Characterization of the binding site for inhibitors of the HPV11 E1-E2 protein interaction on the E2 transactivation domain by photoaffinity labeling and mass spectrometry

An indandione-containing class of inhibitors abrogates DNA replication of human papillomavirus (HPV) types 6 and 11 by binding reversibly to the transactivation domain (TAD) of the viral E2 protein and inhibiting its interaction with the viral E1 helicase. To locate the binding site of this class of protein-protein interaction inhibitors, a benzophenone derivative was used to generate an irreversibly labeled E2-TAD polypeptide. The single site of covalent modification of the E2-TAD was identified by proteolytic digestions using trypsin, LysC, and V8 proteases and characterization of the resulting peptides by LC-MS procedures. Through this methodology, the benzophenone attachment point was located at the terminal methyl of residue Met101. Evidence further pinpointed the site of photoaffinity attachment to the terminal carbon atom, which is significant in providing a definitive example of the ability to locate photoinduced cross-linking to a polypeptide with atomic resolution using solely mass spectrometric detection. The location of the inhibitor binding site vis-à-vis the Glu39 and Glu100 residues sensitive to mutation for HPV 11 E2-TAD is discussed in relation to the crystal structure of the E2-TAD from the related HPV type 16.     

The yield,fatty acid composition and physical properties of milk fat obtained by feeding soya oil to dairy cows

The presence in the bovine mammary gland of a desaturase specific for the conversion of stearic to oleic acid allows the manipulation of the physical properties of milk fat by varying the dietary intake of C₁₆ and C₁₈ fatty acids. In particular, feeding the dairy cow an oil with a high C₁₈: C₁₆ ratio should allow the proportion of milk fat that is liquid at 5°C to be increased, with a consequent improvement in the low-temperature spreadability of butter. In this paper, the effect of feeding concentrate rations containing (a) soya oil as the free oil and as cracked soya beans; (b) various levels of soya oil, the ration being offered twice or 24-times daily, on the thermal properties of the milk fat and on the yield of milk constituents is examined in detail. Feeding ratios containing free soya oil greatly increased the proportion of milk fat liquid at 5°C, whereas cracked soya oil gave only slight increases. Proportion and yield of milk fat were decreased by feeding soya oil twice daily but were increased by continuous feeding.     

The binary system SrF2-MgF2: Phase diagram and study of growth of SrMgF4

The binary phase diagram of the SrF₂-MgF₂ system below 1200°C has been constructed from DTA cooling data. The system shows an eutectic at 48.4 mole % MgF₂ and 871°C, and a peritectic at 50 mole % and 880°C, corresponding to the compound SrMgF₄, previously prepared here by solid state reaction. A solid-solid transition in SrMgF₄ occurs at about 809°C. Small single crystals of SrMgF₄ were obtained by extremely slow cooling of a stoichiometric melt.     

Terpenoids as major precursors of dissolved organic matter in landfill leachates,surface water,and groundwater

13C NMR analyses of hydrophobic dissolved organic matter (DOM) fractions isolated from a landfill leachate contaminated groundwater near Norman, OK; the Colorado River aqueduct near Los Angeles, CA; Anaheim Lake, an infiltration basin for the Santa Ana River in Orange County, CA; and groundwater from the Tomago Sand Beds, near Sydney, Australia, found branched methyl groups and quaternary aliphatic carbon structures that are indicative of terpenoid hydrocarbon precursors. Significant amounts of lignin precursors, commonly postulated to be the major source of DOM, were found only in trace quantities by thermochemolysis/gas chromatography/mass spectrometry of the Norman Landfill and Tomago Sand Bed hydrophobic DOM fractions. Electrospray/tandem mass spectrometry of the Tomago Sand Bed hydrophobic acid DOM found an ion series differing by 14 daltons, which is indicative of aliphatic and aryl-aliphatic polycarboxylic acids. The product obtained from ozonation of the resin acid, abietic acid, gave a similar ion series. Terpenoid precursors of DOM are postulated to be derived from resin acid paper sizing agents in the Norman Landfill, algal and bacterial terpenoids in the Colorado River and Anaheim Lake, and terrestrial plant terpenoids in the Tomago Sand Beds.     

Reduction of poliovirus 1, bacteriophages,Salmonella montevideo,and Escherichia coli O157:H7 on strawberries by physical and disinfectant washes

The efficacy levels of different physical and chemical washing treatments in the reduction of viral and bacterial pathogens from inoculated strawberries were evaluated. Escherichia coli O157:H7, Salmonella Montevideo, poliovirus 1, and the bacteriophages PRD1, phiX174, and MS2 were used as model and surrogate organisms. Chemicals readily available to producers and/or consumers were evaluated as antimicrobial additives for the production of washes. The gentle agitation of contaminated strawberries in water for 2 min led to reductions in microbial populations ranging from 41 to 79% and from 62 to 90% at water temperatures of 22 and 43 degrees C, respectively. Significant reductions (> 98%) in numbers of bacteria and viruses were obtained with sodium hypochlorite (50 to 300 ppm of free chlorine), Oxine or Carnebon (200 ppm of product generating "stabilized chlorine dioxide"), Tsunami (100 ppm of peroxyacetic acid), and Alcide (100 or 200 ppm of acidified sodium chlorite) washes. Overall, 200 ppm of acidified sodium chlorite produced the greatest reductions of microorganisms. Hydrogen peroxide (0.5%) was slightly less effective than free chlorine in a strawberry wash and caused slight fruit discoloration. Cetylpyridinium chloride (0.1%) was effective in the reduction of bacterial species, while trisodium phosphate (1%) was effective against viruses. The consumer-oriented produce wash Fit was very effective (> 99%) in reducing the numbers of bacteria but not in reducing the numbers of viruses. Another wash, Healthy Harvest, was significantly less effective than Fit in reducing bacterial pathogens but more effective for viruses. The performance of automatic dishwashing detergent was similar to that of Healthy Harvest and significantly better than that of liquid dishwashing detergent. Solutions containing table salt (2% NaCl) or vinegar (10%) reduced the numbers of bacteria by about 90%, whereas only the vinegar wash reduced the numbers of viruses significantly (ca. 95%).     

