• Multi-electron reduction of sulfur and carbon disulfide using binuclear uranium(III) borohydride complexes

      Arnold, P.L.; Stevens, C.J.; Bell, N.L.; Lord, Rianne M.; Goldberg, J.M.; Nichol, G.S.; Love, J.B. (2017-03-10)
      The first use of a dinuclear UIII/UIII complex in the activation of small molecules is reported. The octadentate Schiff-base pyrrole, anthracene-hinged ‘Pacman’ ligand LA combines two strongly reducing UIII centres and three borohydride ligands in [M(THF)4][{U(BH4)}2(m-BH4)(LA)(THF)2] 1-M, (M ¼ Li, Na, K). The two borohydride ligands bound to uranium outside the macrocyclic cleft are readily substituted by aryloxide ligands, resulting in a single, weakly-bound, encapsulated endo group 1 metal borohydride bridging the two UIII centres in [{U(OAr)}2(m-MBH4)(LA)(THF)2] 2-M (OAr ¼ OC6H2tBu3-2,4,6, M ¼ Na, K). X-ray crystallographic analysis shows that, for 2-K, in addition to the endo-BH4 ligand the potassium countercation is also incorporated into the cleft through h5-interactions with the pyrrolides instead of extraneous donor solvent. As such, 2-K has a significantly higher solubility in non-polar solvents and a wider U–U separation compared to the ‘ate’ complex 1. The cooperative reducing capability of the two UIII centres now enforced by the large and relatively flexible macrocycle is compared for the two complexes, recognising that the borohydrides can provide additional reducing capability, and that the aryloxide-capped 2-K is constrained to reactions within the cleft. The reaction between 1-Na and S8 affords an insoluble, presumably polymeric paramagnetic complex with bridging uranium sulfides, while that with CS2 results in oxidation of each UIII to the notably high UV oxidation state, forming the unusual trithiocarbonate (CS3)2 as a ligand in [{U(CS3)}2(m-k2:k2-CS3)(LA)] (4). The reaction between 2-K and S8 results in quantitative substitution of the endo-KBH4 by a bridging persulfido (S2)2 group and oxidation of each UIII to UIV, yielding [{U(OAr)}2(m-k2:k2-S2)(LA)] (5). The reaction of 2-K with CS2 affords a thermally unstable adduct which is tentatively assigned as containing a carbon disulfido (CS2)2 ligand bridging the two U centres (6a), but only the mono-bridged sulfido (S)2 complex [{U(OAr)}2(m-S (LA)] (6) is isolated. The persulfido complex (5) can also be synthesised from the mono-bridged sulfido complex (6) by the addition of another equivalent of sulfur.
    • Multi-Proxy Characterisation of the Storegga Tsunami and Its Impact on the Early Holocene Landscapes of the Southern North Sea

      Gaffney, Vincent L.; Fitch, Simon; Bates, M.; Ware, R.L.; Kinnaird, T.; Gearey, B.; Hill, T.; Telford, Richard; Batt, Catherine M.; Stern, Ben; et al. (2020-07-15)
      Doggerland was a landmass occupying an area currently covered by the North Sea until marine inundation took place during the mid-Holocene, ultimately separating the British landmass from the rest of Europe. The Storegga Event, which triggered a tsunami reflected in sediment deposits in the northern North Sea, northeast coastlines of the British Isles and across the North Atlantic, was a major event during this transgressive phase. The spatial extent of the Storegga tsunami however remains unconfirmed as, to date, no direct evidence for the event has been recovered from the southern North Sea. We present evidence of a tsunami deposit in the southern North Sea at the head of a palaeo-river system that has been identified using seismic survey. The evidence, based on lithostratigraphy, geochemical signatures, macro and microfossils and sedimentary ancient DNA (sedaDNA), supported by optical stimulated luminescence (OSL) and radiocarbon dating, suggests that these deposits were a result of the tsunami. Seismic identification of this stratum and analysis of adjacent cores showed diminished traces of the tsunami which was largely removed by subsequent erosional processes. Our results confirm previous modelling of the impact of the tsunami within this area of the southern North Sea, and also indicate that these effects were temporary, localized, and mitigated by the dense woodland and topography of the area. We conclude that clear physical remnants of the wave in these areas are likely to be restricted to now buried, palaeo-inland basins and incised river valley systems.
    • A multi-proxy climate record from a raised bog in County Fermanagh, Northern Ireland: a critical examination of the link between bog surface wetness and solar variability

