cta Column | Spells and a reluctant bride By www.thehindu.com Published On :: Thu, 27 Jun 2024 11:06:36 +0530 Women are more than capable of saving themselves, says Phuphee. They don’t need magic, maybe just a helping hand Full Article Columns
cta Serine octamer reveals its structure By cen.acs.org Published On :: 03 May 2018 16:54:45 +0000 The structure of the protonated eight-membered cluster of serines formed during electrospray ionization has long baffled mass spectrometrists Full Article
cta Contact charges flip expectations By cen.acs.org Published On :: 11 Jun 2018 19:38:47 +0000 Pairs of surfaces taking like charges confound researchers Full Article
cta Settled SRH takes on unpredictable DD By www.thehindu.com Published On :: Thu, 19 May 2016 23:40:15 +0530 Full Article Indian Premier League
cta Royal Challengers’ spectacular comeback continues By www.thehindu.com Published On :: Wed, 25 May 2016 03:18:33 +0530 de Villiers and Iqbal Abdulla help the team make the final from a precarious 68 for six; a rare failure from Kohli Full Article Indian Premier League
cta Do Tamil Nadu's voters prefer spectacle to reality? By www.thehindu.com Published On :: Sat, 03 Feb 2018 16:18:00 +0530 Rajini or Kamal’s success will further reinforce the Tamil voter as one who prefers spectacle to reality Full Article Tamil Nadu
cta JACRA reluctant to offer more fee concessions By jamaica-gleaner.com Published On :: Sun, 10 May 2020 00:25:50 -0500 Recent calls by the Jamaica Manufacturing and Exporters Association, JMEA, for more targeted concessions on raw materials that are processed for re-export sent Jamaica Agricultural Commodities Regulatory Authority, JACRA, back to the drawing board... Full Article
cta Yellowknife memorial garden hopes to return to 'spectacular glory' with new repairs By www.cbc.ca Published On :: Sat, 9 May 2020 17:24:32 EDT The city of Yellowknife is hoping make repairs to a local memorial garden this summer, after it has been the target of vandalism and has fallen into disrepair for a variety of reasons in recent years. Full Article News/Canada/North
cta Golf tournament to use high-tech ID chip badges to track spectators By www.jpost.com Published On :: Sun, 10 May 2020 00:56:47 GMT The sale of draft beer and fountain drinks will be prohibited while all transactions will be restricted to credit cards. Full Article golf high tech Coronavirus
cta Mark Ruffalo says he was reluctant to take up role of 'Hulk' in Avengers By feedproxy.google.com Published On :: Sat, 09 May 2020 21:22:00 +0500 Mark Ruffalo has been playing Bruce Banner-cum-Hulk in Avengers films since 2012 Full Article
cta Golf: Memorial to use high-tech badges to track spectators By feeds.reuters.com Published On :: Sat, 09 May 2020 18:46:11 -0400 The Memorial Tournament in Dublin, Ohio, will use high-tech radio frequency identification (RFID) chips in tournament badges to ensure social distancing is maintained at the July 16-19 PGA Tour event, Golf Digest reported on Saturday. Full Article sportsNews
cta UFC 249 has postfight interviews in Octagon By www.espn.com Published On :: Sat, 9 May 2020 20:18:27 EST Saturday's UFC 249 featured postfight interviews in the Octagon, a departure from safety protocols that were announced earlier this week. Full Article
cta Global Value Chains offer major opportunity for growth and progress in advanced and developing economies, according to OECD-WTO-UNCTAD report to G20 By www.oecd.org Published On :: Fri, 06 Sep 2013 22:53:00 GMT Global value chains (GVCs) have become a dominant feature of world trade and investment, offering new prospects for growth, development and jobs, according to a new joint report by the Organization for Economic Cooperation and Development (OECD), the World Trade Organization (WTO) and the United Nations Conference on Trade and Development (UNCTAD). Full Article
cta 10th OECD-WTO-UNCTAD report on G20 trade and investment measures By www.oecd.org Published On :: Wed, 18 Dec 2013 00:00:00 GMT This report covers investment measures taken between mid May and mid November 2013 and was prepared in response to the G20 Leaders' request of 2 April 2009 for quarterly public reporting on their adherence to their trade and investment policy commitments. Full Article
