PubMed · 15233251
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
Lee Kirsch. Lessons unlearned.. https://pubmed.ncbi.nlm.nih.gov/15233251/
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
Surfactants are almost always present in herbicide treatment solutions with the aim to improve spray droplet retention on and penetration of active ingredients (a.i.s) into plant foliage. The effects of surfactants on the foliar uptake of herbicides are complex and only partially understood. The influence of a range of non-ionic polyoxyethylene surfactants on the uptake of two herbicides, glyphosate and 2,4-dichlorophenoxyacetic acid (2,4-D), was compared using three plant species, wheat, broad bean and common lambsquarters. Surfactants of higher ethylene oxide (EO) content provided greater uptake enhancement for glyphosate, whereas those of lower EO content were more beneficial for 2,4-D uptake. Among surfactants of the same EO content, those containing a C(13)/C(15) linear alkane hydrophobe moiety appeared to be more efficient for promoting the uptake of both herbicides. When a suitable surfactant was used, glyphosate uptake into both bean and wheat foliage increased steadily with increasing surfactant concentration and reached a maximum at 0.5%. In the presence of a constant surfactant, higher percentage uptake of herbicide was obtained with higher a.i. concentrations for glyphosate, but with lower a.i. concentrations in the case of 2,4-D. In the presence of an organosilicone surfactant, the stomatal uptake of glyphosate varied with both surfactant concentration and plant species. The effect of non-silicone surfactants on the cuticular uptake of glyphosate also varied with plant species. It can be concluded that the effects of surfactants on foliar uptake of herbicides depend not only on their chemical structures (hydrophobe and hydrophile moieties) and concentration, but also on the physicochemical properties and concentration of a.i.s and the leaf surface character of the plant species.
[reaction: see text] Epoxide 4 is generated in situ from d-glucal-derived hydroxy mesylate 3. Reaction of epoxide 4 with a series of alkyl- and aryllithium reagents affords 2,3-unsaturated beta-C-glycosides with excellent 1,4-regioselectivity and complete stereoselectivity for the beta-glycoside. Other organometallic reagents demonstrate more complex behavior in their reactions with epoxide 4.
The phase behavior of a thermoseparating cationic hydrophobically modified ethylene oxide polymer (HM-EO) containing tertiary amines has been investigated at different pH, salt and sodium dodecyl sulfate (SDS) concentrations, in order to find a water/HM-EO two-phase system suitable for protein partitioning. The used polymer forms micellar aggregates that can be charged. By changing pH and SDS concentrations the netcharge of the SDS/HM-EO aggregate can be shifted from positive to negative. Bovine serum albumin (BSA) and lysozyme were partitioned in the thermoseparated two-phase systems of the cationic polymer at different pH, salt and SDS concentrations. The dominant attractive interactions between the polymer aggregates and the studied proteins were shown to be of electrostatic (Coulomb) nature rather than hydrophobic interaction. At low ionic strength the positively charged polymeric aggregates attracted negatively charged BSA and repelled positively charged lysozyme. Upon addition of SDS the negatively charged aggregates attracted lysozyme and repelled BSA. Thus, it was possible to direct proteins with different charges to the polymeric phase and redirect them to a polymer-depleted phase by changing the netcharge of the polymeric aggregates. The effect of different salts on the partitioning of BSA in a system of slightly positively charged HM-EO was studied. NaCl and KBr have a significant effect on driving the BSA to the polymer-depleted phase, whereas KF and K2SO4 have a smaller effect on the partitioning. The cloud point temperature of the charged polymer decreased upon addition of SDS near the isoelectric molar ratio of SDS to polymer and also upon salt addition. In the latter case the decrease was smaller than expected from model calculations based on Flory-Huggins theory, which were performed for a charged thermoseparating polymer at different charges and salt concentrations.