Protein crystal growth experiments have been performed by this laboratory on 18 space shuttle missions since April, 1985. In addition, a number of microgravity experiments have also been performed and reported by other investigators, (1 -7). These space shuttle missions have been used to grow crystals of a variety of proteins using vapor diffusion, liquid diffusion, and temperature-induced crystallization techniques. The United States Microgravity Laboratory-1 mission (USML-1, June 25 -July 9,

more »

... 992) was a Space/ab mission dedicated to experiments involved in materials processing. New protein crystal growth hardware was developed to allow in orbit examination of initial crystal growth results, the knowledge from which was used on subsequent days to prepare new crystal growth experiments. /n addition, new seeding hardware and techniques were tested as we//as techniques that would prepare crystals for analysis by x-ray diffraction, a capability projected for the planned Space Station. Hardware that was specifically developed for the USML-1 mission will be discussed along with the experimental results from this mission. INTRODUCTION The study of protein crystal growth in microgravity has generated considerable interest in recent years. Through the support of the National Aeronautics and Space Administration (NASA), we have coordinated a program designed to study protein crystal growth processes in general, and have evaluated the affects of a microgravity environment on these processes. A large co-investigator group, consisting of researchers and/or engineers from universities, NASA, and aerospace or pharmaceutical companies, participated in the hardware development and scientific experiments. Since April, 1985, Joint %+ 1" Science Review for USML-1 and USMP-1 udth the Microgravity Measurement Group, September 22-24, 1993, Huntsville, Alabama, USA. 409 PAGE__ PAGE" IILANK NOT FILMED INTF_TI_'q_ILY 8Ll"k_ https://ntrs.nasa.gov/search.jsp?R=19950007811 2018-07-21T04:45:06+00:00Z experiments have been performed on eighteen U. S. Space Shuttle missions with a variety of crystal growth hardware and crystallization techniques. In a number of cases, results from these experiments indicate that proteins grown in microgravity may be larger, display more uniform morphologies, and yield diffraction data to significantly higher resolutions than the best crystals of these proteins grown on Earth.(8 -11) This paper will discuss the hardware specifically developed for the USML-1 mission and the results obtained for the proteins flown on this mission. I. HARDWARE DEVELOPMENT A. Vapor Diffusion Apparatus A vapor diffusion apparatus (VDA) (9, 12, 13) was used for protein crystallization experiments on thirteen different space shuttle missions. This hardware incorporates a vapor diffusion technique that is closely related to the widely used hanging drop method of protein crystal growth on Earth. (14) This method was chosen for several reasons: 1. most protein crystallography laboratories have extensive experience with this method and a large percentage of the protein crystals described in recent publications have been obtained by this technique; 2. this technique is particularly amenable to crystallization experiments involving small quantities of protein; 3. in a microgravity environment, relatively large, stable droplets of protein solution can be formed with minimal surface contacts, thereby decreasing possible nucleation sites and minimizing wall effects that generally accompany crystallization experiments on Earth. The hardware was developed from a simple piece of equipment that was easily modified and improved throughout the series of shuttle missions. (9, 12, 13) Although microgravity experiments with the VDA clearly demonstrate the beneficial effects of this environment for protein crystal growth, only about 20% of the proteins examined were found to exhibit better morphologies or better quality data than their Earth-grown counterparts. Approximately -40°,/o of the space experiments failed to produce crystals, and the remaining 40% yielded crystals that Were either too small for x-ray analysis or produced data no better than that obtained from the best Earth-grown crystals. It is important to note that results from a single space experiment, in which each protein is typically allotted five crystallization chambers, are being compared to the best crystals ever produced for that particular protein by any method on Earth. Investigators have no opportunity to optimize crystal growth conditions in microgravityo This may account for some occasions in which unsatisfactory results were obtained in microgravity. B. USML-I Glovebox Vapor Diffusion Hardware: To allow crewmen to optimize microgravity crystal growth conditions, new hardware was developed and flown on the USML-1 mission in June, 1992. A glovebox was available in the Spacelab