Hydrogenation of CO2 to methanol and dimethyl ether (DME) is one strategy to tackle the global climate change and meet the portable fuel demand simultaneously. The bimetallic oxide synergy is known to boost the yields of methanol and DME from CO2 hydrogenation. However, the origin of this synergy is still unclear. We synthesized a series of GaZrO x catalysts by the evaporation-induced self-assembly method. The GaZrO x (27%) catalyst displays superior activity than admixtures of the (Ga2O3 + ZrO2) oxides. We propose that the Zr3+–OV–Ga–O species (OV represents the oxygen vacancy) on the GaZrO x catalyst is the active site. Our results demonstrate that the synergistic effect stems from neighboring Ga–O sites and Zr3+–OV sites, as revealed by complementary X-ray photoelectron spectroscopy, time-of-flight secondary ion mass spectrometry, in situ diffuse reflectance infrared Fourier transform spectroscopy, electron paramagnetic resonance spectroscopy, and solid-state NMR spectroscopy results. We demonstrate that H2 is dissociated on polarized Ga–O sites to produce Ga–H and −OH species, while CO2 is trapped by the oxygen vacancies and activated by electron transfer from the Zr3+ ions. The whole picture of the CO2 hydrogenation reaction mechanism on the GaZrO x catalyst is presented. The atomic- and electronic-levels understanding of the active sites and the origin of the synergistic effect open up a new avenue for the rational design of highly active catalysts for CO2 hydrogenation.

Although membrane proteins are crucial participants in photosynthesis and other biological processes, many lack high-resolution structures. Prior to achieving a high-resolution structure, we are investigating whether MS-based footprinting can provide coarse-grained protein structure by following structural changes that occur upon ligand binding, pH change, and membrane binding. Our platform probes topology and conformation of membrane proteins by combining MS-based footprinting, specifically fast photochemical oxidation of proteins (FPOP), and lipid Nanodiscs, which more similar to the native membrane environment than are the widely used detergent micelles. We describe here results that show a protein’s outer membrane regions are more heavily footprinted by OH radicals whereas the regions spanning the lipid bilayer remain inert to the labeling. Nanodiscs generally exhibit more protection of membrane proteins compared to detergent micelles and less shielding to those protein residues that exist outside the membrane. The combination of immobilizing the protein in Nanodiscs and footprinting with the FPOP approach is a feasible approach to map extra-membrane protein surfaces, even at the amino-acid level, and to illuminate intrinsic membrane protein topology.

No abstract

Photosynthetic cyanobacteria are an important contributor to global carbon and nitrogen budgets. A protein, known as the Orange Carotenoid Protein (OCP) protects the photosynthetic apparatus from damage by dissipating excess energy absorbed by the phycobilisome, the major light-harvesting complex in many cyanobacteria. OCP binds one carotenoid pigment, but the color of this pigment depends on conditions. It is orange in the dark and red when exposed to light. We modified the orange and red forms of OCP by using isotopically coded cross-linking agents and then analyzed the structural features by using LC-MS/MS. Unequivocal cross-linking pairs uniquely detected in red OCP indicate that, upon photoactivation, the OCP N-terminal domain (NTD) and C-terminal domain (CTD) reorient relative to each other. Our data also indicate that the intrinsically unstructured loop connecting NTD and CTD is not only involved in the interaction between the two domains in orange OCP but also, together with the N-terminal extension, provides a structural buffer system facilitating an intramolecular breathing motion of the OCP, thus helping conversion back and forth from orange to red form during the OCP photocycle. These results have important implications for understanding the molecular mechanism of action of cyanobacterial photoprotection.

