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.

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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...

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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

Additional bioactive Annonaceous acetogenins have been isolated from the EtOH extract of the bark of Annona bullata Rich. by bioactivity-directed fractionation using lethality to brine shrimp. These acetogenins include bullatencin, a new single tetrahydrofuran acetogenin having a double bond in the hydrocarbon chain; 4-deoxyasimicin, a new adjacent bis-tetrahydrofuran acetogenin; and the uvariamicins, an isomeric mixture of four single tetrahydrofuran acetogenins. These acetogenins showed selective cytotoxicities for certain human solid tumor cell lines comparable to or better than adriamycin. © 1992 Wiley-Liss, Inc.

Bullatencin, 4-deoxyasimicin, and the uvariamicins: additional bioactive Annonaceous acetogenins from Annona bullata Rich. (Annonaceae).

Plasma desorption mass spectrometry of anthocyanidins

Long chain alkyl heteroaromatics in coal identified by tandem mass spectrometry

Analysis of anthocyanins and 3-deoxyanthocyanidins by plasma desorption mass spectrometry

Cell cultures of Mandevilla velutina have proved to be an interesting production system for biomass and secondary metabolites able to inhibit the hypotensive activity of bradykinin, a nonapeptide generated in plasma during tissue trauma. The crude ethyl acetate extract of cultured cells contains about 31- to 79-fold more potent anti-bradykinin compounds (e.g., velutinol A) than that obtained with equivalent extracts of tubers. Somaclonal variation may be an explanation for the wide range of inhibitor activity found in the cell cultures. The heterogeneity concerning morphology, differentiation, carbon dissimilation, and velutinol A production in M. velutina cell cultures is reported. Cell cultures showed an asynchronous growth and cells in distinct developmental stages. Meristematic cells were found as the major type, with several morphological variations. Cell aggregates consisting only of meristematic cells, differentiated cells containing specialized cell structures such as functional chloroplasts (cytodifferentiation) and cells with embryogenetic characteristics were observed. The time course for sucrose metabolism indicated cell populations with significant differences in growth and metabolic rates, with the highest biomass-producing cell line showing a cell cycle 60% shorter and a metabolic rate 33.6% higher than the control (F2 cell population). MALDI-TOF mass spectrometric analysis of velutinol A in selected cell lines demonstrated the existence of velutinol A producing and nonproducing somaclones. These results point to a high genetic heterogeneity in general and also in terms of secondary metabolite content.

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Karl V. Wood

Papers

Bullatencin, 4-deoxyasimicin, and the uvariamicins: additional bioactive Annonaceous acetogenins from Annona bullata Rich. (Annonaceae).

Plasma desorption mass spectrometry of anthocyanidins

Long chain alkyl heteroaromatics in coal identified by tandem mass spectrometry

Analysis of anthocyanins and 3-deoxyanthocyanidins by plasma desorption mass spectrometry

Somaclonal variation: a morphogenetic and biochemical analysis of Mandevilla velutina cultured cells