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1. chinaXiv:201705.00456 [pdf]

Spatially-controlled growth of platinum on gold nanorods with tailoring plasmonic and catalytic properties

Rong, Yun; Dandapat, Anirban; Huang, Youju; Sasson, Yoel; Zhang, Lei; Dai, Liwei; Zhang, Jiawei; Guo, Zhiyong; Chen, Tao
Subjects: Physics >> General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.

We describe the synthesis of bimetallic dendritic platinum decorated gold nanorods (AuNRs) by the spatial control of Pt growth over gold nanorods using a heterogeneous seed-mediated growth method. The amounts of the Au seed and Pt-precursor were changed to achieve a tunable volume fraction of Pt coverage on the Au NRs surface. Pt nanostructures were spatially separated from each other, which was highly favorable for promising optical and catalytic properties. The dendritic-Pt decorated AuNRs with variable Au/Pt ratios were exploited to study their surface plasmonic properties and catalytic activities. Interestingly, the Pt decorated AuNRs showed strong surface plasmon resonance (SPR) peak due to noncompact dendritic Pt shell in contrast to the conventional core–shell Au@Pt nanoparticles (NPs). Moreover, the longitudinal peak of the AuNRs was finely tuned from 820 to 950 nm (NIR region) by controlling the volume fraction of the Pt decoration over the AuNRs. The catalytic activity of the dendritic-Pt decorated AuNRs on the reduction of 4-nitrophenol (4-NP) by sodium borohydride (NaBH4) as reducing agent was studied and found to be superior to the activities compared to the monometallic Au NRs. Considering practical applications, dendritic-Pt decorated AuNRs nanostructures were immobilized successfully on the hydrophilic polyvinylidene difluoride (PVDF) film as an efficient reusable catalyst.

submitted time 2017-05-02 Hits1467Downloads836 Comment 0

2. chinaXiv:201605.01459 [pdf]

Structure and function of Mycobacterium smegmatis 7-keto-8-aminopelargonic acid (KAPA) synthase

Fan, Shanghua; Chen, Guanjun; Li, De-Feng; Wang, Da-Cheng; Fleming, Joy; Zhang, Hongtai; Zhou, Ying; Zhang, Xian-En; Bi, Lijun; Li, De-Feng; Wang, Da-Cheng; Fleming, Joy; Zhang, Hongtai; Zhou, Ying; Zhang, Xian-En; Bi, Lijun; Zhou, Lin; Chen, Tao; Zhou, Jie
Subjects: Biology >> Biophysics >> Biochemistry & Molecular Biology

The biotin biosynthesis pathway is an attractive target for development of novel drugs against mycobacterial pathogens, however there are as yet no suitable inhibitors that target this pathway in mycobacteria. 7-Keto-8-aminopelargonic acid synthase (KAPA synthase, BioF) is the enzyme which catalyzes the first committed step of the biotin synthesis pathway, but both its structure and function in mycobacteria remain unresolved. Here we present the crystal structure of Mycobacterium smegmatis BioF (MsBioF). The structure reveals an incomplete dimer, and the active site organization is similar to, but distinct from Escherichia coli 8-amino-7-oxononanoate synthase (EcAONS), the E. coli homologue of BioF. To investigate the influence of structural characteristics on the function of MsBioF, we deleted bioF in M. smegmatis and confirmed that BioF is required for growth in the absence of exogenous biotin. Based on structural and mutagenesis studies, we confirmed that pyridoxal 5'-phosphate (PLP) binding site residues His129, Lys235 and His200 are essential for MsBioF activity in vivo and residue Glul 71 plays an important, but not essential role in MsBioF activity. The N-terminus (residues 1-37) is also essential for MsBioF activity in vivo. The structure and function of MsBioF reported here provides further insights for developing new anti-tuberculosis inhibitors aimed at the biotin synthesis pathway. (C) 2014 Elsevier Ltd. All rights reserved.

submitted time 2016-05-12 Hits1873Downloads1086 Comment 0

3. chinaXiv:201605.01432 [pdf]

Structure of the MarR family protein Rv0880 from Mycobacterium tuberculosis

Gao, Yun-Rong; Feng, Na; Li, De-Feng; Bi, Li-Jun; Gao, Yun-Rong; Chen, Tao
Subjects: Biology >> Biophysics

Rv0880 from the pathogen Mycobacterium tuberculosis is classified as a MarR family protein in the Pfam database. It consists of 143 amino acids and has an isoelectric point of 10.9. Crystals of Rv0880 belonged to space group P1, with unit-cell parameters a = 54.97, b = 69.60, c = 70.32 angstrom, alpha = 103.71, beta = 111.06, gamma = 105.83 degrees. The structure of the MarR family transcription regulator Rv0880 was solved at a resolution of 2.0 angstrom with an R-cryst and R-free of 21.2 and 24.9%, respectively. The dimeric structure resembles that of other MarR proteins, with each subunit comprising a winged helix-turn-helix domain connected to an alpha-helical dimerization domain.

submitted time 2016-05-12 Hits1705Downloads917 Comment 0

4. chinaXiv:201605.01344 [pdf]

Discovery and characterization of Ku acetylation in Mycobacterium smegmatis

Zhou, Ying; Fleming, Joy; Wang, Liwei; Wang, Yingying; Zhang, Xiaoli; Wei, Wenjing; Bi, Lijun; Chen, Tao; Zhou, Lin; Deng, Jiaoyu; Wang, Xude
Subjects: Biology >> Biophysics

Lysine acetylation is an important post-translational modification and is known to regulate many eukaryotic cellular processes. Little, however, is known about acetylated proteins in prokaryotes. Here, using immunoblotting, mass spectrometry and mutagenesis studies, we investigate the acetylation dynamics of the DNA repair protein Ku and its relationship with the deacetylase protein Sir2 and the non-homologous end joining (NHEJ) pathway in Mycobacterium smegmatis. We report that acetylation of Ku increases with growth, while NHEJ activity decreases, providing support for the hypothesis that acetylation of Ku may be involved in the DNA damage response in bacteria. Ku has multiple lysine sites. Our results indicate that K29 is an important acetylation site and that deficiency of Sir2 or mutation of K29 affects the quantity of Ku and its acetylation dynamics. Our findings expand knowledge of acetylation targets in prokaryotes and indicate a new direction for further research on bacterial DNA repair mechanisms.

submitted time 2016-05-11 Hits1798Downloads1035 Comment 0

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