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Matthew John Voelker, Bogdan Barz, Brigita Urbanc
Oligomers formed by amyloid β-protein (Aβ) are central to Alzheimer's disease (AD) pathology, yet their structure remains elusive. Of the two predominant Aβ alloforms, Aβ40 and Aβ42, the latter is more strongly associated with AD. Here, we structurally characterized Aβ40 and Aβ42 monomers through pentamers which were converted from previously derived coarse-grained (DMD4B-HYDRA) simulations into all-atom conformations and subjected to explicit-solvent MD. Free energy landscapes revealed that structural differences between Aβ40 and Aβ42 conformations increase with oligomer order up to trimers...
July 20, 2017: Journal of Chemical Theory and Computation
Hai-Nan Zhang, Zhao-Wei Xu, He-Wei Jiang, Fan-Lin Wu, Xiang He, Yin Liu, Shu-Juan Guo, Yang Li, Li-Jun Bi, Jiao-Yu Deng, Xian-En Zhang, Sheng-Ce Tao
Tuberculosis is still on the top of infectious diseases list on both mobility and mortality, especially due to drug-resistance of Mycobacterium tuberculosis (M.tb). Ethionamide (ETH) is one of effective second line anti-TB drugs, a synthetic compound similar to isoniazid (INH) structurally, with existing severe problem of ETH resistance. ETH is a prodrug, which is activated by Etha inside M.tb, and etha is transcriptionally repressed by Ethr. We found that c-di-GMP could bind Ethr, enhanced the binding of Ethr to the promoter of etha, and then repressed the transcription of etha, thus caused resistance of M...
July 19, 2017: Scientific Reports
Shelly H Tien, Juliet N Crabtree, Heather L Gray, Erik J Peterson
OBJECTIVES: Influenza infection is a significant cause of respiratory morbidity among pregnant women. Seasonal influenza vaccination engages innate immune receptors to promote protective immunity. A coding polymorphism (R620W) in PTPN22 imparts elevated risk for human infection and autoimmune disease, predisposes to diminished innate immune responses, and associates with reduced immunization responses. We sought to quantify the effects of PTPN22-R620W on humoral and cell-mediated immune responses to the inactivated influenza vaccine among healthy pregnant women...
2017: PloS One
Changkeun Lee, Jiangtao Guo, Weizhong Zeng, Sunghoon Kim, Ji She, Chunlei Cang, Dejian Ren, Youxing Jiang
TMEM175 is a lysosomal K(+) channel that is important for maintaining the membrane potential and pH stability in lysosomes. It contains two homologous copies of a six-transmembrane-helix (6-TM) domain, which has no sequence homology to the canonical tetrameric K(+) channels and lacks the TVGYG selectivity filter motif found in these channels. The prokaryotic TMEM175 channel, which is present in a subset of bacteria and archaea, contains only a single 6-TM domain and functions as a tetramer. Here, we present the crystal structure of a prokaryotic TMEM175 channel from Chamaesiphon minutus, CmTMEM175, the architecture of which represents a completely different fold from that of canonical K(+) channels...
July 19, 2017: Nature
Karthika J Kadassery, Suman Kr Dey, Alan E Friedman, David C Lacy
The formation of metal-oxygen clusters is an important chemical transformation in biology and catalysis. For example, the biosynthesis of the oxygen-evolving complex in the enzyme photosystem II is a complicated stepwise process that assembles a catalytically active cluster. Herein we describe the role that carbonato ligands have in the formation of the known tetrameric complex [Mn(CO)3(μ3-OH)]4 (1). Complex 1 is synthesized in one step via the treatment of Mn2(CO)10 with excess Me3NO·2H2O. Alternatively, when anhydrous Me3NO is used, an OH-free synthetic intermediate (2) with carbonato ligands is produced...
July 19, 2017: Inorganic Chemistry
Yamuna Kalyani Mathiharan, M R N Murthy
Stationary phase survival protein SurE from Salmonella typhimurium is a dimeric protein formed by the swapping of a tetramerization loop involved in the formation of a loose tetramer and a C-terminal helix. It functions as a phosphatase. The two-fold symmetry of the dimeric protein was lost in the mutants H234A and D230A/H234A in which a crucial hydrogen bond in the hinge involved in C-terminal helix swapping was eliminated. The catalytic activity of both mutants was drastically reduced. In contrast to the native protein, H234A exhibited positive cooperativity in its catalytic activity...
