Herbicidal cyanoacrylates with antimicrotubule mechanism of action.

The herbicidal mode of action of the new synthetic cyanoacrylates ethyl (2Z)-3-amino-2-cyano-4-ethylhex-2-enoate (CA1) and its isopropyl ester derivative CA2 was investigated. For initial characterization, a series of bioassays was used indicating a mode of action similar to that of mitotic disrupter herbicides such as the dinitroaniline pendimethalin. Cytochemical fluorescence studies including monoclonal antibodies against polymerized and depolymerized tubulin and a cellulose-binding domain of a bacterial cellulase conjugated to a fluorescent dye were applied to elucidate effects on cell division processes including mitosis and microtubule and cell wall formation in maize roots. When seedlings were root treated with 10 microM of CA1 or CA2, cell division activity in meristematic root tip cells decreased within 4 h. The chromosomes proceeded to a condensed state of prometaphase, but were unable to progress further in the mitotic cycle. The compounds caused a complete loss of microtubular structures, including preprophase, spindle, phragmoplast and cortical microtubules. Concomitantly, in the cytoplasm, an increase in labelling of free tubulin was observed. This suggests that the herbicides disrupt polymerization and microtubule stability, whereas tubulin synthesis or degradation appeared not to be affected. In addition, cellulose labelling in cell walls of root tip cells was not influenced. The effects of CA1 and CA2 were comparable with those caused by pendimethalin. In transgenic Arabidopsis plants expressing a green fluorescent protein-microtubule-associated protein4 fusion protein, labelled arrays of cortical microtubules in living epidermal cells of hypocotyls collapsed within 160 min after exposure to 10 microM CA1 or pendimethalin. Moreover, a dinitroaniline-resistant biotype of goosegrass (Eleusine indica (L) Gaertn) with a point mutation in alpha-tubulin showed cross-resistance against CA1 and CA2. The results strongly indicate that the cyanoacrylates are a new chemical class of herbicide which possess the same antimicrotubule mechanism of action as dinitroanilines, probably including interaction with the same binding site in alpha-tubulin.

Discrete model for laser driven etching and microstructuring of metallic surfaces.

We present a unidimensional discrete solid-on-solid model evolving in time using a kinetic Monte Carlo method to simulate microstructuring of kerfs on metallic surfaces by means of laser-induced jet-chemical etching. The precise control of the passivation layer achieved by this technique is responsible for the high resolution of the structures. However, within a certain range of experimental parameters, the microstructuring of kerfs on stainless steel surfaces with a solution of H3PO4 shows periodic ripples, which are considered to originate from intrinsic dynamics. The model mimics a few of the various physical and chemical processes involved and within certain parameter ranges reproduces some morphological aspects of the structures, in particular ripple regimes. We analyze the range of values of laser beam power for the appearance of ripples in both experimental and simulated kerfs. The discrete model is an extension of one that has been used previously in the context of ion sputtering and is related to a noisy version of the Kuramoto-Sivashinsky equation used extensively in the field of pattern formation.