Toward Selective Synthesis of Protein Olympiadanes via Orthogonal Active Templates in One Step

Unlike small molecules,the topological complexity of macromolecules remains largely unexplored due to the huge synthetic challenge.Herein,we report the development of orthogonal active templates for concise and selective synthesis of protein[n]heterocatenanes toward protein olympiadanes.An active template(AT-Snoop)was first developed based on the isopeptide-bond-forming RrgA domain with comparable efficiency and excellent orthogonality to the previously reported active template(AT-Spy)based on the CnaB2 domain.Their combination facilitated the selective synthesis of protein[n]catenanes from multiple components in one step and the resulting structures were verified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis,size exclusion chromatography,liquid chromatography-mass spectrometry,and proteolytic digestion experiments.The results offered a promising solution to tackling the daunting challenge of precision synthesis of protein olympiadane with five distinct ring components.Not only did the success provide new tools for proteintopology engin eering but alsospurred and fueled the future exploitation of topology-related functional benefits in protein science.

Active Template Synthesis of Protein[n]Catenanes Using Engineered Peptide–Peptide Ligation Tools

The expansion of protein topological diversity requires new and efficient synthetic tools.Herein,we report the second and third generations of the SpyStapler-mediated SpyTag/BDTag ligation system for the efficient synthesis of 4-arm star proteins and the repurposing of the third generation as an active template to enable the synthesis of higher-order protein[n]catenanes(n=3,4,and 5).SpyStapler003 has a higher affinity to its cognate SpyTag and BDTag reactive pairs relative to the original SpyStapler.Hence,it can overcome much more profound steric hindrance in protein ligation and improve the efficiency of the resulting active template tool to facilitate the construction of radial protein[n]catenanes.Various proteins of interest,such as dihydrofolate reductase and the nanobody KN035,can be modularly incorporated into the[n]catenanes with intact activity.Combination of passive and active template strategies gives rise to linear protein[4]catenanes,which further expands the current topological diversity.Moreover,higher-order protein catenation not only leads to enhanced thermal stability and proteolytic resistance but also higher affinity of the nanobody via multivalent effects.Our study provides tools useful for bioconjugation and new topological protein scaffolds for the multivalent display of enzymes and antibodies.

Preparation, Characterization and Photocatalytic Activity of Fe, La Co-doped Nanometer Titanium Dioxide Photocatalysts

A series of photocatalysts of un-doped, single-doped and co-doped nanometer titanium diox- ide （TiO2） have been successfully prepared by template method using Fe（NO3）3.9H2O, La（NO3）3.6H2O, and tetrabutyl titanate as precursors and glucan as template. Scanning electron microscopy, X-ray diffraction, and N2 adsorption-desorption measurement were employed to characterize the morphology, crystal structure and surface structure of the samples. The photo-absorbance of the obtained catalysts was measured by UV-Vis absorption spectroscopy, and the photocatalytic activities of the prepared samples under UV and visible light were estimated by measuring the degradation rate of methyl orange in an aqueous solution. The characterizations indicated that the prepared photocatalysts consisted of anatase phase and possessed high surface area of ca. 163-176 m2/g. It was shown that the Fe and La co-doped nano-TiO2 could be activated by visible light and could thus be used as an effective catalyst in photo-oxidation reactions. The synergistic effect of Fe and La co-doping played an important role in improving the photocatalytic activity. In addition, the possibility of cyclic usage of co-doped nano-TiO2 was also confirmed, the photocatalytic activity of codoped nano-TiO2 remained above 89.6% of the fresh sample after being used four times.

Preparation and Photocatalytic Activity of Ce, H3PW12O40 co-doped TiO2 Hollow Fibers

A series of Ce, H3PW12O40 co-doped TiO2 hollow fibers photocatalysts have been prepared by sol-gel method using ammonium ceric nitrate, H3PW12O40 and tetrabutyltitanate as precursors and cotton fibers as template, followed by calcination at 500 ℃ in N2 atmosphere for 2 h. Scanning electron microscopy, X-ray diffraction, nitrogen adsorption-desorption mea- surements, and UV-Vis spectroscopy are employed to characterize the morphology, crystal structure, surface structure, and optical absorption properties of the samples. The photo- catalytic performance of the samples has been studied by photodegradation phenol in water under UV and visible light irradiation. The results show that the TiO2 fiber materials have hollow structures, and the co-doped TiO2 hollow fibers exhibit higher photocatalytic activities for the degradation of phenol than un-doped, single-doped TiO2 hollow fibers under UV and visible light. In addition, the recyclability of co-doped TiO2 fibers is also confirmed that the TiO2 fiber retains ca. 90% of its activity after being used four times. It is shown that the co-doped TiO2 fibers can be activated by visible light and may be potentially applied to the treatment of water contaminated by organic pollutants. The synergistic effect of Ce and H3PW12O40 co-doping plays an important role in improving the photocatalytic activity.

Rational Design and Cellular Synthesis of Proteins with Unconventional Chemical Topology

Chemical topology refers to the three-dimensional arrangement(i.e.,connectivity and spatial relationship)of a molecule's constituent atoms and bonds.The molecular mechanism for translation defines the linear configuration of all nascent proteins.Nontrivial protein topology arises only upon post-translational processing events and often imparts functional benefits such as enhanced stability,making topology a unique dimension for protein engineering.Utilizing the assembly-reaction synergy,our group has developed several methods for the effective and convenient cellular synthesis of a variety of topological proteins,such as lasso proteins,protein rotaxanes,and protein catenanes.The work opens the access to new protein classes and paves the road toward illustrating the topological effects on structure-function relationship of proteins,which lays solid foundation for exploring topological proteins’practical application.