Philip Coggon

Bio: Philip Coggon is an academic researcher from Duke University. The author has contributed to research in topics: Orthorhombic crystal system & Phosphole. The author has an hindex of 5, co-authored 11 publications receiving 4041 citations.

Crystal and molecular structure of 1-benzylphosphole by X-ray analysis

Abstract: Molecular dimensions for the title compound have been established by single-crystal X-ray analysis from photographic data. Crystals are orthorhombic, space group Pbca with a= 17·62(2), b= 14·60(2), c= 7·67(1)A, Z= 8. The structure was solved by the heavy-atom method and refined by full-matiix least-squares calculations to R 0·073 over 1351 independent observed reflexions. Comparison of the molecular dimensions with those of other heteroaromatic compounds is made. The phospholering has a non-planar geometry, and the mean P–C(phosphole) length of 1·783(5)A is consistent with the interpretation that some electron delocalisation is present in the ring.

Crystal and molecular structure of the germination stimulant strigol by X-ray analysis

Abstract: Single crystal X-ray analysis has defined the constitution and relative stereochemistry of strigol (1) a potent speed germination stimulant for witchweed (Striga lutea Lour.). Crystals are orthorhombic, space group P212121 with Z= 4 in a unit cell of dimensions a= 9·15, b= 12·37, 15·37 A. The crystal structure was elucidated from photographic data by direct phase-determining methods, and the molecular parameters refined by full-matrix least-squares calculations to R 0·082 over 1650 independent reflections.

Microtubules as a target for anticancer drugs.

Abstract: Highly dynamic mitotic-spindle microtubules are among the most successful targets for anticancer therapy. Microtubule-targeted drugs, including paclitaxel and Vinca alkaloids, were previously considered to work primarily by increasing or decreasing the cellular microtubule mass. Although these effects might have a role in their chemotherapeutic actions, we now know that at lower concentrations, microtubule-targeted drugs can suppress microtubule dynamics without changing microtubule mass; this action leads to mitotic block and apoptosis. In addition to the expanding array of chemically diverse antimitotic agents, some microtubule-targeted drugs can act as vascular-targeting agents, rapidly depolymerizing microtubules of newly formed vasculature to shut down the blood supply to tumours.

Promotion of microtubule assembly in vitro by taxol

Abstract: TAXOL (Fig. 1) was isolated from the plant Taxus brevifolia (western yew) by Wani et al., who reported that the molecule has antitumour activity in several experimental systems1. In our laboratory we have found that taxol, a low molecular weight neutral compound, completely inhibits division of exponentially growing HeLa cells at low concentrations of drug (0.25 µM) that have no significant effects on DNA, RNA or protein synthesis during a 4-h incubation with the cells. HeLa cells incubated with taxol for 20 h are blocked in late G2 and/or M (ref. 2). We report here that taxol acts as a promoter of calf brain microtubule assembly in vitro, in contrast to plant products such as colchicine and podophyllotoxin, which inhibit assembly. Taxol decreases the lag time for microtubule assembly and shifts the equilibrium for assembly in favour of the microtubule, thereby decreasing the critical concentration of tubulin required for assembly. Microtubules polymerised in the presence of taxol are resistant to depolymerisation by cold (4 °C) and CaCl2 (4 mM).

Bioprospecting for Microbial Endophytes and Their Natural Products

Abstract: Endophytic microorganisms are to be found in virtually every plant on earth. These organisms reside in the living tissues of the host plant and do so in a variety of relationships, ranging from symbiotic to slightly pathogenic. Because of what appears to be their contribution to the host plant, the endophytes may produce a plethora of substances of potential use to modern medicine, agriculture, and industry. Novel antibiotics, antimycotics, immunosuppressants, and anticancer compounds are only a few examples of what has been found after the isolation, culture, purification, and characterization of some choice endophytes in the recent past. The potential prospects of finding new drugs that may be effective candidates for treating newly developing diseases in humans, plants, and animals are great.

Plant sesquiterpenes induce hyphal branching in arbuscular mycorrhizal fungi

Abstract: Arbuscular mycorrhizal (AM) fungi form mutualistic, symbiotic associations with the roots of more than 80% of land plants. The fungi are incapable of completing their life cycle in the absence of a host root. Their spores can germinate and grow in the absence of a host, but their hyphal growth is very limited. Little is known about the molecular mechanisms that govern signalling and recognition between AM fungi and their host plants. In one of the first stages of host recognition, the hyphae of AM fungi show extensive branching in the vicinity of host roots before formation of the appressorium, the structure used to penetrate the plant root. Host roots are known to release signalling molecules that trigger hyphal branching, but these branching factors have not been isolated. Here we have isolated a branching factor from the root exudates of Lotus japonicus and used spectroscopic analysis and chemical synthesis to identify it as a strigolactone, 5-deoxy-strigol. Strigolactones are a group of sesquiterpene lactones, previously isolated as seed-germination stimulants for the parasitic weeds Striga and Orobanche. The natural strigolactones 5-deoxy-strigol, sorgolactone and strigol, and a synthetic analogue, GR24, induced extensive hyphal branching in germinating spores of the AM fungus Gigaspora margarita at very low concentrations.

Taxol stabilizes microtubules in mouse fibroblast cells.

Abstract: Taxol, a potent inhibitor of human HeLa and mouse fibroblast cell replication, blocked cells in the G2 and M phase of the cell cycle and stabilized cytoplasmic microtubules. The cytoplasmic microtubules of taxol-treated cells were visualized by transmission electron microscopy and indirect immunofluorescence microscopy. More than 90% of the cells treated with 10 micro M taxol for 22 hr at 37 degrees C displayed bundles of microtubules that appeared to radiate from a common site (or sites), in addition to their cytoplasmic microtubules. Untreated cells that were kept in the cold (4 degrees C) for 16 hr lost their microtubules, whereas cells that were pretreated with taxol for 22 hr at 37 degrees C continued to display their microtubules and bundles of microtubules in the cold. Taxol inhibited the migration behavior of fibroblast cells, but these cells did not lose their ability to produce mobile surface projections such as lamellipodia and filopodia.