© 2019 NASA Nebraska EPSCoR

Funded NASA Nebraska EPSCoR

Projects at the National Level

Professor Gloria Borgstahl: University of Nebraska Medical Center

Large Volume Crystal Growth of Superoxide Dismutase Complexes in Microgravity for Neutron Diffraction Studies

Superoxide dismutases (SODs) are important antioxidant enzymes that protect all living cells against toxic oxygen metabolites, also known as reactive oxygen species (ROS). SODs are one of the fastest known enzymes with a kcat/Km of 109 M-1s-1and are rate-limited only by the diffusion of the substrate and products. SODs are the first line of defense to protect organisms against metabolically generated and/or ionizing radiation-induced ROS. SOD protects cells by dismuting two molecules of superoxide anions to form hydrogen peroxide and molecular oxygen via a cyclic oxidation-reduction reaction. SODs contain metal ions in their active sites. Humans have Cu/ZnSOD in the cytosol and extracellular spaces and MnSOD in their mitochondria. Mutations in SOD lead to aging and degenerative diseases such as amyotrophic lateral sclerosis (ALS), diabetes, and cancer.

The project is studying SODs from the model system Escherichia coli as they are easy to produce, stable, and the active sites are identical with human homologs. Bacteria have both Fe and MnSOD. Despite the biological and medical importance of SOD, the complete enzymatic mechanism is still unknown. Precise structural data are needed. The binding sites of the diatomic substrate and product as well as the source of the protons in the reaction have been studied, but their exact identification has not been possible.

 

This detailed information can only be determined by neutron diffraction. Complexes of Fe and MnSOD including structural intermediates and mutants will be the targets for large volume crystal (≥ 1mm3) growth for structure determination by neutron macromolecular crystallography (NMC). The quiescent environment afforded by microgravity is known to grow crystals large enough for neutron studies.

 

In 2001, the Borgstahl laboratory successfully grew large crystals of SOD using microgravity conditions on the International Space Station (ISS). With NASA’s renewed interest in implementing the microgravity environment on the ISS for protein crystal growth the project is moving forward with exciting early microgravity crystallization results for SOD. Existing crystallization facilities, such as the Granada Crystallization Facility (GCF) that employs capillary counterdiffusion protocols or the Handheld High Density Protein Crystal Growth (HDPCG) hardware that uses vapor diffusion methods are being used to achieve these goals.

 

A microgravity environment is essential to form a stable supersaturation gradient to obtain the large crystals required for NMC. Then NMC is being performed with collaborators at Oak Ridge National Laboratory (ORNL). The principal outcome being the identification of the role of hydrogen atoms in enzymatic activity, discerning superoxide from peroxide and water from hydroxide ion by their protonation state and deciphering a structure-based mechanism for Mn and FeSODs more precisely than from previous X-ray crystallographic models determined from Earth-grown crystals. These contributions will also provide criteria needed for the protein engineering of desirable properties into enzymatic metal centers for proton coupled electron transfer.

Check out this great feature on Dr. Gloria Borgstahl's (UNMC) Perfect Crystals experiment from ISS News! https://www.nasa.gov/mission_pa…/…/research/news/SSSH_7jan19

Concluded: Professor Axel Enders: University of Nebraska-Lincoln

Novel Materials and Devices for Deep Space Probes and Satellites

The project is working to develop boron carbide polymers from C2B10Hx icosahedra building blocks, with controlled p-type and n-type semiconducting doping.  Based on these materials, the project is establishing the process parameters to synthesize several micrometer thick films and multi-layers by plasma-enhanced chemical vapor deposition.  The neutron-absorbing properties of films will enable three distinctive but intrinsically related applications relevant to NASA which include: (i) light-weight coatings for deep-space probes to shield them from intense neutron exposure during exploration, (ii) effective neutron-voltaics devices (like photovoltaics, but powered by neutrons) to power deep space probes, and (iii) all-boron carbide gamma-blind neutron detectors of unprecedented efficiency to provide insight into cosmic rays, solar neutrons, neutron stars, pulsars and supernovas during NASA's deep space missions.  The research program includes a materials science approach to establish the fundamental basis of boron carbides and the development of proof-of-concept devices.

Concluded: Professor George Gogos: University of Nebraska-Lincoln

Highly Permanent Biomimetic Micro/Nanostructured Surfaces by Femtosecond Laser Surface Processing for Thermal Management Systems

Nebraska Professors George Gogos, Dennis Alexander and Sidy Ndao are leading an interdisciplinary effort to create functionalized metallic surfaces for thermal management systems in space applications.  They treat a surface with a laser to create microstructures and nanostructures, thus giving the metal entirely different and desirable properties.

Functionalizing metal surfaces is preferred over coatings and polymers which are not very permanent, especially at high temperatures.  Unlike polymers such as Teflon, functionalized metallic surfaces with newly created microstructures remain unaltered over time resulting in a permanent and consistent surface.

The NASA EPSCoR grant is allowing further research into enhancements of thermal management for NASA applications by using titanium and silicon carbide in the functionalization process to improve thermal heat management during space travel.

The team has strong NASA collaborations at NASA’s Glenn Research Center, including work with Dr. Janet Hurst, Dr. Mohammad Hasan, and Dr. Vehda Nayagam.  A doctoral student on the team is the recipient of the prestigious NASA Space Technology Research Fellowship, the first awarded to a Nebraska student.

This research is making an impact on the research capacity in Nebraska.  In addition, multiple local industry partnerships have formed for patent application development and the advancement of manufacturing technologies and practices within the state.