Binding and biological properties of lipopolysaccharide Proteus vulgaris O25 (48/57)–chitosan complexes

In this study the negatively charged Proteus vulgaris O25 LPS was chosen for studying interaction with polycationic chitosan. The complex formation of LPS with chitosan was demonstrated using gradient centrifugation and laser interferometry method. The presented results have shown that laser interferometry method is sensitive enough for LPS–chitosan interaction studies. The changing in the ultra structure of LPS during binding with chitosan was observed by electronic microscope. The interaction of P. vulgaris O25 LPS with chitosan was shown to modulate significantly the biological activities of LPS. The toxicity of P. vulgaris O25 LPS decreased 10-fold after forming complexes with chitosan at injection to mice in the similar concentration of endotoxin. The complex LPS–chitosan was less effective than LPS alone in Limulus amabocyte lysate assay. Induction of TNF biosynthesis by LPS–chitosan complex was found to be 65% lower than that by parent LPS at concentration of 100 ng/ml.     

Size and Temperature Effects on the Surface Plasmon Resonance in Silver Nanoparticles

The surface plasmon energy in spherical silver nanoparticles embedded in silica host matrix depends on the size and temperature of the nanoparticles. The dependences of the surface plasmon energy were studied for silver nanoparticles in the size range 11?C30?nm and in the temperature interval 293?C650?K. As the size of the nanoparticles decreases or the temperature increases, the surface plasmon resonance shifts to red. When the size of the nanoparticles decreases, the scattering rate of the conduction electrons increases, which results in the nonlinear red shift of the surface plasmon resonance. The red shift with temperature is linear for larger nanoparticles and becomes nonlinear for smaller ones. As the temperature of the nanoparticles increases, the volume thermal expansion of the nanoparticles leads to the red shift of the surface plasmon resonance. The thermal volume expansion coefficient depends on the size and temperature. It increases with a decrease of the nanoparticle size and an increase of the temperature.     

Long-wavelength fluorescence lifetime labels

Fluorescence lifetime (FLT) measurements in the long-wavelength red and near-infrared (NIR) range are expected to improve the reliability and robustness of fluorescence-based detection. This review provides a summary of suitable classes of red and NIR luminescent reporters for use in FLT-based applications.     

Fbxo28 promotes mitotic progression and regulates topoisomerase IIα-dependent DNA decatenation

Topoisomerase IIα is an essential enzyme that resolves topological constraints in genomic DNA. It functions in disentangling intertwined chromosomes during anaphase leading to chromosome segregation thus preserving genomic stability. Here we describe a previously unrecognized mechanism regulating topoisomerase IIα activity that is dependent on the F-box protein Fbxo28. We find that Fbxo28, an evolutionarily conserved protein, is required for proper mitotic progression. Interfering with Fbxo28 function leads to a delay in metaphase-to-anaphase progression resulting in mitotic defects as lagging chromosomes, multipolar spindles and multinucleation. Furthermore, we find that Fbxo28 interacts and colocalizes with topoisomerase IIα throughout the cell cycle. Depletion of Fbxo28 results in an increase in topoisomerase IIα?dependent DNA decatenation activity. Interestingly, blocking the interaction between Fbxo28 and topoisomerase IIα also results in multinucleated cells. Our findings suggest that Fbxo28 regulates topoisomerase IIα decatenation activity and plays an important role in maintaining genomic stability.     

Distance Dependence of Metal-Enhanced Fluorescence

In recent years both the mechanism and applications of metal-enhanced fluorescence (MEF) have attracted significant attention, yet many fundamental aspects of MEF remain unanswered or addressed. In this study, we address a fundamental aspect of MEF. Using fluorescein-labeled different length DNA scaffolds, covalently bound to silver nanodeposits, we have experimentally measured the distance dependence of the MEF effect. The enhanced fluorescence signatures, i.e., MEF, follow quite closely the theoretical decay of the near-field of the nanoparticles, calculated using finite difference time domain approaches. This implies that the mechanisms of MEF are partially underpinned by the magnitude and distribution of the electric field around near-field nanoparticles.     

Mechanically activated transformations in the coordination sphere of platinum complexes induced by impact grinding of solid K2PtX6 (X=Cl, Br) and K2PtCl4 salts

Mechanical treatment of solid K₂PtX₆ (X=Cl, Br) salts under air or argon leads to the formation of paramagnetic platinum(III) complexes via homolytic cleavage of Pt---X bonds. Lewis acid sites (LASs) were also detected on the surface of mechanically activated K₂PtCl₆ using a paramagnetic probe. The latter species can be attributed to coordinatively unsaturated platinum(IV) complexes formed as a result of heterolysis of Pt---Cl bonds. Mechanical treatment of solid K₂PtCl₄, on the contrary, does not lead to homolytic Pt---Cl bond cleavage. In this case only heterolysis of the Pt---Cl bond takes place, leading to the formation of coordinatively unsaturated platinum(II) complexes.