NanoRacks-Self-Assembly in Biology and the Origin of Life (NanoRacks-SABOL) - 11.22.16

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Science Objectives for Everyone
In degenerative brain diseases like Alzheimer’s, proteins clump together in the brain and form fibrous plaques, known as amyloids. These structures are made from proteins that normally dissolve in liquid, but they become insoluble when they self-assemble. NanoRacks-Self-Assembly in Biology and the Origin of Life (NanoRacks-SABOL) seeks to successfully grow amyloid fibers in microgravity for the first time, aiming to compare them with fibers grown on the ground.
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The following content was provided by Samuel Durrance, Ph.D., and is maintained in a database by the ISS Program Science Office.
Experiment Details

OpNom: NanoRacks Module-30

Principal Investigator(s)
Samuel Durrance, Ph.D., Florida Institute of Technology, Melbourne, FL, United States

Daniel Kirk, Ph.D., Florida Institute of Technology, Melbourne, FL, United States
Hector Gutierrez, Ph.D., Florida Institute of Technology, Melbourne, FL, United States

Florida Institute of Technology, Melbourne, FL, United States
NanoRacks LLC, Webster, TX, United States

Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)

Sponsoring Organization
National Laboratory (NL)

Research Benefits
Scientific Discovery

ISS Expedition Duration

Expeditions Assigned
Information Pending

Previous Missions
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Experiment Description

Research Overview

  • NanoRacks-Self-Assembly in Biology and the Origin of Life (NanoRacks-SABOL) grows lysozyme amyloid fibers in weightlessness for the first time, and compares the characteristics to fibers grown in the ground control experiment.
  • NanoRacks-SABOL may lead to new treatments or understanding of neurodegenerative diseases, such as Alzheimer’s.


Self-assembly processes in biology can create complex new products with useful properties not present in the original components. The NanoRacks-Self-Assembly in Biology and the Origin of Life (NanoRacks-SABOL) experiment is directed toward an understanding of the physical principles involved. The self-assembly process studied here is the growth of long, linear protein fibers directly from a solution of the individual proteins. The growth of lysozyme fibers has been well studied in the laboratory and it provides a model for the study of this self-assembly process. The first image below shows atomic force microscope (AFM) images of the early and late stages of growth of long thin fibers from a solution of lysozyme proteins. The left image shows two cases, indicated with arrows, where lysozyme fibers are forming helical pairs. Helix formation has been observed in the early stages of fiber self-organization; however, it stops when fibers become bound into a network and can no longer rotate as shown in the right image. As the fibers settle out of solution they form a tangled network of fibers as shown in the right image. Growing amyloid fibers in weightlessness allows the fibers to remain suspended without fluid shear or agitation, and should allow them to remain distributed within the solution as they form. This may permit helix formation to continue beyond the 2-4 fibers that merge in ground-based studies to form larger composite fibers.
This self-assembly process also has implications in Alzheimer’s disease. Postmortem studies of the neurons taken from victims of Alzheimer’s disease show an accumulation of fibers composed of either Tau proteins or Amyloid-β peptides; both of which have been shown to self-assemble in solution through interactions similar to those of lysozyme. It is not clear whether amyloid deposits are the cause or a symptom of the disease or whether they will form in vivo (within a living organism) the same way they form in vitro (within an artificial environment), but it is clear that a better understanding the formation process will greatly benefit neurodegenerative disease research.
The optimal methods for lysozyme preparation, fiber formation, and fiber characterization are well understood. Acidic conditions (pH = 2.5) are required to partially unfold the molecule and expose hydrophobic domains, rendering it susceptible to aggregation. At this pH, lysozyme has a charge of approximately +26 resulting in a strong coulomb repulsion that inhibits aggregation. This is overcome by heating the sample to 55oC to increase Brownian motion and incubating it at this temperature for up to 30 days.
A primary goal of the SABOL program is to develop a capability with enough flexibility to study many different types of protein fibers in weightlessness. The NanoRacks-SABOL experiment is housed within a 1U volume as shown in the second image below. It consists of a 3x3 array of 9 vials, each with an actuation mechanism used to introduce the protein powder into the buffer solution and each with individual heaters. There is a custom shell, a support structure for the vials, and a USB interface. There are two printed circuit boards. The side printed circuit board (PCB) contains the components used to measure and control temperature of each vial individually, and to perform data acquisition. The top PCB contains the components necessary to command the actuation mechanisms at the appropriate times.
One of the challenging aspects of the NanoRacks-SABOL experiment is how to keep the lysozyme powder separated from the buffer solution until it is time to start the incubation period in orbit, while also keeping the complete vial system sealed at all times. The vials themselves and all the internal components are made out of Polypropylene. A vial is shown in cross section in the third image below for both the unactuated and an actuated configuration.
Each vial has two separate compartments initially isolated from each other. One compartment consists of a tube with a volume slightly greater than 2 mL that contains 2 mL of the buffer solution; the other compartment consists of a small piston with just enough volume to hold 0.04 g of lysozyme powder. The image on the left shows a vial in the unactuated configuration and the one on the right shows it in the actuated configuration. During International Space Station (ISS) orbital operations, each of the samples is individually activated. Each of the sample holders also has an independent thermal control system. When a given sample is activated its temperature is set to the incubation temperature 55 ± 1.5°C and maintained there by a thermal control system throughout the incubation period. In this way the aggregation period for all the samples is varied from the maximum of 26 days to the minimum of 3 days.

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Space Applications
The investigation required development of a small automated laboratory for studying self-organizing processes, which can be utilized by other investigators in the future. Protein research in microgravity holds promise for a wide range of medical research.

Earth Applications
The investigation explores the spontaneous self-assembly of amyloid proteins into long fibers. Amyloid fibers produced on the ground settle due to gravity preventing them from growing large enough for detailed study. In microgravity, they stay suspended and continue growing into large bundles, which are easier for scientists to analyze. Understanding the structure and mechanisms of these protein clusters provides new insight into how they work, and how scientists might develop treatments for amyloid-related diseases, including Alzheimer’s disease.

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Operational Requirements and Protocols

Ambient transport up, but late load. Activation by ISS Docking + 5 days. Refrigerate at end of vehicle stage ops to prepare for return in +4°C cold stowage.

NanoRacks Module-30 uses generic NanoRacks Platform-1/2 procedures for on-orbit ops. NanoRacks Module-30 transfers to the ISS and is activated by ISS Docking + 5 days. The module is activated by installing it in a USB interface within NanoRacks Platform-1 or -2 for power and data transfer. Data is downlinked using the Platform’s STELLA capability. The module is refrigerated to +4°C for cold-stow return.

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Decadal Survey Recommendations

Information Pending

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Results/More Information

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Related Websites
Self-Assembly in Biology and the Origin of Life (SABOL)

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Atomic force microscope images of lysozyme aggregation showing advanced stages of the amyloid fiber formation process. Left: Shows the merging of fibers into a helix configuration as indicated by the two arrows. Right: The gravitational settling of fibers creates a tangled interlocking network preventing fibers from rotating and halting helix formation. Image courtesy of Samuel Durrance.

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CAD Model of NanoRacks-SABOL NanoLab Module Laboratory. Image courtesy of Samuel Durrance.

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Aggregation Mechanism Used in Each of the 9 Vials for the NanoRacks-SABOL investigation. Image courtesy of Samuel Durrance.

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