Imaging real-time aggregation of amyloid beta protein (1-42) by atomic force microscopy

Amyloid beta protein (AbetaP) is the major fibrillar constituent of senile plaques. However, no causative role for AbetaP-fibers in Alzheimer's disease (AD) pathology is established. Globular AbetaPs are continuously released during normal cellular metabolism at pico- to nano-molar concentration. We used atomic force microscopy (AFM) to examine aggregation of freshly prepared AbetaP(1-42) and to examine the role of AbetaP concentration, imaging medium (air, water, or PBS) and agonists/antagonists on AbetaP-fibrillogenesis. At even very high and non-physiological AbetaP concentrations, 24-48 h of real-time AFM imaging (a) in water show only multiple layers of globular aggregates and no fibrils and (b) in PBS show mainly the globular structures and some short fibrils. On-line addition of Zn, an agonist for AbetaP-fibrillogenesis, induced a slow but non-fibrillar aggregation of globular AbetaPs. EDTA, a chelator of Zn and calcium (a modulator of AbetaP-mediated toxicity) induced a reversible change in the Zn-mediated aggregation. These results strongly suggest that no AbetaP-fibers are formed for the physiologically relevant concentration and thus the plaque-associated fibers may not account for the AD pathophysiology.     

Resolution of a complex ionic mixture of an apparently homogenous protein preparation by preparative electrophoresis

Preparations of recombinant envelope glycoprotein E2 of hepatitis C virus (r-HCV E2), found to be homogeneous by N-terminal amino acid sequencing and mass spectrometry, resolved into multiple ionic species (isoforms) when analysed by isoelectric focusing (IEF) gel electrophoresis in the p1 range of 3-10. These isoforms possessed pI values in the range of 4.5-8.2. The major isoform with p1 value of approximately 7.1 was separated from the rest of them by employing a method developed on Gradiflow BF 200, a device based on preparative electrophoresis. This isoform was adjudged to be homogenous by IEF and by native polyacrylamide gel electrophoresis (PAGE).     

Ivermectin and nodulisporic acid receptors in Drosophila melanogaster contain both gamma-aminobutyric acid-gated Rdl and glutamate-gated GluCl alpha chloride channel subunits

35S-labeled derivatives of the insecticides nodulisporic acid and ivermectin were synthesized and demonstrated to bind with high affinity to a population of receptors in Drosophila head membranes that were previously shown to be associated with a glutamate-gated chloride channel. Nodulisporic acid binding was modeled as binding to a single population of receptors. Ivermectin binding was composed of at least two kinetically distinct receptor populations, only one of which was associated with nodulisporic acid binding. The binding of these two ligands was modulated by glutamate, ivermectin, and antagonists of invertebrate gamma-aminobutyric acid (GABA)ergic receptors. Because solubilized nodulisporic acid and ivermectin receptors comigrated as 230-kDa complexes by gel filtration, antisera specific for both the Drosophila glutamate-gated chloride channel subunit GluCl alpha (DmGluCl alpha) and the GABA-gated chloride channel subunit Rdl (DmRdl) proteins were generated and used to examine the possible coassembly of these two subunits within a single receptor complex. DmGluCl alpha antibodies immunoprecipitated all of the ivermectin and nodulisporic acid receptors solubilized by detergent from Drosophila head membranes. DmRdl antibodies also immunoprecipitated all solubilized nodulisporic receptors, but only approximately 70% of the ivermectin receptors. These data suggest that both DmGluCl alpha and DmRdl are components of nodulisporic acid and ivermectin receptors, and that there also exists a distinct class of ivermectin receptors that contains the DmGluCl alpha subunit but not the DmRdl subunit. This co-association of DmGluCl alpha and DmRdl represents the first biochemical and immunological evidence of coassembly of subunits from two different subclasses of ligand-gated ion channel subunits.     

