Thermal investigation of heavy crude oil by simultaneous TG–DSC–FTIR and EDXRF

Present study investigates thermal behavior of two heavy crude oils with different °API values by simultaneous thermogravimetry–differential scanning calorimetry–fourier transform infrared spectroscopy (TG–DSC–FTIR), and an evaluation of the chemical element levels present in the oils’ ashes was done by energy dispersive X-ray fluorescence spectrometry. TG and DSC curves were obtained for two samples in nitrogen atmosphere. Among all inorganic components evaluated, the highest concentration in the two oils was SO₃. Thus this study may contribute to a better understanding of the thermal behavior of heavy crude oils and their composition.     

Study on the Regioselectivity of Rhodium-Catalyzed Ring Opening Reactions of C1-Substituted 7-Oxabenzonorbornadienes with Boronic Acids

An optimized condition for the rhodium-catalyzed ring-opening reaction of C₁-substituted oxabicyclic alkenes with aryl boronic acids was developed and the effect of aryl boronic acid as well as the effect of C₁ substitution on the oxabicyclic alkenes was studied. Aryl boronic acids carrying electron-donating substituents provided the ring-opened products in excellent yields regardless of the position, while electron-withdrawing substituents were more susceptible to steric interactions. Although two different regioisomers are possible, all the rhodium-catalyzed ring-opening reactions of C₁ substituted oxabicyclic alkenes studied with aryl boronic acids were found to be highly regioselective, giving single regioisomers in all cases.     

Rapid Aqueous Borohydride Reduction of Carbonyls Under Sealed-Tube Microwave Conditions

Ketones and aldehydes are conveniently and rapidly reduced to the corresponding alcohols in good yields using sodium borohydride under sealed-tube microwave conditions in either 95% ethanol or water. In purely aqueous systems, highly aliphatic substrates are sluggish, but this can be overcome by introducing sodium dodecyl sulfate (SDS) at the critical micelle concentration. With a 2:1 substrate/borohydride ratio and a reaction temperature of 100 °C, reduction is typically complete within 1 min in 95% ethanol and 5 min in water/SDS. The methodology is well suited for parallel and combinatorial synthetic approaches.     

Illicium Sesquiterpenes: Divergent Synthetic Strategy and Neurotrophic Activity Studies

Majucin‐type sesquiterpenes from Illicium sp., such as jiadifenolide ( 2 ), jiadifenin ( 3 ), and (1R,10S)‐2‐oxo‐3,4‐dehydroxyneomajucin ( 4 , ODNM), possess a complex caged chemical architecture and remarkable neurotrophic activities. As such, they represent attractive small‐molecule leads against various neurodegenerative diseases. We present an efficient, enantioselective, and unified synthesis of 2 , 3 , and 4 and designed analogues that diverge from tetracyclic key intermediate 7 . The synthesis of 7 is highlighted by the use of an enantioselective Robinson annulation reaction (construction of the AB rings), a Pd‐mediated carbomethoxylation reaction (construction of the C ring), and a one‐pot oxidative reaction cascade (construction of the D ring). Evaluation of the neurotrophic activity of these compounds led to the identification of several highly potent small molecules that significantly enhanced the activity of nerve growth factor (NGF) in PC‐12 cells. Moreover, efforts to define the common pharmacophoric motif suggest that substitution at the C‐10 center significantly affects bioactivity, while the hemiketal moiety of 2 and 3 and the C‐1 substitution might not be critical to the neurotrophic activity.     

Characterization of the patina formed on a low tin bronze exposed to aqueous hydrogen sulfide

The dark gray corrosion layer (patina) formed on the surface of a polished low tin bronze alloy following exposure to a deoxygenated and saturated aqueous solutions of H₂S has been characterized by X‐ray photoelectron spectroscopy, scanning electron microscopy‐energy dispersive spectroscopy and X‐ray diffraction. The system represents a model for bronze corrosion in reducing conditions where sulfate‐reducing bacteria in soils or deoxygenated seawater may generate H₂S during respiration. The initial surface was dominated by metallic copper together with Sn, Pb and Zn oxides and hydroxides. Surface enrichment of Pb and Zn was noted because of a smearing effect during polishing. At least some of the lead was crystalline. In contrast, the corrosion layer formed by H₂S(aq) exposure was dominated by polycrystalline Cu₂S (low and high chalcocite) and smaller concentrations of CuSO₄ · nH₂O. This surface was enriched with Zn as Zn(OH)₂. Lead was present as redeposited PbS (galena) crystallites in at least two different morphologies. Unlike bronzes exposed to oxidizing conditions, which develop protective SnO₂ layers, the H₂S(aq)‐exposed surface was considerably depleted in Sn. Copyright © 2014 John Wiley & Sons, Ltd.     

