Development of a rapidly deployed Department of Energy emergency response element.

The Federal Radiological Emergency Response Plan (FRERP) directs the Department of Energy (DOE) to maintain a viable, timely, and fully documented response option capable of supporting the responsible Lead Federal Agency in the event of a radiological emergency impacting any state or United States territory (e.g., CONUS). In addition, the DOE maintains a response option to support radiological emergencies outside the continental United States (OCONUS). While the OCONUS mission is not governed by the FRERP, this response is operationally similar to that assigned to the DOE by the FRERP The DOE is prepared to alert, activate, and deploy radiological response teams to augment the Radiological Assistance Program and/or local responders. The Radiological Monitoring and Assessment Center (RMAC) is a phased response that integrates with the Federal Radiological Monitoring and Assessment Center (FRMAC) in CONUS environments and represents a stand-alone DOE response for OCONUS environments. The FRMAC/RMAC Phase I was formally "stood up" as an operational element in April 1999. The FRMAC/RMAC Phase II proposed "stand-up" date is midyear 2000.

A unique four-stranded model of a homologous recombination intermediate.

This paper proposes a model of four-stranded DNA synapsis during recombination between homologous segments of two DNA duplexes. The proposed intermediate is one of only two known models having relative chain orientations about the synaptic junction that are consistent with recent topological results on the integrative recombination of bacteriophage lambda. This model has the advantage of providing a mechanism for recognition of sequence homology between duplexes through specific hydrogen-bond formation; other models are discussed in comparison. The new model is based on an alternative family of DNA structures having chain directions opposite to those of the Watson-Crick family of structures. Idealized coordinates for generating both right- and left-handed forms of these alternative structures are presented for further study.

Transitions between B-DNA and Z-DNA: a dilemma.

The intramolecular conformational change which occurs in double-stranded (dG-dC) oligonucleotides and polynucleotides in high salt solutions is currently assumed to be a transition between the presently accepted structures for B-DNA and Z-DNA. However, a serious dilemma results from the fact that these two structures are from topologically different families of helical duplexes. Mechanisms for interconversion between the two forms, under typical experimental conditions, are highly improbable from a physical-chemical viewpoint. The alternative possibility is that the structure of one of the forms in the transition is not as assumed. The resulting dilemma is addressed and alternative relationships between right- and left-handed DNA forms are discussed.

Deoxyribonucleic acid structure: a new model.

Models of deoxyribonucleic acid (DNA) having chain directions opposite to those of the Watson and Crick model offer strikingly different alternatives for DNA structures. Satisfactory models of the B and C forms of DNA have been built. Left-handed models readily form by twisting right-handed ones, and models can be bent into tight supercoils.