Properties of Air Dried Radiation Processed Amniotic Membranes under Different Storage Conditions

Amniotic membranes collected from the placentae of screened donors were processed, air dried and sterilized by gamma irradiation at 25 kGy. Effect of storage under different temperature and humidity conditions (10 degrees C, RH 80-90%; 10 degrees C, RH 40-50%; 40 degrees C, RH 50-60% and 40 degrees C, RH 10-20%) on the properties of the membrane were examined. Infrared (IR) spectral scanning was carried out to examine degradation or change if any in the tissue under different storage conditions. The degradation of amnion on irradiation with gamma rays or during storage after irradiation would tend to produce the relative variation in IR absorption troughs. This kind of addendum was absent in all the samples indicating no qualitative change in the material property of amnion. Water absorption and water vapour transmission rate (WVTR) of the membrane remained unchanged even after 6 months. No effect on the microbial permeability of membrane was observed during storage. The amniotic membranes were found to be impermeable to different strains of bacteria - Bacillus, Escherichia coli, Pseudomonas, Citrobacter, Flavimonas and Staphylococcus. The results indicate that amniotic membranes processed by air-drying are stable and can be stored under different environmental conditions without compromise to their clinical performance.     

A pheromonotropic peptide of Helicoverpa zea,with melanizing activity,interaction with PBAN,and distribution of immunoreactivity

The sequence of an 18-amino acid residue peptide was deduced from the gene encoding PBAN and other peptides with common C-termini in Helicoverpa zea. The peptide caused melanization in larvae and pheromone production in females of H. zea, and was designated pheromonotropic melanizing peptide (Hez-PMP). The peptide has a 83% sequence homology with a pheromonotropic peptide isolated from Pseudaletia separata. PMP caused melanization and mortality when injected into larvae just before molting. Whereas intense melanization was caused with a dose of 1,000 pmol, peak mortality occurred at 100 pmol, with 50% of larvae dying within 48 h after injection. Pheromonotropic activity of PMP was dose dependent. Co-injection of Hez-PMP and Hez-PBAN into a female resulted in suppression of the pheromonotropic effect of PBAN. Whole-mount immunocytochemical studies revealed PMP-like immunoreactivity in frontal ganglion, subesophageal, thoracic, and abdominal ganglia as well as the esophageal nerve.     

Identification of potent inhibitors of Helicoverpa armigera gut proteinases from winged bean seeds

Dry mature seeds of winged bean (Psophocarpus tetragonolobus L., DC.) (WB) contain several proteinase inhibitors. Two-dimensional gel analysis of WB seed protein followed by activity visualization using a gel-X-ray film contact print technique revealed at least 14 trypsin inhibitors (TIs) in the range of 28-6 kD. A total of seven inhibitors (WBTI-1 to 7) were purified by heat treatment and gel filtration followed by elution from preparative native gels. Based on their biochemical characterization such as molecular mass, pI, heat stability, and susceptibility to inactivation by reducing agents, WBTI-1 to 4 are Kunitz type inhibitors while WBTI-5 to 7 are classified as Bowman-Birk type serine proteinase inhibitors. Although Kunitz type TIs (20-24 kD) of WB have been reported, the smaller TIs that belong to the Bowman-Birk type have not been previously characterized. Seven major TIs isolated from WB seed were individually assessed for their potential to inhibit the gut proteinases (HGP) of Helicoverpa armigera, a pest of several economically important crops, which produces at least six major and several minor trypsin/chymotrypsin/elastase-like serine proteinases in the gut. WBTI-1 (28 kD) was identified as a potent inhibitor of HGP relative to trypsin and among the other WBTIs; it inhibited 94% of HGP activity while at the same concentration it inhibited only 22% of trypsin activity. WBTI-2 (24 kD) and WBTI-4 (20 kD) inhibited HGP activity greater than 85%. WBTI-3,-5,-6 and-7 showed limited inhibition of HGP as compared with trypsin. These results indicate that WBTIs have different binding potentials towards HGP although most of the HGP activity is trypsin-like. We also developed a simple and versatile method for identifying and purifying proteinase inhibitors after two-dimensional separation using the gel-X-ray film contact print technique.     

