Stereocontrol mechanism in CO/p-methylstyrene copolymerisation catalysed by aryl-alpha-diimine Pd(II) complexes

Structural analysis of the first steps of isotactic CO/p-methylstyrene copolymerisation, catalysed by aryl-alpha-diimine Pd(II) complexes, highlights the influence of steric effects on the stereoselectivity of olefin insertion.     

Interactions of pyridinecarboxylic acid chelators with brain metal ions: Cu(II), Zn(II), and Al(III)

Abstract  

The interactions of Cu(II), Zn(II), and Al(III) with 1,6-dimethyl-4-hydroxy-3-pyridinecarboxylic acid (DQ716) and 2,6-dimethyl-3-hydroxy-4-pyridinecarboxylic acid (DT726), possible chelating agents in Alzheimer’s disease, were investigated in aqueous solution. The proton dissociation constants of the ligands, the stability constants, and the coordination modes of the metal complexes formed were determined by pH-potentiometric, UV–vis spectrophotometric, and ¹H NMR methods. The nitrogen of the pyridine ring changes the proton affinity of the carboxylate and phenolate moieties and these pyridine derivatives form stronger complexes with Cu(II), Zn(II), and Al(III) than salicylic acid. Interactions of the ligands with human serum albumin as their potential transporter in blood were investigated at physiological pH through ultrafiltration by UV–vis and fluorescence spectroscopy.     

Urinary peptides as a diagnostic tool for renal failure detected by matrix-assisted laser desorption/ionisation mass spectrometry: an evaluation of their clinical significance

The development of new analytical methodologies related to the proteome for the evaluation of renal physiology and pathology is surely of wide interest for physicians, giving them new tools for monitoring complications associated with diabetes, such as end-stage renal disease. In the present study, the clinical significance of the urinary abundance of two peptides, SGSVIDQSRVLNLGPITR (the uromodulin precursor, m/z 1912) and IGPHypGPHypGLMGPP [present in the collagen-α-5(IV) chain precursor, m/z 1219], detected by matrix- assisted laser desorption/ionisation mass spectrometry (MALDI/MS) in microalbuminuric or nephropathic diabetic patients and in non-diabetic nephropathic patients was evaluated. A progressive increase in the abundance of the ion at m/z 1219 and a decrease in the abundance of the ion at m/z 1912 have been found in diabetic microalbuminuric, diabetic-nephropathic and nephropathic patients. Linear correlations are present between serum creatinine values and the abundances of the ions at m/z 1219 (positive correlation, r=0.3645, P<0.0001) and at m/z 1912 (negative correlation, r=-0.3053, P<0.0005). Correlations between the MALDI data and the estimated glomerular filtration rate were also found, while relationships with urinary albumin excretion were found only in sub-sets of patients. Analysis of receiver operating characteristic curves showed a sensitivity up to 96% and a specificity of up to 84% for the two ionic species, or their ratio, for distinguishing diabetic patients with different degrees of nephropathy from healthy subjects, proving that the urinary abundance of the two peptides at m/z 1219 and m/z 1912, determined with MALDI/MS, may be considered as a possible diagnostic tool for the determination of progression toward renal failure, also with the aim of monitoring kidney function, in diabetic patients.     

A cationic Zn(II) porphyrazine induces a stable parallel G-quadruplex conformation in human telomeric DNA

A water soluble Zn(II) porphyrazine drives the conformational equilibrium of the G-quadruplex of a human telomeric sequence exclusively towards a parallel conformation upon complexation.     

Wedge-shaped fracturing in the pull out of FRP stiffeners from quasi-brittle substrates

Fiber-Reinforced-Polymer (FRP) strips can be glued to the surface of concrete or masonry structures to improve their strength. Pull-out tests on FRP bonds have shown a progressive failure of the adhesive joint involving early-stage cracking parallel to the axis of the FRP stiffener, and an inclined crack initiating at the free end of the stiffener and extending into the quasi-brittle substrate in the latest stage. The subsurface crack produces a characteristic wedge-shaped spall. There is no consensus on the reasons for the transition from cracking along the bond to cracking within the substrate. Therefore a Linear Elastic Fracture Mechanics model problem is presented here that accounts for and provides improved understanding of the formation of the subsurface crack. The boundary value problem is solved analytically using the distributed dislocation technique. Competition between crack extension along the adhesive joint and into the substrate is quantified using a quantized crack propagation criterion, whereby the crack does not advance in infinitesimal continuous increments, but instead in finite steps of length comparable to the characteristic dimensions of the material microstructure. The model predicts results that are in good agreement with experimental evidence.     

Long-Time Behavior of the Mean Curvature Flow with Periodic Forcing

We consider the long-time behavior of the mean curvature flow in heterogeneous media with periodic fibrations, modeled as an additive driving force. Under appropriate assumptions on the forcing term, we show existence of generalized traveling waves with maximal speed of propagation, and we prove the convergence of solutions to the forced mean curvature flow to these generalized waves.     

Dynamics of quasicontinuous systems

Quasicontinuous functions are continuous on a residual subset of their domain. The class includes many standard examples from dynamical systems, including the baker transformation and interval exchange maps. We present standard results of continuous topological dynamics (such as that sensitive dependence follows from transitivity and dense periodic points) which extend to quasicontinuous dynamics     

Iloprost Attenuates Oxidative Stress-Dependent Activation of Collagen Synthesis Induced by Sera from Scleroderma Patients in Human Pulmonary Microvascular Endothelial Cells

Endothelial cell injury is an early event in systemic sclerosis (SSc) pathogenesis and several studies indicate oxidative stress as the trigger of SSc-associated vasculopathy. Here, we show that circulating factors present in sera of SSc patients increased reactive oxygen species (ROS) production and collagen synthesis in human pulmonary microvascular endothelial cells (HPMECs). In addition, the possibility that iloprost, a drug commonly used in SSc therapy, might modulate the above-mentioned biological phenomena has been also investigated. In this regard, as compared to sera of SSc patients, sera of iloprost-treated SSc patients failed to increased ROS levels and collagen synthesis in HPMEC, suggesting a potential antioxidant mechanism of this drug.