      Swindles, Graeme T.; Plunkett, G.; Roe, H.M. (2007)
      A proxy climate record from a raised bog in County Fermanagh, Northern Ireland, is presented. The record spans the interval between 2850 cal. yr BC and cal. yr AD 1000 and chronological control is achieved through the use of tephrochronology and 14C dating, including a wiggle-match on one section of the record. Palaeoclimatic inferences are based on a combination of a testate amoebae-derived water table reconstruction, peat humification and plant macrofossil analyses. This multiproxy approach enables proxy-specific effects to be identified. Major wet shifts are registered in the proxies at ca. 1510 cal. yr BC, 750 cal. yr BC and cal. yr AD 470. Smaller magnitude shifts to wetter conditions are also recorded at ca. 380 cal. yr BC, 150 cal. yr BC, cal. yr AD 180, and cal. yr AD 690. It is hypothesised that the wet shifts are not merely local events as they appear to be linked to wider climate deteriorations in northwest Europe. Harmonic analysis of the proxies illustrates statistically significant periodicities of 580, 423-373, 307 and 265 years that may be related to wider Holocene climate cycles. This paper illustrates how the timing of climate changes registered in peat profiles records can be precisely constrained using tephrochronology to examine possible climatic responses to solar forcing. Relying on interpolated chronologies with considerable dating uncertainty must be avoided if the climatic responses to forcing mechanisms are to be fully understood.
    • Multi-proxy palaeoecological approaches to submerged landscapes: a case study from ‘Doggerland’, in the southern North Sea

      Gearey, B.J.; Hopla, E.-J.; Boomer, I.; Smith, D.; Marshall, P.; Fitch, Simon; Griffiths, S.; Tapping, D.R. (2017-06-16)
      Abstract: This paper focuses on the submerged landscapes of the southern North Sea, an area often referred to as Doggerland, which was inundated as a result of relative sea-level rise at the start of the Holocene. The timing, pattern and process of environmental changes and the implica­ tions for prehistoric (Mesolithic) human communities living in this area have long been a subject of debate and discussion. Recent developments in marine geophysics have pemtitted the mapping of the pre-submergence landscape, leading to the identification oflandforms including river channels and other contexts suitable for the preservation of palaeoecological records. The paper describes multi-proxy (pollen, foraminifera, plant macrofossil and insect) palaeoenvironmental analyses of a vibrocore sequence recovered from a palaeochannel feature c. 80 km off the coast of eastern England. The palaeocbsnnel preserves sediments of Late Pleistocene and Holocene age (MIS2/l); the record suggests that channel incision, probably duting the early Holocene, was followed by a phase of peat formation (c. 9-10 cal ka BP) indicating paludification and the subsequent reactiva­ tion of the cbsnnel (c. 9-6 cal ka BP), initially under freshwater and increasingly brackish/saline conditions, and a final transition to full marine conditions (6-5 cal ka BP). The pollen, macrofossil and beetle records indicate the presence of pre-submergence deciduous woodland, but detailed interpretation of the data is hindered by taphonomic complications.The paper concludes with a dis­ cussion of the problems and potentials of using palaeoenvironmental data to reconstruct complex patterns of environmental change across Doggerland in four dimensions, and considers specific questions concerning the implications of such processes for Mesolithic human communities.
    • Multi-scale mechanical characterization of highly swollen photo-activated collagen hydrogels