Metal chelate affinity precipitation of RNA and purification of plasmid DNA

The affinity of metal chelates for amino acids, such as histidine, is widely used in purifying proteins, most notably through six-histidine `tails'. We have found that metal affinity interactions can also be applied to separation of single-stranded nucleic acids through interactions involving exposed purines. Here we describe a metal affinity precipitation method to resolve RNA from linear and plasmid DNA. A copper-charged copolymer of N-isopropyl acrylamide (NIPAM) and vinyl imidazole (VI) is used to purify plasmid from an alkaline lysate of E. coli. The NIPAM units confer reversible solubility on the copolymer while the imidazole chelates metal ions in a manner accessible to interaction with soluble ligands. RNA was separated from the plasmid by precipitation along with the polymer in the presence of 800 mM NaCl. Bound RNA could be recovered by elution with imidazole and separated from copolymer by a second precipitation step. RNA binding showed a strong dependence on temperature and on the type of buffer used.     

Conjugation of penicillin acylase with the reactive copolymer of N-isopropylacrylamide: a step toward a thermosensitive industrial biocatalyst

Conjugation of penicillin acylase (PA) to poly-N-isopropylacrylamide (polyNIPAM) was studied as a way to prepare a thermosensitive biocatalyst for industrial applications to antibiotic synthesis. Condensation of PA with the copolymer of NIPAM containing active ester groups resulted in higher coupling yields of the enzyme (37%) compared to its chemical modification and copolymerization with the monomer (9% coupling yield) at the same NIPAM:enzyme weight ratio of ca. 35. A 10-fold increase of the enzyme loading on the copolymer resulted in 24% coupling yield and increased by 4-fold the specific PA activity of the conjugate. Two molecular forms of the conjugate were found by gel filtration on Sepharose CL 4B: the lower molecular weight fraction of ca. 10(6) and, presumably, cross-linked protein-polymer aggregates of MW > 10(7). Michaelis constant for 5-nitro-3-phenylacetamidobenzoic acid hydrolysis by the PA conjugate (20 microM) was found to be slightly higher than that of the free enzyme (12 microM), and evaluation of V(max) testifies to the high catalytic efficiency of the conjugated enzyme. PolyNIPAM-cross-linked PA retained its capacity to synthesize cephalexin from d-phenylglycin amide and 7-aminodeacetoxycephalosporanic acid. The synthesis-hydrolysis ratios of free and polyNIPAM-cross-linked enzyme in cephalexin synthesis were 7.46 and 7.49, respectively. Thus, diffusional limitation, which is a problem in the industrial production of beta-lactam antibiotics, can be successfully eliminated by cross-linking penicillin acylase to a smart polymer (i.e., polyNIPAM).     

Production of phytase by Mucor racemosus in solid-state fermentation

Phytase production was studied by three Mucor and eight Rhizopus strains by solid-state fermentation (SSF) on three commonly used natural feed ingredients (canola meal, coconut oil cake, wheat bran). Mucor racemosus NRRL 1994 (ATCC 46129) gave the highest yield (14.5 IU/g dry matter phytase activity) on coconut oil cake. Optimizing the supplementation of coconut oil cake with glucose, casein and (NH(4))(2)SO(4), phytase production in solid-state fermentation was increased to 26 IU/g dry matter (DM). Optimization was carried out by Plackett-Burman and central composite experimental designs. Using the optimized medium phytase, alpha-amylase and lipase production of Mucor racemosus NRRL 1994 was compared in solid-state fermentation and in shake flask (SF) fermentation. SSF yielded higher phytase activity than did SF based on mass of initial substrate. Because this particular isolate is a food-grade fungus that has been used for sufu fermentation in China, the whole SSF material (crude enzyme, in situ enzyme) may be used directly in animal feed rations with enhanced cost efficiency.