cta Líneas directrices de la OCDE para empresas multinacionales - La importancia de una conducta responsable por parte de las empresas By www.oecd.org Published On :: Thu, 26 Jun 2014 10:26:00 GMT Este folleto contiene información esencial sobre las Líneas Directrices de la OCDE para empresas multinacionales, que en la actualidad constituyen las recomendaciones más exhaustivas aprobadas por los gobiernos sobre la conducta responsable de las empresas. Full Article
cta These Spectacular Places in the World Actually Looks Unreal By feedproxy.google.com Published On :: Our planet is extremely a magical place filled with surprises. Full Article
cta Guidance Document for Demonstrating Efficacy of Pool and Spa Disinfectants and Field Testing By www.oecd.org Published On :: Thu, 09 Aug 2012 13:10:00 GMT This Guidance Document describes how applicants could demonstrate that a proposed new pool and spa disinfectant would satisfy the regulator’s efficacy criteria. While meeting the performance characteristics can be expected to satisfy the regulator’s efficacy requirements, the regulator may choose to consider alternative scientific information and argument aimed at satisfying the efficacy criteria. Full Article
cta Qantas uses HERPES disinfectant to clean planes to stop coronavirus spreading in Australia By www.dailymail.co.uk Published On :: Thu, 27 Feb 2020 07:08:47 GMT Qantas flew three planes carrying passengers from the epicentre of the coronavirus outbreak back to Australia. The airline stepped up cleaning efforts to make sure future passengers weren't at risk. Full Article
cta Indusind Media & Communications ... vs Perfect Octave Media Projects Ltd on 20 March, 2020 By indiankanoon.org Published On :: Fri, 20 Mar 2020 00:00:00 +0530 os Nobody has appeared on behalf of the respondent even after service of notice and as a result the petition has been heard ex parte. The respondent has not appeared at any stage and has filed neither reply nor any affidavit of evidence 2. The petitioner company carries on the business of receiving signals from broadcasters of various television channels and of redistributing the same through franchisee cable network. The respondent company carries on business as a broadcaster/eontent provider. Both the parties are service providers and as such amenable to the jurisdiction of this Tribunal. 3. Through this petition, the petitioner is seeking recovery of Bs.13,41,756/- said to be the outstanding dues inclusive of interest as on 15.03.2016 along with interest @ 18% til the date of realization from the respondent. The dues are towards carriage fee for the services availed by the respondent from the petitioner for carriage of its television channels. Full Article
cta Un milion de hectare de culturi sunt lovite de secetă By www.forbes.ro Published On :: Sun, 10 May 2020 05:23:31 +0000 Adrian Oros, ministrul Agriculturii, a declarat, sâmbătă, că din primele evaluări există aproape un milion de hectare de culturi afectate de secetă în România, iar unii fermieri se gândesc să reînsămânţeze pentru a-şi diminua pierderile, informează Agerpres. The post Un milion de hectare de culturi sunt lovite de secetă appeared first on Forbes.ro. Full Article Afaceri Agricultură Adrian Oros agricultura fermieri seceta
cta Great expectations By indiatogether.org Published On :: Wed, 01 Oct 2003 00:00:00 +0000 The India Together editorial Full Article
cta Nurses away from home to serve expectant mothers By timesofindia.indiatimes.com Published On :: Sun, 10 May 2020 04:22:00 IST Full Article
cta Apple iPhone 12 Pro Vs Samsung Galaxy Note 20+: Expectations From Upcoming Flagships By www.gizbot.com Published On :: Sun, 10 May 2020 06:01:53 +0530 Smartphones are evolving every year and the speed of transition is pretty quick, where the devices get a complete overhaul every year with respect to looks, features, and specifications. Samsung and Apple are some of the brands that are known for Full Article
cta Skoda Octavia RS 245 Deliveries: 44 Out Of 200 Allocated Units Sold In Bengaluru By www.drivespark.com Published On :: Fri, 08 May 2020 10:31:46 +0530 Skoda Octavia RS 245 deliveries have commenced in the country. The company has started to deliver the performance sedan as the nation-wide lockdown has been eased at select cities including Bengaluru. Full Article
