Correlations between microstructural characterization and thermal properties of well defined poly(ε-caprolactone) samples by ring opening polymerization with neutral and cationic bis(2,4,6-triisopropylphenyl)tin(IV) compounds

In this paper a study of correlations between the microstructure of well defined poly(ε-caprolactone) (PCL) samples and their physical properties such as thermal degradation, crystallization kinetics and melting behavior is described. The PCL samples were obtained in the presence of the compound benzyl-methoxy-bis(2,4,6-triisopropylphenyl)tin (1), acting as single-site and living initiator, as well as in the presence of compounds Tip₂SnRR′ [Tip = 2,4,6-triisopropylbenzene; R = R′ = CHCH₂ (2); R = CH₂Ph, R′ = Br (3)] activated by ionizing agents. PCL samples having different end groups, molecular weight and molecular weight distribution were obtained. The samples were fully characterized by GPC and NMR. The thermal degradation of the synthesized samples were studied by thermogravimetric analysis (TGA) in air flow. The experimental results suggested that the presence of ester chain end groups has a beneficial effect on the thermal stability of the PCL samples, independently on the molecular weights and molecular weight distribution. The crystallization behavior was studied in isothermal conditions at 37 °C, 40 °C, and 43 °C through differential scanning calorimetry (DSC). In this case, either the molecular weight (M_w) or the polydispersivity index (PDI) have a significant effect on the kinetics of crystallization of PCLs.     

Heavy metal uptake in the enological food chain

The research presented here describes the assessment of a number of physiological and xenobiotic metal concentrations occurring throughout the enological production processes of two native wines from Irpinia, Aglianico and Fiano of Avellino. In order to evaluate the wines’ metal content throughout the entire wine-making process, samples of grapes and musts from both wines were taken at time intervals during the fermentation and maturation phases. Copper, chromium, nickel, iron, zinc, lead and cadmium levels were analysed by atomic absorption spectrophotometry. The concentration of metals obtained were compared to the limits fixed by the Organization Internationale de la Vigne et du Vin (O.I.V.) and in the Italian ad European legislation.     

Heterotypic Sam–Sam Association between Odin‐Sam1 and Arap3‐Sam: Binding Affinity and Structural Insights

Arap3 is a phosphatidylinositol 3 kinase effector protein that plays a role as GTPase activator (GAP) for Arf6 and RhoA. Arap3 contains a sterile alpha motif (Sam) domain that has high sequence homology with the Sam domain of the EphA2‐receptor (EphA2‐Sam). Both Arap3‐Sam and EphA2‐Sam are able to associate with the Sam domain of the lipid phosphatase Ship2 (Ship2‐Sam). Recently, we reported a novel interaction between the first Sam domain of Odin (Odin‐Sam1), a protein belonging to the ANKS (ANKyrin repeat and Sam domain containing) family, and EphA2‐Sam. In our latest work, we applied NMR spectroscopy, surface plasmon resonance (SPR) and isothermal titration calorimetry (ITC) to characterize the association between Arap3‐Sam and Odin‐Sam1. We show that these two Sam domains interact with low micromolar affinity. Moreover, by means of molecular docking techniques, supported by NMR data, we demonstrate that Odin‐Sam1 and Arap3‐Sam might bind with a topology that is common to several Sam‐Sam complexes. The revealed structural details form the basis for the design of potential peptide antagonists that could be used as chemical tools to investigate functional aspects related to heterotypic Arap3‐Sam associations.     

Design,Synthesis and Bioevaluation of an EphA2 Receptor‐Based Targeted Delivery System

Because of its overexpression in a range of solid tumors, the EphA2 receptor is a validated target for cancer therapeutics. We recently described a new targeted delivery system based on specific EphA2‐targeting peptides conjugated with the chemotherapeutic agent paclitaxel. Here, we investigate the chemical determinants responsible for the stability and degradation of these agents in plasma. Introducing modifications in both the peptide and the linker between the peptide and paclitaxel resulted in drug conjugates that are both long‐lived in rat plasma and that markedly decrease tumor size in a prostate cancer xenograft model compared with paclitaxel alone treatment. These studies identify critical rate‐limiting degradation sites on the peptide–drug conjugates, enabling the design of agents with increased stability and efficacy. These results provide support for our central hypothesis that peptide–drug conjugates targeting EphA2 represent an innovative and potentially effective strategy to selectively deliver cytotoxic drugs to cancer cells.     

Mitochondrial oxidative alterations following partial hepatectomy

Mitochondria, isolated from rat livers during the early phase of liver regeneration (7-24 h after partial hepatectomy), show: (i) decrease in the rate of ATP synthesis; (ii) increase of malondialdehyde and of oxidized protein production; (iii) decrease of the content of intramitochondrial glutathione and of protein thiols on mitochondrial proteins; (iv) increase of the glutathione bound to mitochondrial proteins by disulfide bonds. These observations suggest an increase of production of oxygen radicals in liver mitochondria, following partial hepatectomy, which can alter the function of the enzymes involved in the oxidative phosphorylation. Blue-native gel electrophoresis of rat liver mitochondria, isolated after partial hepatectomy, shows, during the early phase of liver regeneration (0-24 h after partial hepatectomy), a progressive decrease of the content of F0F1-ATP synthase complex. The amount of glutathione bound to the F0F1-ATP synthase, electroeluted from the blue-native gels, progressively increased during the early phase of liver regeneration. It is concluded that partial hepatectomy causes mitochondrial oxidative stress that, in turn, modifies proteins (such as F0F1-ATP synthase) involved in the mitochondrial oxidative phosphorylation.     

