February 16, 2022
“I’m kind of a product of very successful outreach.” — Nayomi Plaza, BioSANS user
Nayomi Plaza studies how to make wood products more durable, but as a student she got started by asking for experimental advice from scientists with quite the opposite agenda—improving cellulose degradation for biofuels. Though the end goals are different, both questions seek insights into the nanoscale structure and function of plant cell walls, a fundamental science topic supported by the structural biology and imaging resources of DOE’s Biological and Environmental Research (BER) Program.
“My overarching research direction is to try to gain a holistic understanding of how to make wood more durable to different environmental conditions,” says Plaza, a materials research engineer at the U.S. Department of Agriculture Forest Products Laboratory (FPL) in Madison, Wisconsin. “Not just humidity, decay, and degradation, but also things like fire.”
To do this, Plaza set out to fill a gap that existed in the research on wood vulnerability—an understanding of what is going on at the nanometer scale. This includes structures between 1 and 100 nanometers in length such as proteins, a strand of human DNA (2.5 nanometers wide), ribosomes, and viruses. For context, a human hair is 100,000 nanometers in diameter.
“It is typically very hard to measure samples at the submicron level to the Angstrom level,” Plaza says, which is a range from 1,000 nanometers down to 0.1 nanometer. Therefore, a lot of studies focus on properties of wood at the macroscale—anything longer than a millimeter (one million nanometers) that can be seen with the naked eye—such as mass loss caused by degradation, moisture content, and mechanical properties without pinpointing the underlying mechanisms. “The studies tend to have this gap on the specifics because it is hard to measure what the change was at those length scales. So, I have been addressing the nanoscale gap that tends to be seen in multiscale studies.”
Choosing the right technique
Plaza soon learned that small-angle neutron scattering (SANS) is well-suited to studying wood nanostructures. “The biofuels people were looking at similar material from a different perspective, but the mechanics of the experiments are quite similar,” she says. “Looking at their data gave me an idea of how to plan my own experiments—how much time, what is the contrast. All that stuff is independent of the question. It’s more about experimental details.”
Plaza started off investigating how wood absorbs water and how the water molecules change its structure. “It’s a very hard thing to measure because you have a lot of light elements in your material, and water is also light.” She needed a technique that could not only analyze the structurally complex wood samples at the nanometer scale intact, but also discern water from the other light elements in the sample. SANS fit the bill. The next step was to determine how to access the resources that offered this technique.
“When I first started exploring these questions, my PhD advisers weren’t neutron scattering people,” Plaza says. “So, in 2012 they sent me to the National School on Neutron and X-ray Scattering.”
Each summer, Oak Ridge National Laboratory (ORNL) and Argonne National Laboratory (ANL) jointly host about 60 graduate students at DOE national user facilities to learn hands-on how to use experimental neutron and X-ray scattering technologies in their research. The two- to three-week course held at ANL’s Advanced Photon Source and ORNL’s Spallation Neutron Source (SNS) and High Flux Isotope Reactor (HFIR) features lectures, tutorials, and experimentation led by experts on using facility resources to study the structures and behaviors of materials at the atomic scale. The school is supported by DOE’s Basic Energy Sciences Program.
Plaza also took a course on structural biology taught by Flora Meilleur, a neutron scattering scientist at ORNL, and spent a year at ORNL as a DOE Office of Science Graduate Student Research fellow from 2015 to 2016 using capabilities offered at the Center for Structural Molecular Biology (CSMB), a user resource sponsored by BER. Through these experiences, she began making her first connections with beamline scientists at SNS and HFIR, including Sai Venkatesh Pingali, an instrument scientist at ORNL’s Biological Small-Angle Neutron Scattering Instrument (Bio-SANS), with whom she has published several research papers.
“Getting to know about the resources early on really helped me graduate on time,” Plaza says. “I started doing my beamline proposal to request access, and we were successful getting beam time right away. Everybody was eager to share not only the resources but their expertise. They would ask what science question you were after and try to figure out whether the experimental plan would help or if there was an easier way. They are great at providing all the information you might need and then a little bit more if you let them.”
Plaza’s initiative paid off. As of 2021, she had produced nine1-9 papers or conference proceedings about her work using BER structural biology resources.
In her first paper5, in Cellulose, Bio-SANS revealed that water infiltration increased the spacing between elementary fibrils in wood—the smallest structural units of cellulose—and is a major contributor to the tangential swelling in wood cell walls. Understanding the nanoscale mechanisms that contribute to moisture-induced swelling may help accelerate development of forest products with enhanced moisture durability, she says. This work has helped informed a nanoscale model that now includes the presence of diffusion channels inside cellulose microfibrils, which are thought to play a role in degradation mechanisms like corrosion or fungal decay.
Plaza and her collaborators followed up with a SANS study6 showing that certain wood adhesives penetrate the same spaces within wood cellulose microfibrils as water. They propose that this behavior may be key to designing moisture-durable wood adhesives.
Next, they investigated how brown rot, a particularly problematic fungus for the timber industry, decays wood9. “We’ve seen that SANS is particularly helpful in further understanding the mechanisms of the degradation of the cell wall at the nanoscale level,” Plaza says. “We’ve also been studying how different protection treatments may prevent that nanostructural degradation8.”
Many paths to access BER resources
The path Plaza took to learning about BER resources available for her research is not the same one everyone must travel. She encourages new users to explore the resource web pages, take virtual or in-person facility tours, and reach out to resource leads to ask questions. “They’re very helpful and happy to provide answers,” she says. “But they can’t do that if you don’t reach out to them.”
