Oxygen migration on the graphene surface. 2. Thermochemistry of basal-plane diffusion (hopping)

Thermodynamic affinities, activation energies and diffusion coefficients for oxygen mobility on the graphene surface are calculated using density functional theory (DFT). We report and discuss the effects of geometry, charge distribution and heteroatom substitution on the migration of epoxy oxygen on the basal plane: both the driving force and the ease of surface hopping are very sensitive to their variations. A significant decrease in the hopping energy barrier is observed when graphene contains free edge sites and oxygen functionalities, as well as upon an increase in electron density; conversely, the barrier increases as a consequence of electron removal, and the propensity for graphene ‘unzipping’ also increases. There is a correlation between the hopping barrier and the C–O bond strength of the leaving epoxide group. Under the most favorable conditions investigated, oxygen mobility is quite high, of the same order as that of gas-phase O₂ in micropores (ca. 10⁻⁹ m²/s). This is consistent with the increasingly acknowledged role of basal-plane oxygen as a protagonist (e.g., reaction intermediate), instead of a spectator, in the wide variety of adsorption and reaction processes involving sp²-hybridized carbon materials.     

Determining the residual alcohol in biodiesel through its flash point

A simple low cost method is proposed for the quantitative analysis of residual alcohol in biodiesel through determination of the flash point, with which it is correlated. Methyl ester biodiesels from vegetable oils such as corn, soy and sunflower were prepared. The ethyl ester was obtained from soy oil and methyl biodiesel was also synthesized from bovine fat. In all cases it became very evident that there is a direct correlation between the flash point and the residual alcohol content in the prepared biodiesel. Therefore this parameter can be used to directly determine the residual alcohol content of the product.     

Antioxidant activity of pine bark procyanidins in bulk corn oil and corn oil‐in‐water emulsions

In this work, the ability of pine bark procyanidins to hinder oxidation in bulk corn oil and corn oil‐in‐water‐emulsion has been investigated. A preliminary characterisation of the obtained aqueous (AF) and organic (OW) fractions and subfractions suggested a very polar character and showed that both fractions possess remarkable antioxidant activity when minimum concentrations of 2 mg/mL are used. OW fractions and subfractions derived from both pine varieties were able to inhibit oxidation in oils. More specifically, two organic subfractions were the most efficient for retarding the degradation process, with levels of 62% and 50% after 8 days of treatment, respectively. Organic subfractions obtained from both varieties of pine also rendered possible inhibition levels in oil‐in‐water‐emulsions up to 80% after 4 days of oxidation, more than 3 times higher than the levels provided by tocopherol, a well‐known model commercial antioxidant, which confirms the excellent antioxidant potential of procyanidins from pine bark. Practical application: Lipid deterioration leads to losses in quality and nutritional value and to the development of off‐flavours in many foodstuffs. One way to overcome this drawback is by using antioxidants of natural origin, which is a subject of a great scientific and industrial interest, reflected by the growing number of papers and patents published during the last years. Since aqueous and organic fractions obtained from Pinus pinaster and Pinus radiata bark turned out to be an adequate source of procyanidins in previous investigations of our group, their possible antioxidant role in model lipid systems was investigated. This approach entails also another benefit in terms of waste valorisation, since pine bark is a typical residue of agroforestal industries.     

Current advances in the non‐chromatographic fractionation and characterization of PEGylated proteins

For more than 30 years, PEGylation has been used to improve the physicochemical properties of several proteins and therapeutic drugs having a major impact in the biopharmaceutical industry. The purification of PEGylated proteins usually involves two basic challenges: (1) the separation of PEG‐proteins from other reaction products; and (2) the sub‐fractionation of PEG‐proteins on the basis of their degree of PEGylation and positional isomerism. Currently, most PEGylated protein purification processes are based on chromatographic techniques, especially size exclusion chromatography (SEC) and ion exchange chromatography (IEX). Nonetheless, other less frequently used strategies based on non‐chromatographic techniques such as ultrafiltration, electrophoresis, capillary electrophoresis, and aqueous two‐phase systems have been developed in order to fractionate and analyze PEGylated derivates. This review presents current advances in some of the most widely used non‐chromatographic strategies for the fractionation and analysis of PEG‐protein conjugates. Copyright © 2010 Society of Chemical Industry     

THE EFFECT OF TEMPERATURE TREATMENT ON PENETRANT TRANSPORT IN COAL

The macromolecular structure of coals thermally treated at 35^°C, 100^°C and 150^°C was investigated by dynamic penetrant transport in thin coal sections. The effects of temperature, carbon content in coal, and penetrant type on the transport mechanism were investigated. Dynamic swelling studies showed that penetrant transport into coal is a function of the average molecular weight between crosslinks, M_c. The penetrant transport mechanism at low activity is Fickian diffusion. The transport mechanism deviates from Fickian diffusion to anomalous transport, when the carbon content in coal and penetrant activity increase. Variations of the diffusion coefficients and relaxation constants were determined using a diffusion/relaxation coupled model.     

