Robustness Of DNA Research Articles

Modular, Articulated Models of DNA and Peptide Nucleic Acids for Nanotechnology Education

ABSTRACT Dynamic and flexible nucleic acid models can provide current and future scientists with physical intuition for the structure of DNA and the ways that DNA and its synthetic mimics can be used to build self-assembling structures and advanced nanomachines. As more research labs and classrooms dive into the field of structural nucleic acid nanotechnology, students and researchers need access to interactive, dynamic, handheld models. Here, we present a 3D-printable kit for the construction of DNA and peptide nucleic acid (PNA). We have engineered a previous modular DNA kit to reduce costs while improving ease of assembly, flexibility, and robustness. We have also expanded the scope of available snap-together models by creating the first 3D-printable models of γPNA, an emerging material for nuclease- and protease-resistance nanotechnology. Building on previous research, representative nucleic acid duplexes were split into logical monomer segments, and atomic coordinates were used to create solid models for 3D printing. We used a human factors approach to customize 3 types of articulated snap-together connectors that allow for physically relevant motion characteristic of each interface in the model. Modules are easy to connect and separate manually but stay together when the model is manipulated. To greatly reduce cost, we bundled these segments for printing, and we created a miniaturized version that uses less than half the printing material to build. Our novel 3D-printed articulated snap-together models capture the flexibility and robustness of DNA and γPNA nanostructures. Resulting handheld helical models replicate the geometries in published structures and can now flex to form crossovers and allow biologically relevant zipping and unzipping to allow complex demonstrations of nanomachines undergoing strand displacement reactions. Finally, the same tools used to create these models can be readily applied to other types of backbones and nucleobases for endless research and education possibilities.

Trial by Fire: Comparing DNA Degradation in Blood versus Semen after Fire Exposure

Criminals have long used fire to try to destroy evidence of other crimes. Historically this cover-up attempt has had enough success that today investigators may assume evidence has either been consumed by the fire or ruined by the fire-fighting efforts. Yet research indicates evidence can endure fire and still yield partial or even full DNA profiles. However, there has been little investigation into the robustness of DNA from one biological fluid compared to another. This study examines whether fire degrades the DNA from blood more than the DNA from semen. The two biological fluids were exposed to fire, the DNA from these samples was extracted using Qiagen kits, and DNA degradation was quantified using a real-time polymerase chain reaction. DNA was quantified from 59 postfire samples plus 10 positive controls. Data analysis indicated the DNA degradation levels were not significantly different between blood samples and semen samples. However, DNA degradation levels varied significantly between samples on different substrates (nylon versus polyester).