Both the National School and individual contacts can provide information on collecting and analyzing data, operating the instruments, sample considerations, and how to write research proposals. Most importantly, Plaza encourages prospective users to expect a learning curve and not get discouraged if things don’t work out the first time.
Collaboration is key
“I’m kind of a product of very successful outreach,” Plaza says. She’s now building off the collaborative environment by paying it forward. When she was a resident at ORNL, resource experts suggested complementary techniques, and fellow researchers shared their experimental successes and setbacks. Today, as Chair of the Biological Small-angle Neutron Scattering Scientific Review Committee for the SNS/HFIR user program, she helps others shape their research directions.
She also offers insight from her SANS experience to scientists studying different length scales and environmental conditions. During her research, achieving the precise humidity control needed to replicate the environmental conditions she wanted to study in her wood samples was difficult. Legacy preparations risked obscuring the changes she was trying to observe. Through discussions with SNS and HFIR beamline staff and engineers, Plaza developed a relative humidity chamber, designed and custom-built at the FPL machine shop. Now in its third iteration, the chambers are available for use by other researchers.
Next up, in January 2022, Plaza will meet at BioSANS with Magdalena Broda, an assistant professor in the Department of Wood Science and Thermal Techniques at Poznan University of Life Sciences in Poland and currently working in the U.S. thanks to a Fullbright Scholarship. Broda obtained a pair of 1,200-year-old samples of waterlogged oak—one from a medieval bridge found in Lednica Lake, Poland, and another from a canoe found in Lake Mendota in Madison, Wisconsin. Together Plaza and Broda hope to determine how wood nanostructure degrades over time and how that affects the nanoscale water distribution inside wood cell walls. Determining the process at a nanometer scale may lead to improved protective treatments for everything from building materials to archaeological artifacts. It’s a new direction from her previous work, yet nonetheless intricately related. “There’s a lot to learn from each other even though the ultimate outcome of the work is not the exact same,” Plaza says.
1) Ibach, Rebecca Ehlinger; Plaza, Nayomi Z; Pingali, Sai Venkatesh. Small angle neutron scattering reveals wood nanostructural features in decay resistant chemically modified wood. Frontiers in Forests and Global Change (in press).
2) Jakes, Joseph E.; Plaza, Nayomi Z.; Arzola Villegas, Xavier; Frihart, Charles R. 2017. Improved understanding of moisture effects on outdoor wood–adhesive bondlines. Gen. Tech. Rep. FPL–GTR–246. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. 9 p.
3) Jakes, Joseph E.; Charles R. Frihart; Christopher G. Hunt; Daniel J. Yelle; Nayomi Z. Plaza; Linda F. Lorenz; and Daniel J. Ching. 2018. Integrating Multiscale Studies of Adhesive Penetration into Wood. Forest Products Journal 68 (4): 340–48. https://doi.org/10.13073/FPJ-D-17-00067
4) Jakes, Joseph E., Charles R. Frihart, Christopher G. Hunt, Daniel J. Yelle, Nayomi Z. Plaza, Linda F. Lorenz, and Daniel J. Ching. Integrating Multiscale Studies of Adhesive Penetration into Wood In: Hunt, CG, Smith, GD, Yan, N., eds. Proceedings, 2017 international conference on wood adhesives. Peachtree Corners, GA: Forest Products Society: 6 p. 2017
5) Plaza, N.Z.; Pingali, S.V.; Qian, S.; et al. 2016. Informing the improvement of forest products durability using small angle neutron scattering. Cellulose 23, 1593–1607. https://doi.org/10.1007/s10570-016-0933-y
6) Plaza, Nayomi Z.; Jakes, Joseph E.; Frihart, Charles R.; Hunt, Christopher G.; Yelle, Daniel J.; Lorenz, Linda F.; Heller, William T.; Pingali, Sai Venkatesh; Stone, Donald S. 2017. Small-angle neutron scattering as a new tool to evaluate moisture-induced swelling in the nanostructure of chemically modified wood cell walls. Forest Products Journal. 68(4): 349-352.
7) Plaza, Nayomi Z; Jakes, Joseph E; Frihart, Charles R; Hunt, Christopher G; Yelle, Daniel J; Lorenz, Linda F. Small angle neutron scattering as a tool to evaluate moisture-induced swelling in the nanostructure of chemically modified wood cell walls In: Hunt, CG, Smith, GD, Yan, N., eds. Proceedings, 2017 international conference on wood adhesives. Peachtree Corners, GA: Forest Products Society: 6 p. 2017
8) Plaza, N.Z.; Ibach, R.E.; Pingali, S.V. 2021. Probing the nanostructural mechanisms behind decay resistance of chemically modified wood using small angle neutron scattering. In: 2021 International conference of the Forest Products Society. June 15-17, 2021. Virtual. LaGrange, GA: Forest Products Society: 159-163.
9) Zhu, Yuan; Plaza, Nayomi; Kojima, Yuka; Yoshida, Makoto; Zhang, Jiwei; Jellison, Jody; Pingali, Sai Venkatesh; O’Neill, Hugh; Goodell, Barry. 2020. Nanostructural analysis of enzymatic and non-enzymatic brown rot fungal deconstruction of the lignocellulose cell wall. Frontiers in Microbiology. 11: 1389. https://doi.org/10.3389/fmicb.2020.01389