This study investigated an endoglucanase (EGII) from Rhizopus stolonifer var. reflexus TP-02 that consists of a C-terminal catalytic domain and an N-terminal carbohydrate-binding module joined by a linker rich in glycine, serine, threonine, and alanine. Site-directed mutagenesis was applied to characterize the conformation and dynamics of the linker. Mutants were expressed in Escherichia coli BL21 and purified by Ni-chelating column. Structural analysis indicated that glycine provided flexibility in the enzymatic process. G67P, G91Y, G101Y, G108Y, G109Y, G112P, H61G, H75G, and Y103G were selected on the basis of the results of the bioinformatics and Ramachandran plot analysis for the linker. The catalytic activities of EGII and its mutants on CMC-Na, microcrystalline cellulose (Avicel), and phosphoric acid-swollen celluloses (PASC) showed that flexible amino acids strengthened the activity of the enzyme. It indicated that flexible amino acids could improve the flexibility of the linker. Overall, the linker affected the catalytic efficiency of the endoglucanase in hydrolyzing cellulose chains.
In this paper, we investigate the resource allocation scheme for an unmanned-aerial-vehicle-enable (UAV-enabled) two-way relaying system with simultaneous wireless information and power transfer (SWIPT), where two user equipments (UEs) exchange information with the help of UAV relay and harvest energy through power splitting (PS) scheme. Under the transmission power constraints at UEs and UAV relay, a non-convex intractable optimization problem is formulated which maximizes the sum retained energy of two UEs while satisfying the minimum signal-to-noise ratio requirement. We decouple the complicated beamforming and PS factors optimization problem into three solvable subproblems and propose an efficient alternating optimization scheme. Subsequently, in order to reduce the complexity, a robust scheme based on generalized singular value decomposition (GSVD) is designed. Finally, numerical results verify the robustness and effectiveness of two proposed schemes.
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