Preliminary Cost and Performance Models for Mercury Control at Coal-Fired Power Plants

The U.S. Environmental Protection Agency (EPA) has announced it will regulate mercury emissions from coal-fired power plants, with proposed regulations to be issued in 2003. The feasibility and cost of achieving mercury emission reductions is thus a subject of considerable current interest. To assess mercury control options, the Integrated Environmental Control Model (IECM) developed for the U.S. Department of Energy's National Energy Technology Laboratory (DOE/NETL) has been expanded to include performance and cost models for a variety of mercury control options. These preliminary models are based on a review of recent mercury information collection request (ICR) data, and on the results of pilot plant studies and other data sources employing carbon injection with and without flue gas humidification. Illustrative results using the IECM show that the feasibility and cost of achieving different levels of mercury reduction depend strongly on the fuel type and power plant configuration. In most cases, the presence of a flue gas desulfurization (FGD) unit or a selective catalytic reduction (SCR) system can have a significant (beneficial) impact on mercury removal efficiency and cost. However, because of limitations on the scale and coverage of available data, there is considerable uncertainty in current estimates of mercury control costs and capabilities. Current models and estimates will be refined as new data become available from on- going programs

Multi-Polluntant Emission Control of Electric Power Plants

In contrast to past regulations for power plant air pollutants, there is a growing interest in a multi-pollutant perspective that would simultaneously address criteria pollutants, air toxics, and greenhouse gases

Identification of Arabidopsis Cyclase-associated Protein 1 as the First Nucleotide Exchange Factor for Plant Actin

The actin cytoskeleton powers organelle movements, orchestrates responses to abiotic stresses, and generates an amazing array of cell shapes. Underpinning these diverse functions of the actin cytoskeleton are several dozen accessory proteins that coordinate actin filament dynamics and construct higher-order assemblies. Many actin-binding proteins from the plant kingdom have been characterized and their function is often surprisingly distinct from mammalian and fungal counterparts. The adenylyl cyclase-associated protein (CAP) has recently been shown to be an important regulator of actin dynamics in vivo and in vitro. The disruption of actin organization in cap mutant plants indicates defects in actin dynamics or the regulated assembly and disassembly of actin subunits into filaments. Current models for actin dynamics maintain that actin-depolymerizing factor (ADF)/cofilin removes ADP–actin subunits from filament ends and that profilin recharges these monomers with ATP by enhancing nucleotide exchange and delivery of subunits onto filament barbed ends. Plant profilins, however, lack the essential ability to stimulate nucleotide exchange on actin, suggesting that there might be a missing link yet to be discovered from plants. Here, we show that Arabidopsis thaliana CAP1 (AtCAP1) is an abundant cytoplasmic protein; it is present at a 1:3 M ratio with total actin in suspension cells. AtCAP1 has equivalent affinities for ADP– and ATP–monomeric actin (Kd ∼ 1.3 μM). Binding of AtCAP1 to ATP–actin monomers inhibits polymerization, consistent with AtCAP1 being an actin sequestering protein. However, we demonstrate that AtCAP1 is the first plant protein to increase the rate of nucleotide exchange on actin. Even in the presence of ADF/cofilin, AtCAP1 can recharge actin monomers and presumably provide a polymerizable pool of subunits to profilin for addition onto filament ends. In turnover assays, plant profilin, ADF, and CAP act cooperatively to promote flux of subunits through actin filament barbed ends. Collectively, these results and our understanding of other actin-binding proteins implicate CAP1 as a central player in regulating the pool of unpolymerized ATP–actin