Chloroviruses \u3ci\u3eN\u3c/i\u3e-linked glycans share a new type of conserved core architecture unprecedented in any form of life / [Published as] N-Linked Glycans of Chloroviruses Sharing a Core Architecture without Precedent

N-glycosylation is a fundamental modification of proteins that exists in the three domains of life and in some viruses, including the chloroviruses, for which a new type of core N-glycan is described. This N-glycan core structure common to all chloroviruses is a pentasaccharide with a β-glucose linked to an asparagine residue that is not located in the typical sequon N-X-T/S. The glucose is linked to a terminal xylose unit and a hyperbranched fucose, in turn substituted with a terminal galactose and a second xylose residue. The third position of the fucose unit is always linked to a rhamnose, which is a semi-conserved element because its absolute configuration is virus-dependent. Additional decorations occur on this core N-glycan and represent a molecular signature for each chlorovirus. Includes supplemental materials

Structure of the unusual Sinorhizobium fredii HH103 lipopolysaccharide and its role in symbiosis

Rhizobia are soil bacteria that form important symbiotic associations with legumes, and rhizobial surface polysaccharides, such as K-antigen polysaccharide (KPS) and lipopolysaccharide (LPS), might be important for symbiosis. Previously, we obtained a mutant of Sinorhizobium fredii HH103, rkpA, that does not produce KPS, a homopolysaccharide of a pseudaminic acid derivative, but whose LPS electrophoretic profile was indistinguishable from that of the WT strain. We also previously demonstrated that the HH103 rkpLMNOPQ operon is responsible for 5-acetamido-3,5,7,9-tetradeoxy-7-(3-hydroxybutyramido)-L-glyc-ero-L-manno-nonulosonic acid [Pse5NAc7(3OHBu)] production and is involved in HH103 KPS and LPS biosynthesis and that an HH103 rkpM mutant cannot produce KPS and displays an altered LPS structure. Here, we analyzed the LPS structure of HH103 rkpA, focusing on the carbohydrate portion, and found that it contains a highly heterogeneous lipid A and a peculiar core oligosaccharide composed of an unusually high number of hexuronic acids containing b-configured Pse5NAc7(3OHBu). This pseudaminic acid derivative, in its a-configuration, was the only structural component of the S. fredii HH103 KPS and, to the best of our knowledge, has never been reported from any other rhizobial LPS. We also show that Pse5NAc7(3OHBu) is the complete or partial epitope for a mAb, NB6-228.22, that can recognize the HH103 LPS, but not those of most of the S. fredii strains tested here. We also show that the LPS from HH103 rkpM is identical to that of HH103 rkpA but devoid of any Pse5NAc7(3OHBu) residues. Notably, this rkpM mutant was severely impaired in symbiosis with its host, Macroptilium atropurpureum.Fil: Di Lorenzo, Flaviana. Università degli Studi di Napoli Federico II; ItaliaFil: Speciale, Immacolata. Università degli Studi di Napoli Federico II; ItaliaFil: Silipo, Alba. Università degli Studi di Napoli Federico II; ItaliaFil: Alías Villegas, Cynthia. Universidad de Sevilla; EspañaFil: Acosta Jurado, Sebastián. Universidad de Sevilla; EspañaFil: Rodríguez Carvajal, Miguel Ángel. Universidad de Sevilla; EspañaFil: Dardanelli, Marta Susana. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Instituto de Biotecnología Ambiental y Salud - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Biotecnología Ambiental y Salud; ArgentinaFil: Palmigiano, Angelo. Consiglio Nazionale delle Ricerche; ItaliaFil: Garozzo, Domenico. Consiglio Nazionale delle Ricerche; ItaliaFil: Ruiz Sainz, José Enrique. Universidad de Sevilla; EspañaFil: Molinaro, Antonio. University of Naples Federico II; ItaliaFil: Vinardell, José María. Universidad de Sevilla; Españ

The N-glycan structures of the antigenic variants of chlorovirus PBCV-1 major capsid protein help to identify the virus-encoded glycosyltransferases

The chlorovirus Paramecium bursaria chlorella virus 1 (PBCV-1) is a large dsDNA virus that infects the microalga Chlorella variabilis NC64A. Unlike most other viruses, PBCV-1 encodes most, if not all, of the machinery required to glycosylate its major capsid protein (MCP). The structures of the four N-linked glycans from the PBCV-1 MCP consist of nonasaccharides, and similar glycans are not found elsewhere in the three domains of life. Here, we identified the roles of three virus-encoded glycosyltransferases (GTs) that have four distinct GT activities in glycan synthesis. Two of the three GTs were previously annotated as GTs but the third GT was identified in this study. We determined the GT functions by comparing the wild-type glycan structures from PBCV-1 with those from a set of PBCV-1 spontaneous GT genes mutants resulting in antigenic variants having truncated glycan structures. According to our working model, the virus gene a064r encodes a GT with three domains: domain 1 has a β-L-rhamnosyltransferase activity, domain 2 has an α -L-rhamnosyltransferase activity and domain 3 is a methyltransferase that decorates two positions in the terminal α -L-rhamnose (Rha) unit. The a075l gene encodes a β -xylosyltransferase that attaches the distal D-xylose (Xyl) unit to the L-fucose (Fuc) that is part of the conserved N-glycan core region. Lastly, gene a071r encodes a GT that is involved in the attachment of a semiconserved element, α-D-Rha, to the same L-Fuc in the core region. Our results uncover GT activities that assemble four of the nine residues of the PBCV-1 MCP N-glycans. Includes supplemental material