The alga Chlorella protothecoides is known to produce oil suitable for biodiesel preparation by heterotrophic cultivation in media containing glucose as a carbon source. In this study, sugar cane juice was used as alternative carbon supply for oil production. As a result, the highest oil content of 53.0% by cell dry weight was achieved. Fermentation in a 5 L bioreactor showed that algae using sugar cane juice hydrolysate (SCH) grow faster than that using glucose. Conversion ratios of sugar/biomass and sugar/oil using SCH were 15.2 and 8.8% higher than that using glucose, respectively. Biodiesel prepared from algal oil by transesterification is mainly composed of 9-octadecenoic acid methyl ester, 9,12-octadecadienoic acid methyl ester, and hexadecenoic acid methyl ester. Our results suggest that sugar cane is a good feedstock for biodiesel production. Response surface methodology upon exploring the effect of C/N and concentration of yeast extraction (YE) on the yield of biomass and oil was performed. The optimal production with the highest output-cost coefficient of 0.061 ± 0.004 was achieved when C/N was 26.9 and YE was 0.60 g L−1.

"Chemistry-on-the-complex" synthetic methods have allowed the selective addition of 1-ethynylpyrene appendages to the 3-, 5-, 3,8- and 5,6-positions of Ir -coordinated 1,10-phenanthroline via Sonogashira cross-coupling. The resulting suite of complexes has given rise to the first rationalization of their absorption and emission properties as a function of the number and position of the pyrene moieties. Strong absorption in the visible region (e.g. 3,8-substituted Ir-3: λ =481 nm, ϵ=52 400 m cm ) and long-lived triplet excited states (e.g. 5-substituted Ir-2: τ =367.7 μs) were observed for the complexes in deaerated CH Cl . On testing the series as triplet sensitizers for triplet-triplet annihilation upconversion, those Ir complexes bearing pyrenyl appendages at the 3- and 3,8-positions (Ir-1, Ir-3) were found to give optimal upconversion quantum yields (30.2 % and 31.6 % respectively).

An improved label-free approach for highly sensitive and selective detection of 3,3',4,4'-tetrachlorobiphenyl (PCB-77), a type of polychlorinated biphenyl, via surface-enhanced Raman spectroscopy (SERS) using DNA aptamer-modified Ag-nanorod arrays as the effective substrate is reported. The devised system consists of Ag-nanorod (Ag-NR) arrays with the PCB-77 binding aptamers anchored covalently to the Ag surfaces through a thiol linker. The aptamers are made of single-stranded DNA (ssDNA) oligomers, with one end standing on the Ag surface, and upon conjugation with PCB-77, the ssDNA molecules can change their conformation to hairpin loops, so that the Raman intensity of guanines at the other end of the DNA strand increases accordingly. As such, the intensity ratio I(656 cm(-1))/I(733 cm(-1)) increases concomitantly with the increase of the concentration of PCB-77, making the quantitative evaluation of trace amounts of PCB-77 attainable. Moreover, it is found that the DNA aptamer-based Ag-NR arrays can be more responsive with a lower and optimal density of the DNA molecules modified on the substrate surface, and the best sensitivity for detection of PCB-77 can be achieved with the lower detection limit approaching 3.3 × 10(-8) M. This work therefore demonstrates that the design of aptamer-modified Ag-NRs can be used as a practically promising SERS substrate for label-free trace detection of persistent organic pollutants (POPs) in the environment.

As a potential source of biomass supplies, cassava (Manihot esculenta Crantz) has been studied for bioethanol production, but not for the production of biodiesel. In this study, we used cassava hydrolysate as an alternative carbon source for the growth of microalgae (Chlorella protothecoides) which accumulated oil in vivo, with high oil content up to 53% by dry mass under a 5-L scale fermentation condition. The oils were extracted and converted into biodiesel by transesterification. The biodiesel obtained consisted of mainly unsaturated fatty acids methyl ester (over 82%), cetane acid methyl ester, linoleic acid methyl ester, and oleic acid methyl ester. This work suggests the feasibility of an alternative choice for producing biodiesel from cassava by microalgae fermentation. We report herewith the optimized condition for the fermentation and for the hydrolysis of cassava as the carbon source.