Photo-oxidative and soil burial degradation of irrigation tubes based on biodegradable polymer blends

Irrigation tubes based on biodegradable polymers were prepared via an extrusion-drawing process by Irritec and compared to conventional pipes made of high-density polyethylene (HDPE). A commercial polylactide/poly (butyleneadipate-co-butyleneterephthalate) (PLA/PBAT) blend (Bio-Flex®) and Mater-Bi® were used. The polymers were characterized from rheological and mechanical points of view. Irrigation pipes were subjected to photoaging with continued exposure to UV radiation up to 22 days. The degradability in the soil of irrigation tube samples was studied. The influence of temperature and UV irradiation on soil burial degradation was investigated. A soil burial degradation test was carried out at 30 °C and 50 °C for up to 70 days. The degree of degradation was evaluated from the weight loss percentage. The degradation rate of irrigation tube samples based on Mater-Bi® was higher at 30 °C and was stimulated after 14 days of UV irradiation. Higher temperatures or UV aging encouraged the disintegration in soil of Bio-Flex®-based irrigation tubes. Furthermore, tube samples, before and after UV and soil burial degradation, were analyzed by Attenuated Total Reflection-Fourier Transform Infra-Red (ATR-FTIR) spectroscop

La verità ingiallita nel fototesto della Divina Mimesis

This essay is devoted to analyse the Divina Mimesis by Pier Paolo Pasolini. It is considered an original example of phototext. The review of the rhetoric strategies adopted by the author is based on two approaches. On the one hand, it is pointed toward the relationship between the textual ekphrastic fragments and the photographs that make up the iconografia ingiallita. However, the correlation is even though mostly explained by only allusive references to images. On the other hand, the analysis is dedicated to the composition of the photo sequence, whose links are mainly characterized by analogy or contradiction. Through this survey it is possible to display that even in this work (in a similar manner already skilled in La rabbia) the writer relies the complex and laborious authentication function of the speech on editing of the poema fotografico.L’obiettivo di questo saggio è quello di analizzare la Divina Mimesis di Pier Paolo Pasolini considerata come esempio originale di fototesto. L’esame delle strategie retoriche messe in atto dall’autore si gioca su due fronti. Esso è rivolto per un verso al rapporto fra i frammenti testuali ecfrastici e le fotografie che compongono l’«iconografia ingiallita», che è un legame per lo più esplicitato soltanto da riferimenti allusivi alle immagini. Per altro verso l’analisi è dedicata alla composizione della sequenza fotografica, i cui nessi prevalenti sono caratterizzati dall’analogia o dalla contraddizione. Attraverso tale indagine è possibile mostrare come anche in quest’opera (con modalità simili sperimentate già nella Rabbia) lo scrittore affidi al montaggio del «poema fotografico» la complessa e ardua funzione di autentificazione del discorso

Il doppio talento dell’attrice che scrive. Per una mappa delle “divagrafie”

Le interazioni fra performance e scrittura sono varie e multiformi e rientrano a pieno titolo nella categoria del «doppio talento», utilizzata dalla critica finora soprattutto in riferimento alla sovrapposizione fra linguaggio letterario e figurativo o musicale. Da una prima ricognizione nel contesto italiano dalla seconda metà del ’900 agli anni Zero emergono delle costanti: i libri firmati dalle «stelle italiane» disegnano una parabola che dal memoir giunge alla narrativa finzionale, passando per la tappa intermedia delle ‘autobiografie delle personagge’, che mettono in racconto frammenti di vita di un personaggio rappresentato dall’attrice. Si intende dunque tracciare le linee generali di una «mappa dell’attrice che scrive», individuando nodi teorici e categorie paradigmatiche in riferimento ad alcuni casi di studio particolarmente significativi.Les interactions entre la performance et l’écriture sont variées et multiformes et rentrent pleinement dans la catégorie du « double talent », utilisée jusqu’ici par la critique notamment pour faire référence à l’entrelacement du langage littéraire et du langage figuratif ou musical. Un premier repérage dans le contexte italien, de la seconde moitié du vingtième siècle à la première décennie de notre siècle met en évidence certaines constantes. Les livres signés par les « stars italiennes » dessinent une parabole allant du mémoire à la fiction romanesque, en passant par l’étape intermédiaire des « autobiographies des personnages féminins », c’est-à-dire des textes qui inscrivent dans l’histoire des fragments de la vie d’un personnage représenté par l’actrice. L’essai trace ainsi les grandes lignes d’une « cartographie de l’actrice qui écrit » en identifiant des questions théoriques et des catégories paradigmatiques qui s’appuient sur des études de cas particulièrement significatifs.The interactions between performance and writing are varied and multifaceted. They fall entirely into the category of “double talent”, which has been used by critics to refer to the interweaving of literary language and figurative or musical language. An initial survey of the Italian context, from the second half of the twentieth century to the first decade of our century, highlights certain constants. The books signed by “Italian stars” range from autobiography to fiction, through the intermediate stage of “autobiographies of female characters”, i.e. texts that inscribe in history fragments of the life of the character played by the actress. The essay thus outlines a “cartography of the actress who writes” by pinpointing theoretical questions and paradigmatic categories on the basis of individual case studies