      Tronci, G.; Grant, Colin A.; Thompson, N.H.; Russell, S.J.; Wood, David J. (2014-11)
      Biological hydrogels have been increasingly sought after as wound dressings or scaffolds for regenerative medicine, owing to their inherent biofunctionality in biological environments. Especially in moist wound healing, the ideal material should absorb large amounts of wound exudate while remaining mechanically competent in situ. Despite their large hydration, however, current biological hydrogels still leave much to be desired in terms of mechanical properties in physiological conditions. To address this challenge, a multi-scale approach is presented for the synthetic design of cyto-compatible collagen hydrogels with tunable mechanical properties (from the nano- up to the macro-scale), uniquely high swelling ratios and retained (more than 70%) triple helical features. Type I collagen was covalently functionalized with three different monomers, i.e. 4-vinylbenzyl chloride, glycidyl methacrylate and methacrylic anhydride, respectively. Backbone rigidity, hydrogen-bonding capability and degree of functionalization (F: 16 ± 12–91 ± 7 mol%) of introduced moieties governed the structure–property relationships in resulting collagen networks, so that the swelling ratio (SR: 707 ± 51–1996 ± 182 wt%), bulk compressive modulus (Ec: 30 ± 7–168 ± 40 kPa) and atomic force microscopy elastic modulus (EAFM: 16 ± 2–387 ± 66 kPa) were readily adjusted. Because of their remarkably high swelling and mechanical properties, these tunable collagen hydrogels may be further exploited for the design of advanced dressings for chronic wound care.
    • Multianalyte determination of the kinetic rate constants of drug-cyclodextrin supermolecules by high performance affinity chromatography

      Wang, C.; Ge, J.; Zhang, J.; Guo, T.; Chi, L.; He, Z.; Xu, X.; York, Peter; Sun, L.; Li, H. (2014-09-12)
      The kinetics of the dissociation is fundamental to the formation and the in vivo performance of cyclodextrin supramolecules. The individual determination of the apparent dissociation rate constant (kd,app) using high performance affinity chromatography (HPAC) is a tedious process requiring numerous separate studies and massive data fitting. In this study, the multianalyte approach was employed to simultaneously measure the kd,app values of three drugs through one injection based on the investigation of the dependence of drug-cyclodextrin interaction kinetics on the mobile phase composition. As a result, the kd,app values increased when decreasing the ion strength, increasing the ionization of drugs and adding extra organic solvents. The values of kd,app for acetaminophen, phenacetin and S-flurbiprofen estimated by the multianalyte approach were 8.54+/-1.81, 5.36+/-0.94 and 0.17+/-0.02s(-1), respectively, which were in good agreement with those determined separately (8.31+/-0.58, 5.01+/-0.42 and 0.15+/-0.01s(-1)). For both of the single and multiple flow rate peak profiling methods, the results of the multianalyte approach were statistically equivalent with that of the single compound analysis for all of the three drugs (p>0.05). The multianalyte approach can be employed for the efficient evaluation of the drug-cyclodextrin kinetics with less variance caused by cyclodextrin column bleeding.
    • Multicentric osteosarcoma associated with DISH, in a 19th Century burial from England.

      Ortner, D.J.; Ponce, P.; Ogden, Alan R.; Buckberry, Jo (2010)
      Osteosarcoma is a rare type of malignant neoplasm that is most frequent in adolescents and young adults although it can develop at any age. It can metastasize from a primary site in bone to other bones and soft tissues. Usually the disorder causes a single bone-forming lesion (unicentric) but some cases have multicentric, bone-forming lesions. Some of these lesions develop at different sites at different times. In a second variant of multicentric osteosarcoma, synchronous bone-forming lesions develop at multiple sites. Distinguishing between these two types of multicentric osteosarcoma is challenging in a clinical context and the criteria for doing so are unlikely to be met in an archaeological burial. Wolverhampton burial HB 39 was excavated from an early-nineteenth century cemetery site in England. It consists of the incomplete skeleton of an adult male of at least 45 years of age with multicentric osteosarcoma. The individual represented by this burial also had diffuse idiopathic skeletal hyperostosis (DISH). Three of the bone-forming lesions associated with osteosarcoma developed on the bony outgrowths related to DISH.
    • Multifocal spectacles increase variability in toe clearance and risk of tripping in the elderly