cta Golf-Memorial to use high-tech badges to track spectators By feeds.reuters.com Published On :: Sun, 10 May 2020 04:13:01 +0530 The Memorial Tournament in Dublin, Ohio, will use high-tech radio frequency identification (RFID) chips in tournament badges to ensure social distancing is maintained at the July 16-19 PGA Tour event, Golf Digest reported on Saturday. Full Article golfNews
cta Golf: Memorial to use high-tech badges to track spectators By feeds.reuters.com Published On :: Sun, 10 May 2020 08:55:55 +0530 The Memorial Tournament in Dublin, Ohio, will use high-tech radio frequency identification (RFID) chips in tournament badges to ensure social distancing is maintained at the July 16-19 PGA Tour event, Golf Digest reported on Saturday. Full Article sportsNews
cta Study reveals early family history-based screening of colorectal cancer may help in diagnosis By www.newkerala.com Published On :: Sun, 26 Apr 2020 16:42:01 +0530 Full Article
cta Mike Lombardi won't rule out Cam Newton to Patriots despite Bill Belichick's reluctance By sports.yahoo.com Published On :: Sat, 09 May 2020 17:04:48 GMT Former Patriots executive Mike Lombardi still won't rule out New England signing Cam Newton at some point despite Bill Belichick indicating he plans to roll with the current QB group he has now. Full Article article Sports
cta CTA calls for additional 30 day lockdown for Tibetans in India By www.newkerala.com Published On :: Sun, 10 May 2020 07:06:02 +0530 Full Article
cta The indexing ambiguity in serial femtosecond crystallography (SFX) resolved using an expectation maximization algorithm By journals.iucr.org Published On :: An expectation maximization algorithm is implemented to resolve the indexing ambiguity which arises when merging data from many crystals in protein crystallography, especially in cases where partial reflections are recorded in serial femtosecond crystallography (SFX) at XFELs. Full Article text
cta Structure–function study of AKR4C14, an aldo-keto reductase from Thai Jasmine rice (Oryza sativa L. ssp. Indica cv. KDML105) By journals.iucr.org Published On :: Rice AKR in the apo structure reveals the ordered open conformation and its key residues which form the substrate channel wall and determine its substrate preference for straight-chain aldehydes. Full Article text
cta Structure of Thermococcus litoralis Δ1-pyrroline-2-carboxylate reductase in complex with NADH and L-proline By journals.iucr.org Published On :: The paper reports the structure of a Δ1-pyrroline-2-carboxylate reductase from the archaeon Thermococcus litoralis, a key enzyme involved in the second step of trans-4-Hydroxy-L-proline metabolism, conserved in archaea, bacteria and humans. Full Article text
cta Bis(2-methyllactato)borate tetrahydrate By scripts.iucr.org Published On :: 2019-07-12 The asymmetric unit of the title compound (systematic name: 3,3,8,8-tetramethyl-1,4,6,9-tetraoxa-λ4-boraspiro[4.4]nonane-2,7-dione tetrahydrate), C8H12BO6·4H2O, consists of half a bis(2-methyllactato)borate molecule and two water molecules of solvation. In the crystal, O—H⋯O hydrogen bonds link the components into a three-dimensional network. Full Article text
cta (2S,3S,4R,4a'R,5R,5a'R,11a'R,12'S,12a'R)-5-(Acetoxymethyl)-2',2',10',10'-tetramethyloctahydro-3H,8'H-spiro[furan-2,7'-[1,3]dioxino[4',5':5,6]pyrano[3,2-d][1,3,6]trioxocine]-3,4,12'-triyl tria By scripts.iucr.org Published On :: 2019-07-12 While the crystal structure analysis of the title compound, C26H38O15, a synthetic derivative of sucrose, was originally reported 40 years ago [Drew et al. (1979). Carbohydr. Res. 71, 35–42], the present work has allowed for the determination of its absolute configuration through the application of resonant scattering techniques. Full Article text
