Template-Assisted Enzymatic Synthesis of Oligopeptides from a Polylactide Chain

Peptides are often attached to polymer materials, as bioactive components, for the control of interactions between the material and its surrounding proteins and cells. However, synthesizing peptides and attaching them to polymers can be challenging and laborious. Herein, we describe the grafting of oligopeptides to an aliphatic polyester, using a one-step chemo-enzymatic synthesis with papain as the biocatalySt. To enable enzyme-mediated functionalization of the polyester, ethyl hept-6-enoylalaninate (grafter) was synthesized and attached to polylactide chains using thiol-ene click reactions. The oligopeptides were grafted onto the polylactide chains using two different synthetic routes: the grafting from strategy, in which the grafter was attached to the polyester prior to oligopeptide synthesis, or the grafting to strategy, in which oligopeptides were synthesized on the grafter first, then attached to the polymer chain. The final products were analyzed and their structures were confirmed using nuclear magnetic resonance (NMR). The peptide attachment was evaluated using size exclusion chromatography (SEC), contact angle measurement and energy-dispersive X-ray spectroscopy scanning electron microscopy (EDS-SEM). Furthermore, the mechanistic aspects of the synthesis of the oligopeptides on the grafter were studied using molecular dynamics (MD) simulations. The simulation revealed that hydrogen bonding (between the P1 amide nitrogen of the grafter backbone and the carbonyl oxygen of D158 in the papain) maintain the grafter in a productive conformation to stabilize the transition state of nitrogen inversion, a key step of the biocatalytic mechanism. Apart from being biologically relevant, both experimental and computational results suggest that the designed grafter is a good template for initiating chemo-enzymatic synthesis. The results also showed that the grafting to strategy was more successful compared to the grafting from strategy. Overall, a successful synthesis of predefined peptide functionalized polylactide was prepared, where the oligopeptides were grafted in an easy, time efficient, and environmentally friendly way. QC 2017121

Idrocarburi e aree ad alta diversit\ue0 culturale e biologica: un\u2019analisi geografica in Amazzonia

Le operazioni di esplorazione ed estrazione di idrocarburi in diversi contesti geografici sono ampiamente documentate tra le attivit\ue0 antropiche di maggiore impatto sui sistemi socio-ecologici e sul cambiamento climatico, cosi come \ue8 riconosciuta la necessit\ue0 di politiche pi\uf9 efficaci e l'uso di tecnologie pi\uf9 pulite. Lo studio presentato in questo contributo mira a: 1) analizzare e mappare le interazioni tra le attivit\ue0 legate agli idrocarburi e le aree che presentano un'elevata diversit\ue0 e sensibilit\ue0 culturale e biologica; 2) Discutere proposte di criteri geografici per individuare aree unburnable, ovvero dove lasciare gli idrocarburi sottoterra. La metodologia si basa sulla costruzione di un geodatabase open source dell'area di studio, che corrisponde all'Amazzonia dell'Ecuador e alla Region amazzonica di Loreto in Per\uf9, area riconosciuta per la sua elevata diversit\ue0 ecologica e culturale. \uc8 stata condotta un\u2019analisi in ambiente QGIS delle sovrapposizioni tra gli aspetti socio-ecologici (aree protette, territori indigeni) e le attivit\ue0 di esplorazione e produzione di idrocarburi (riserve, blocchi, pozzi, oleodotti), oltre alla revisione di documenti scientifici e non su questi aspetti. Alcuni risultati dell'analisi GIS mostrano che quasi l'intera area di studio fa parte della provincia geologica del Putumayo-Oriente-Mara\uf1on, con una stima di 7290 milioni barili di petrolio equivalente sottoterra, dove le concessioni di idrocarburi coprono il 33% della superficie e si trovano circa 1780 pozzi. Le aree protette ricadenti nelle concessioni risultano essere il 18% e importanti sono anche le sovrapposizioni con i territori indigeni, evidenziando cos\uec l'urgenza di politiche pi\uf9 efficaci per garantire la sostenibilit\ue0 ambientale e sociale e la definizione di criteri geografici per individuare aree unburnable

Transverse strange quark spin structure of the nucleon

We investigate the transverse quark spin densities of the nucleon with the lowest moment within the framework of the SU(3) chiral quark-soliton model, emphasizing the strange quark spin density. Based on previous results of the vector and tensor form factors, we are able to determine the impact-parameter dependent probability densities of transversely polarized quarks in an unpolarized nucleon as well as those of unpolarized quarks in a transversely polarized nucleon. We find that the present numerical results for the transverse spin densities of the up and down quarks are in good agreement with those of the lattice calculation. We predict the transvere spin densities of the strange quark. It turns out that the polarized strange quark is noticeably distorted in an unpolarized proton.Comment: 10 pages. 16 figures. Submitted to Physical Review

Tagaeri Taromenane: popoli incontattati dell\u2019Amazzonia Ecuadoriana ed espansione della frontiera petrolifera, quali territori per l\u2019autodeterminazione e i diritti umani?

