Enzymatic surface modification and functionalization of PET: A water contact angle,FTIR, and fluorescence spectroscopy study

The purpose of this study was to investigate the changes induced by a lypolytic enzyme on the surface properties of polyethylene terephthalate (PET). Changes in surface hydrophilicity were monitored by means of water contact angle (WCA) measurements. Fourier Transform Infrared spectroscopy (FTIR) in the Attenuated Total Reflectance mode (ATR) was used to investigate the structural and conformational changes of the ethylene glycol and benzene moieties of PET. Amorphous and crystalline PET membranes were used as substrate. The lipolytic enzyme displayed higher hydrolytic activity towards the amorphous PET substrate, as demonstrated by the decrease of the WCA values. Minor changes were observed on the crystalline PET membrane. The effect of enzyme adhesion was addressed by applying a protease after‐treatment which was able to remove the residual enzyme protein adhering to the surface of PET, as demonstrated by the behavior of WCA values. Significant spectral changes were observed by FTIR–ATR analysis in the spectral regions characteristic of the crystalline and amorphous PET domains. The intensity of the crystalline marker bands increased while that of the amorphous ones decreased. Accordingly, the crystallinity indexes calculated as band intensity ratios (1,341/1,410 cm^?1 and 1,120/1,100 cm^?1) increased. Finally, the free carboxyl groups formed at the surface of PET by enzyme hydrolysis were esterified with a fluorescent alkyl bromide, 2‐(bromomethyl)naphthalene (BrNP). WCA measurements confirmed that the reaction proceeded effectively. The fluorescence results indicate that the enzymatically treated PET films are more reactive towards BrNP. FTIR analysis showed that the surface of BrNP‐modified PET acquired a more crystalline character. Biotechnol. Bioeng. 2009;103: 845–856. © 2009 Wiley Periodicals, Inc.     

Pivotal Role of the RB Family Proteins in in Vitro Thyroid Cell Transformation

Rat thyroid differentiated cells (PC Cl 3) are an excellent model system with which to study the interaction between differentiation and cell transformation. We previously demonstrated that PC Cl 3 cells expressing the adenovirus E1A gene no longer depend on thyrotropin for growth and do not express thyroid differentiation markers. Here we show that an E1A mutant unable to bind the RB protein failed to transform the PC Cl 3 cells. Conversely, mutations in the E1A p300 interacting region did not affect its transforming ability. The pivotal role of RB family proteins in the thyroid cell transformation is supported by the thyrotropin independence induced by the E7 gene of human papilloma virus type 16, but not by a mutated form in the RB-binding region.     

Stable interaction between alpha5beta1 integrin and Tie2 tyrosine kinase receptor regulates endothelial cell response to Ang-1

During angiogenic remodeling, Ang-1, the ligand of Tie2 tyrosine kinase, is involved in vessel sprouting and stabilization through unclear effects on nascent capillaries and mural cells. In our study, we hypothesized that the Ang-1/Tie2 system could cross-talk with integrins, and be influenced by the dynamic interactions between extracellular matrix and endothelial cells (ECs). Here, we show that alpha5beta1 specifically sensitizes and modulates Tie2 receptor activation and signaling, allowing EC survival at low concentrations of Ang-1 and inducing persistent EC motility. Tie2 and alpha5beta1 interact constitutively; alpha5beta1 binding to fibronectin increases this association, whereas Ang-1 stimulation recruits p85 and FAK to this complex. Furthermore, we demonstrate that Ang-1 is able to mediate selectively alpha5beta1 outside-in FAK phosphorylation. Thus, Ang-1 triggers signaling pathways through Tie2 and alpha5beta1 receptors that could cross-talk when Tie2/alpha5beta1 interaction occurs in ECs plated on fibronectin. By using blocking antibodies, we consistently found that alpha5beta1, but not alphavbeta3 activation, is essential to Ang-1-dependent angiogenesis in vivo.     