The Cell Surface Receptor CD44: NMR‐Based Characterization of Putative Ligands

The cell surface receptor CD44 is a glycoprotein belonging to the hyaluronan‐binding proteins, termed hyaladherins. CD44 is expressed in a wide variety of isoforms in many cells and, in particular, is present on the surface of malignant cells where it is involved in the onset and progression of cancer. In a first attempt to identify novel CD44‐binding agents, we first characterized, with NMR spectroscopic techniques, several agents that were reported to bind to human CD44 (hCD44). To our surprise, however, none of these putative CD44‐binding agents, including a peptide that is in phase 2 clinical trials (A6 peptide) and a recently reported fragment hit, were found to interact significantly with recombinant hCD44(21–178). Nonetheless, we further report that a fragment‐screening campaign, with solution NMR spectroscopy as the detection method, identified a viable fragment hit that bound in a potentially functional pocket on the surface of CD44, opposite to the hyaluronic acid binding site. We hypothesize that this pocket could be indirectly associated with the cellular and in vivo activity of the A6 peptide, which would provide a novel framework for the possible development of therapeutically viable CD44 antagonists.     

Copolymerization and terpolymerization of glycolide with lactones by dimethyl(salicylaldiminato)aluminum compounds

The aliphatic poly(esters) are the most common biodegradable and biocompatible synthetic materials used by far for diverse biomedical applications. Co‐polymers and ter‐polymers of glycolide with ε‐caprolactone and lactide are produced in the presence of dimethyl aluminum compounds, bearing salicylaldiminato bidentate ligands differing for the steric hindrance on the ortho position of the phenolato ring. The formation of random poly[glycolide‐co‐(ε‐caprolactone)] samples is favored with more encumbered catalyst. Transesterification reactions of the second mode also contribute to randomize the structure. Copolymers from semi‐crystalline to amorphous are produced by decreasing the glycolide/ε‐caprolactone feed ratio. The terpolymerization of glycolide with ε‐caprolactone and rac‐lactide with the same catalysts affords amorphous and random poly[(glycolide‐co‐lactide‐co‐(ε‐caprolactone)] samples. The incorporation of the monomers is in this case determined by the bulkiness of the catalysts and by the higher coordination ability of the cyclic diesters. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42567.     

Stability and Cell Permeability of Sulfonyl Fluorides in the Design of Lys-Covalent Antagonists of Protein-Protein Interactions

Recently we reported on aryl-fluorosulfates as possible stable and effective electrophiles for the design of lysine covalent, cell permeable antagonists of protein–protein interactions (PPIs). Here we revisit the use of aryl-sulfonyl fluorides as Lys-targeting moieties, incorporating these electrophiles in XIAP (X-linked inhibitor of apoptosis protein) targeting agents. We evaluated stability in buffer and reactivity with Lys311 of XIAP of various aryl-sulfonyl fluorides using biochemical and biophysical approaches, including displacement assays, mass spectrometry, SDS gel electrophoresis, and denaturation thermal shift measurements. To assess whether these modified electrophilic “warheads” can also react with Tyr, we repeated these evaluations with a Lys311Tyr XIAP mutant. Using a direct cellular assay, we could demonstrate that selected agents are cell permeable and interact covalently with their intended target in cell. These results suggest that certain substituted aryl-sulfonyl fluorides can be useful Lys- or Tyr-targeting electrophiles for the design of covalent pharmacological tools or even future therapeutics targeting protein–protein interactions.     

Targeting zinc finger domains with small molecules: solution structure and binding studies of the RanBP2-type zinc finger of RBM5

The RNA binding motif protein 5 (RBM5), also known as Luca15 or H37, is a component of prespliceosomal complexes that regulates the alternative splicing of several mRNAs, such as Fas and caspase-2. The RBM5 gene is located at the 2p21.3 chromosomal region, which is strongly associated with lung cancer and many other cancers. Both increased and decreased levels of RBM5 can play a role in tumor progression. In particular, downregulation of rbm5 is involved in lung cancer and other cancers upon Ras activation, and, also, represents a molecular signature associated with metastasis in various solid tumors. On the other hand, upregulation of RBM5 occurs in breast and ovarian cancer. Moreover, RBM5 was also found to be involved in the early stage of the HIV-1 viral cycle, representing a potential target for the treatment of the HIV-1 infection. While the molecular basis for RNA recognition and ubiquitin interaction has been structurally characterized, small molecules binding this zinc finger (ZF) domain that might contribute to characterizing their activity and to the development of potential therapeutic agents have not yet been reported. Using an NMR screening of a fragment library we identified several binders and the complex of the most promising one, compound 1, with the RBM5 ZF1 was structurally characterized in solution. Interestingly, the binding mechanism reveals that 1 occupies the RNA binding pocket and is therefore able to compete with the RNA to bind RBM5 RanBP2-type ZF domain, as indicated by NMR studies.