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Biomedical subjects

R B Thompson

Publications and source records attributed to R B Thompson.

105 records · Page 6Linked to original sources
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Fluorescence-based biosensing of zinc using carbonic anhydrase.

Measurement of free zinc levels and imaging of zinc fluxes remains technically difficult due to low levels and the presence of interfering cations such as Mg and Ca. We have developed a series of fluorescent zinc indicators based on the superb sensitivity and selectivity of a protein, human apo-carbonic anhydrase II, for Zn(II). These indicators transduce the level of free zinc as changes in intensity, wavelength ratio, lifetime, and/or anisotropy; the latter three approaches permit quantitative imaging of zinc levels in the microscope. A unique attribute of sensors incorporating biological macromolecules as transducers is their capability for modification by site-directed mutagenesis. Thus we have produced variants of carbonic anhydrase with improved affinity for zinc, altered selectivity, and enhanced binding kinetics, all of which are difficult to modify in small molecule indicators.

Animals↗
PubMedDate not supplied

Management factors affecting ammonia volatilization from land-applied cattle slurry in the Mid-Atlantic USA.

Ammonia (NH3) volatilization commonly causes a substantial loss of crop-available N from surface-applied cattle slurry. Field studies were conducted with small wind tunnels to assess the effect of management factors on NH3 volatilization. Two studies compared NH3 volatilization from grass sward and bare soil. The average total NH3 loss was 1.5 times greater from slurry applied to grass sward. Two studies examined the effect of slurry dry matter (DM) content on NH3 loss under hot, summer conditions in Maryland, USA. Slurry DM contents were between 54 and 134 g kg(-1). Dry matter content did not affect total NH3 loss, but did influence the time course of NH3 loss. Higher DM content slurries had relatively higher rates of NH3 volatilization during the first 12 to 24 h, but lower rates thereafter. Under the hot conditions, the higher DM content slurries appeared to dry and crust more rapidly causing smaller rates of NH3 volatilization after 12 to 24 h, which offset the earlier positive effects of DM content on NH3 volatilization. Three studies compared immediate incorporation with different tillage implements. Total NH3 loss from unincorporated slurry was 45% of applied slurry NH4+-N, while losses following immediate incorporation with a moldboard plow, tandem-disk harrow, or chisel plow were, respectively, 0 to 3, 2 to 8, and 8 to 12%. These ground cover and DM content data can be used to improve predictions of NH3 loss under specific farming conditions. The immediate incorporation data demonstrate management practices that can reduce NH3 volatilization, which can improve slurry N utilization in crop-forage production.

Ammonia↗