On the mechanism of gating charge movement of ClC-5, a human Cl(-)/H(+) antiporter

ClC-5 is a Cl(-)/H(+) antiporter that functions in endosomes and is important for endocytosis in the proximal tubule. The mechanism of transport coupling and voltage dependence in ClC-5 is unclear. Recently, a transport-deficient ClC-5 mutant (E268A) was shown to exhibit transient capacitive currents. Here, we studied the external and internal Cl(-) and pH dependence of the currents of E268A. Transient currents were almost completely independent of the intracellular pH. Even though the transient currents are modulated by extracellular pH, we could exclude that they are generated by proton-binding/unbinding reactions. In contrast, the charge movement showed a nontrivial dependence on external chloride, strongly supporting a model in which the movement of an intrinsic gating charge is followed by the voltage-dependent low-affinity binding of extracellular chloride ions. Mutation of the external Glu-211 (a residue implicated in the coupling of Cl(-) and proton transport) to aspartate abolished steady-state transport, but revealed transient currents that were shifted by ~150 mV to negative voltages compared to E268A. This identifies Glu(ext) as a major component of the gating charge underlying the transient currents of the electrogenic ClC-5 transporter. The molecular events underlying the transient currents of ClC-5 emerging from these results can be explained by an inward movement of the side chain of Glu(ext), followed by the binding of extracellular Cl(-) ions.     

Purification,biochemical characterization and gene sequencing of a thermostable raw starch digesting α-amylase from Geobacillus thermoleovorans subsp. stromboliensis subsp. nov.

This study reports the purification and biochemical characterization of a raw starch-digesting α-amylase from Geobacillus thermoleovorans subsp. stromboliensis subsp. nov. (strain Pizzo^T). The molecular weight was estimated to be 58 kDa by SDS–PAGE. The enzyme was highly active over a wide range of pH from 4.0–10.0. The optimum temperature of the enzyme was 70°C. It showed extreme thermostability in the presence of Ca²⁺, retaining 50% of its initial activity after 90 h at 70°C. The enzyme efficiently hydrolyzed 20% (w/v) of raw starches, concentration normally used in starch industries. The α-amylase showed an high stability in presence of many organic solvents. In particular the residual activity was of 73% in presence of 15% (v/v) ethyl alcohol, which corresponds to ethanol yield in yeast fermentation process. By analyzing its complete amyA gene sequence (1,542 bp), the enzyme was proposed to be a new α-amylase.     

α-Tocopheryl succinate pre-treatment attenuates quinone toxicity in prostate cancer PC3 cells

α-Tocopheryl succinate is one of the most effective analogues of vitamin E for inhibiting cell proliferation and inducing cell death in a variety of cancerous cell lines while sparing normal cells or tissues. αTocopheryl succinate inhibits oxidative phosphorylation at the level of mitochondrial complexes I and II, thus enhancing reactive oxygen species generation which, in turn, induces the expression of Nrf2-driven antioxidant/detoxifying genes. The cytoprotective role of Nrf2 downstream genes/proteins prompted us to investigate whether and how α-tocopheryl succinate increases resistance of PC3 prostate cancer cells to pro-oxidant damage. A 4 h α-tocopheryl succinate pre-treatment increases glutathione intracellular content, indicating that the vitamin E derivative is capable of training the cells to react to an oxidative insult. We found that α-tocopheryl succinate pre-treatment does not enhance paraquat-/hydroquinone-induced cytotoxicity whereas it exhibits an additional/synergistic effect on H₂O₂-/docetaxel-induced cytotoxicity.     

ERK1/2-dependent regulation of U937 cell survival after exposure to peroxynitrite

A short-term growth of U937 cells in serum-free medium causes a prompt, mitochondrial permeability transition (MPT)-dependent necrotic response after exposure to an otherwise non-toxic concentration of peroxynitrite. This event is mediated by inhibition of extracellular signal-regulated kinase 1 and 2 (ERK1/2) phosphorylation, essential for the cytosolic phospholipase A(2)-dependent arachidonic acid (AA) release evoked by peroxynitrite. Reduced availability of the lipid messenger would therefore limit the efficiency of the AA-dependent survival signalling and cause an MPT-based necrosis. Since peroxynitrite further reduces the extent of ERK1/2 phosphorylation, regardless of whether cells had been grown in serum-free or -containing medium, it appears that basal ERK1/2 phosphorylation is a critical determinant for the survival response of U937 cells to a non-toxic, but nevertheless MPT-committing, concentration of peroxynitrite.