«Al posto del cervello avevo un grande schermo illuminato». Goliarda Sapienza e i «misteri» del cinema

Il saggio ripercorre la «parabola eccentrica» dell’attrice-scrittrice a partire dai suoi noti “romanzi di cinema” fino all’abbozzo inedito L’uomo Luchino Visconti, la cui trascrizione è offerta in calce al saggio

Comparative investigation on the soil burial degradation behaviour of polymer films for agriculture before and after photo-oxidation

Polymer films based on biodegradable polymers, polyethylene (PE) and modified PE with oxo-degradable additive were prepared by film blowing. Carbon black (1%) was added to all the films. Commercial biodegradable Ecovio\uae and Mater-Bi\uae samples were used. Mechanical properties, soil burial degradation and surface wettability were investigated, before and after UV irradiation. Chemical modifications induced by UV and soil degradation, or a synergic effect, were highlighted by Attenuated Total Reflection-Fourier Transform Infra-Red (ATR-FTIR). Photo-oxidized film samples with an elongation at break equal to 50% and 0.5 the initial value were selected for the soil burial degradation test at 30 \ub0C. Weight loss measurements were used to follow biodegradation in soil. Predictably, the degradation in soil was higher for biodegradable polymer-based films than for the PE-based ones. UV irradiation increased surface wettability and encouraged the disintegration in soil of all the samples. In fact, photo-oxidation produced a molar mass reduction and hydrophilic end groups, thus increasing surface erosion and weight loss. This paper not only supplies new criteria to evaluate the performance of biodegradable films in agriculture, before and after lifetime, but also provides a comparative analysis on the soil burial degradation behaviour with traditional ones

New Insight in Copper-Ion Binding to Human Islet Amyloid: The Contribution of Metal-Complex Speciation To Reveal the Polypeptide Toxicity

Type-2 diabetes (T2D) is considered to be a potential threat on a global level. Recently, T2D has been listed as a misfolding disease, such as Alzheimer's and Parkinson's diseases. Human islet amyloid polypeptide (hIAPP) is a molecule cosecreted in pancreatic β cells and represents the main constituent of an aggregated amyloid found in individuals affected by T2D. The trace-element serum level is significantly influenced during the development of diabetes. In particular, the dys-homeostasis of Cu2+ ions may adversely affect the course of the disease. Conflicting results have been reported on the protective role played by complex species formed by Cu2+ ions with hIAPP or its peptide fragments in vitro. The histidine (His) residue at position 18 represents the main binding site for the metal ion, but contrasting results have been reported on other residues involved in metal-ion coordination, in particular those toward the N or C terminus. Sequences that encompass regions 17–29 and 14–22 were used to discriminate between the two models of the hIAPP coordination mode. Due to poor solubility in water, poly(ethylene glycol) (PEG) derivatives were synthesized. A peptide fragment that encompasses the 17–29 region of rat amylin (rIAPP) in which the arginine residue at position 18 was substituted by a histidine residue was also obtained to assess that the PEG moiety does not alter the peptide secondary structure. The complex species formed by Cu2+ ions with Ac-PEG-hIAPP(17–29)-NH2, Ac-rIAPP(17–29)R18H-NH2, and Ac-PEG-hIAPP(14–22)-NH2 were studied by using potentiometric titrations coupled with spectroscopic methods (UV/Vis, circular dichroism, and EPR). The combined thermodynamic and spectroscopic approach allowed us to demonstrate that hIAPP is able to bind Cu2+ ions starting from the His18 imidazole nitrogen atom toward the N-terminus domain. The stability constants of copper(II) complexes with Ac-PEG-hIAPP(14–22)-NH2 were used to simulate the different experimental conditions under which aggregate formation and oxidative stress of hIAPP has been reported. Speciation unveils: 1) the protective role played by increased amounts of Cu2+ ions on the hIAPP fibrillary aggregation, 2) the effect of adventitious trace amounts of Cu2+ ions present in phosphate-buffered saline (PBS), and 3) a reducing fluorogenic probe on H2O2 production attributed to the polypeptide alone

The copper(II) and zinc(II) coordination mode of HExxH and HxxEH motif in small peptides: The role of carboxylate location and hydrogen bonding network