An Eulerian PDE approach for computing tissue thickness

We outline an Eulerian framework for computing the thickness of tissues between two simply connected boundaries that does not require landmark points or parameterizations of either boundary. Thickness is defined as the length of correspondence trajectories, which run from one tissue boundary to the other, and which follow a smooth vector field constructed in the region between the boundaries. A pair of partial differential equations (PDEs) that are guided by this vector field are then solved over this region, and the sum of their solutions yields the thickness of the tissue region. Unlike other approaches, this approach does not require explicit construction of any correspondence trajectories. An efficient, stable, and computationally fast solution to these PDEs is found by careful selection of finite differences according to an upwinding condition. The behavior and performance of our method is demonstrated on two simulations and two magnetic resonance imaging data sets in two and three dimensions. These experiments reveal very good performance and show strong potential for application in tissue thickness visualization and quantification.     

Determination of N-glycosylation sites and site heterogeneity in glycoproteins

An approach for the characterization of glycosylation sites and oligosaccharide heterogeneity in glycoproteins based on a combination of nonspecific proteolysis, deglycosylation, and matrix-assisted laser desorption/ionization Fourier transform mass spectrometry (MALDI-FT MS) is described. Glycoproteins were digested with Pronase yielding primarily glycopeptides and amino acids. Nonglycosylated peptide fragments were susceptible to complete Pronase digestion to their constituent amino acids. Steric hindrance prohibited the digestion of the peptide moiety attached to the glycan. Glycopeptides were desalted and concentrated using solid-phase extraction and analyzed by MALDI MS. The oligosaccharides were also analyzed by MALDI MS after releasing the glycans from glycoproteins using PNGase F. The peptide moiety of the glycopeptides was identified by subtracting the masses of the glycans derived from PNGase F treatment from the masses of the glycopeptides. The experimental strategy was validated using glycoproteins with known oligosaccharide structures, ribonuclease B and chicken ovalbumin. This procedure was then used to determine the N-glycosylation sites and site heterogeneity of a glycoprotein whose glycosylation pattern was unknown, namely, the Xenopus laevis egg cortical granule lectin. This procedure is useful for determining protein site heterogeneity and structural heterogeneities of the oligosaccharide moiety of glycoproteins.     

Gallium arsenide deep-level optical emitter for fibre optics

Fibre-optic components fabricated on the same substrate as integrated circuits are important for future high-speed communications. One industry response has been the costly push to develop indium phosphide (InP) electronics. However, for fabrication simplicity, reliability and cost, gallium arsenide (GaAs) remains the established technology for integrated optoelectronics. Unfortunately, the GaAs bandgap wavelength (0.85 microm) is far too short for fibre optics at 1.3-1.5 microm. This has led to work on materials that have a large lattice mismatch on GaAs. Here we demonstrate the first light-emitting diode (LED) that emits at 1.5 microm fibre-optic wavelengths in GaAs using optical transitions from arsenic antisite (As(Ga)) deep levels. This is an enabling technology for fibre-optic components that are lattice-matched to GaAs integrated circuits. We present experimental results showing significant internal optical power (24 mW) and speed (in terahertz) from GaAs optical emitters using deep-level transitions. Finally, we present theory showing the ultimate limit to the efficiency-bandwidth product of semiconductor deep-level optical emitters.     

Dialysis Disequilibrium Syndrome Revisited

An aggressive dialysis in a grossly azotemic patient, especially one with severe metabolic acidosis, can lead to dialysis disequilibrium syndrome (DDS). Mild forms present as nausea, vomiting, restlessness, and headache. Severe manifestations include seizures, obtundation, coma, and even death. This clinical picture is caused by cerebral edema induced by one or more of the following mechanisms:

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The chemistry of Norwegian groundwaters: IV. The pH-dependence of element concentrations in crystalline bedrock groundwaters

A total of 1604 samples of crystalline bedrock groundwaters in Norway have been analysed for pH, major and minor elements. A subset of 476 samples were also analysed for a wide range of trace elements by ICP-MS. The pH of the samples ranges from 5.4 to 9.8, with a predominance of pH values between 8.0 and 8.2. The data-set is divided into five 20-percentile groups according to increasing pH. The concentrations of 60 elements are then displayed as box-plots for each pH group. A line through the five medians yields a visual demonstration of the relationship with, and sensitivity to, pH variations for concentrations of each element. Twelve characteristic trends are distinguishable, from which some of the main hydrogeochemical processes related to pH and groundwater evolution can be inferred.