Conversion and hydroconversion of hydrocarbons on zeolite-based catalysts: an FT-IR study

The interaction of HZSM5 and Mo-ZSM5 with benzene, naphthalene, toluene, ortho-xylene, para-xylene, n-butane, isobutane, n-heptane, and methylcyclohexane, in the range 100–773 K has been investigated using FT-IR spectroscopy. Hydrogen bonded species with the internal bridging and the external terminal OHs has been detected. The reactivity at high temperature has also been studied. The access to the internal cavities and to the strongly acidic OHs is at least partly hindered in the case of Mo-ZSM5. The catalytic activity of ZSM5 was moderated by the addition of molybdenum, with lower cracking and higher liquid yields.     

An FT-IR study of the adsorption of aromatic hydrocarbons and of 2,6-lutidine on H-FER and H-ZSM-5 zeolites

The interaction of aromatic hydrocarbons benzene, toluene, o-, m- and p-xylene and of methyl pyridines (in particular 2,6-lutidine) with H-ZSM-5 and H-FER zeolites has been studied. Two different H-ZSM-5 samples with strongly different intensity ratios between the two main OH stretching bands have been used. Benzene, toluene and p-xylene enter easily the cavities and give rise to three different H-bonded complexes. Two of them are strongly bonded while the third is likely a very hindered and distorted one. o-Xylene enters slowly the cavities and m-xylene even more slowly. Faster diffusion occurs at higher temperatures. On the contrary, xylenes do not enter the FER cavities. In spite of its steric hindrance, supposed to be the same of m-xylene, 2,6-lutidine enters fast the ZSM channels and is protonated by the internal sites. On the contrary, it does not enter the FER cavities, but it is protonated too on the external silanols sites. Evidence is provided for some kind of heterogeneity of the internal sites of ZSM-5 zeolite. Additionally, it is concluded that other effects besides the molecular sieving effect may play a role in the access and diffusion of molecules into the zeolite channels.     

A simple model for the semicontinuous heterophase polymerization: Ethyl methacrylate as a case example

A simple but comprehensive model considering homogeneous and micellar nucleation, coagulation, entry of radicals to particles and to micelles and radicals' exit from particles, is presented. The model is validated, in a starved semicontinuous heterophase polymerization of ethyl methacrylate, at three monomer addition rates. The model accurately describes the overall and instantaneous conversion, the average particle density and diameter, and the number and weight average molar masses evolutions over time. It is found that even though the average number of radicals is much smaller than 0.5, the system is not 0-1. An empirical function was used to describe the gel effect. The homogeneous nucleation was the prevailing mechanism for particle formation and large exit rates of radicals were observed. POLYM. ENG. SCI., 60: 223–232, 2019. © 2019 Society of Plastics Engineers     

GOLPH3 Regulates EGFR in T98G Glioblastoma Cells by Modulating Its Glycosylation and Ubiquitylation

Protein trafficking is altered when normal cells acquire a tumor phenotype. A key subcellular compartment in regulating protein trafficking is the Golgi apparatus, but its role in carcinogenesis is still not well defined. Golgi phosphoprotein 3 (GOLPH3), a peripheral membrane protein mostly localized at the trans-Golgi network, is overexpressed in several tumor types including glioblastoma multiforme (GBM), the most lethal primary brain tumor. Moreover, GOLPH3 is currently considered an oncoprotein, however its precise function in GBM is not fully understood. Here, we analyzed in T98G cells of GBM, which express high levels of epidermal growth factor receptor (EGFR), the effect of stable RNAi-mediated knockdown of GOLPH3. We found that silencing GOLPH3 caused a significant reduction in the proliferation of T98G cells and an unexpected increase in total EGFR levels, even at the cell surface, which was however less prone to ligand-induced autophosphorylation. Furthermore, silencing GOLPH3 decreased EGFR sialylation and fucosylation, which correlated with delayed ligand-induced EGFR downregulation and its accumulation at endo-lysosomal compartments. Finally, we found that EGF failed at promoting EGFR ubiquitylation when the levels of GOLPH3 were reduced. Altogether, our results show that GOLPH3 in T98G cells regulates the endocytic trafficking and activation of EGFR likely by affecting its extent of glycosylation and ubiquitylation.