Reversible covalent immobilization of ligands and proteins on polyacrylamide gels

Ligands and proteins were covalently but reversibly immobilized on polyacrylamide gels using novel acrylic monomers whose syntheses are reported here. These reagents have an acrylyl group at one end for copolymerization into gels, an N-succinimidyl ester at the other allowing rapid immobilization of molecules having an available primary amino group, and a cleavable disulfide bond in the middle. Two immobilization methods were developed using these reagents. In the first method, a ligand with a primary amino group was treated with the immobilization reagent in anhydrous ethanol and the resulting amide derivative was purified and copolymerized with acrylamide and bisacrylamide resulting in the desired reversible immobilization. In the second method, the immobilization reagents (at densities up to 50 mumol/ml) were directly copolymerized with acrylamide and bisacrylamide to form activated gels of the desired shape and porosity. Proteins or other ligands in aqueous buffers were then added to the activated gels resulting in their covalent immobilization. Ligands or proteins immobilized using the methods reported here remained stably bound even when gels were subjected to boiling in detergents or high-ionic-strength buffers. Immobilized ligands were readily released (greater than 97%) from gels by treatment with quantitative amounts of aqueous dithiothreitol (DTT) under mild conditions. Immobilized proteins were also released (up to 87%) from the gels by DTT treatment. Small ligands (e.g., aminohexyl glycosides), active enzymes, and glycoproteins were immobilized, and then recovered, using these reagents.     

Multiple carbohydrate receptors on lymphocytes revealed by adhesion to immobilized polysaccharides

Phosphomannan polysaccharides and fucoidan, a polymer of fucose 4-sulfate, have been demonstrated to inhibit adhesion of lymphocytes to tissue sections that contain high endothelial venules (Stoolman, L. M., T. S. Tenforde, and S. D. Rosen, 1984, J. Cell Biol., 99:1535-1540). We have investigated the potential cell surface carbohydrate receptors involved by quantitating adhesion of rat cervical lymph node lymphocytes to purified polysaccharides immobilized on otherwise inert polyacrylamide gels. One-sixth of the lymphocytes adhered specifically to surfaces derivatized with PPME (a phosphomannan polysaccharide prepared from Hansenula holstii yeast), whereas up to half of the cells adhered to surfaces derivatized with fucoidan. Several lines of evidence demonstrated that two distinct receptors were involved. Adhesion to PPME-derivatized gels was labile at 37 degrees C (decreasing to background levels within 120 min) whereas adhesion to fucoidan-derivatized gels was stable. Soluble PPME and other phosphomannans blocked adhesion only to PPME-derivatized gels; fucoidan and a structurally related fucan blocked adhesion to fucoidan-derivatized gels. Other highly charged anionic polysaccharides, such as heparin, did not block adhesion to either polysaccharide-derivatized gel. Adhesion to PPME-derivatized gels was dependent on divalent cations, whereas that to fucoidan-derivatized gels was not. The PPME-adherent lymphocytes were shown to be a subpopulation of the fucoidan-adhesive lymphocytes which contained both saccharide receptors. These data reveal that at least two distinct carbohydrate receptors can be found on peripheral lymphocytes.     

Tumor cell haptotaxis on immobilized N-acetylglucosamine gradients

Polyacrylamide surfaces covalently derivatized with quantifiable gradients of glycosides superimposed on a uniform adhesive background of coimmobilized Arg-Gly-Asp-containing adhesion peptide were synthesized. Substrate-directed cell redistribution (haptotaxis) was measured by seeding derivatized surfaces uniformly with B16F10 murine melanoma cells. After 4-32 hr, cells on gradients of N-acetylglucosamine (GlcNAc) redistributed markedly; higher cell densities were found at gel positions having a higher immobilized GlcNAc density. In contrast, cells seeded on otherwise identical gels having a uniform concentration of immobilized GlcNAc, or on gels having gradients of glucose or galactose, did not redistribute. Soluble inhibitors containing nonreducing terminal GlcNAc (but not those with terminal GalNAc or Gal) blocked redistribution on immobilized GlcNAc gradients. Redistribution was not affected by the presence or absence of serum in the medium. An affinity-purified antibody against beta-1,4-galactosyltransferase, a GlcNAc-binding protein reported to be expressed on B16F10 cell surfaces, attenuated GlcNAc-directed redistribution. When cells were seeded on surfaces derivatized with various uniform densities of immobilized GlcNAc coimmobilized with an invariant density of immobilized Arg-Gly-Asp-peptide, neither cell attachment nor proliferation rate were enhanced on the gels having a higher GlcNAc density. These data indicate that the redistribution on immobilized GlcNAc gradients was due to cell motility. Although gels derivatized with Arg-Gly-Asp-peptide alone supported strong B16F10 cell adhesion, surfaces derivatized with uniform high concentrations of GlcNAc did not. We conclude that cell recognition of substratum gradients that support, at best, weak adhesion (GlcNAc) on an otherwise uniform strongly adhesive background (Arg-Gly-Asp-peptide) may be sufficient to direct cell migration.     

