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Alessandro Agostini, Daniel M Palm, Harald Paulsen, Donatella Carbonera
Optically detected magnetic resonance (ODMR) of triplet states populated by photoexcitation in the Water-Soluble Chlorophyll Protein (WSCP) from Lepidium virginicum has been performed, using both absorption and fluorescence detection. Well resolved Triplet minus Singlet (T-S) spectra have been obtained, which have been interpreted in terms of electronic interactions among the four chlorophylls (Chls) forming two dimers in WSCP tetramer. Localization of the triplet state on a single Chl leads to a redistribution of the oscillator strenght in the remaining three Chls of the complex...
May 21, 2018: Journal of Physical Chemistry. B
Yuki Inoue, Daisuke Sakamaki, Yusuke Tsutsui, Masayuki Gon, Yoshiki Chujo, Shu Seki
The tetramers of azapentacene derivatives with unique hash mark (#)-shaped structures were prepared in a quite facile manner. The #-shaped tetramers are optically active because of possessing extended biaryl skeletons, and the structure of the tetramer composed of four dihydrodiazapentacene (DHDAP) units (1) was investigated as the first example of this kind of molecule. The tetramer 1 showed characteristic chiroptical properties reflecting its orthogonally arranged quadruple DHDAP moieties, as well as redox activity...
May 21, 2018: Journal of the American Chemical Society
Elisabeth M Fatila, Maren Pink, Eric B Twum, Jonathan A Karty, Amar H Flood
The importance of phosphate in biology and chemistry has long motivated investigation of its recognition. Despite this interest, phosphate's facile oligomerization is only now being examined following the discovery of complexes of anion-anion dimers of hydroxyanions. Here we address how oligomerization dictates phosphate's recognition properties when engaged with planar cyanostar macrocycles that can also oligomerize by stacking. The crystal structure of cyanostar with phosphate shows an unprecedented tetrameric stack of cyanostar macrocycles threaded by a phosphate trimer, [H2 PO4 ···H2 PO4 ···H2 PO4 ]3- ...
March 21, 2018: Chemical Science
Rakieb Andargachew, Ryan J Martinez, Elizabeth M Kolawole, Brian D Evavold
TCR affinity for peptide MHC dictates the functional efficiency of T cells and their propensity to differentiate into effectors and form memory. However, in the context of chronic infections, it is unclear what the overall profile of TCR affinity for Ag is and if it differs from acute infections. Using the comprehensive affinity analysis provided by the two-dimensional micropipette adhesion frequency assay and the common indirect affinity evaluation methods of MHC class II tetramer and functional avidity, we tracked IAb GP61-80 -specific cells in the mouse model of acute (Armstrong) and chronic (clone 13) lymphocytic choriomeningitis virus infection...
May 18, 2018: Journal of Immunology: Official Journal of the American Association of Immunologists
Kyosuke Sakai, Takeaki Yamamoto, Keiji Sasaki
The spatial structure of an electromagnetic field can determine the characteristics of light-matter interactions. A strong gradient of light in the near field can excite dipole-forbidden atomic transitions, e.g., electric quadrupole transitions, which are rarely observed under plane-wave far-field illumination. Structured light with a higher-order orbital angular momentum state may also modulate the selection rules in which an atom can absorb two quanta of angular momentum: one from the spin and another from the spatial structure of the beam...
May 17, 2018: Scientific Reports
Katie Tungatt, Garry Dolton, Sophie B Morgan, Meriem Attaf, Anna Fuller, Thomas Whalley, Johanneke D Hemmink, Emily Porter, Barbara Szomolay, Maria Montoya, John A Hammond, John J Miles, David K Cole, Alain Townsend, Mick Bailey, Pierre J Rizkallah, Bryan Charleston, Elma Tchilian, Andrew K Sewell
There is increasing evidence that induction of local immune responses is a key component of effective vaccines. For respiratory pathogens, for example tuberculosis and influenza, aerosol delivery is being actively explored as a method to administer vaccine antigens. Current animal models used to study respiratory pathogens suffer from anatomical disparity with humans. The pig is a natural and important host of influenza viruses and is physiologically more comparable to humans than other animal models in terms of size, respiratory tract biology and volume...
May 2018: PLoS Pathogens
Tzu-Ping Ko, Shu-Jung Lai, Tung-Ju Hsieh, Chia-Shin Yang, Yeh Chen
Sialic acid presentation on the cell surface by some pathogenic strains of bacteria allows their escape from the host immune system. It is one of the major virulence factors. Bacterial biosynthesis of sialic acids starts with the conversion of UDP-GlcNAc to UDP and ManNAc by a hydrolyzing 2-epimerase. Here we present the crystal structure of this enzyme, named NeuC, from Acinetobacter baumannii The protein folds into two Rossmann-like domains and forms dimers and tetramers as does the epimerase part of the bifunctional UDP-GlcNAc 2-epimerase / ManNAc kinase (GNE)...