July 17, 2017: Journal of Biomolecular Structure & Dynamics
Liqun Chen, Alexander E Aleshin, Gulimiran Alitongbieke, Yuqi Zhou, Xindao Zhang, Xiaohong Ye, Mengjie Hu, Gaoang Ren, Ziwen Chen, Yue Ma, Duo Zhang, Shuai Liu, Weiwei Gao, Lijun Cai, Lingjuan Wu, Zhiping Zeng, Fuquan Jiang, Jie Liu, Hu Zhou, Gregory Cadwell, Robert C Liddington, Ying Su, Xiao-Kun Zhang
Retinoid X receptor-alpha (RXRα) binds to DNA either as homodimers or heterodimers, but it also forms homotetramers whose function is poorly defined. We previously discovered that an N-terminally-cleaved form of RXRα (tRXRα), produced in tumour cells, activates phosphoinositide 3-kinase (PI3K) signalling by binding to the p85α subunit of PI3K and that K-80003, an anti-cancer agent, inhibits this process. Here, we report through crystallographic and biochemical studies that K-80003 binds to and stabilizes tRXRα tetramers via a 'three-pronged' combination of canonical and non-canonical mechanisms...
July 17, 2017: Nature Communications
Furong Wang, Pascal Pernot, Pierre Archirel, Daniel Ortiz, Sophie Le Caer, Mehran Mostafavi
NMR measurements show that diethyl carbonate (DEC, a solvent with a low dielectric constant) solutions of LiClO4 contain (LiClO4)n oligomers. The reduction of these species by solvated electrons and pre-solvated electrons is followed by picosecond pulse radiolysis measurements. The data analysis shows that several anions absorbing in the NIR and visible range are formed after the 7 ps electron pulse. In contrast with THF solutions of LiClO4, the anionic monomer (LiClO4)- is not observed in DEC solutions. This is due to the fact that DEC is a non-polar solvent favoring the clustering of the monomers in the non-irradiated solution as shown by NMR results, and also due to the instability of the anionic monomer...
July 15, 2017: Journal of Physical Chemistry. B
David A Korasick, Harkewal Singh, Travis A Pemberton, Min Luo, Richa Dhatwalia, John J Tanner
Many enzymes form homooligomers, yet the functional significance of self-association is seldom obvious. Herein, we examine the connection between oligomerization and catalytic function for proline utilization A (PutA) enzymes. PutAs are bifunctional enzymes that catalyze both reactions of proline catabolism. Type A PutAs are the smallest members of the family, possessing a minimal domain architecture consisting of N-terminal proline dehydrogenase and C-terminal L-glutamate-γ-semialdehyde dehydrogenase modules...
July 15, 2017: FEBS Journal
Yanzhi Bai, Zhenhai Yu, Ran Liu, Nana Li, Shuai Yan, Ke Yang, Bingbing Liu, Dongqing Wei, Lin Wang
Static pressure is an alternative method to chemical pressure for tuning the crystal structure, bonds, and physical properties of materials, and is a significant technique for the synthesis of novel materials and fundamental research. In this letter, we report the crystallization and phase transformation of p-xylene under high pressure. Our optical micrographic observations and the appearance of lattice modes in the Raman and infrared (IR) spectra indicated that p-xylene crystallizes at ∼0.1 GPa. The X-ray diffraction (XRD) pattern at 0...
July 13, 2017: Scientific Reports
Tadeo E Saldaño, Giuseppe Zanotti, Gustavo Parisi, Sebastian Fernandez-Alberti
Native transthyretin (TTR) homotetramer dissociation is the first step of the fibrils formation process in amyloid disease. A large number of specific point mutations that destabilize TTR quaternary structure have shown pro-amyloidogenic effects. Besides, several compounds have been proposed as drugs in the therapy of TTR amyloidosis due to their TTR tetramer binding affinities, and therefore, contribution to its integrity. In the present paper we have explored key positions sustaining TTR tetramer dynamical stability...
2017: PloS One
Karl Kempf, Oxana Kempf, Manuel Orozco, Ursula Bilitewski, Rainer Schobert
Spiroscytalin, a natural 3-spirotetramic acid of hitherto uncertain absolute configuration, was synthesized for the first time by a one-pot Knoevenagel-IMDA reaction of an l-phenylalanine-derived tetramic acid and (R)-2-methyl-deca-6E,8E-dienal. Its absolute configuration was assigned by the known configurations of the starting compounds and by NOESY correlations. Its identity with the natural isolate was proved by the comparison of the NMR and circular dichroism spectra and of the specific optical rotations...
July 19, 2017: Journal of Organic Chemistry
Michael T Hensel, Tao Peng, Anqi Cheng, Stephen C De Rosa, Anna Wald, Kerry J Laing, Lichen Jing, Lichun Dong, Amalia S Magaret, David M Koelle
Herpes simplex virus type (HSV) infection is restricted to epithelial cells and neurons and is controlled by CD8 T-cells. These cells both traffic to epithelial sites of recurrent lytic infection and to ganglia, and persist at the dermal-epidermal junction for up to 12 weeks after lesion resolution. We previously showed that cutaneous lymphocyte-associated antigen (CLA), a functional E-selectin ligand (ESL), is selectively expressed on circulating HSV-2-specific CD8 T-cells. CLA/ESL mediates adhesion of T-cells to inflamed vascular endothelium...
