Hydrogen Bond Dynamics of Cellulose through Inelastic Neutron Scattering Spectroscopy.

This work explores the dynamics of hydrogen bond networks in cellulose through inelastic neutron scattering (INS) and periodic CASTEP calculations. Estimated spectra were based on the crystal structure of cellulose Iα and Iß and replicate the INS spectrum of cellulose samples with remarkable similarity, allowing a reliable assignment of INS bands to vibrational modes of cellulose. Comparison of cellulose samples from varied sources, from bacterial to kraft pulp, allows the identification of characteristic INS bands, arising from C2-OH torsional motions, which easily identify which allomorph-Iα or Iß-is prevalent. A high crystallinity index is revealed by the presence of well-defined INS bands associated with highly cooperative CH bending modes along the chain. Hydrating kraft cellulose samples clearly affects those INS bands related with the hydroxymethyl group, identified as the preferred binding site for water molecules. At high humidity content level, a significant proportion of the water molecules is aggregated in clusters within the amorphous cellulose domains. The formation of ice microcrystals leads to a partial disruption of the hydrogen-bond network, as can be concluded from the observed red-shift of the torsional OH vibrational modes. The full assignment and interpretation of cellulose's INS spectra herein provided is a sound basis for future use of INS spectroscopy in the characterization of functionalized cellulose fibers and composite materials.

Bacterial cellulose membranes as drug delivery systems: an in vivo skin compatibility study.

Bacterial cellulose (BC) is a highly pure form of cellulose, produced in the form of a swollen membrane by several bacteria that demonstrated to be able to modulate the skin release of model drugs. In the present study, the skin irritation potential of BC was evaluated in human subjects. BC membranes with and without glycerin (acting as plasticizer) were tested. No significant differences were observed for transepidermal water loss (TEWL) measurements in comparison with negative control, 2 and 24 h after patch removal, which is an indicator of an absence of barrier disruption. Similar results were found for erythema. Clinical scores were zero at both times for all volunteers, with the exception of five volunteers that exhibited weak reactions. BC with glycerin provided a skin moisturizing effect statistically higher than the negative control (p=0.044), which was not observed for BC alone. The good skin tolerance found after a single application under occlusion reinforces the putative interest of BC membranes as supports for drug topical delivery. Besides modifying the mechanical properties, the inclusion of glycerin results in a skin moisturizing effect which could be clinically relevant for the treatment for skin diseases characterized by dryness, such as psoriasis and atopic dermatitis.

Photodegradation of the fungicide thiram in aqueous solutions. Kinetic studies and identification of the photodegradation products by HPLC-MS/MS.

In this study, the relevance of photodegradation processes on the persistence of the fungicide thiram in waters was investigated. The photodegradation of thiram in Milli-Q water and in aqueous solutions of humic and fulvic acids, as well as the photodegradation in spiked river water were studied. Both pure thiram and one of its commercial formulations were used to prepare the solutions which were irradiated in a solar light simulator. In general, thiram photodegradation follows pseudo-first order kinetics. The half-life time of thiram 2mgL(-1) in Milli-Q water was 28min. However, the degradation rate of thiram was significantly increased (p=0.02) by the inert components of the thiram commercial formulation as well as by commercial humic acids and by fulvic acids isolated from river water (p<0.004). Thus, the half-life time of thiram decreased to 24min in the presence of the inert formulation components, while, in the presence of both humic and fulvic acids (10mgL(-1)) it decreased to 22min. Furthermore, thiram photodegradation in natural river water showed that there is a significant enhancement of the degradation rate constant of thiram relatively to Milli-Q water, corresponding to a decrease of about 38% in its half-life time. This increase of the degradation rate in river water seems to be higher than that observed in the presence of FA, suggesting that beyond organic matter, other natural river components can increase the thiram photodegradation rate. These results allow us to conclude that photodegradation by solar radiation can be an important degradation pathway of thiram in natural waters. HPLC-MS/MS allowed to identify, for the first time, three products of the photodegradation of thiram in aqueous solution. Three compounds were identified and their structure was corroborated by the MS(n) spectra fragmentation profile. Pathways for the formation of the products from thiram photodegradation are proposed and discussed.

Miscanthus x giganteus extractives: a source of valuable phenolic compounds and sterols.

The chemical composition of the lipophilic extracts of bark and core, of the Miscanthus x giganteus stalk, was studied by gas chromatography-mass spectrometry (GC-MS). Aromatic compounds, sterols, and fatty acids, followed by long-chain fatty alcohols, were the major families of components present in the M. x giganteus stalk. Aromatic compounds are more abundant in the M. x giganteus bark (521 mg/kg of bark), with vanillic acid, vanillin, and p-hydroxybenzaldehyde as the major compounds of this family. In the M. x giganteus core, sterols represent about 949 mg/kg of dry core with beta-sitosterol, 7-oxo-beta-sitosterol, stigmasterol, and campesterol as the major components. The detection of small amounts of esters in the GC-MS analysis with short columns explains the small increase in the abundance of the identified families after alkaline hydrolysis. The high content of valuable sterols and aromatic compounds in M. x giganteus and, particularly, in the core, which is considered a residue in most applications, can open new perspectives for the integrated upgrading of this grass within the biorefinery perspective.

Genotype and sex effects on carcass and meat quality of suckling kids protected by the PGI "Cabrito de Barroso".

Carcass composition and meat quality traits were evaluated in 55 suckling kids (27 males and 28 females) from Serrana (S), Bravia (B) and Serrana×Bravia (S×B) crossbred genotypes. Kids were slaughtered at 8-11kg of live weight according to "Cabrito de Barroso-PGI" specifications and carcasses' left sides were totally dissected. Dressing percentage (based on ELW) did not vary between genotypes and sexes. Genotype B carcasses have better conformation, expressed in higher compactness index and muscle/bone ratio. Sex had no effect on the composition of dissected carcass but females deposited more internal fat than males. S genotype had significantly less muscle content and higher dissectible fat compared to B and S×B genotypes, suggesting differences in maturity stages. The carcass' bone content (20.4-21.4%) did not differ significantly between genotypes. The longissimus thoracis et lumborum (LTL) and gluteobiceps (GB) muscles were used for meat quality determinations. Genotype had a significant effect on meat traits and fatty acid composition of the analysed muscles: B genotype and LTL muscle showed lower final pH, S×B genotype had darker and more red muscles, GB muscle had a higher shear force value and lower collagen solubility. Few sex effects were observed on meat quality traits as well as on fatty acid composition. Average percentage of desirable fatty acids in kids was superior to 60% with male S genotype displaying a lower value. Genotypes B and B×S, males and GB muscle had more favorable PUFA:SFA ratios.