cta Bis(μ2-4-nitrophenolato)bis(4-nitrophenolato)di-μ3-oxido-octaphenyltetratin chloroform sesquisolvate [+ solvate]: a tetranuclear stannoxane By scripts.iucr.org Published On :: 2019-08-06 The title tetranuclear stannoxane, [Sn4(C6H5)8(C6H4NO3)4O2]·1.5CHCl3·solvent, crystallized with two independent complex molecules, A and B, in the asymmetric unit together with 1.5 molecules of chloroform. There is also a region of disordered electron density, which was corrected for using the SQUEEZE routine [Spek (2015). Acta Cryst. C71, 9–18]. The oxo-tin core of each complex is in a planar `ladder' arrangement and each Sn atom is fivefold SnO3C2 coordinated, with one tin centre having an almost perfect square-pyramidal coordination geometry, while the other three Sn centres have distorted shapes. In the crystal, the complex molecules are arranged in layers, composed of A or B complexes, lying parallel to the bc plane. The complex molecules are linked by a number of C—H⋯O hydrogen bonds within the layers and between the layers, forming a supramolecular three-dimensional structure. Full Article text
cta [Oxybis(ethane-1,2-diyl)]bis(dimethylammonium) octamolybdate dihydrate By scripts.iucr.org Published On :: 2019-11-19 The title compound, (C8H22N2O)2[Mo8O26]·H2O, (cis-H2L)2[β-Mo8O26]·H2O, where L = (bis[2-N,N-dimethylamino)ethyl] ether), was synthesized from bis[2-(dimethylamino)ethyl] ether and MoO3 under solvothermal conditions and characterized by multinuclear NMR and single-crystal X-ray diffraction techniques. The structure displays two [oxybis(ethane-1,2-diyl)]bis(dimethylammonium), or [cis-H2L]2+, cations, a central [β-Mo8O26]4− anionic cluster consisting of eight distorted MoO6 octahedra, and two water molecules in their deuterated form. The central anion lies across an inversion center. The [cis-H2L]2+ cations are hydrogen bonded to the central [β-Mo8O26]4− cluster via bridging water molecules. In the crystal, O—H⋯O hydrogen bonds link the components into chains along [010]. Weak C—H⋯O hydrogen bonds link these chains into a three-dimensional network. Full Article text
cta Bis(1-dodecyl-4-aza-1-azoniabicyclo[2.2.2]octane)tetraisothiocyanatocobalt(II) By scripts.iucr.org Published On :: 2020-01-28 The title compound, [Co(C18H37N2)2(NCS)4], consists of a cobalt(II) ion positioned on the origin of the triclinic unit cell. It is coordinated by the N atoms of two trans-oriented 1-dodecyl-4-aza-1-azoniabicyclo[2.2.2]octane (DABCO+) cations, which carry n-dodecyl chains at the non-coordinating N atoms. The distorted octahedral coordination environment of the CoII ion is completed through four N atoms of isothiocyanate ions, which are arranged within the equatorial plane. Non-classical hydrogen bonding of the types C—H⋯N and C—H⋯S between the filamentous molecules lead to the formation of layers parallel to (001). Full Article text
cta 2-(Octadecylsulfanyl)-1,3-thiazole By scripts.iucr.org Published On :: 2020-02-11 The title compound, C21H39NS2, crystallizes with two molecules in the asymmetric unit, both having a linear 18-carbon alkyl chain bound through a thioether group. No π–π stacking or hydrogen bonding is observed. The orientation of the alkyl chains facilitates intermolecular interactions between te chains. The structure is metrically orthorhombic but crystallizes in the monoclinic space group P21 and was found to be twinned by pseudomerohedry (emulating orthorhombic symmetry) and by inversion. The twin factions refined to 0.37 (4), 0.13 (4), 0.31 (5), and 0.19 (4). Full Article text
cta 12,15-Dimethyl-8-oxatetracyclo[8.8.0.02,7.011,16]octadeca-1(18),2,4,6,11(16),12,14-heptaen-10-ol By scripts.iucr.org Published On :: 2020-03-10 In the title compound, C19H18O2, the pyran ring is in a half-chair conformation. The fused ring system comprising the benzene and cyclohexene rings is essentially planar (r.m.s. deviation = 0.053 Å) and forms a dihedral angle of 27.95 (6)° with the other benzene ring. In the crystal, O—H⋯O hydrogen bonds connect the molecules into chains propagating along [001]. Full Article text
cta 2,2,3,3,4,4,5,5-Octafluorohexane-1,6-diol By scripts.iucr.org Published On :: 2020-04-07 In the crystal of the title compound, C6H6F8O4, O—H⋯O hydrogen bonds involving the hydroxy groups connect the molecules, forming a two-dimensional network parallel to (100). These hydrogen-bonding interactions appear to drive the O—C—C—O torsion angles into a gauche–trans–trans series of conformations along the backbone of the molecule. Full Article text
