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Release date: 07/01


Dynamically Controlled Protein Crystal Growth (DCPCG)


Missions: Expedition Three, ISS Mission 7A.1, STS-105 Space Shuttle Flight

Experiment Location on ISS: U.S. Lab EXPRESS Rack No. 1

Principal Investigator: Dr. Lawrence (Larry) DeLucas, Center for Biophysical Sciences and Engineering, University of Alabama at Birmingham

Project Manager: Tim Owen, NASA's Marshall Space Flight Center, Huntsville, Ala.


Overview

Proteins are the building blocks of our bodies, and the living world around us. Within our bodies, some proteins make it possible for red blood cells to carry oxygen, while others help transmit nerve impulses that allow us to see, hear, smell and touch. Other proteins play crucial roles in causing diseases. Pharmaceutical companies may be able to develop new or improved drugs to fight those diseases once the exact structure of the proteins is known. These protein structures can be established only after growing biological crystals of proteins.

The low-gravity environment of space often improves the quality of biological crystals beyond those grown on Earth. Scientists frequently grow these crystals by dissolving a protein in a specific liquid solution, and then allowing that solution to evaporate. DCPCG is the first hardware for space that can control the rate of this evaporation, and will hopefully provide more perfect crystals.

By sending X-rays through crystals, scientists are then able to produce computer models of the three-dimensional structures of proteins and other biological macromolecules. A macromolecule is a large molecule (protein, DNA, RNA, etc.) containing thousands of atoms.

Knowledge of the precise three-dimensional atomic structure of a biological macromolecule is an important component in biotechnology, particularly in the areas of protein engineering and rational drug design.

Objectives

Currently, the limiting step to structural solutions for further success in the biological sciences, and for pharmaceutical design, is the growth of high-quality protein crystals suitable for X-ray diffraction.

Growing protein crystals suitable for X-ray diffraction is often a major barrier in protein structure determination. There are many examples in which crystallization of the protein takes considerably longer than its structure determination by X-ray analysis. The objective of this project is to improve the crystallization process by dynamically controlling parameters that influence crystal formation. Present protein crystal growth experimental techniques provide little or no control over crystal growth rates and separation of the nucleation and growth phases. Yet it is clear that the approach to nucleation and the rate of crystal growth are important from a theoretical viewpoint and previous ground-based experiments. The importance of being able to separate and control these two phases has been extensively shown for small molecule solution crystal growth. Since many similarities exist between small and macromolecular crystal growth processes, it is important that control methods are developed for macromolecular systems.

The Dynamically Controlled Protein Crystal Growth investigation during Expedition Three on the International Space Station has several objectives. These objectives are:

  • To develop an automated crystallization system that provides real-time control of the supersaturation level via control of the protein concentration.
  • To determine the difference in vapor diffusion rates - the speed at which the liquid solution surrounding the protein evaporates, or moves from a lower concentration to a higher concentration - compared to similar experiments conducted within the gravity on Earth.
  • To measure and compare crystal growth rates in the low-gravity environment of space to those grown on Earth.
  • To assess the relationship between crystal movement and distribution on crystal growth rates - why crystals grow more slowly in space.
  • To develop a mathematical and numerical model that corroborates the results of low-gravity crystal growth versus Earth-based results.
  • To optimize, in both Earth-based and space-based experiments, the rate of protein crystal growth.
  • To assess the difference in quality of crystals grown under optimized conditions, once these conditions are established, for space-based and Earth-based protein experiments.
  • To assess the usefulness of real-time control for improving the success of protein crystal growth experiments on Earth and in space.

The principal investigator for the Dynamically Controlled Protein Crystal Growth experiment during Expedition Three is Dr. Larry DeLucas, with the Center for Biophysical Sciences and Engineering (formerly the Center for Macromolecular Crystallography) at the University of Alabama at Birmingham. The university is developing the DCPCG hardware for the NASA Biotechnology Program Office under a NASA contract.

Tim Owen, with the Microgravity Sciences and Applications Department of the Microgravity Research Program Office at NASA's Marshall Space Flight Center in Huntsville, Ala., is the project manager for the experiment.

Experiment Operations

Scientists hope the Dynamically Controlled Protein Crystal Growth project will refine the methods and hardware for growing biological macromolecules using real-time, or dynamic, control of the protein solution. Past protein crystal experiments have largely been passive -- requiring little, if any, crew or ground control interaction.

