simultaneous determination of swertiamarin and its metabolites (5Z)-5-ethylidene-8-hydroxy-3,4,5,6,7,8-hexahydro-1H-pyrano[3,4-c]pyridin-1-one and erythrocentaurin in broth of Aspergillus niger by HPLC

When cultivated with Aspergillus niger, swertiamarin, an important drug, is rapidly transformed into erythrocentaurin and (5Z)-5-ethylidene-8-hydroxy-3,4,5,6,7,8-hexahydro-1H-pyrano[3,4-c]pyridin-1-one (M(1)), a new compound with high anti-inflammatory activity. A simple and rapid HPLC method for simultaneous determination of swertiamarin and its two metabolites in broth of A. niger is described. The chromatographic separation was achieved on a C(18) ODS column (250 x 4.6 mm i.d.) by gradient elution with 0.04% formic acid in water and 0.04% formic acid in acetonitrile as the gradient mixtures. The flow rate was 1 mL/min, the detection wavelength was 237 nm and the column temperature was kept at 30 degrees C. The retention times of swertiamarin, erythrocentaurin and M(1) were 14.6, 16.8 and 24.8 min, respectively. The mean absolute recoveries of three analysts were over 96%. Quantification limits were 0.02 microg/mL for swertiamarin and 0.05 microg/mL for both of the two metabolites. The method was applied for the quantification of swertiamarin and its two metabolites during the fermentation process and the evaluation of the bioavailabilities in the Caco-2 monolayer.     

Anomalous adsorptive properties of HIV protease: indication of two-dimensional crystallization?

Adsorption of HIV protease onto surfaces that are usually considered to be protein-resistant was studied quantitatively using surface plasmon resonance. Adsorption onto gold surfaces functionalized by OH-terminated alkyl chains was much stronger than onto oligo(ethylene glycol)-terminated surfaces. Equilibrium and kinetic adsorption constants were determined. An anomalous mutual attraction between adsorbate molecules was observed, indicating the possibility of two-dimensional crystallization of HIV protease. These results are applicable for the design of sensors/biosensors for HIV protease resistance detection and for proper manipulation of this enzyme in laboratory devices.     

N‐Heterocyclic Carbenes as Promotors for the Rearrangement of Phosphaketenes to Phosphaheteroallenes: A Case Study for OCP to OPC Constitutional Isomerism

The concept of isomerism is essential to chemistry and allows defining molecules with an identical composition but different connectivity (bonds) between their atoms (constitutional isomers) and/or a different arrangement in space (stereoisomers). The reaction of phosphanyl ketenes, (NHP)?P=C=O (NHP=N‐heterocyclic phosphenium) with N‐heterocyclic carbenes (NHCs) leads to phosphaheteroallenes (NHP)?O?P=C=NHC in which the PCO unit has been isomerized to OPC. Based on the isolation of several intermediates and DFT calculations, a mechanism for this fundamental isomerisation process is proposed.