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- Chen, Shan, 1986-
(författare)
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Stability and inactivation mechanisms of two transaminases
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In the past decades, more and more enzymes are employed as biocatalysts in industrial processes because of their advantages, such as high efficiency, substrate selectivity and stereoselectivity. Among them, amine transaminases (ATAs) are pyridoxal 5’-phosphate (PLP) dependent enzymes. ATAs have gained attention for their excellent performance in chiral amine synthesis, and their broad substrate acceptance. However, the low operational stability of amine transaminases still limits their application in industry.The amine transaminase from Chromobacterium violaceum (Cv-ATA) has been selected for further investigation for its relatively low operational stability. Co-solvents and various additives have been added to the enzyme storage solution to improve its storage stability at various temperatures. Co-lyophilization of Cv-ATA with surfactants has been applied to improve its enzymatic activity in neat organic solvents.As a PLP-dependent dimeric enzyme, the Cv-ATA is not primarily inactivated due to tertiary structural changes. Instead, both dimer dissociation and PLP release may affect the enzyme stability. Therefore, the inactivation pathway of the Cv-ATA during operational conditions was explored. The unfolding of the enzyme was detected by several methods, and the detection of fluorescence intensity spectrum of tryptophan is extensively applied for its high sensitivity. The phosphate group of PLP can be coordinated into the phosphate group binding cup, which may influence the enzyme structural stability. Therefore, the effect of both PLP and inorganic phosphate ions (present in phosphate buffer) on the enzyme stability was explored.The amine transaminase from Vibrio fluvialis (Vf-ATA) is another amine transaminase, which catalyses the same biocatalytic reaction and has a similar substrate scope as Cv-ATA. However, there is still a lack of data on the stability of Vf-ATA. Consequently, the operational stability of Vf-ATA in various environments was studied.
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- Yang, Xun, et al.
(författare)
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Diamond Based Optical Metasurfaces for Broadband Wavefront Shaping in Harsh Environment
- 2024
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Ingår i: Laser and Photonics Reviews. - 1863-8899 .- 1863-8880. ; In Press
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Tidskriftsartikel (refereegranskat)abstract
- Metasurface enables a new class of “meta-optics” that can manipulate light at subwavelength scale. Despite that versatile metasurfaces have been demonstrated based on a wide range of materials, the vulnerability of conventional materials to harsh environments, i.e., low resistance to corrosion, low transparency at short wavelength, and lack of thermal/mechanical stability, greatly limit their applications in extreme conditions. Diamond is well-known for exceptional properties, including the highest thermal conductivity, high damage resistance, extraordinary hardness, and chemical inertness. Therefore, diamond based metasurface is generally expected to benefit from its material merits for extreme use. However, the performance of diamond metasurface in harsh environments remains unexplored up to date. To address this question, this work is designed to study the suitability of single-crystal diamond based metasurface for broadband applications under harsh environments. As an example, diamond metasurfaces with representative functionalities, including holographic wavefront-shaping, DUV-focusing, are investigated under high-temperature, acid/alkali, and abrasive conditions, respectively. The findings prove the capability of diamond metasurfaces for applications in broadband and harsh conditions, which not only provides a practical and scalable scheme to encode on-demand functionalities into diamond, but also unlocks a capable candidate to develop robust, large bandwidth, and durable meta-optics for advanced wavefront shaping under extreme conditions.
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