cta Synthesis, characterization, and crystal structure of aquabis(4,4'-dimethoxy-2,2'-bipyridine)[μ-(2R,3R)-tartrato(4−)]dicopper(II) octahydrate By scripts.iucr.org Published On :: 2019-06-11 Typical electroless copper baths (ECBs), which are used to chemically deposit copper on printed circuit boards, consist of an aqueous alkali hydroxide solution, a copper(II) salt, formaldehyde as reducing agent, an l-(+)-tartrate as complexing agent, and a 2,2'-bipyridine derivative as stabilizer. Actual speciation and reactivity are, however, largely unknown. Herein, we report on the synthesis and crystal structure of aqua-1κO-bis(4,4'-dimethoxy-2,2'-bipyridine)-1κ2N,N';2κ2N,N'-[μ-(2R,3R)-2,3-dioxidosuccinato-1κ2O1,O2:2κ2O3,O4]dicopper(II) octahydrate, [Cu2(C12H12N2O2)2(C4H2O6)(H2O)]·8H2O, from an ECB mock-up. The title compound crystallizes in the Sohncke group P21 with one chiral dinuclear complex and eight molecules of hydrate water in the asymmetric unit. The expected retention of the tartrato ligand's absolute configuration was confirmed via determination of the absolute structure. The complex molecules exhibit an ansa-like structure with two planar, nearly parallel bipyridine ligands, each bound to a copper atom that is connected to the other by a bridging tartrato `handle'. The complex and water molecules give rise to a layered supramolecular structure dominated by alternating π stacks and hydrogen bonds. The understanding of structures ex situ is a first step on the way to prolonged stability and improved coating behavior of ECBs. Full Article text
cta Absolute structure of (3aS,5S,7aS,7bS,9aR,10R,12aR,12bS)-7b-hydroxy-4,4,7a,9a,12a-pentamethyl-10-[(2'R)-6-methylheptan-2-yl]-2,8,9-trioxooctadecahydrobenzo[d]indeno[4,5-b]azepin-5-yl acetate from 62-year-old By scripts.iucr.org Published On :: 2019-08-23 The structure of the title compound, C32H51NO6, was determined from 62-year-old crystals at room temperature and refined with 100 K data in a monoclinic (C2) space group. This compound with a triterpenoid structure, now confirmed by this study, played an important role in the determination of the structure of lanosterol. The molecules pack in linear O—H⋯O hydrogen-bonded chains along the short axis (b), while parallel chains display weak van der Waals interactions that explain the needle-shaped crystal morphology. The structure exhibits disorder of the flexible methylheptane chain at one end of the main molecule with a small void around it. Crystals of the compounds were resistant to data collection for decades with the available cameras and Mo Kα radiation single-crystal diffractometer in our laboratory until a new instrument with Cu Kα radiation operating at 100 K allowed the structure to be solved and refined. Full Article text
cta Crystal structures of 2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetrakis(pentafluorophenyl)porphyrin as the chloroform monosolvate and tetrahydrofuran monosolvate By scripts.iucr.org Published On :: 2020-01-17 The crystal structures of the title compounds, two solvates (CHCl3 and THF) of a symmetric and highly substituted porphyrin, C44H2Br8F20N4 or OBrTPFPP, are described. These structures each feature a non-planar porphyrin ring, exhibiting a similar conformation of the strained ring independent of solvent identity. These distorted porphyrins are able to form hydrogen bonds and sub-van der Waals halogen interactions with enclathrated solvent; supramolecular interactions of proximal macrocycles are additionally affected by solvent choice. The crystal studied for compound 1·CHCl3 was refined as an inversion twin. One pentafluorophenyl group was modelled as disordered over two sites [occupancy ratio = 0.462 (7):0.538 (7)]. The chloroform solvate was also modelled as disordered over two orientations [occupancy ratio = 0.882 (7): 0.118 (7). Full Article text
