Molecular structure does not easily identify the intricate noncovalent interactions that govern many areas of biology and chemistry, including design of new materials and drugs. We develop an approach to detect noncovalent interactions in real space, based on the electron density and its derivatives. Our approach reveals the underlying chemistry that compliments the covalent structure. It provides a rich representation of van der Waals interactions, hydrogen bonds, and steric repulsion in small molecules, molecular complexes, and solids. Most importantly, the method, requiring only knowledge of the atomic coordinates, is efficient and applicable to large systems, such as proteins or DNA. Across these applications, a view of nonbonded interactions emerges as continuous surfaces rather than close contacts between atom pairs, offering rich insight into the design of new and improved ligands.

/pdf/revealing-noncovalent-interactions-1oqknfvmfi.pdf

Revealing noncovalent interactions.

Roles of glycine betaine and proline in improving plant abiotic stress resistance

Noncovalent interactions hold the key to understanding many chemical, biological, and technological problems. Describing these noncovalent interactions accurately, including their positions in real space, constitutes a first step in the process of decoupling the complex balance of forces that define noncovalent interactions. Because of the size of macromolecules, the most common approach has been to assign van der Waals interactions (vdW), steric clashes (SC), and hydrogen bonds (HBs) based on pairwise distances between atoms according to their vdW radii. We recently developed an alternative perspective, derived from the electronic density: the non-covalent interactions (NCI) index [J. Am. Chem. Soc. 2010, 132, 6498]. This index has the dual advantages of being generally transferable to diverse chemical applications and being very fast to compute, since it can be calculated from promolecular densities. Thus, NCI analysis is applicable to large systems, including proteins and DNA, where analysis of noncova...

/pdf/nciplot-a-program-for-plotting-noncovalent-interaction-5bhkffn4zn.pdf

NCIPLOT: A Program for Plotting Noncovalent Interaction Regions

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.

Plant sesquiterpenes induce hyphal branching in arbuscular mycorrhizal fungi

http://nhjy.hzau.edu.cn/kech/ssyy/qysd/njsl/21.pdf

Potential biochemical indicators of salinity tolerance in plants

An improved method for high performance liquid chromatography with electrochemical detection (HPLC-EC) is presented for artemisinin analysis. It involves increased concentration of organic phase, elimination of the degassing step in sample preparation, and reduced time for heating and degassing in mobile phase preparation and recycling. The HPLC-EC method was compared to a gas chromatographic (GC) method, which measured artemisinin indirectly through two of its degradation products, labelled A and B. Both methods provided a good separation of artemisinin from artemisitene, arteannuin B, and the semisynthetic dihydroartemisinin. Peak B provided a higher correlation to the levels of artemisinin detected by HPLC-EC. Peaks A, B and Z (a small peak preceding A and B) were identified through electron impact and chemical ionization spectra from GC-mass spectral analysis.

A comparison of gas chromatography and high performance liquid chromatography for artemisinin analyses

Phytoalexins and secondary products, where are they and how can we measure them?

Gigantetronenin [1] and gigantrionenin [6], two new monotetrahydrofuran Annonaceous acetogenins each possessing a double bond along the hydrocarbon chain, have been isolated from the bark of Goniothalamus giganteus by the use of brine shrimp lethality for bioactivity-directed fractionation. The structures were elucidated based on spectroscopic and chemical methods. Compounds 1 and 6 both show selective and potent cytotoxicities to human tumor cells in culture as well as toxicity to brine shrimp. A known cytotoxic acetogenin, annomontacin [11], was also isolated from this plant. The biogenetic pathway of the acetogenins from G. giganteus is discussed.

Gigantetronenin and gigantrionenin: novel cytotoxic acetogenins from Goniothalamus giganteus.

Etude de l'huile essentielle extraite des fleurs, feuilles de Ocimum micranthum, variete de basilic couramment utilisee en Amerique du Sud et l'ouest de l'Inde. Le but est d'utiliser la plante comme source de composes chimiques a proprietes aromatiques

Essential oil constituents of Ocimum micranthum Willd

A new Annonaceous acetogenin, gonionenin (1), has been isolated from the bark of Goniothalamus giganteus (Annonaceae). C-21/22 double bonds in (1) and in gigantetronenin (10) were oxidized and then cyclized to give pairs of adjacent bis-THF (4 and 7) and nonadjacent bis-THF (11 and 14) acetogenins, respectively. This is the first reported preparation of bis-THF Annonaceous acetogenins through double-bond epoxidation and cyclization from mono-THF acetogenins. The resulting bis-THF compounds (4, 7, 11, 14) showed enhanced bioactivities, versus (1) and (10), with (11) and (14) being over a billion times more cytotoxic than adriamycin against certain solid tumor cell lines

Karl V. Wood

Papers

A comparison of gas chromatography and high performance liquid chromatography for artemisinin analyses

Phytoalexins and secondary products, where are they and how can we measure them?

Gigantetronenin and gigantrionenin: novel cytotoxic acetogenins from Goniothalamus giganteus.

Essential oil constituents of Ocimum micranthum Willd

Gonionenin: A New Cytotoxic Annonaceous Acetogenin from Goniothalamus giganteus and the Conversion of Mono-THF Acetogenins to Bis-THF Acetogenins