Assessment of Bleached and Unbleached Nanofibers from Pistachio Shells for Nanopaper Making

Cellulose and lignocellulose nanofibrils were extracted from pistachio shells utilizing environmentally friendly pulping and totally chlorine-free bleaching. The extracted nanofibers were used to elaborate nanopaper, a continuous film made by gravimetric entanglement of the nanofibers and hot-pressed to enhance intramolecular bonding. The elaborated nanopapers were analyzed through their mechanical, optical, and surface properties to evaluate the influence of non-cellulosic macromolecules on the final properties of the nanopaper. Results have shown that the presence of lignin augmented the viscoelastic properties of the nanopapers by ≈25% compared with fully bleached nanopaper; moreover, the hydrophobicity of the lignocellulose nanopaper was achieved, as the surface free energy was diminished from 62.65 to 32.45 mNm−1 with an almost non-polar component and a water contact angle of 93.52°. On the other hand, the presence of lignin had an apparent visual effect on the color of the nanopapers, with a ΔE of 51.33 and a ΔL of −44.91, meaning a substantial darkening of the film. However, in terms of ultraviolet transmittance, the presence of lignin resulted in a practically nonexistent transmission in the UV spectra, with low transmittance in the visible wavelengths. In general, the presence of lignin resulted in the enhancement of selected properties which are desirable for packaging materials, which makes pistachio shell nano-lignocellulose an attractive option for this field.

Dynamic Structure and Stability of DNA Duplexes Bearing a Dinuclear Hg(II)-Mediated Base Pair

Quantum mechanical (QM) and hybrid quantum mechanical/molecular mechanical (QM/MM) molecular dynamics simulations of a recently reported dinuclear mercury(II)-mediated base pair were performed aiming to analyse its intramolecular bonding pattern, its stability, and to obtain clues on the mechanism of the incorporation of mercury(II) into the DNA. The dynamic distance constraint was employed to find initial structures, control the dissociation process in an unbiased fashion and to determine the free energy required. A strong influence of the exocyclic carbonyl or amino groups of neighbouring base pairs on both the bonding pattern and the mechanism of incorporation was observed. During the dissociation simulation, an amino group of an adenine moiety of the adjacent base pair acts as a turnstile to rotate the mercury(II) ion out of the DNA core region. The calculations provide an important insight into the mechanism of formation of this dinuclear metal-mediated base pair and indicate that the exact location of a transition metal ion in a metal-mediated base pair may be more ambiguous than derived from simple model building.

NetWheels: A web application to create high quality peptide helical wheel and net projections

Helices are one of the most common secondary structures found in peptides and proteins. The wheel and net projections have been proposed to represent in two dimensions the tridimensional helical structures and facilitate the observation of their properties, especially in terms of residues polarity and intramolecular bonding. Nevertheless, there are few software options to create these projections. We have developed a web-based application that has several futures to create, customize and export these projections and is freely available at http://lbqp.unb.br/NetWheels.

Neural plasticity and memory: molecular mechanism

Deciphering the cellular and molecular mechanisms of memory has been an important topic encompassing the learning and memory domain besides the neurodegenerative disorders. Synapses accumulate cognitive information from life-lasting alterations of their molecular and structural composition. Current memory storage models identify posttranslational modification imperative for short-term information storage and mRNA translation for long-term information storage. However, the precise account of these modifications has not been summarized at the individual synapse level. Therefore, herein we describe the spatiotemporal reorganization of synaptic plasticity at the dendritic spine level to elucidate the mechanism through which synaptic substructures are remodeled; though at the molecular level, such mechanisms are still quite unclear. It has thus been concluded that the existing mechanisms do not entirely elaborate memory storage processes. Further efforts are therefore encouraged to delineate the mechanism of neuronal connectivity at the chemical level as well, including inter- or intramolecular bonding patterns at the synaptic level, which may be a permissive and vital step of memory storage.