cta Crystal structures of (η4-cycloocta-1,5-diene)bis(1,3-dimethylimidazol-2-ylidene)iridium(I) iodide and (η4-cycloocta-1,5-diene)bis(1,3-diethylimidazol-2-ylidene)iridium(I) iodide By scripts.iucr.org Published On :: 2020-04-03 The title complexes, (η4-cycloocta-1,5-diene)bis(1,3-dimethylimidazol-2-ylidene)iridium(I) iodide, [Ir(C5H8N2)2(C8H12)]I, (1) and (η4-cycloocta-1,5-diene)bis(1,3-diethylimidazol-2-ylidene)iridium(I) iodide, [Ir(C7H12N2)2(C8H12)]I, (2), were prepared using a modified literature method. After carrying out the oxidative addition of the amino acid l-proline to [Ir(COD)(IMe)2]I in water and slowly cooling the reaction to room temperature, a suitable crystal of 1 was obtained and analyzed by single-crystal X-ray diffraction at 100 K. Although this crystal structure has previously been reported in the Pbam space group, it was highly disordered and precise atomic coordinates were not calculated. A single crystal of 2 was also obtained by heating the complex in water and letting it slowly cool to room temperature. Complex 1 was found to crystallize in the monoclinic space group C2/m, while 2 crystallizes in the orthorhombic space group Pccn, both with Z = 4. Full Article text
cta Catalytically important damage-free structures of a copper nitrite reductase obtained by femtosecond X-ray laser and room-temperature neutron crystallography By scripts.iucr.org Published On :: 2019-06-23 Copper-containing nitrite reductases (CuNiRs) that convert NO2− to NO via a CuCAT–His–Cys–CuET proton-coupled redox system are of central importance in nitrogen-based energy metabolism. These metalloenzymes, like all redox enzymes, are very susceptible to radiation damage from the intense synchrotron-radiation X-rays that are used to obtain structures at high resolution. Understanding the chemistry that underpins the enzyme mechanisms in these systems requires resolutions of better than 2 Å. Here, for the first time, the damage-free structure of the resting state of one of the most studied CuNiRs was obtained by combining X-ray free-electron laser (XFEL) and neutron crystallography. This represents the first direct comparison of neutron and XFEL structural data for any protein. In addition, damage-free structures of the reduced and nitrite-bound forms have been obtained to high resolution from cryogenically maintained crystals by XFEL crystallography. It is demonstrated that AspCAT and HisCAT are deprotonated in the resting state of CuNiRs at pH values close to the optimum for activity. A bridging neutral water (D2O) is positioned with one deuteron directed towards AspCAT Oδ1 and one towards HisCAT N∊2. The catalytic T2Cu-ligated water (W1) can clearly be modelled as a neutral D2O molecule as opposed to D3O+ or OD−, which have previously been suggested as possible alternatives. The bridging water restricts the movement of the unprotonated AspCAT and is too distant to form a hydrogen bond to the O atom of the bound nitrite that interacts with AspCAT. Upon the binding of NO2− a proton is transferred from the bridging water to the Oδ2 atom of AspCAT, prompting electron transfer from T1Cu to T2Cu and reducing the catalytic redox centre. This triggers the transfer of a proton from AspCAT to the bound nitrite, enabling the reaction to proceed. Full Article text
cta Structure and mechanism of copper–carbonic anhydrase II: a nitrite reductase By scripts.iucr.org Published On :: 2020-02-21 Nitric oxide (NO) promotes vasodilation through the activation of guanylate cyclase, resulting in the relaxation of the smooth muscle vasculature and a subsequent decrease in blood pressure. Therefore, its regulation is of interest for the treatment and prevention of heart disease. An example is pulmonary hypertension which is treated by targeting this NO/vasodilation pathway. In bacteria, plants and fungi, nitrite (NO2−) is utilized as a source of NO through enzymes known as nitrite reductases. These enzymes reduce NO2− to NO through a catalytic metal ion, often copper. Recently, several studies have shown nitrite reductase activity of mammalian carbonic anhydrase II (CAII), yet the molecular basis for this activity is unknown. Here we report the crystal structure of copper-bound human CAII (Cu–CAII) in complex with NO2− at 1.2 Å resolution. The structure exhibits Type 1 (T-1) and 2 (T-2) copper centers, analogous to bacterial nitrite reductases, both required for catalysis. The copper-substituted CAII active site is penta-coordinated with a `side-on' bound NO2−, resembling a T-2 center. At the N terminus, several residues that are normally disordered form a porphyrin ring-like configuration surrounding a second copper, acting as a T-1 center. A structural comparison with both apo- (without metal) and zinc-bound CAII (Zn–CAII) provides a mechanistic picture of how, in the presence of copper, CAII, with minimal conformational changes, can function as a nitrite reductase. Full Article text