Characterization of a 6×6-mm2 75-μm cell MPPC suitable for the Cherenkov Telescope Array project

This paper presents the latest characterization results of a novel Low Cross-Talk (LCT) large-area (6×6-mm2) Multi-Pixel Photon Counter (MPPC) detector manufactured by Hamamatsu, belonging to the recent LCT5 family and achieving a fill-factor enhancement and cross-talk reduction. In addition, the newly adopted resin coating is demonstrated to yield improved photon detection capabilities in the 290–350 nm spectral range, making the new LCT MPPC particularly suitable for emerging applications like Cherenkov Telescopes. For a 3×3-mm2 version of the new MPPC under test, a comparative analysis of the large pixel pitch (75-µm) detector versus the smaller pixel pitch (50-µm) detector is also undertaken. Furthermore, measurements of the 6×6-mm2 MPPC response versus the angle of incidence are provided for the characterized device

Temperature characterization of the CITIROC front-end chip of the ASTRI SST-2M Cherenkov camera

The Cherenkov Imaging Telescope Integrated Read Out Chip, CITIROC, is the front-end chip of the camera for the ASTRI SST-2M, one of the prototypes for the small sized telescopes of the Cherenkov Telescope Array, CTA. The telescope, operating in the energy range from a few TeV to beyond 300 TeV, is characterized by innovative technological solutions. The optical system is arranged in a dual-mirror configuration and the focal plane camera consists of a matrix of multi-pixel Silicon Photo-Multipliers. Among others, one of the most important project issue consists in the thermal characterization of the camera that, in the ASTRI SST-2M prototype, is thermo-controlled in a narrow temperature range. A set of at least nine similar telescopes will form the ASTRI mini-array proposed to be installed at the CTA southern site. In the cameras of the ASTRI mini-array telescopes the thermal control could be relaxed with a considerable gain in terms of power consumption, cost and simplicity. So, a study of the temperature dependence of the camera components is needed. The present work addresses this issue showing the results of the measurements carried out on CITIROC as a function of the temperature. We focused our investigation on the pedestal stability, linearity of the charge output signal, preamplifier gain and trigger uniformity in the temperature range 15-30°C. Our results show, for each of the above-mentioned measurable quantities, that temperature dependency is at the level of a few percent

ASTRI SST-2M camera electronics

ASTRI SST-2M is an Imaging Atmospheric Cherenkov Telescope (IACT) developed by the Italian National Institute of Astrophysics, INAF. It is the prototype of the ASTRI telescopes proposed to be installed at the southern site of the Cherenkov Telescope Array, CTA. The optical system of the ASTRI telescopes is based on a dual mirror configuration, an innovative solution for IACTs, and the focal plane of the camera is composed of silicon photo-multipliers (SiPM), a recently developed technology for light detection, that exhibit very fast response and an excellent single photoelectron resolution. The ASTRI camera electronics is specifically designed to directly interface the SiPM sensors, detecting the fast pulses produced by the Cherenkov flashes, managing the trigger generation, the digital conversion of the signals and the transmission of the data to an external camera server connected through a LAN. In this contribution we present the general architecture of the camera electronics developed for the ASTRI SST-2M prototype, with special emphasis to some innovative solutions

The innovative Cherenkov camera based on SiPM sensors of the ASTRI-Horn telescope: from the T/M and electrical design to the full assembly and testing in a harsh environment

ASTRI-Horn is a prototypal telescope of an imaging atmospheric Cherenkov telescope developed by the Italian National Institute of Astrophysics (INAF), proposed for the Cherenkov Telescope Array (CTA) Observatory. The CTA Observatory represents the next generation of imaging atmospheric Cherenkov telescopes and will explore the very highenergy domain from a few tens of GeV up to few hundreds of TeV. It will be composed of large-, medium-, and small sized telescopes; ASTRI-Horn is an end-to-end prototype proposed for the Small Sized array. The main scientific instrument of the ASTRI-Horn telescope is an innovative and compact Camera with Silicon- Photomultiplier based detectors and a specifically designed fast read-out electronics based on a custom peak-detector mode. The thermo-mechanical assembly is designed to host both the entire electronics chain, from the sensors to the raw data transmission system and the calibration system, and the complete thermoregulation system. This contribution gives a high level description of the T/M and electrical design of the Cherenkov Camera, it describes the assembling procedure of its different subsystems and their integration into the complete camera system. A discussion about possible design improvements coming from the problems/difficulties encountered during assembly is also presented. Finally, results from engineering tests conducted in-field are also presented

The ASTRI camera for the Cherenkov Telescope Array

The Cherenkov Telescope Array (CTA) foresees, in its southern site (Chile), the implementation of up to 70 small-sized telescopes (SSTs), which will extend the energy coverage up to hundreds of TeV. It has been proposed that one of the first set of CTA SSTs will be represented by the ASTRI mini-array, which includes (at least) nine ASTRI telescopes. The endto-end prototype of such telescopes, named the ASTRI SST-2M, is installed in Italy and it is now completing the overall commissioning and entering the science verification phase. ASTRI telescopes are characterized by an optical system based on a dual-mirror Schwarzschild-Couder design and a camera at the focal plane composed of silicon photomultiplier sensors managed by a fast read-out electronics specifically designed. Based on a custom peak-detector mode, the ASTRI camera electronics is designed to perform Cherenkov signal detection, trigger generation, digital conversion of the signals and data transmission to the camera server. In this contribution we will describe the main features of the ASTRI camera, its performance and results obtained during the commissioning phase of the ASTRI SST-2M prototype in view of the ASTRI mini-array implementation