      Buckley, John G.; Elliott, David B.; Johnson, Louise; Scally, Andy J. (2007)
      PURPOSE. Epidemiologic studies have indicated that elderly people who wear multifocal spectacles have an increased risk of tripping, particularly on stairs. Yet no studies have experimentally examined how wearing multifocal spectacles affects stair and step negotiation. The purpose of this study was to determine the effects of wearing multifocal compared with single-distance vision spectacles on minimum toe clearance and risk of tripping during step negotiation in the elderly. METHODS. Nineteen healthy subjects (mean age, 71.4 years) performed a single step up to a new level (heights, 7.5, 15, and 22 cm) while wearing multifocal (bifocals and progressive addition lenses) or single-distance vision spectacles. Minimum horizontal and vertical toe clearance were assessed by analyzing data collected with a five-camera, three-dimensional motion-analysis system. RESULTS. There was no difference in mean minimum toe clearance in subjects when wearing multifocal compared with single-distance vision spectacles. However, there was greater within-subject variability in vertical toe clearance when wearing multifocal spectacles (variance ratio, 1.53; P = 0.0004). Subjects were also significantly more likely to trip when wearing multifocal compared with single-vision spectacles (one-sided Fisher's exact test P = 0.025). CONCLUSIONS. Because of increased within-subject variability in vertical toe clearance when wearing multifocal spectacles, elderly individuals may be at greater risk of falling when negotiating steps and stairs if they do not also consistently increase margins of safety (mean vertical toe clearance). This suggests that some elderly who are at high risk of falling may benefit from wearing single-distance vision rather than multifocal spectacles when walking.
    • Multigram scale synthesis of polycyclic lactones and evaluation of antitumor and other biological properties

      Grau, L.; Romero, M.; Privat-Contreras, C.; Presa, Daniela; Viñas, M.; Morral, J.; Pors, Klaus; Rubio-Martinez, J.; Pujol, M.D. (2020-01-01)
      An efficient four-step synthesis of tetracyclic lactones from 1,4-benzodioxine-2-carboxylic acid was developed. Ellipticine derivatives exhibit antitumor activity however only a few derivatives without carbazole subunit have been studied to date. Herein, several tetracyclic lactones were synthesized and biologically evaluated. Several compounds (2a, 3a, 4a and 5a) were found to be inhibitors of the Kras-Wnt pathway. The lactone 2a also exerted a potent inhibition of Tau protein translation and was shown to have capacity for CYP1A1-bioactivation. The results obtained are further evidence of the therapeutic potential of tetracyclic lactones related to ellipticine. Molecular modeling studies showed that compound 2a is inserted between helix α3 and α4 of the KRas protein making interactions with the hydrophobic residues Phe90, Glu91, Ile9364, Hie94, Leu133 and Tyr137and a hydrogen bond with residue Arg97.
    • A multinuclear 1H, 13C and 11B solid-state MAS NMR study of 16- and 18-electron organometallic ruthenium and osmium carborane complexes

      Barry, Nicolas P.E.; Kemp, T.F.; Sadler, P.J.; Hanna, J.V. (2014-02)
      The first 1H, 13C, 31P and 11B solid state MAS NMR studies of electron- deficient carborane-containing ruthenium and osmium complexes [Ru/Os(p-cym)(1,2-dicarba-closo-dodecaborane-1,2- dithiolate)] are reported. The MAS NMR data from these 16-electron complexes are compared to those of free carborane-ligand and an 18-electron triphenylphosphine ruthenium adduct, and reveal clear spectral differences between 16- and 18-electron organometallic carborane systems in the solid state.
    • Multiple changes in cell wall antigens of isogenic mutants of Streptococcus mutans

      Harrington, Dean J.; Russell, R.R.B. (1993-09)
      Isogenic mutants of Streptococcus mutans LT11, deficient in the production of the wall-associated protein antigens A and B, were generated by recombinant DNA technology. The hydrophobicity, adherence, and aggregation of the mutants were compared with those of the parent strain. These studies indicated that hydrophobicity, adherence, and saliva- or sucrose-induced aggregation were unaltered in the A- mutant but that hydrophobicity and adherence to saliva-coated hydroxylapatite were greatly reduced in the B- mutant whilst sucrose-dependent adherence and aggregation were increased. To determine whether these changes correlated with changes in the mutated gene product alone, the levels of a number of cell wall antigens were determined in each of the mutants. The loss of antigen A resulted in significantly reduced levels of wall-associated lipoteichoic acid, and loss of antigen B resulted in reductions in both antigen A and lipoteichoic acid. Data presented here thus suggest that changes in the expression of one wall antigen can have a dramatic effect on the levels of others.
    • Multiple Introductions and Recent Spread of the Emerging Human Pathogen Mycobacterium ulcerans across Africa

