Chestnut Shell as Unexploited Source of Fermentable Sugars: Effect of Different Pretreatment Methods on Enzymatic Saccharification

Chestnut shell (CS) is an agronomic residue mainly used for extraction of antioxidants or as adsorbent of metal ions. It also contains some polysaccharide that has not been considered as potential source of fermentable sugars for biofuel production until now. In this study, the effect of different pretreatment methods on CS was evaluated in order to obtain the greatest conversion of cellulose and xylan into fermentable sugars. Hot acid impregnation, steam explosion (acid-catalysed or not), and aqueous ammonia soaking (AAS) were selected as pretreatments. The pretreated biomass was subjected to saccharification with two enzyme cocktails prepared from commercial preparations, and evaluation of the best pretreatment and enzyme cocktail was based on the yield of fermentable sugars produced. As AAS provided the best result after preliminary experiments, enhancement of sugar production was attempted by changing the concentrations of ammonium hydroxide, enzymes, and CS. The optimal pretreatment condition was 10 % ammonium hydroxide, 70 °C, 22 h with CS at 5 % solid loading. After saccharification of the pretreated CS for 72 h at 50 °C and pH 5.0 with a cocktail containing cellulase (Accellerase 1500), beta-glucosidase (Accellerase BG), and xylanase (Accellerase XY), glucose and xylose yields were 67.8 and 92.7 %, respectively.     

Derivatives of 3-Deoxy-3-(N-Hydroxyamino)-D-Ribose

Abstract

A series of 3-(N-arylmethyl-N-hydroxyamino)-l,2-O-cyclopentylidene-3-deoxy-5-O-toluoyl-α-D-riboses has been prepared. The blocking groups used were chosen to allow an easy nucleosidation of these compounds to spin labelled analogs of natural nucleosides. The conformational behavior of the N-arylmethyl-N-hydroxyamino group has been studied using ³/_CH NMR coupling data and molecular mechanics computations. Upon spontaneous oxidation, these hydroxylamines led to the corresponding aminoxyl free radicals which were submitted to EPR spectroscopy and quantum mechanical computations at a semiempirical level (PM3).     

Optical constants of organic insulators in the UV range extracted from reflection electron energy loss spectra

Reflection electron energy loss spectroscopy (REELS) spectra were measured for seven insulating organic compounds (DNA, Irganox 1010, Kapton, polyethylene [PE], poly(methyl methacrylate) [PMMA], polystyrene [PS] and polytetrafluoroethylene [PTFE]). Optical constants and energy band gaps were extracted from the measured REELS spectra after elimination of multiple electron scattering via a deconvolution and fitting the normalised single scattering energy loss spectra to Drude and Drude–Lindhard model dielectric functions, constrained by the Kramers–Kronig sum and f-sum rules. Satisfactory agreement is found for those optical constants for which literature data exists. For PTFE, the observed features in the optical data correspond to its electronic structure.     

Photoactivatable V-Shaped Bifunctional Quinone Methide Precursors as a New Class of Selective G-quadruplex Alkylating Agents

Combining the selectivity of G-quadruplex (G4) ligands with the spatial and temporal control of photochemistry is an emerging strategy to elucidate the biological relevance of these structures. In this work, we developed six novel V-shaped G4 ligands that can, upon irradiation, form stable covalent adducts with G4 structures via the reactive intermediate, quinone methide (QM). We thoroughly investigated the photochemical properties of the ligands and their ability to generate QMs. Subsequently, we analyzed their specificity for various topologies of G4 and discovered a preferential binding towards the human telomeric sequence. Finally, we tested the ligand ability to act as photochemical alkylating agents, identifying the covalent adducts with G4 structures. This work introduces a novel molecular tool in the chemical biology toolkit for G4s.     

Exploiting Protein N-Terminus for Site-Specific Bioconjugation

Although a plethora of chemistries have been developed to selectively decorate protein molecules, novel strategies continue to be reported with the final aim of improving selectivity and mildness of the reaction conditions, preserve protein integrity, and fulfill all the increasing requirements of the modern applications of protein conjugates. The targeting of the protein N-terminal alpha-amine group appears a convenient solution to the issue, emerging as a useful and unique reactive site universally present in each protein molecule. Herein, we provide an updated overview of the methodologies developed until today to afford the selective modification of proteins through the targeting of the N-terminal alpha-amine. Chemical and enzymatic strategies enabling the selective labeling of the protein N-terminal alpha-amine group are described.     

Influence of surface heterogeneity in electroosmotic flows—Implications in chromatography, fluid mixing, and chemical reactions in microdevices

We analyze the influence of surface heterogeneity, inducing a random ζ-potential at the walls in electroosmotic incompressible flows. Specifically, we focus on how surface heterogeneity modifies the physico-chemical processes (transport, chemical reaction, mixing) occurring in microchannel and microreactors. While the macroscopic short-time features associated with solute transport (e.g. chromatographic patterns) do not depend significantly on ζ-potential heterogeneity, spatial randomness in the surface ζ-potential modifies the spectral properties of the advection-diffusion operator, determining different long-term properties of transport/reaction phenomena compared to the homogeneous case. Examples of physical relevance (chromatography, infinitely fast reactions) are addressed.     

Organocatalytic Stereoselective Iodoamination of Alkenes

A new chiral thiohydantoin catalyst is used for the stereoselective iodoamination of alkenes. N‐iodosuccinimide as the source of the electrophilic iodine is activated by catalytic amounts of different additives which also influence the regioselectivity of some cyclizations.     

XPS study of Cr segregation in a martensitic stainless steel

Cr martensitic steels are promising materials for structural applications in future nuclear fusion reactors. Because the embrittlement after tempering treatments can be a serious problem, the fracture mode of a steel with 10.5 wt% of Cr treated at 700°C for 18 h has been investigated through Charpy tests in the temperature range from −100°C to +150°C. X-ray photoelectron spectroscopy (XPS) analyses carried out on the fracture surfaces evidenced the segregation of Cr in both ductile and brittle (quasicleavage) fields. The unexpected result indicates that Cr segregation weakens the atomic bonds; thus, the fracture path in both the cases corresponds to the zones with higher Cr content.