The cloud point was determined for aqueous solutions of four kinds of poly(N-isopropylacrylamide) samples synthesized by radical polymerization in methanol, tert-butanol, benzene, and 1,4-dioxane by the use of azobis(isobutyronitrile) as an initiator, in the range of the weight fraction of the sample from 0.5 to 10%. It has then been found that the cloud points so determined for the samples synthesized in benzene and 1,4-dioxane are definitely lower than those for the samples synthesized in methanol and tert-butanol, although all the samples have almost the same stereochemical composition and the same end group. The observed deviation may be regarded as arising from the difference in the primary structure between the samples.
Higher plants efficiently conserve energy ATP in cellulose biosynthesis by expression of sucrose synthase, in which the high free energy between glucose and fructose in sucrose can be conserved and used for the synthesis of UDP-glucose. A mixture of sucrose synthase and bacterial cellulose synthase proceeded to form UDP-glucose from sucrose plus UDP and to synthesize 1,4--glucan from the sugar nucleotide. The mutant sucrose synthase, which mimics phosphorylated sucrose synthase, enhanced the reaction efficiency (V max ͞K m ) on 1,4--glucan synthesis, in which the incorporation of glucose from sucrose was increased at low concentrations of UDP. Because UDP formed after glucosyl transfer can be directly recycled with sucrose synthase, UDPglucose formed appears to show high turnover with cellulose synthase in the coupled reaction. The expression of sucrose synthase in Acetobacter xylinum not only changed sucrose metabolism but also enhanced cellulose production, in which UDP-glucose was efficiently formed from sucrose. Although the level of UDP-glucose in the transformant with mutant sucrose synthase cDNA was only 1.6-fold higher than that in plasmid-free cells, the level of UDP was markedly decreased in the transformant. The results show that sucrose synthase serves to channel carbon directly from sucrose to cellulose and recycles UDP, which prevents UDP build-up in cellulose biosynthesis.
Our results indicate that appendectomy has a negative association with and perhaps a preventive effect on the development of ulcerative colitis in the Japanese population. Furthermore, appendectomy also appears to reduce the extent and recurrence of ulcerative colitis.
Eukaryotic structural maintenance of chromosome proteins (SMC) are major components of cohesin and condensins that regulate chromosome structure and dynamics during cell cycle. We here determine the crystal structure of human condensin SMC hinge heterodimer with ϳ30 residues of coiled coils. The structure, in conjunction with the hydrogen exchange mass spectrometry analyses, revealed the structural basis for the specific heterodimer formation of eukaryotic SMC and that the coiled coils from two different hinges protrude in the same direction, providing a unique binding surface conducive for binding to single-stranded DNA. The characteristic hydrogen exchange profiles of peptides constituted regions especially across the hinge-hinge dimerization interface, further suggesting the structural alterations upon single-stranded DNA binding and the presence of a half-opened state of hinge heterodimer. This structural change potentially relates to the DNA loading mechanism of SMC, in which the hinge domain functions as an entrance gate as previously proposed for cohesin. Our results, however, indicated that this is not the case for condensins based on the fact that the coiled coils are still interacting with each other, even when DNA binding induces structural changes in the hinge region, suggesting the functional differences of SMC hinge domain between condensins and cohesin in DNA recognition.
The mean-square radius of gyration hS 2 i, second virial coefficient A 2 , and intrinsic viscosity ½ were determined in methanol at 25.0 C for two kinds of poly(N-isopropylacrylamide) (PNIPA) synthesized by radical polymerization in tert-butanol and benzene by the use of azobis(isobutyronitrile) as an initiator. In all cases of the three quantities, it is found that the value is smaller for the PNIPA synthesized in benzene than for that synthesized in tert-butanol and the difference between the two kinds of PNIPA increases with increasing the weight-average molecular weight M w. The average chain dimension of the former PNIPA should then be smaller than that of the latter. Since the two kinds of PNIPA were shown to have the same stereochemical composition (and also the same chain end group), the difference in the average chain dimension may be regarded as arising from the difference in the primary structure, i.e., the number of branch points. Considering the fact that the average dimension of a given polymer chain in general decreases with increasing the number of branch points, it may be concluded that the number is larger in the former PNIPA than in the latter. The behavior of the interpenetration function É and the Flory-Fox factor È as functions of M w is also examined, confirming the conclusion.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.