Onboard the Space Station, the Dynamically Controlled Protein Crystal Growth experiment consists of a Vapor Locker (V-Locker) connected to a Command and Data Management Locker (C-Locker). These lockers are located in the EXPRESS Rack No. 1 in the U.S. Lab of the Space Station.

The V-Locker has four subsystems. A Growth Reservoir Subsystem contains 38 growth chambers housing protein sample solutions. The Nitrogen Management Subsystem provides two dry nitrogen gas closed-loop systems to dehydrate the protein sample solutions. Scientists on the ground can control dehydration rates and amounts by telescience command and control, thus allowing them to control the rate at which crystallization occurs.

Also part of the V-Locker is a Laser Light Scattering Subsystem, which detects events leading up to, and including, formation of crystals in the sample chambers. A separate Video Subsystem is the integral link in the V-Locker that allows scientists and investigators to verify and evaluate in near real time the presence of crystals within the sample chambers, monitor crystal growth and monitor crystal integrity during the flight.

The C-Locker houses electronics equipment to control the V-Locker. Cables from the C-Locker connected to the V-Locker provide power distribution and conditioning, command and data management, video control and recording and parameter status monitoring and reporting. The C-Locker serves as the single communications interface during crew experiment and control, as well as the communications interface to controllers on the ground.

The experiment is scheduled for launch onboard Space Shuttle mission STS-105, ISS mission 7A.1. The experiments are scheduled to be returned to Earth onboard Shuttle mission STS-108, ISS mission UF-1.

Crew involvement during this time will be to transfer the V-Locker and C-Locker from the Shuttle to the Space Station. After the transfer, the crew will connect cables between the two lockers enabling communication and power, and then activate the experiments. The flight crew will periodically check the operation of the system to ensure that it is operating properly. The reverse procedure will be used to deactivate the experiment for its return to Earth for further study.

Most of the day-to-day experiment execution will be accomplished by the DCPCG experiment operations team. Scientist and engineers located at both the UAB Remote Operations Control Center (ROCC) in Birmingham and the MSFC Telescience Support Center (TSC) will closely monitor the crystal growth progress as well as the overall health and status of the DCPCG payload. Inputs to the onboard DCPCG experiment will be made as necessary by DCPCG personnel through remote telescience commanding. During the course of the Expedition Three mission, several DCPCG experiment runs will occur. The telescience command capability will thereby allow optimization and enhancement of the science return.

Background/Flight History

Protein crystal growth experiments have been conducted by the Center for Biophysical Sciences and Engineering on almost 40 previous Space Shuttle missions, beginning in 1985.

Benefits

Structural studies using microgravity-grown protein crystals may provide information that can be used in the development of new drugs. With the advent of genomic information from humans and many other species, the role proteins play in diseases and degenerative conditions are becoming clearer, and the need for information about the structure of these proteins more critical.

Further biological structure growth experiments will be part of the ongoing research conducted aboard the International Space Station. The Space Station provides a platform for growing some crystals that require longer periods of near-weightlessness than has been available on short duration Space Shuttle flights.

Benefits from protein growth experiments have already been seen. Many of the crystallization experiments conducted on the Space Shuttle have yielded crystals that furthered structural biology projects. For example, crystallization experiments have been conducted with recombinant human insulin. These studies have yielded X-ray diffraction data that helped scientists to determine higher-resolution structures of insulin formations. This structural information is valuable for ongoing research toward more effective treatment of diabetes.

Other successful crystallization experiments in space have provided enhanced X-ray diffraction data on a protein involved in the human immune system. These studies have contributed to the search for drugs to decrease inflammation problems associated with open-heart surgery. The crystallization of proteins in the near-weightless environment of space has allowed valuable insight into the science of macromolecular crystallography.

Crystallization experiments conducted on the International Space Station, involving not only human but also animal and plant proteins, promise to help answer key questions about the world around us.

More Information

Additional information and photos on this Expedition Three experiment is available at:

http://www.scipoc.msfc.nasa.gov/
www.flightprojects.msfc.nasa.gov/
http://crystal.nasa.gov/
http://science.nasa.gov/PhysicalScience.htm


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