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JAPAN NANONET BULLETIN
-- 52nd Issue -- September 1, 2005
Nanotechnology Researchers Network Center of Japan
Ministry of Education, Culture, Sports, Science and Technology (MEXT)
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IN THIS ISSUE
Nanonet Interview:
"Attracted to thermophilic bacteria --From the mechanism for the
thermostability of proteins to the origin of life--"
Tairo OSHIMA, Director, Institute of Environmental Microbiology,
Kyowa Kako Co., Ltd.
Young Researchers' Introduction:
"Self-organization of designed disk-like molecules and construction
of novel nanoscaled devices"
Mutsumi KIMURA, Associate Professor, Department of Functional
Polymer Science, Faculty of Textile Science and Technology, Shinshu
University
-- NANO CALENDAR --
For information on nanotechnology related symposiums and conferences
held in the world,
http://www.nanonet.go.jp/english/calendar/
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NANONET INTERVIEW
Attracted to thermophilic bacteria --From the mechanism for the
thermostability of proteins to the origin of life--
(Issued in Japanese: March 2, 2004)
Tairo OSHIMA, Director, Institute of Environmental Microbiology,
Kyowa Kako Co., Ltd.
Organisms often live in places which seem unlivable. For instance,
thermophilic bacteria live in and around hot springs and deep-sea
hydrothermal vents where temperatures can exceed 100 degree C. Prof.
Oshima wondered how they can live in an environment with such high
temperatures and what factors determine the temperature limit for life.
He has been looking at the structures of proteins for the answers.
Prof. Oshima first learned thermophilic bacteria at NASA's Ames
Research Center. After returning to Japan, he began isolating
thermophilic bacteria and analyzing the structures and functions of
their proteins because he wanted to determine how they can survive at
such high temperatures. In 1968, he isolated a new type of
thermophilic bacterium from a hot spring in Izu and named it "Thermus
thermophilus". It has a growth temperature that is greater than 80
degree C, which was the highest growth temperature for thermophilic
bacteria at that time. He found that its body length of 2 micrometers
and the structure of its cell envelope are very similar to Escherichia
coli, which is widely used in biochemical research. Therefore, it can
be compared to Escherichia coli, and, like E. coli, it is also
suitable for the gene manipulation at high temperatures.
After Prof. Oshima found that the thermostability of transfer RNA in
thermophilic bacteria is caused by a slight difference in the base
pairs, his interest shifted to modifying proteins to increase
thermostability. However, it is extremely difficult to design proteins
with the proper conformation to make them thermally stable. So, he
employed "directed evolution", in which forced evolution is used in
order to obtain functions for specific purposes by introducing a
mutation into a protein-encoding gene. A gene is extracted from a
mesophile such as E.coli or Bacillus subtilis, and is introduced into
a chromosome of the thermophilic bacterium, and the resulted
transformant is then grown at elevated temperatures. Only strains in
which the integrated gene is mutated to encode a thermally stable
protein can grow, and thus, he was able to modify the thermostability
of the proteins by screening strains in this way.
Thermophilic bacteria are a key to the birth of living organisms in
the primordial earth. The comparison of the base sequences of the
ribosomal RNA, which all living organisms have in common, has shown
that thermophilic bacteria are the dominant organism near the root of
the evolutionary tree. Prof. Oshima thinks that they could be the
origin of all living organisms. He calls them the "commonote," or
universal ancestor. In order to speculate the nature of the commonote,
he researched the common characteristics of all hyperthermophilic
bacteria that grow at temperatures higher than 90 degree C. However,
they do not always have the same characteristics as their ancestors
because existing hyperthermophilic bacteria have diverged during 4
eons of evolution. He expects to discover more about the commonote
from the "Ocean Drilling Program" of the Japan Marine Science and
Technology Center (currently, Japan Agency for Marine-Earth Science
and Technology), in which researchers will drill 4,000 m below the sea
floor. The temperature around a hydrothermal vent is higher than 100
degree C in some places, and many scientists believe that the
environment around the vent is close to the environment during the
birth of all living organisms. He says, "We know that there are living
organisms in the geosphere below the sea floor, and there may be an
unimaginable number of living organisms there."
T. thermophilus that Prof. Oshima discovered has been kept in culture
collections around the world as a usable thermophilic bacterium.
Currently, thermophilic bacteria are used in research projects on
protein structural genomics, which many countries perform. Japan's
National Project on Protein Structural Genomics "Protein 3000" is one
of those research projects. DNA polymerase, used for the polymerase
chain reaction (PCR), which is an artificial DNA-copying technology
used in molecular therapy, gene diagnosis and research on cancer, is
also an enzyme originating from thermophilic bacteria. Thermophilic
bacteria are used in many fields because of their thermostability. He
said, "A few decades ago, nobody even thought that they would have
applications in medical fields. Things may turn out unexpectedly good
like my research on thermophilic bacteria. So, you should research
what interests you most." He has also recently focused on compost.
There is compost, supplied from a compost factory for sewage-treatment,
on his lab's deck. "It was thought that the highest temperature of
fermenting compost was around 75 to 80 degree C, but the temperature
of our compost is higher than 90 degree C. We will find new bacteria
that have not been written about in the textbooks and literatures,"
says Prof. Oshima with a smile. There may be more unexpected results
from this compost research.
(Interviewer: Fumie Shimizu, Cosmopia Inc.)
For more information,
http://www.nanonet.go.jp/english/mailmag/2005/052a.html
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YOUNG RESEARCHERS' INTRODUCTION
Self-organization of designed disk-like molecules and construction
of novel nanoscaled devices
(Issued in Japanese: March 9, 2004)
Mutsumi KIMURA, Associate Professor, Department of Functional
Polymer Science, Faculty of Textile Science and Technology, Shinshu
University
The self-organization of functional molecules into well-defined,
nanometer-sized structures is an important process for the
construction of molecular-based devices. pi-conjugated disk-like
molecules, such as triphenylene, porphyrin, and phthalocyanine, are
attractive building units for the formation of highly-ordered columnar
stacks. These ordered stacks enable efficient electron, or hole,
transport parallel to the columnar axis. We have investigated the self
-organization of designed disk-like molecules to obtain stable
columnar stacks.
We prepared organic-inorganic composites containing one-dimensional
ordered stacks of amphiphilic disk-like molecules by liquid crystal
template sol-gel polymerization. The amphiphilic disk-like molecules
contain a central phthalocyanine core, alkyl spacers, and peripheral
hydrophilic chains. Sol-gel polymerization of tetraethoxysilane in the
presence of the amphiphilic disk-like molecules resulted in the
formation of organic-inorganic composites containing one-dimensional
ordered stacks. The disk-like molecules were assembled into one-
dimensional columnar aggregates in aqueous solution through strong pi-
pi interactions. Sol-gel polymerization of inorganic monomers at the
surface of supramolecular aggregates allowed the creation of the
highly ordered organic-inorganic composites. In addition, the
deposition of inorganic walls preserved the morphologies of the
flexible organic supramolecular structures and wrapping with an
inorganic wall caused single columns consisting of one-dimensional
stacks of molecular disks to form. The isolated, ordered stacks within
the silica can be considered as molecular cables, which have a central
electron-conducting wire of stacked disk-like molecules surrounded by
an insulating silica wall. The electron conduction properties of a
single stack are the subject of future studies.
For more information,
http://www.nanonet.go.jp/english/mailmag/2005/052b.html
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