Nel 1999 l\u2019Ecuador, primo paese al mondo, istituiva una zona Intangibile riservata al diritto all\u2019autodeterminazione dei popoli incontattati Tagaeri- Taromenane. Nel 2007 la Zona Intangibile Tagaeri-Taromenane (ZITT) veniva finalmente delimitata occupando un\u2019area di 7500 km2 della regione amazzonica ai confini con il Peru, perpetuamente vietata ad ogni attivit\ue0 industriale. Contemporaneamente veniva istituita anche una buffer zone di 10 km per garantire una ulteriore area di rispetto. Tuttavia trattandosi di popolazioni nomadi che per secoli si sono mosse su un\u2019area di circa 20.000 km2 tra i fiumi Napo e Curaray (in direzione Nord sud) e tra i primi rilievi andini e la confluenza del Nashino con il Curaray (in direzione ovest est) la Zona Intangibile non risulta adeguata alla territorialit\ue0 Tagaeri-Taromenane. Accanto alla mobilit\ue0 dei popoli in isolamento si assiste alla mobilit\ue0 della frontiera petrolifera. Il lavoro utilizza il ruolo della scala (cartografica e geografica) e le sue implicazioni cognitive per osservare ci\uf2 che sta accadendo attorno, vicino e all'interno della zona intangibile, da una visione continentale al dettaglio della sua storia e della sua istituzione. Gli strumenti cartografici e geografici ci aiutano a visualizzare l\u2019oggi e immaginare il domani, sapendo che il destino di questo angolo dell'Amazzonia non \ue8 necessariamente definito: si tratta di una regione ad alta complessit\ue0 territoriale con la possibilit\ue0 di articolare una rete tra aree protette, territori indigeni e corridoi ecologici culturali, alla ricerca di percorsi alternativi di sviluppo locale

Star-forming dwarf galaxies in the Virgo cluster: the link between molecular gas, atomic gas, and dust

We present $^{12}$CO(1-0) and $^{12}$CO(2-1) observations of a sample of 20 star-forming dwarfs selected from the Herschel Virgo Cluster Survey, with oxygen abundances ranging from 12 + log(O/H) ~ 8.1 to 8.8. CO emission is observed in ten galaxies and marginally detected in another one. CO fluxes correlate with the FIR 250 $\mu$m emission, and the dwarfs follow the same linear relation that holds for more massive spiral galaxies extended to a wider dynamical range. We compare different methods to estimate H2 molecular masses, namely a metallicity-dependent CO-to-H2 conversion factor and one dependent on H-band luminosity. The molecular-to-stellar mass ratio remains nearly constant at stellar masses <~ 10$^9$ M$_{\odot}$, contrary to the atomic hydrogen fraction, M$_{HI}$/M$_*$, which increases inversely with M$_*$. The flattening of the M$_{H_2}$/M$_*$ ratio at low stellar masses does not seem to be related to the effects of the cluster environment because it occurs for both HI-deficient and HI-normal dwarfs. The molecular-to-atomic ratio is more tightly correlated with stellar surface density than metallicity, confirming that the interstellar gas pressure plays a key role in determining the balance between the two gaseous components of the interstellar medium. Virgo dwarfs follow the same linear trend between molecular gas mass and star formation rate as more massive spirals, but gas depletion timescales, $\tau_{dep}$, are not constant and range between 100 Myr and 6 Gyr. The interaction with the Virgo cluster environment is removing the atomic gas and dust components of the dwarfs, but the molecular gas appears to be less affected at the current stage of evolution within the cluster. However, the correlation between HI deficiency and the molecular gas depletion time suggests that the lack of gas replenishment from the outer regions of the disc is lowering the star formation activity.Comment: 19 pages, 11 figures, accepted for publication in Astronomy & Astrophysic

Feasibility study and design concept for an orbiting ice-penetrating radar sounder to characterize in three-dimensions the Europan ice mantle down to (and including) any ice/ocean interface

This report presents a radar sounding model based on the range of current working hypotheses for the nature of Europa's icy shell.Institute for Geophysic

Capillary barriers during rainfall events in pyroclastic deposits of the vesuvian area

In the present paper, the capillary barrier formation at the interface between soil layers, which is characterized by textural discontinuities, has been analyzed. This mechanism has been investigated by means of a finite element model of a two-layer soil stratification. The two considered formations, belonging to the pyroclastic succession of the “Pomici di Base” Plinian eruption (22 ka, Santacroce et al., 2008) of the Somma–Vesuvius volcano, are affected by shallow instability phenomena likely caused by progressive saturation during the rainfall events. This mechanism could be compatible with the formation of capillary barriers at the interface between layers of different grain size distributions during infiltration. One-dimensional infiltration into the stratified soil was parametrically simulated considering rainfall events of increasing intensity and duration. The variations in the suction and degree of saturation over time allowed for the evaluation of stability variations in the layers, which were assumed as part of stratified unsaturated infinite slopes

Bias in meta-analyses using Hedges’ d

The type of metric and weighting method used in meta-analysis can create bias and alter coverage of confidence intervals when the estimated effect size and its weight are correlated. Here, we investigate bias associated with the common metric, Hedges’ d, under conditions common in ecological meta-analyses. We simulated data from experiments, computed effect sizes and their variances, and performed meta-analyses applying three weighting schemes (inverse variance, sample size, and unweighted) for varying levels of effect size, within-study replication, number of studies in the meta-analysis, and among-study variance. Unweighted analyses, and those using weights based on sample size, were close to unbiased and yielded coverages close to the nominal level of 0.95. In contrast, the inverse-variance weighting scheme led to bias and low coverage, especially for meta-analyses based on studies with low replication. This bias arose because of a correlation between the estimated effect and its weight when using the inverse-variance method. In many cases, the sample size weighting scheme was most efficient, and, when not, the differences in efficiency among the three methods were relatively minor. Thus, if using Hedges’ d, we recom