Daniel Curtis

A CCHC metal-binding domain in Nanos is essential for translational regulation.

The Drosophila Nanos protein is a localized repressor of hunchback mRNA translation in the early embryo, and is required for the establishment of the anterior–posterior body axis. Analysis of nanos mutants reveals that a small, evolutionarily conserved, C‐terminal region is essential for Nanos function in vivo, while no other single portion of the Nanos protein is absolutely required. Within the C‐terminal region are two unusual Cys‐Cys‐His‐Cys (CCHC) motifs that are potential zinc‐binding sites. Using absorption spectroscopy and NMR we demonstrate that the CCHC motifs each bind one equivalent of zinc with high affinity. nanos mutations disrupting metal binding at either of these two sites in vitro abolish Nanos translational repression activity in vivo. We show that full‐length and C‐terminal Nanos proteins bind to RNA in vitro with high affinity, but with little sequence specificity. Mutations affecting the hunchback mRNA target sites for Nanos‐dependent translational repression were found to disrupt translational repression in vivo, but had little effect on Nanos RNA binding in vitro. Thus, the Nanos zinc domain does not specifically recognize target hunchback RNA sequences, but might interact with RNA in the context of a larger ribonucleoprotein complex.

Meeting the Needs of a Nuclear-Renewables Electrical Grid with a Fluoride-Salt–Cooled High-Temperature Reactor Coupled to a Nuclear Air-Brayton Combined-Cycle Power System

The traditional role of nuclear power has been the production of base-load electricity. However, the needs of the electricity grid are changing because of (a) the introduction of significant electricity generation by nondispatchable wind and solar and (b) increasing restrictions on using fossil fuels because of concerns about climate change. To meet these changing requirements, a fluoride-salt–cooled high-temperature reactor (FHR) with a nuclear air-Brayton combined-cycle power system is proposed. This technology (a) can be the enabling technology for a low-carbon nuclear-renewables electrical grid and (b) can substantially improve nuclear power plant economics by increasing plant revenue by 50% or more relative to a base-load nuclear power plant. This is because the plant can be operated at full power to produce base-load electricity, stabilize the grid, produce process heat to reduce sales of low-priced electricity, and produce peak electricity with auxiliary natural gas or hydrogen. The market basis for this reactor is described with implications on the design requirements for an FHR.

Light Water Reactors with Crushed Rock Thermal Storage for Industrial Heat and High-Value Electricity

Abstract A crushed rock heat storage facility with storage capacities of gigawatt-hours is proposed to couple to light water reactors (LWRs) to enable base-load LWR operation with (1) variable electricity to the grid and heat to industry and (2) substantially higher revenue in deregulated electricity markets with significant solar or wind generation capacity. At times of low electricity prices, crushed rock is heated by hot air in a two-stage process. Air is initially heated by a steam-air heat exchanger using LWR steam and then with electric resistance heaters before circulating from the top to bottom of the crushed rock pile. Depending upon the design, peak rock temperatures can be from 250°C to 800°C. Heat is recovered by circulating air from the bottom to the top of the crushed rock pile with the hot air sent to industrial furnaces or thermal electric power plants. For industrial applications the hot air is a partial replacement for the burning of fossil fuels in industrial furnaces. Many of the challenges and questions associated with such a system are being addressed by (1) the development of the Red Leaf shale oil process, where crushed oil shale in 30-m-high piles is heated with hot gases to thermally decompose solid kerogen to produce a light crude oil, and (2) firebrick resistance-heated energy storage (FIRES), where low-price electricity is used to heat firebrick to provide stored heat for space heating and in the future may provide heat for electricity production or industrial heat.