This is an R24 proposal to establish a Regional and National Resource in modern Electron-Spin Resonance (ESR) Technology for use by the biomedical community. This resource will build upon 20 years of a very successful National Biomedical Center: ACERT (funded by an NIH P41 grant), in which the new ESR technologies that were developed, driven by biomedical collaborators, were then provided to extensive collaborators and service projects. In its new configuration as an R24 resource, it will focus on user services and collaborations utilizing the already established extensive and unique technologies that have already been developed. We have a well- established administration and operations scheme for this objective. Through outreach efforts we plan to significantly expand the user base both nationally and internationally. We will be providing extensive educational and training capabilities for the expanded user base. This will include a series of workshops, on-line resources, in house training and visits to other labs. The outreach will include tutorial papers in key journals, virtual meetings with the International ESR Society, video lectures on YouTube, and advertisements in leading Journals and Newsletters. The ESR resources we provide are in many ways unique in the world. In addition to our commercial spectrometers for cw and pulse ESR covering the frequency range of 9 to 35 GHz, we have extensive and unique custom-home built spectrometers covering the range of frequencies 9 to 240 GHz. These spectrometers are dedicated to a full range of ESR methods utilized by the biomedical community, especially including techniques for conducting pulse dipolar ESR (PDS), which provides distances between labeled protein and RNA sites from which protein tertiary structure may be inferred. It is applicable to protein complexes in their natural states. ACERT has developed methods that both significantly increase the sensitivity to low sub- micromolar protein concentrations and very small samples, and they greatly increase the throughput, enabling a greater rate of processing of the many samples studied in PDS. While PDS supplies protein structures, the additional techniques of multi-frequency ESR and pulsed 2D-ESR at ambient temperatures supply details of protein dynamics, important in learning about structure/function; this includes the unique ability to study in real time nanosecond to microsecond dynamics, which will address such issues as domain motions in proteins. Our innovative software enables the fitting of the complex 1- and 2-D spectra to extract the details of the complex protein motions, and our recent developments of signal processing software have led to unique packages for greatly increasing the signal-to-noise of weak ESR signals while providing great fidelity, as well as accurately transforming the results of PDS experiments into (complex) distance distributions. These software methods will also enhance the throughput of the Resource.