      Vandelannoote, K.; Meehan, Conor J.; Eddyani, M.; Affolabi, D.; Phanzu, D.M.; Eyangoh, S.; Jordaens, K.; Portaels, F.; Mangas, K.; Seemann, T.; et al. (2017-03)
      Buruli ulcer (BU) is an insidious neglected tropical disease. Cases are reported around the world but the rural regions of West and Central Africa are most affected. How BU is transmitted and spreads has remained a mystery, even though the causative agent, Mycobacterium ulcerans, has been known for more than 70 years. Here, using the tools of population genomics, we reconstruct the evolutionaryhistoryofM. ulceransbycomparing165isolatesspanning48yearsandrepresenting11endemiccountriesacrossAfrica. The genetic diversity of African M. ulcerans was found to be restricted due to the bacterium’s slow substitution rate coupled with its relatively recent origin. We identified two specific M. ulcerans lineages within the African continent, and inferred that M. ulcerans lineage Mu_A1 existed in Africa for several hundreds of years, unlike lineage Mu_A2, which was introduced much more recently, approximately during the 19th century. Additionally, we observed that specific M. ulcerans epidemic Mu_A1 clones were introduced during the same time period in the three hydrological basins that were well covered in our panel. The estimated time span of the introduction events coincides with the Neo-imperialism period, during which time the European colonial powers divided the African continent among themselves. Using this temporal association, and in the absence of a known BU reservoir or—vector on the continent, we postulate that the so-called "Scramble for Africa" played a significant role in the spread of the disease across the continent.
    • Multiple spatial frequency channels in human visual perceptual memory

      Nemes, Vanda A.; Whitaker, David J.; Heron, James; McKeefry, Declan J. (2011-12-08)
      Current models of short-term visual perceptual memory invoke mechanisms that are closely allied to low-level perceptual discrimination mechanisms. The purpose of this study was to investigate the extent to which human visual perceptual memory for spatial frequency is based upon multiple, spatially tuned channels similar to those found in the earliest stages of visual processing. To this end we measured how performance on a delayed spatial frequency discrimination paradigm was affected by the introduction of interfering or ‘memory masking’ stimuli of variable spatial frequency during the delay period. Masking stimuli were shown to induce shifts in the points of subjective equality (PSE) when their spatial frequencies were within a bandwidth of 1.2 octaves of the reference spatial frequency. When mask spatial frequencies differed by more than this value, there was no change in the PSE from baseline levels. This selective pattern of masking was observed for different spatial frequencies and demonstrates the existence of multiple, spatially tuned mechanisms in visual perceptual memory. Memory masking effects were also found to occur for horizontal separations of up to 6 deg between the masking and test stimuli and lacked any orientation selectivity. These findings add further support to the view that low-level sensory processing mechanisms form the basis for the retention of spatial frequency information in perceptual memory. However, the broad range of transfer of memory masking effects across spatial location and other dimensions indicates more long range, long duration interactions between spatial frequency channels that are likely to rely contributions from neural processes located in higher visual areas.
    • Multiple-approaches to the identification and quantification of cytochromes P450 in human liver tissue by mass spectrometry

      Seibert, C.; Davidson, B.R.; Fuller, B.J.; Patterson, Laurence H.; Griffiths, W.J.; Wang, Y. (2009)
      Here we report the identification and approximate quantification of cytochrome P450 (CYP) proteins in human liver microsomes as determined by nano-LC-MS/MS with application of the exponentially modified protein abundance index (emPAI) algorithm during database searching. Protocols based on 1D-gel protein separation and 2D-LC peptide separation gave comparable results. In total, 18 CYP isoforms were unambiguously identified based on unique peptide matches. Further, we have determined the absolute quantity of two CYP enzymes (2E1 and 1A2) in human liver microsomes using stable-isotope dilution mass spectrometry, where microsomal proteins were separated by 1D-gel electrophoresis, digested with trypsin in the presence of either a CYP2E1- or 1A2-specific stable-isotope labeled tryptic peptide and analyzed by LC-MS/MS. Using multiple reaction monitoring (MRM) for the isotope-labeled tryptic peptides and their natural unlabeled analogues quantification could be performed over the range of 0.1-1.5 pmol on column. Liver microsomes from four individuals were analyzed for CYP2E1 giving values of 88-200 pmol/mg microsomal protein. The CYP1A2 content of microsomes from a further three individuals ranged from 165 to 263 pmol/mg microsomal protein. Although, in this proof-of-concept study for CYP quantification, the two CYP isoforms were quantified from different samples, there are no practical reasons to prevent multiplexing the method to allow the quantification of multiple CYP isoforms in a single sample.
    • A multivariate analysis of work-life balance outcomes from a large-scale telework programme