Copper(II) and zinc(II) complexes with two hexapeptides encompassing HExxH and HxxEH motif were characterized by means of a combined experimental and theoretical approach. Parallel tempering and density functional theory (DFT) investigations show the presence of different hydrogen bonding networks between the copper(II) and zinc(II) complexes with the two peptides, suggesting a significant contribution of these noncovalent interactions to the stability constant values. The glutamate carboxylate group has a direct role in metal ion binding. The location of this amino acid along the sequence of the investigated peptides is critical to determine thermodynamic and spectroscopic features of the copper(II) complex species, whereas is less relevant in the zinc(II) complexes formation. Electrospray ionization mass spectrometry (ESI-MS) characterization of the zinc(II) complex species show that in the [ZnH−2L] two deprotonated amide nitrogen atoms are involved in the metal coordination environment, an uncommon behavior in zinc(II) complexes for multi-histidine ligands

Somatostatin: A Novel Substrate and a Modulator of Insulin-Degrading Enzyme Activity

Insulin-degrading enzyme (IDE) is an interesting pharmacological target for Alzheimer's disease (AD), since it hydrolyzes beta-amyloid, producing non-neurotoxic fragments. It has also been shown that the somatostatin level reduction is a pathological feature of AD and that it regulates the neprilysin activity toward beta-amyloid. In this work, we report for the first time that IDE is able to hydrolyze somatostatin [k(cat) (s(-1)) = 0.38 (+/-0.05); K-m (M) = 7.5 (+/-0.9) x 10(-6)] at the Phe6-Phe7 amino acid bond. On the other hand, somatostatin modulates IDE activity, enhancing the enzymatic cleavage of a novel fluorogenic beta-amyloid through a decrease of the K-m toward this substrate, which corresponds to the 10-25 amino acid sequence of the A beta(1-40). Circular dichroism spectroscopy and surface plasmon resonance imaging experiments show that somatostatin binding to IDE brings about a concentration-dependent structural change of the secondary and tertiary structure(s) of the enzyme, revealing two possible binding sites. The higher affinity binding site disappears upon inactivation of IDE by ethylenediaminetetra acetic acid, which chelates, the catalytic Zn2+ ion. As a whole, these features suggest that the modulatory effect is due to an allosteric mechanism: somatostatin binding to the active site of one IDE subunit (where somatostatin is cleaved) induces an enhancement of IDE proteolytic activity toward fluorogenic beta-amyloid by another subunit. Therefore, this investigation on IDE-somatostatin interaction contributes to a more exhaustive knowledge about the functional and structural aspects of IDE and its pathophysiological implications in the amyloid deposition and somatostatin homeostasis in the brain. (C) 2008 Elsevier Ltd. All rights reserved

The Inorganic Side of NGF: Copper(II) And Zinc(II) Affect the NGF Mimicking Signalling of the N-Terminus Peptides Encompassing the Recognition Domain of TrkA Receptor

The nerve growth factor (NGF) N-terminus peptide, NGF(1-14), and its acetylated form, Ac-NGF(1-14), were investigated to scrutinise the ability of this neurotrophin domain to mimic the whole protein. Theoretical calculations demonstrated that non-covalent forces assist the molecular recognition of TrkA receptor for both peptides. Combined parallel tempering/docking simulations discriminated the effect of the N-terminal acetylation on the recognition of NGF(1-14) towards the domain 5 of TrkA (TrkA-D5). Experimental findings demonstrated that both NGF(1-14) and Ac-NGF(1-14) activate TrkA signaling pathways essential for neuronal survival. The NGF-induced TrkA internalization was slightly inhibited in the presence of Cu2+ and Zn2+ ions, whereas the metal ions elicited the NGF(1-14)-induced internalization of TrkA and no significant differences were found in the weak Ac-NGF(1-14)-induced receptor internalization. The crucial role of the metals was confirmed by experiments with the metal-chelator bathocuproine disulfonic acid, which discriminated different levels of inhibitory effects in the signalling cascade, due to different metal affinity of NGF, the free amino and the acetylated peptides. The NGF signaling cascade, activated by NGF (1−14) and Ac-NGF(1-14), induced CREB phosphorylation, but the copper addition further stimulated the Akt, ERK and CREB phosphorylation only for NGF and NGF(1-14). A dynamic and quick influx of both peptides into PC12 cells was tracked by live cell imaging with confocal microscopy. A significant role of copper ions was found in the modulation of peptide sub-cellular localization, especially at the nuclear level. Furthermore, a strong copper ionophoric ability of NGF(1-14) was measured. The Ac-NGF(1-14) peptide, which binds copper ions with a lower stability constant than NGF(1-14), exhibited a lower nuclear localization with respect to the total cellular uptake. These findings were correlated to the metal-induced increase of CREB and BDNF expression upon NGF(1-14) stimulation. In summary, we here validate NGF(1-14) and Ac-NGF(1-14) as first examples of monomer and linear peptides able to activate the NGF-TrkA signaling cascade. Metal ions modulate the activity of both NGF protein and the NGF-mimicking peptides. Such findings demonstrate that NGF(1-14) sequence can reproduce the signal transduction of whole protein, therefore represent a very promising drug candidate for further preclinical studies