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"In-situ" observation experiment measuring the precise growth rate of protein crystals on board Kibo has been completed

Last Updated: January 22, 2013

"In-situ observation of growth mechanisms of protein crystals and their perfection under microgravity* (NanoStep)" has been completed using the Solution Crystallization Observation Facility (SCOF) on board Kibo, the Japanese Experiment Module (JEM).

*Principle Investigator (PI): Katsuo Tsukamoto, Professor, Tohoku University

The NanoStep experiments, in four months since its first series started on August 6 (Mon.), 2012, to December 14 (Fri.), three series of experiments in total were conducted as follows.

First series: August 6 (Mon.) to September 7 (Fri.)
Second series: October 1 (Mon.) to November 2 (Fri.)
Third series: November 12 (Mon.) to December 14 (Fri.)

Many high-quality proteins and improvement of crystal perfection created in space have been reported so far. The reason for these is considered that under the microgravity environment where there is no convection occurs, protein molecules are slowly crystallized (grows slowly).

However, according to the experiments performed by the PI and his colleagues, there are cases that the rates of crystal growth in microgravity are same, or even faster than the ones grown on the ground.

This suggests that there are some different factors that improve the crystal perfection. If such factors that affect the perfection of crystals in relation to the protein growth mechanisms through this series of experiments are found, the findings can be applied to the crystal growth on the ground.

A crystal growth rate highly depends on the mechanisms of the crystal growth. Hence, the mechanisms can be known by measuring the driving force (supersaturation) dependency of the crystal growth rate. In the series of NanoStep experiments, in-situ observation and the precise measurement were performed under a wide range of crystal growth conditions, even as measured the surface status and concentration gradient of crystal interfaces using a reflection-type laser interferometer. The measurement using the reflection-type laser interferometer is the world's first.

Through this series of experiments, the followings have been discovered.

1. Far more precise crystal growth-rate data than those obtained on ground were obtained, and the differences of mechanisms with those obtained on ground became clear. Because there is a lot of variation in the on-ground data, such a detailed study of growth mechanisms is not possible.

2. It has been thought that there is no undesirable influence by impurities if a highly-pure protein solution is used. In one of this series of experiments, a refined, high-purity solution was used, which generated a better result than the ones grown on ground.

The above findings were quickly obtained because a system was built beforehand to realize the almost simultaneous analysis of the vast amount of obtained data, in order to perform the in-situ observation and data analysis in mind. This enabled encompassing all the necessary data. More detailed analysis will be conducted in near future.

If the protein crystallization process under microgravity and the factors which hinder the crystal perfection are found, future similar space experiments will proceed smoothly. This is not limited to proteins, but the founding will enable the correct analysis of the effects of impurities in the process of inorganic and organic crystallization which will lead to the improvement of crystal quality to be created on the ground.

【Remarks from PI, Katsuo Tsukamoto, Professor, Tohoku University】

Fabulous! We obtained a lot of precise data in a short time which are not possible on Earth. We can boast our "in-situ" observation research to the world. We look forward to the analysis by an international cooperation.

Interference figure of a protein crystal surface The size of the crystal is about 500μm. (Credit: Tohoku Univ./JAXA)

*All times are Japan Standard Time (JST)

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