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Abstract: In this paper, we report the synthesis and bioactivity of four synthetic analogues of 28-homobrassinosteroids, in order to evaluate the influence in bioactivity when the C-6 keto group is replaced by different functional groups. The synthetic analogues are 6-deoxo-28-homocastasterone [(22R,23R)-stigmasta-2α,3α,22,23-tetraol], 6α-hydroxy-28-homocastasterone [(22R,23R)-stigmasta-2α,3α,6α,22,23-pentaol], 6β-hydroxy-28-homocastasterone [(22R,23R)-stigmasta-2α,3α,6β,22,23-pentaol], and [(22R,23R)-6α-fluorostigmasta-2α,3α,22,23-tetraol]. Results indicate that replacement of the 6-keto moiety by an β or α hydroxyl group led to a decrease in activity, whereas the 6-deoxo analogue showed a very low activity, confirming the importance of an electronegative moiety at C-6 to observe hormonal potency. The 6α-fluorinated analogue elicited a low activity, similar to that of the 6-deoxo analogue. [Copyright &y& Elsevier]

Recently, an environmental criteria was required for every product and process. The great amount of pollution caused by the paper and cellulose industry effluents, especially those produced from nonwood fibrous materials, e.g., rice straw and bagasse. Using new technologies or redesigning products to meet new environments criteria is necessary. The production of cellulose by microorganisms is considered as one of the most beneficial sources for environment requirements. Microbial polysaccharides are valuable commodities, since they display many useful properties and can be produced in large quantities. This article reviews previous research on the biosynthesis of bacterial cellulose, structural features, properties, as well as potential applications as new industrial materials, i.e., paper industry, wastes treatment, sewage purification, food, medicine, etc. Suggestions for an economic production process for bacterial cellulose and cellulose derivatives also were reported. [ABSTRACT FROM AUTHOR]

Cellulose is one of the most abundant polymers in nature. Different living systems evolved simultaneously, using structurally similar proteins to synthesize and metabolize polysaccharides. In the growing plant, cell wall loosening, together with cellulose biosynthesis, enables turgor-driven cell expansion. It has been postulated that endo-1,4-β-glucanases (EGases) play a central role in these complex activities. Similarly, microorganisms use a consortium of lytic enzymes to convert cellulose into soluble sugars. Most, if not all, cellulases have a modular structure with two or more separate independent functional domains. Binding to cellulose is mediated by a cellulose-binding domain (CBD), whereas the catalytic domain mediates hydrolysis. Today, EGases and CBDs are known to exist in a wide range of species and it is evident that both possess immense potential in modifying polysaccharide materials in-vivo and in-vitro. The hydrolytic function is utilized for polysaccharide degradation in microbial systems and cell wall biogenesis in plants. The CBDs exerts activity that can be utilized for effective degradation of crystalline cellulose, plant cell wall relaxation, expansion and cell wall biosynthesis. Applications range from modulating the architecture of individual cells to an entire organism. These genes, when expressed under specific promoters and appropriate trafficking signals can be used to alter the nutritional value and texture of agricultural crop and their final products. EGases and CBDs may also find applications in the modification of physical and chemical properties of composite materials to create new materials possessing improved properties. [Copyright &y& Elsevier]