Repulsive interaction can be a key design element of molecular rotary motors.

Low-barrier molecular rotary motors having rotaxane architecture can be constructed using a cucurbituril host and a polyyne guest serving as stator and rotator, respectively. The repulsive interaction between these components is supported by molecular mechanics calculations with model systems and experimentally verified by X-ray crystallography with several synthetic host-guest complexes, all suggesting that the diyne rod floats at the center of the macrocyclic host with no apparent van der Waals contacts between them. Further support for these interactions is suggested by microcalorimetry measurements.

Herbicide-resistance conferred by expression of a catalytic antibody in Arabidopsis thaliana.

Engineering herbicide resistance in crops facilitates control of weed species, particularly those that are closely related to the crop, and may be useful in selecting lines that have undergone multiple transformation events. Here we show that herbicide-resistant plants can be engineered by designing an herbicide and expressing a catalytic antibody that destroys the herbicide in planta. First, we developed a carbamate herbicide that can be catalytically destroyed by the aldolase antibody 38C2. This compound has herbicidal activity on all three plant species tested. Second, the light chain and half of the heavy chain (Fab) of the catalytic antibody were targeted to the endoplasmic reticulum in two classes of Arabidopsis thaliana transformants. Third, the two transgenic plants were crossed to produce an herbicide-resistant F1 hybrid. The in vitro catalytic activity of the protein from F1 hybrids corroborates that catalytic antibodies can be constitutively expressed in transgenic plants, and that they can confer a unique trait.

Determination of plant resistance to carbamate herbicidal compounds inhibiting cell division and early growth by seed and plantlets bioassays.

Herbicide-resistant plants can be generated by either traditional breeding procedures or genetic engineering. Analyses of plant responses to a newly developed herbicide or the tolerance level of a newly developed plant line to a given herbicide are based on various bioassays. Here, we describe several methods for quantitative measurements of plants' responses to propham application, as a model herbicide of the carbamate family. Dose-response assays include seed germination and analyses of shoot and root elongation on paper. To better reflect the natural interaction between the plant, the soil and the herbicide, a protocol for germination and root elongation on sand is described. Finally, a more sensitive bioassay is based on plant growth on agar medium. The described protocols are simple, reproducible and can be easily adopted for a variety of plant species and for various herbicides. Plants' response to a given herbicide can be determined within a few weeks.