Patterns of Root Colonization in Epacridaceous Plants Collected from Different Sites

Root colonization was studied in ten species of the Epacridaceaeat three sites in Victoria by morphological and cross-inoculationexperiments. The sites and genera chosen were Cranbourne [Epacrisimpressa Labill. andLeucopogon ericoides(Smith) R. Br.] andRye [L. parviflorus(Andrews) Lindley] on the Mornington Peninsula,and the Grampians[Astroloma conostephioides(Sond.) Benth.,A.humifusum(Cav.) R. Br.,A pinifolium(R. Br.) Benth,Brachylomadaphnoides(Smith) Benth.,E. impressa, E. impressavar.grandifloraBenth.andStyphelia adscendensR. Br.] in western Victoria. For morphologicalstudies, samples of roots from each species at each site werecleared and stained and examined microscopically. For cross-inoculationstudies, cuttings from each site were struck in potting mediuminoculated with soil from the same and other sites. The ericoidmycorrhizae in the roots of plants found at or grown in Cranbourneand Rye soils were similar. Both were significantly differentfrom the internal hyphae found in the roots of plants foundat or grown in Grampians soils, which were three times largerin diameter and formed dense coils which filled the host celland invaded adjacent epidermal cells. This suggests that morethan one fungus is involved in the relationships, that the MorningtonPeninsula sites had a different fungus from the Grampians siteand that host specificity is low. Vesicular structures werealso found commonly on plants at the Grampians site, in contrastwith other sites. Epacridaceae; root; fungus; mycorrhiza; morphology; inoculation     

Ultrasound imaging in an experimental model of fatty liver disease and cirrhosis in rats

Background

Atypical scrapie was first identified in Norwegian sheep in 1998 and has subsequently been identified in many countries. Retrospective studies have identified cases predating the initial identification of this form of scrapie, and epidemiological studies have indicated that it does not conform to the behaviour of an infectious disease, giving rise to the hypothesis that it represents spontaneous disease. However, atypical scrapie isolates have been shown to be infectious experimentally, through intracerebral inoculation in transgenic mice and sheep. The first successful challenge of a sheep with 'field' atypical scrapie from an homologous donor sheep was reported in 2007.

Results

This study demonstrates that atypical scrapie has distinct clinical, pathological and biochemical characteristics which are maintained on transmission and sub-passage, and which are distinct from other strains of transmissible spongiform encephalopathies in the same host genotype.

Conclusions

Atypical scrapie is consistently transmissible within AHQ homozygous sheep, and the disease phenotype is preserved on sub-passage.     

Mapping of citrullinated fibrinogen B-cell epitopes in rheumatoid arthritis by imaging surface plasmon resonance

Introduction  

Rheumatoid arthritis (RA) frequently involves the loss of tolerance to citrullinated antigens, which may play a role in pathogenicity. Citrullinated fibrinogen is commonly found in inflamed synovial tissue and is a frequent target of autoantibodies in RA patients. To obtain insight into the B-cell response to citrullinated fibrinogen in RA, its autoepitopes were systematically mapped using a new methodology.     

Quantification of global transcription patterns in prokaryotes using spotted microarrays

We describe an analysis, applicable to any spotted microarray dataset produced using genomic DNA as a reference, that quantifies prokaryotic levels of mRNA on a genome-wide scale. Applying this to Mycobacterium tuberculosis, we validate the technique, show a correlation between level of expression and biological importance, define the complement of invariant genes and analyze absolute levels of expression by functional class to develop ways of understanding an organism's biology without comparison to another growth condition.     

An annotated catalogue of salivary gland transcripts in the adult female mosquito, Ædes ægypti*

Background

The number of completely sequenced plastid genomes available is growing rapidly. This array of sequences presents new opportunities to perform comParative analyses. In comParative studies, it is often useful to compare across wide phylogenetic spans and, within angiosperms, to include representatives from basally diverging lineages such as the genomes reported here: Nuphar advena (from a basal-most lineage) and Ranunculus macranthus (a basal eudicot). We report these two new plastid genome sequences and make comparisons (within angiosperms, seed plants, or all photosynthetic lineages) to evaluate features such as the status of ycf15 and ycf68 as protein coding genes, the distribution of simple sequence repeats (SSRs) and longer dispersed repeats (SDR), and patterns of nucleotide composition.

Results

The Nuphar [GenBank:NC_008788] and Ranunculus [GenBank:NC_008796] plastid genomes share characteristics of gene content and organization with many other chloroplast genomes. Like other plastid genomes, these genomes are A+T-rich, except for rRNA and tRNA genes. Detailed comparisons of Nuphar with Nymphaea, another Nymphaeaceae, show that more than two-thirds of these genomes exhibit at least 95% sequence identity and that most SSRs are shared. In broader comparisons, SSRs vary among genomes in s of abundance and length and most contain repeat motifs based on A and T nucleotides.

Conclusion

SSR and SDR abundance varies by genome and, for SSRs, is proportional to genome size. Long SDRs are rare in the genomes assessed. SSRs occur less frequently than predicted and, although the majority of the repeat motifs do include A and T nucleotides, the A+T bias in SSRs is less than that predicted from the underlying genomic nucleotide composition. In codon usage third positions show an A+T bias, however variation in codon usage does not correlate with differences in A+T-richness. Thus, although plastome nucleotide composition shows "A+T richness", an A+T bias is not apparent upon more in-depth analysis, at least in these aspects. The pattern of evolution in the sequences identified as ycf15 and ycf68 is not consistent with them being protein-coding genes. In fact, these regions show no evidence of sequence conservation beyond what is normal for non-coding regions of the IR.