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Crystallization of enzymes in presence of impurities is important for
clarifying the role of enzymes in natural world. Although it is proposed that
impurities inhibit nucleation of enzyme crystallization, details are unclear.
In this study, crystallization of cellobiohydrolase from Aspergillus niger was
investigated by dynamic and time-resolved static
light scattering using cellobiose as an impurity. We aimed to clarify how
cellobiose inhibits cellobiohydrolase crystallization and to
crystallize cellobiohydrolase in concentrated cellobiose without using seeds.
The contribution of attractive forces to total intermolecular interactions of
cellobiohydrolase monomers increased with the molar ratio of
Association dynamics of cellobiohydrolase using lithium sulfate, however,
showed that the initial aggregation rate decreased with an increase in R(cb/ce). Because binding sites of
cellobioses to cellobiohydrolase molecules differed from those for the growth
of protein crystals, the binding of cellobioses would increase the chemical
potential of the cellobiohydrolase monomers, which gradually reduced supersaturation for growth as the aggregate size increased.
This result was in contrast with the conventional idea that cellobiose inhibits
the nucleation of cellobiohydrolase crystals. Gentle agitation of cellobiose-containing cellobiohydrolase solutions during sitting-drop
vapor-diffusion growth resulted in the growth of cellobiohydrolase single
crystals for all R(cb/ce)
conditions without using seeds.
In the late 1980s, a popular children’s book “Little Black Sambo”(hereafter,LBS) disappeared from all bookstores in Japan.The book was alleged to have racist characteristics such as the name of the boy, the way the illustrations caricatured blacks, etc. Mori (1997) revised the original story by changing the protagonist from a black boy to a black Labrador puppy, with eliminating the word “Sambo”,which had a historically pejorative connotation in the US. Mori (2005) conducted an experiment to compare the entertainment value of the two versions of LBS using four-year-old children and found no difference. Mori (2005) also casted a suspicion that the real reason why the book was withdrawnin Japan was a matter of piracy rather than racism. All Japanese publishers at that time had not properly obtained the copyright. Nowadays there are several versions of LBS available in bookstores all over Japan.