cta The active form of quinol-dependent nitric oxide reductase from Neisseria meningitidis is a dimer By scripts.iucr.org Published On :: 2020-03-21 Neisseria meningitidis is carried by nearly a billion humans, causing developmental impairment and over 100 000 deaths a year. A quinol-dependent nitric oxide reductase (qNOR) plays a critical role in the survival of the bacterium in the human host. X-ray crystallographic analyses of qNOR, including that from N. meningitidis (NmqNOR) reported here at 3.15 Å resolution, show monomeric assemblies, despite the more active dimeric sample being used for crystallization. Cryo-electron microscopic analysis of the same chromatographic fraction of NmqNOR, however, revealed a dimeric assembly at 3.06 Å resolution. It is shown that zinc (which is used in crystallization) binding near the dimer-stabilizing TMII region contributes to the disruption of the dimer. A similar destabilization is observed in the monomeric (∼85 kDa) cryo-EM structure of a mutant (Glu494Ala) qNOR from the opportunistic pathogen Alcaligenes (Achromobacter) xylosoxidans, which primarily migrates as a monomer. The monomer–dimer transition of qNORs seen in the cryo-EM and crystallographic structures has wider implications for structural studies of multimeric membrane proteins. X-ray crystallographic and cryo-EM structural analyses have been performed on the same chromatographic fraction of NmqNOR to high resolution. This represents one of the first examples in which the two approaches have been used to reveal a monomeric assembly in crystallo and a dimeric assembly in vitrified cryo-EM grids. A number of factors have been identified that may trigger the destabilization of helices that are necessary to preserve the integrity of the dimer. These include zinc binding near the entry of the putative proton-transfer channel and the preservation of the conformational integrity of the active site. The mutation near the active site results in disruption of the active site, causing an additional destabilization of helices (TMIX and TMX) that flank the proton-transfer channel helices, creating an inert monomeric enzyme. Full Article text
cta Structures of substrate- and product-bound forms of a multi-domain copper nitrite reductase shed light on the role of domain tethering in protein complexes By scripts.iucr.org Published On :: 2020-04-25 Copper-containing nitrite reductases (CuNiRs) are found in all three kingdoms of life and play a major role in the denitrification branch of the global nitrogen cycle where nitrate is used in place of dioxygen as an electron acceptor in respiratory energy metabolism. Several C- and N-terminal redox domain tethered CuNiRs have been identified and structurally characterized during the last decade. Our understanding of the role of tethered domains in these new classes of three-domain CuNiRs, where an extra cytochrome or cupredoxin domain is tethered to the catalytic two-domain CuNiRs, has remained limited. This is further compounded by a complete lack of substrate-bound structures for these tethered CuNiRs. There is still no substrate-bound structure for any of the as-isolated wild-type tethered enzymes. Here, structures of nitrite and product-bound states from a nitrite-soaked crystal of the N-terminal cupredoxin-tethered enzyme from the Hyphomicrobium denitrificans strain 1NES1 (Hd1NES1NiR) are provided. These, together with the as-isolated structure of the same species, provide clear evidence for the role of the N-terminal peptide bearing the conserved His27 in water-mediated anchoring of the substrate at the catalytic T2Cu site. Our data indicate a more complex role of tethering than the intuitive advantage for a partner-protein electron-transfer complex by narrowing the conformational search in such a combined system. Full Article text
cta Open-access and free articles in Acta Crystallographica Section D: Biological Crystallography By journals.iucr.org Published On :: Full Article Still image