Publications

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Hot‐pressed silicon carbide, containing aluminum, boron, and carbon additives (ABC‐SiC), was subjected to three‐body and two‐body wear testing using diamond abrasives over a range of sizes. In general, the wear resistance of ABC‐SiC, with suitable heat treatment, was superior to that of commercial SiC. When the fine‐scale (3 μm) diamond abrasives were used, it was found that thermal annealing at 1300°C increased the resistance to three‐body wear by a factor of almost three, and two‐body wear by a factor of almost two, compared with as‐hot‐pressed samples. Higher annealing temperatures, however, led to a decline in wear resistance from its highest value. Similar behavior was seen for 1300°C‐annealed samples subjected to 15 μm diamond abrasive, although higher‐temperature annealing at 1500°–1600°C enhanced the wear resistance again. When coarse abrasives (72 μm) were used, the wear resistance progressively increased with increased annealing temperature from ∼1000° to 1600°C. Corresponding transmission and scanning electron microscopy studies indicated that, whereas transgranular, conchoidal cracking was dominant in the mild abrasive wear with fine‐scale (3 μm) abrasives, intergranular cracking and subsequent grain pullout was far more predominant in the more severe abrasive wear with coarse abrasives. Because the hardness and indentation toughness were barely altered during thermal treatment, the observed wear behavior was attributed mainly to the thermally induced microstructural changes, including the crystallization of glassy grain‐boundary films, the possible strengthening of the boundaries due to the enhancement of the aluminum, and the formation of aluminum‐rich, coherent nanoscale precipitates in the matrix grains above 1300°C.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Using a degenerate primer designed from triterpene synthase sequences, we have isolated a new gene from the medicinal plant Artemisia annua . The predicted protein is highly similar to β‐amyrin synthases (EC 5.4.99.–), sharing amino acid sequence identities of up to 86%. Expression of the gene, designated AaBAS , in Saccharomyces cerevisiae , followed by GC/MS analysis, confirmed the encoded enzyme as a β‐amyrin synthase. Through engineering the sterol pathway in S. cerevisiae , we explore strategies for increasing triterpene production, using AaBAS as a test case. By manipulation of two key enzymes in the pathway, 3‐hydroxy‐3‐methylglutaryl‐CoA reductase and lanosterol synthase, we have improved β‐amyrin production by 50%, achieving levels of 6 mg·L −1 culture. As we have observed a 12‐fold increase in squalene levels, it appears that this strain has the capacity for even higher β‐amyrin production. Options for further engineering efforts are explored.