Organocatalytic Control over a Fuel-Driven Transient-Esterification Network**

Signal transduction in living systems is the conversion of information into a chemical change, and is the principal process by which cells communicate. In nature, these functions are encoded in non-equilibrium (bio)chemical reaction networks (CRNs) controlled by enzymes. However, man-made catalytically controlled networks are rare. We incorporated catalysis into an artificial fuel-driven out-of-equilibrium CRN, where the forward (ester formation) and backward (ester hydrolysis) reactions are controlled by varying the ratio of two organocatalysts: pyridine and imidazole. This catalytic regulation enables full control over ester yield and lifetime. This fuel-driven strategy was expanded to a responsive polymer system, where transient polymer conformation and aggregation are controlled through fuel and catalyst levels. Altogether, we show that organocatalysis can be used to control a man-made fuel-driven system and induce a change in a macromolecular superstructure, as in natural non-equilibrium systems.     

Theoretical and Experimental Analysis of Protoporphyrin IX Photodegradation Using Multi-Wavelength Light Sources

Photodynamic procedures have been used in many applications, ranging from cancer treatment to microorganism inactivation. Photodynamic reactions start with the activation of a photosensitizing molecule with light, leading to the production of cytotoxic molecules that promote cell death. However, establishing the correct light and photosensitizer dosimetry for a broadband light source remains challenging. In this study, we proposed a theoretical mathematical model for the photodegradation of protoporphyrin IX (PpIX), when irradiated by multi-wavelength light sources. The theoretical model predicts the experimental photobleaching (temporal change in PpIX concentration) of PpIX for different light sources. We showed that photobleaching occurs independently of the light source wavelengths but instead depends only on the number of absorbed photons. The model presented here can be used as an important mathematical approach to better understand current photodynamic therapy protocols and help achieve optimization of the doses delivered.     

Surface Design for Immobilization of an Antimicrobial Peptide Mimic for Efficient Anti-Biofouling

Microbial surface attachment negatively impacts a wide range of devices from water purification membranes to biomedical implants. Mimics of antimicrobial peptides (AMPs) constituted from poly(N-substituted glycine) „peptoids“ are of great interest as they resist proteolysis and can inhibit a wide spectrum of microbes. We investigate how terminal modification of a peptoid AMP-mimic and its surface immobilization affect antimicrobial activity. We also demonstrate a convenient surface modification strategy for enabling alkyne–azide „click“ coupling on amino-functionalized surfaces. Our results verified that the N- and C-terminal peptoid structures are not required for antimicrobial activity. Moreover, our peptoid immobilization density and choice of PEG tether resulted in a „volumetric“ spatial separation between AMPs that, compared to past studies, enabled the highest AMP surface activity relative to bacterial attachment. Our analysis suggests the importance of spatial flexibility for membrane activity and that AMP separation may be a controlling parameter for optimizing surface anti-biofouling.     

Three‐Pronged Attack by Homologous Far‐red/NIR AIEgens to Achieve 1+1+1>3 Synergistic Enhanced Photodynamic Therapy

Photodynamic therapy (PDT) has long been shown to be a powerful therapeutic modality for cancer. However, PDT is undiversified and has become stereotyped in recent years. Exploration of distinctive PDT methods is thus highly in demand but remains a severe challenge. Herein, an unprecedented 1+1+1>3 synergistic strategy is proposed and validated for the first time. Three homologous luminogens with aggregation‐induced emission (AIE) characteristics were rationally designed based on a simple backbone. Through slight structural tuning, these far‐red/near‐infrared AIE luminogens are capable of specifically anchoring to mitochondria, cell membrane, and lysosome, and effectively generating reactive oxygen species (ROS). Notably, biological studies demonstrated combined usage of three AIE photosensitizers gives multiple ROS sources simultaneously derived from several organelles, which gives superior therapeutic effect than that from a single organelle at the same photosensitizers concentration. This strategy is conceptually and operationally simple, providing an innovative approach and renewed awareness of improving therapeutic effect through three‐pronged PDT.