      Maruyama, Takao; Hopkinson, Peter G.; James, P. (2009)
      A multivariate analysis identified six predictors to explain positive work-life balance (WLB) among 1,566 teleworkers. Time flexibility variables were found to be most dominant. Gender or having dependent children was not significant. These results demonstrated that controlling working hours was the most important ability for sampled teleworkers to achieve positive WLB.
    • Muscle deterioration due to rheumatoid arthritis: assessment by quantitative MRI and strength testing

      Farrow, Matthew; Biglands, J.; Tanner, S.; Hensor, E.M.A.; Buch, M.H.; Emery, P.; Tan, A.L. (2021-03-02)
      RA patients often present with low muscle mass and decreased strength. Quantitative MRI offers a non-invasive measurement of muscle status. This study assessed whether MRI-based measurements of T2, fat fraction, diffusion tensor imaging and muscle volume can detect differences between the thigh muscles of RA patients and healthy controls, and assessed the muscle phenotype of different disease stages. Thirty-nine RA patients (13 'new RA'-newly diagnosed, treatment naïve, 13 'active RA'-persistent DAS28 >3.2 for >1 year, 13 'remission RA'-persistent DAS28 1 year) and 13 age and gender directly matched healthy controls had an MRI scan of their dominant thigh. All participants had knee extension and flexion torque and grip strength measured. MRI T2 and fat fraction were higher in the three groups of RA patients compared with healthy controls in the thigh muscles. There were no clinically meaningful differences in the mean diffusivity. The muscle volume, handgrip strength, knee extension and flexion were lower in all three groups of RA patients compared with healthy controls. Quantitative MRI and muscle strength measurements can potentially detect differences within the muscles between RA patients and healthy controls. These differences may be seen in RA patients who are yet to start treatment, those with persistent active disease, and those who were in clinical remission. This suggests that the muscles in RA patients are affected in the early stages of the disease and that signs of muscle pathology and muscle weakness are still observed in clinical remission.
    • A muscle mimetic polyelectrolyte–nanoclay organic–inorganic hybrid hydrogel: its self-healing, shape-memory and actuation properties

      Banerjee, S.L.; Swift, Thomas; Hoskins, Richard; Rimmer, Stephen; Singha, N.K. (2019)
      Here in, we describe a non-covalent (ionic interlocking and hydrogen bonding) strategy of self-healing in a covalently crosslinked organic-inorganic hybrid 15 nanocomposite hydrogel, with special emphasize on it's improved mechanical stability. The hydrogel was prepared via in-situ free radical polymerization of sodium acrylate (SA) and successive crosslinking in the presence of poly(2-(methacryloyloxy)ethyl trimethyl ammonium chloride) (PMTAC) grafted cationically armed starch and organically modified montmorillonite (OMMT). This hydrogel shows stimuli triggered self-healing following damage in both neutral and acidic solutions (pH=7.4 and pH=1.2). This was elucidated by tensile strength and rheological analyses of the hydrogel segments joined at their fractured points. Interestingly this hydrogel can show water based shape memory effects. It was observed that the ultimate tensile strength (UTS) of the self-healed hydrogel at pH = 7.4 was comparable to extensor digitorum longus (EDL) muscle of the New Zealand white rabbit. The as synthesized self-healable hydrogel was found to be non-cytotoxic against NIH 3T3 fibroblast cells.
    • The mutagenic activity of ethylmethanesulphonate, benzidine and benzo[a]pyrene at the hprt locus of wild-type L5178Y mouse lymphoma cells