May 15, 2018: Journal of Biological Chemistry
Zacharias J Kinney, C Scott Hartley
o-Phenylene tetramers have been coassembled with linkers into macrocycles through imine condensation. Variation of linker connectivity and length allows both [1 + 1] and [2 + 2] macrocycles to be obtained, complementing (previously reported) [3 + 3] macrocycles. For the [1 + 1] macrocycles, linker length has a clear effect on o-phenylene geometry and macrocycle stability. For the [2 + 2] macrocycles, both homo- and heterochiral configurations are observed, suggesting limited communication of helix handedness in these systems...
May 15, 2018: Organic Letters
Louise F Risnes, Asbjørn Christophersen, Shiva Dahal-Koirala, Ralf S Neumann, Geir K Sandve, Vikas K Sarna, Knut Ea Lundin, Shuo-Wang Qiao, Ludvig M Sollid
Little is known about the repertoire dynamics and persistence of pathogenic T cells in HLA-associated disorders. In celiac disease, a disorder with a strong association with certain HLA-DQ allotypes, presumed pathogenic T cells can be visualized and isolated with HLA-DQ:gluten tetramers, thereby enabling further characterization. Single and bulk populations of HLA-DQ:gluten tetramer-sorted CD4+ T cells were analyzed by high-throughput DNA sequencing of rearranged TCR-α and -β genes. Blood and gut biopsy samples from 21 celiac disease patients, taken at various stages of disease and in intervals of weeks to decades apart, were examined...
May 14, 2018: Journal of Clinical Investigation
Norbert Mücke, Lara Kämmerer, Stefan Winheim, Robert Kirmse, Jan Krieger, Maria Mildenberger, Jochen Baßler, Ed Hurt, Wolfgang H Goldmann, Ueli Aebi, Katalin Toth, Jörg Langowski, Harald Herrmann
Intermediate filaments (IFs) are principal components of the cytoskeleton, a dynamic integrated system of structural proteins that provides the functional architecture of metazoan cells. They are major contributors to the elasticity of cells and tissues due to their high mechanical stability and intrinsic flexibility. The basic building block for the assembly of IFs is a rod-like, 60-nm-long tetrameric complex made from two antiparallel, half-staggered coiled coils. In low ionic strength, tetramers form stable complexes that rapidly assemble into filaments upon raising the ionic strength...
May 10, 2018: Biophysical Journal
Kazuhiko Ochiai, Daigo Azakami, Masami Morimatsu, Hinako Hirama, Shota Kawakami, Takayuki Nakagawa, Masaki Michishita, Ai S Egusa, Takanori Sasaki, Masami Watanabe, Toshinori Omi
Mutations in the p53 gene are associated with more than half of all human cancers. These mutations often cause a disruption of the tumor-suppressor function of p53 and induce genomic instabilities. Wild‑type p53 requires tetramerization to function as an initiator of cell cycle arrest and apoptosis. Although alterations in p53 tetramerization caused by mutation have been well studied, there are few cell lines containing an endogenous mutation in the tetramerization domain of p53. Here, we report the discovery of a canine mammary gland tumor cell line CTB‑m2, which contains the Leu332Gln (L332Q) mutation corresponding to Leu344 in the tetramerization domain of human p53...
May 2, 2018: Oncology Reports
Meng Yuan, Iain W McNae, Yiyuan Chen, Elizabeth A Blackburn, Martin A Wear, Paul A M Michels, Linda A Fothergill-Gilmore, Ted Hupp, Malcolm D Walkinshaw
We have tested the effect of all 20 proteinogenic amino acids on the activity of the M2 isoenzyme of pyruvate kinase (M2PYK) and show that within physiologically relevant concentrations, phenylalanine, alanine, tryptophan, methionine, valine, and proline act as inhibitors while histidine and serine act as activators. Size exclusion chromatography has been used to show that all amino acids, whether activators or inhibitors, stabilise the tetrameric form of M2PYK. In the absence of amino-acid ligands an apparent tetramer-monomer dissociation K d is estimated to be ~0...
May 10, 2018: Biochemical Journal
Kazushi Matsumura, Maki Zouda, Yasuhiro Wada, Fumiyoshi Yamashita, Mitsuru Hashida, Yasuyoshi Watanabe, Hidefumi Mukai
Radiolabeled antibodies, polyethylene glycol-conjugated (PEGylated) peptides, liposomes, and other materials were investigated as positron-emission tomography (PET) probes. These substances accumulate in tumors but often remain too long in circulation. We investigated the combination of intravenous urokinase injection and its substrate linker as a triggered radioisotope clearance enhancement system to improve imaging contrast. To this end, we synthesized a four-arm PEGylated 64 Cu-bombesin analog tetramer with a urokinase substrate linker...
May 7, 2018: International Journal of Pharmaceutics
Hans Malte, Gunnar Lykkeboe
For a century the influence of the Bohr effect on the utilization of blood borne oxygen has been deemed secondary to its influence on the uptake of carbon dioxide by the blood. Here we show that the opposite is the case. Using a simple two-ligand, two-state formulation we modelled the simultaneous oxygen and proton binding to hemoglobin as well as the resulting acid-base changes of the surrounding solution. Blocking of the Bohr effect in this model system results in a dramatic increase in the oxygen affinity, as expressed by the oxygen partial pressure at half saturation, the P50 ...
