Glycan analysis of the chicken synaptic plasma membrane glycoproteins - a major synaptic N-glycan carries the LewisX determinant

The majority of plasma membrane components are glycosylated. It is now widely accepted that this post-translational modification is crucial during the establishment, maintenance and function of the nervous system. Despite its significance, structural information about the glycosylation of nervous system specific glycoproteins is very limited. In the present study the major glycan structure of the chicken synaptic plasma membrane (SPM) associated glycoprotein glycans were determined. N-glycans were released by hydozinnolysis, labelled with 2-aminobenzam,ide, treated with neuraminidase and subsequently fractionated by size exclusion chromatography. Individual fractions were characterized by combination of high-pressure liquid chromatography, exoglicosidase treatment or reagent array analysis method (RAAM). In addition to oligomannose-type glycans, core-fucosylated complex glycans with biantennary bisecting glycans carrying the LewisX epitope were most abundant. The overall chicken glycan profile was strikingly similar to the rat brain glycan profile. The presence of the LewisX determinant in relatively large proportions suggests a tissue-specific function for these glycans

The inverse problem of determining the filtration function and permeability reduction in flow of water with particles in porous media

The original publication can be found at www.springerlink.comDeep bed filtration of particle suspensions in porous media occurs during water injection into oil reservoirs, drilling fluid invasion of reservoir production zones, fines migration in oil fields, industrial filtering, bacteria, viruses or contaminants transport in groundwater etc. The basic features of the process are particle capture by the porous medium and consequent permeability reduction. Models for deep bed filtration contain two quantities that represent rock and fluid properties: the filtration function, which is the fraction of particles captured per unit particle path length, and formation damage function, which is the ratio between reduced and initial permeabilities. These quantities cannot be measured directly in the laboratory or in the field; therefore, they must be calculated indirectly by solving inverse problems. The practical petroleum and environmental engineering purpose is to predict injectivity loss and particle penetration depth around wells. Reliable prediction requires precise knowledge of these two coefficients. In this work we determine these quantities from pressure drop and effluent concentration histories measured in one-dimensional laboratory experiments. The recovery method consists of optimizing deviation functionals in appropriate subdomains; if necessary, a Tikhonov regularization term is added to the functional. The filtration function is recovered by optimizing a non-linear functional with box constraints; this functional involves the effluent concentration history. The permeability reduction is recovered likewise, taking into account the filtration function already found, and the functional involves the pressure drop history. In both cases, the functionals are derived from least square formulations of the deviation between experimental data and quantities predicted by the model.Alvarez, A. C., Hime, G., Marchesin, D., Bedrikovetski, P

Analysis of potentially mobile phosphorus in arable soils using solid state nuclear magnetic resonance

In many intensive agroecosystems continued inputs of phosphorus (P) over many years can significantly increase soil P concentrations and the risk of P loss to surface waters. For this study we used solid-state ³¹P nuclear magnetic resonance (NMR) spectroscopy, high-power decoupling with magic angle spinning (HPDec–MAS) NMR, and cross polarization with magic angle spinning (CP–MAS) NMR to determine the chemical nature of potentially mobile P associated with aluminum (Al) and calcium (Ca) in selected arable soils. Three soils with a range of bicarbonate-extractable Olsen P concentrations (40–102 mg P kg⁻¹) were obtained from a long-term field experiment on continuous root crops at Rothamsted, UK, established in 1843 (sampled 1958). This soil has a threshold or change point at 59 mg Olsen P kg⁻¹, above which potentially mobile P (as determined by extraction with water or 0.01 M CaCl₂) increases much more per unit increase in Olsen P than below this point. Results showed that CaCl₂ and water preferentially extracted Al-P and Ca-P forms, respectively, from the soils. Comparison among the different soils also indicated that potentially mobile P above the threshold was largely present as a combination of soluble and loosely adsorbed (protonated–cross polarized) P forms largely associated with Ca, such as monetite (CaHPO₄) and dicalcium phosphate dihydrate (CaHPO₄·2H₂O), and some Al-associated P as wavellite. The findings of this study demonstrate that solid-state NMR has the potential to provide accurate information on the chemical nature of soil P species and their potential mobility