Annual Report 2006

also surveyed in the genetic stocks. The
strongest cocoon filament showed an intensity
of over 4.5 g/d, or 1 g/d higher than ordinary
races. These strains might be useful resources
for breeding new silkworm races.
Chemical and physical modifications
of silk and the development of
characteristic silk products
13
C solution and solid-state NMR analyses
were employed to investigate native structure
and degradation pattern of silk sericin. Sericin
samples were prepared from Sericin Hope
silkworm, which secrets almost exclusively
sericin. The 13 C solution NMR spectra of native
sericin solution obtained from Sericin Hope
larvae exhibited that sericin was largely
random coil structure before spinning. The
structural changes by thermal degradation
were followed by 13 C solution NMR measurements.
The 13 C NMR spectrum after thermal
degradation exhibited obvious peak splitting at
Asp Cα, Cβ and Cγ peaks. This observation
indicated that Asp residues might be a weak
point toward hydrolysis.
It was examined to form the artificial skein
and blood tube using cocoon filaments. The
basement of artificial skein was weaved by
using single cocoon filament which reeled up
from a cocoon (Fig. 6), the artificial blood tube
basement was made by the formation of
knitting and winding with cocoon filaments. In
order to produce the silk tube except sericin, it
was degummed (dissolving sericin), the fibroin
solution was put on the tube, and the fibroin
was fixed with alcohol treatment.
As the changing treatment of the fibers
characteristics, the knit materials made of silk,
cotton and wool were treated with high
temperature. The activated value of the
antibacterial activity was investigated. As a
result, the value of silk was the biggest among
them.
The silk thread characteristics of the
silkworm races, Koishimaru, Ohkusa and
Shohkoh were investigated. As a result, it was
recognized that they were very similar to the
silk characteristics of Edo period (1603-1867).
The flexible type silk reeling machine was
developed to produce five kinds of thick silk
fibers, that is, the high bulk silk, the special flat
silk, the combination silk yarn of high bulk silk
and special flat silk, the super thick silk and the
covered silk yarn. Those thick silk fibers are
produced by reeling from large number of
cocoons, for example, from around 200 cocoons
to 300 hundred cocoons per one thread. Using
these fibers, jackets, sweaters and shawls were
produced; those products show each specific
characteristic on the aspects of bulkiness, luster
and texture.
Fig. 6
Artificial skein basement weaved by using single
cocoon filament for the warp and weft filaments