Annual Report 2006

Characterization silk fibiroin and
other biopolymers from chemical
and physical respect and
development of their applications
to wound covering materials and
others
The primary structure of sericin A was
determined by RT-PCR; it consists of 1,271
amino acid residues with a high serine content
up to 44% in molar ratio, and additionally, the
presence of repetitive sequences with 86 and 8
amino acids per repeat was revealed. The
sequences were predicted less preferable to
form β-sheet structure compared to the 38-
amino acid-repeats that constitute sericin M.
This is consistent with the experimental result
using cast films; sericin M tends to favorably
form β-sheet structure through humidity
compared to sericin A. Electron microscopic
observations of liposomes showed that newly
constructed silk fibroin recovered from
posterior silk gland quickly penetrates
phospholipids membranes without bursting
them. Observations of the planar lipid bilayer
membrane showed that the regenerated silk
fibroin after autoclaving penetrates phospholipids
membrane as well.
New process for forming the film of hornet
silk using the harmless solvent system has been
developed. This hornet silk film was found to
exhibit the quite low cell adhesion activity
when the film coexists with serum. This finding
indicates that the hornet silk film is useful for
the biomaterials. The sequence of a silk protein
from Japanese spider was
determined from a partial cDNA clone. The
repeating unit was composed of several
segments such as a polyalanine, glycine-glicine-
Xaa with Xaa being alanine, tyrosine, glutamine
or leucine. Circular dichiroism (CD) studies
showed the stable secondary structures of
spider silk in silk gland.
The compressive modulus of silk fibroin
sponge influenced growth rate of fibroblasts
cultured in the sponge, and the higher cell
growth rate was observed in the softer silk
sponge. The secondary structure changes of
silk fibroin in the sponge construction during
storage were observed by 13 C solid-state NMR
measurement.
I nsect Biotechnology and Sericology Department
Building of the data retrieval
system for the genetic resources
of silkworm
The database on the preserved silkworm
races that have been maintained as the genetic
resources by National Institute of
Agrobiological Sciences is presently disclosed
on the following ; http://ss.nises.affrc.go.jp/
nisesDB/bombygen/tablemaster-eng.html in
English (Table 1 and Fig. 1). This database is
configured with a hierarchical tree structure. It
is troublesome to find the target characteristic
races. So, the retrieval function was added to
supplement the faults and to correspond
quickly. Some database softwares which have
retrieval function on the Web are commercially
available. But we did not use these database
softwares for providing security of the private
server. The program function was added on
the retrieval system configured with HTML by
using JavaScript. Still more, the retrieval
system was composed of the preserved
silkworm races and the commercial races. The
system made it possible to gain access to the
preserved silkworm races and to the
commercial silkworm races either in Japanese
or English for many users.
Improvement and application of
mapping systems in the silkworm,
Molecular linkage map has been improved
and finally 330 EST-cDNA clones have been
mapped on 28 linkage groups. The methods for