July 12, 2017: Journal of Virology
Simon A Mortensen, Bjørn Sander, Rasmus K Jensen, Jan S Pedersen, Monika Golas, Jens C Jensenius, Annette G Hansen, Steffen Thiel, Gregers R Andersen
No abstract text is available yet for this article.
July 12, 2017: Proceedings of the National Academy of Sciences of the United States of America
Guan Yang, Bianca L Artiaga, Sarah T Lewis, John P Driver
CD1d-restricted invariant natural killer T (iNKT) cells are innate-like T cells that share phenotypic characteristics of both NK and conventional T cells (Tconv). Although iNKT cells have been well characterized in mice and humans, functional CD1d and CD1d-restricted iNKT cells are not universally expressed in mammals. Swine express iNKT cells that can be detected using α-galactosylceramide (α-GalCer)-loaded CD1d tetramers. In the present study, we characterized iNKT cells from the blood, spleen, lymph node, lung and liver of commercial mixed-breed pigs, and compared their phenotype to NK cells and Tconv...
July 8, 2017: Developmental and Comparative Immunology
Xiangying Yu, Zhong-Ping Yao
In this study, travelling wave ion mobility mass spectrometry has been used to investigate chiral differentiation of common chiral amino acids, through separation of binuclear copper bound tetrameric ions formed with chiral selector tryptophan, proline, tyrosine, phenylalanine or histidine. Significant chiral recognition was observed for amino acids with aromatic rings or long and active side chains, with peak-to-peak resolutions up to 1.826. Tryptophan and histidine offered better enantioselectivity, compared to other chiral selectors...
August 15, 2017: Analytica Chimica Acta
Denis Rusjan, Martina Persic, Matevž Likar, Katerina Biniari, Maja Mikulic-Petkovsek
Alterations in phenolic contents were studied in esca symptomatic (Sym) and asymptomatic (Asym) vines of 'Cabernet Sauvignon' based on wood conditions (healthy - HLT, necrotic - Nec and rotten - Rot) and vine parts (head, trunk and rootstock). In Asym vines, only Alternaria alternate was identified in Nec wood, while the HLT wood of Sym vines was colonised by Botryospaeriaceae sp. and Aureobasidium pullulans, Nec wood by Fomitiporia mediterranea and Rot wood by Fomitiporia mediterranea and Phaeomoniella chlamydospora...
July 10, 2017: Journal of Agricultural and Food Chemistry
T Srinivasa Reddy, Steven H Privér, Nedaossadat Mirzadeh, Suresh K Bhargava
We report the application of cationic tri- and tetra-nuclear gold(I) phosphine complexes [Au3(μ-dppen)3]X3 and [Au4(μ-dppa)4]X4 (X=OTf, PF6) [OTf=trifluoromethanesulfonate, dppen=trans-1,2-bis(diphenylphosphino)ethene, dppa=bis(diphenylphosphino)acetylene] for cancer treatment. The results of cytotoxicity tests on four different cancer cells [prostate (DU145), cervical (HeLa), breast (MDAMB-231) and fibro sarcoma (HT1080)] indicate these complexes possess remarkable tumor cell growth inhibitory effects and high selectivity towards cancer cells...
June 28, 2017: Journal of Inorganic Biochemistry
Nozomi Saito, Yutaro Kondo, Tsukasa Sawato, Masanori Shigeno, Ryo Amemiya, Masahiko Yamaguchi
Pendant-type (P)-helicene oligomers with p-phenylene ethynylene main chains up to a tetramer were synthesized by a building block method. The (P)-tetramer reversibly formed a ladderlike bimolecular aggregate upon cooling and disaggregated upon heating in trifluoromethylbenzene. Two bis(tetramer)s, in which two (P)-tetramers were connected by hexadecamethylene linkers, were also synthesized. The head-to-tail bis(tetramer) formed an intramolecular aggregate, and the head-to-head bis(tetramer) formed an intermolecular aggregate in toluene...
July 7, 2017: Journal of Organic Chemistry
Cheng-Yang Yue, Xiao-Wu Lei, Xin-Xiu Lu, Yan Li, Jun-Chao Wei, Wei Wang, Yun-Dong Yin, Ning Wang
By using transition-metal (TM) complex cationic dyes as structure-directing agents and photosensitizers, a series of inorganic-organic hybrid metal halides, namely, [TM(2,2'-bipy)3]AgPb2I7 [TM = Ni (1), Co (2) and Zn (3)], [Co(2,2'-bipy)3]CuPb2Br7 (4) and [TM(2,2'-bipy)3]AgPb2Br7 [TM = Ni (5) and Fe (6)], have been solvothermally prepared and structurally characterized. Compounds 1-3 feature 1D [AgPb2I7](2-) chains built from the condensation of [Ag2I6] dimers and [Pb4I14] tetramers, and compounds 4, 5 and 6 contain similar 1D [CuPb2Br7](2-) and [AgPb2Br7](2-) chains, respectively...
July 18, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
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