May 10, 2018: Journal of Applied Physiology
Alex Inthasot, Shun-Te Tung, Sheng-Hsien Chiu
In 1987, Pedersen, Cram, and Lehn were awarded the Nobel Prize in Chemistry to honor their achievements in, among other things, the selective recognition of alkali metal ions by synthetic hosts. Almost three decades later, the 2016 Nobel Prize went to Stoddart, Sauvage, and Feringa for the development of artificial molecular machines, in which interlocked molecules play a significant role. Surprisingly, although many rotaxane- and catenane-based molecular machines have been constructed using various templating approaches, alkali metal ions, which are good templates for crown ether synthesis, have only rarely been applied as templates for the assembly of these interlocked molecules...
May 10, 2018: Accounts of Chemical Research
Ruchi Gupta, Campbell J Hogan, Matthew A Perugini, Tatiana P Soares da Costa
Recombinant wheat DHDPS was produced for the first time in milligram quantities and shown to be an enzymatically active tetramer in solution using analytical ultracentrifugation and small angle X-ray scattering. Wheat is an important cereal crop with an extensive role in global food supply. Given our rapidly growing population, strategies to increase the nutritional value and production of bread wheat are of major significance in agricultural science to satisfy our dietary requirements. Lysine is one of the most limiting essential amino acids in wheat, thus, a thorough understanding of lysine biosynthesis is of upmost importance to improve its nutritional value...
May 9, 2018: Planta
Lilian González-Segura, Carlos Mújica-Jiménez, Javier Andrés Juárez-Díaz, Rodrigo Güemez-Toro, León P Martínez-Castilla, Rosario A Muñoz-Clares
The photosynthetic phosphoenolpyruvate carboxylase isozymes from C4 plants (PEPC-C4) play a critical role in their atmospheric CO2 assimilation and productivity. They are allosterically activated by phosphorylated trioses or hexoses, such as D-glucose-6-phosphate, and inhibited by L-malate or L-aspartate. Additionally, PEPC-C4 isozymes from grasses are activated by glycine, serine or alanine, but the allosteric site for these compounds remained unknown. Here we report a new crystal structure of the isozyme from Zea mays ( Zm PEPC-C4) with glycine bound at the monomer-monomer interfaces of the two dimers of the tetramer, making interactions with residues of both monomers...
May 9, 2018: Journal of Biological Chemistry
Jie Geng, John D Altman, Sujatha Krishnakumar, Malini Raghavan
When complexed with antigenic peptides, human leukocyte antigen (HLA) class I (HLA-I) molecules initiate CD8+ T cell responses via interaction with the T cell receptor (TCR) and co-receptor CD8. Peptides are generally critical for the stable cell surface expression of HLA-I molecules. However, for HLA-I alleles such as HLA-B*35:01, peptide-deficient (empty) heterodimers are thermostable and detectable on the cell surface. Additionally, peptide-deficient HLA-B*35:01 tetramers preferentially bind CD8 and to a majority of blood-derived CD8+ T cells via a CD8-dependent binding mode...
May 9, 2018: ELife
M Claireaux, M Galperin, D Benati, A Nouël, M Mukhopadhyay, J Klingler, P de Truchis, D Zucman, S Hendou, F Boufassa, C Moog, O Lambotte, L A Chakrabarti
Follicular helper T cells (Tfh) play an essential role in the affinity maturation of the antibody response by providing help to B cells. To determine whether this CD4+ T cell subset may contribute to the spontaneous control of HIV infection, we analyzed the phenotype and function of circulating Tfh (cTfh) in patients from the ANRS CO21 CODEX cohort who naturally controlled HIV-1 replication to undetectable levels and compared them to treated patients with similarly low viral loads. HIV-specific cTfh (Tet+ ), detected by Gag-major histocompatibility complex class II (MHC-II) tetramer labeling in the CD45RA- CXCR5+ CD4+ T cell population, proved more frequent in the controller group ( P = 0...
May 8, 2018: MBio
Verónica Demicheli, Diego M Moreno, Rafael Radi
Human MnSOD is a homotetramer and represents an essential mitochondrial antioxidant enzyme, which catalyzes the dismutation of superoxide radicals (O2˙-) at near diffusion-controlled rates. Under a variety of disease conditions and in the process of aging, nitric oxide (˙NO) can outcompete MnSOD and react with O2˙- to yield the potent oxidant peroxynitrite (ONOO-). Then, peroxynitrite can promote the regio-specific nitration of MnSOD at active site tyrosine 34, which turns the enzyme inactive. In this review we assess the kinetic aspects of the formation of peroxynitrite in the presence of MnSOD and the biochemical mechanisms of peroxynitrite-mediated MnSOD nitration...
May 23, 2018: Metallomics: Integrated Biometal Science
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