      Kennelly, J.C.; Clare, C.B.; Campbell, J.; Lane, M.P.; Harrington, Dean J.; Cole, H.; Garner, R.C. (1990)
      Ethylmethanesulphonate (EMS), benzidine (BZD) and benzo[a]pyrene (B[a]P) were assayed for ability to induce mutation at the hprt locus of wild-type L5178Y mouse lymphoma cells. EMS was assayed in the absence of metabolic activation, B[a]P in the presence of metabolic activation (S-9 mix) and BZD both in the absence and presence of S-9. Treatment with EMS minus S-9 and B[a]P plus S-9, especially when the S-9 content of the incubation was 2% (v/v), produced strong dose-related increases in mutant frequency. BZD failed to induce mutation at the hprt locus, either in the absence or presence of S-9.
    • A mutant O-GlcNAcase enriches Drosophila developmental regulators

      Selvan, N.; Williamson, Ritchie; Mariappa, D.; Campbell, D.G.; Gourlay, R.; Ferenbach, A.T.; Aristotelous, T.; Hopkins-Navratilova, I.; Trost, M.; van Aalten, D.M.F. (2017)
      Protein O-GlcNAcylation is a reversible post-translational modification of serines/threonines on nucleocytoplasmic proteins. It is cycled by the enzymes O-GlcNAc transferase (OGT) and O-GlcNAc hydrolase (O-GlcNAcase or OGA). Genetic approaches in model organisms have revealed that protein O-GlcNAcylation is essential for early embryogenesis. Drosophila melanogaster OGT/supersex combs (sxc) is a polycomb gene, null mutants of which display homeotic transformations and die at the pharate adult stage. However, the identities of the O-GlcNAcylated proteins involved, and the underlying mechanisms linking these phenotypes to embryonic development, are poorly understood. Identification of O-GlcNAcylated proteins from biological samples is hampered by the low stoichiometry of this modification and limited enrichment tools. Using a catalytically inactive bacterial O-GlcNAcase mutant as a substrate trap, we have enriched the O-GlcNAc proteome of the developing Drosophila embryo, identifying, amongst others, known regulators of Hox genes as candidate conveyors of OGT function during embryonic development.
    • Mutation of the Maturase Lipoprotein Attenuates the Virulence of Streptococcus equi to a Greater Extent than Does Loss of General Lipoprotein Lipidation

      Hamilton, A.; Robinson, C.; Sutcliffe, I.C.; Slater, J.; Maskell, D.J.; Davis-Poynter, N.; Smith, K.; Waller, A.S.; Harrington, Dean J. (2006-12)
      Streptococcus equi is the causative agent of strangles, a prevalent and highly contagious disease of horses. Despite the animal suffering and economic burden associated with strangles, little is known about the molecular basis of S. equi virulence. Here we have investigated the contributions of a specific lipoprotein and the general lipoprotein processing pathway to the abilities of S. equi to colonize equine epithelial tissues in vitro and to cause disease in both a mouse model and the natural host in vivo. Colonization of air interface organ cultures after they were inoculated with a mutant strain deficient in the maturase lipoprotein ( prtM138-213, with a deletion of nucleotides 138 to 213) was significantly less than that for cultures infected with wild-type S. equi strain 4047 or a mutant strain that was unable to lipidate preprolipoproteins ( lgt190-685). Moreover, mucus production was significantly greater in both wild-type-infected and lgt190-685-infected organ cultures. Both mutants were significantly attenuated compared with the wild-type strain in a mouse model of strangles, although 2 of 30 mice infected with the lgt190-685 mutant did still exhibit signs of disease. In contrast, only the prtM138-213 mutant was significantly attenuated in a pony infection study, with 0 of 5 infected ponies exhibiting pathological signs of strangles compared with 4 of 4 infected with the wild-type and 3 of 5 infected with the lgt190-685 mutant. We believe that this is the first study to evaluate the contribution of lipoproteins to the virulence of a gram-positive pathogen in its natural host. These data suggest that the PrtM lipoprotein is a potential vaccine candidate, and further investigation of its activity and its substrate(s) are warranted.