A high-throughput microscale method to release N-linked oligosaccharides from glycoproteins for matrix-assisted laser desorption/ionization time-of-flight mass spectrometric analysis

This report describes a convenient method for the rapid and efficient release of N-linked oligosaccharides from low microgram amounts of glycoproteins. A 96-well MultiScreen assay system containing a polyvinylidene difluoride (PVDF) membrane is employed to immobilize glycoproteins for subsequent enzymatic deglycosylation. Recombinant tissue-type plasminogen activator (rt-PA) is used to demonstrate the deglycosylation of 0.1-50 micrograms of a glycoprotein. This method enabled the recovery of a sufficient amount of N-linked oligosaccharides released enzymatically with peptide N-glycosidase F (PNGaseF) from as little as 0.5 microgram rt-PA for subsequent analysis by matrix-assisted laser desorption/ionization time-of-flight (MALDI- TOF) mass spectrometry. The immobilization of rt-PA to the PVDF membrane did not sterically inhibit the PNGaseF-mediated release of oligosaccharides from rt-PA as determined by tryptic mapping experiments. Comparison of the oligosaccharides released from 50 micrograms of rt-PA by either the 96-well plate method or by a standard solution digestion procedure showed no significant differences in the profiles obtained by high-pH anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD). Both neutral and sialylated oligosaccharide standards spiked into wells were recovered equally as determined by HPAEC-PAD. One advantage of this approach is that reduction and alkylation can be performed on submicrogram amounts of glycoproteins with easy removal of reagents prior to PNGaseF digestion. In addition, this method allows 60 glycoprotein samples to be deglycosylated in 1 day with MALDI-TOF or HPAEC-PAD analysis being performed on the following day.      

Irradiation induces G2/M cell cycle arrest and apoptosis in p53-deficient lymphoblastic leukemia cells without affecting Bcl-2 and Bax expression

The tumor suppressor p53 has been implicated in gamma irradiation-induced apoptosis. To investigate possible consequences of wild-type p53 loss in leukemia, we studied the effect of a single dose of gamma irradiation upon p53-deficient human T-ALL (acute lymphoblastic leukemia) CCRF - CEM cells. Exposure to 3 - 96 Gy caused p53-independent cell death in a dose and time-dependent fashion. By electron microscopic and other criteria, this cell death was classified as apoptosis. At low to intermediate levels of irradiation, apoptosis was preceded by accumulation of cells in the G2/M phase of the cell division cycle. Expression of Bcl-2 and Bax were not detectably altered after irradiation. Expression of the temperature sensitive mouse p53 V135 mutant induced apoptosis on its own but only slightly increased the sensitivity of CCRF - CEM cells to gamma irradiation. Thus, in these, and perhaps other leukemia cells, a p53- and Bcl-2/Bax-independent mechanism is operative that efficiently senses irradiation effects and translates this signal into arrest in the G2/M phase of the cell cycle and subsequent apoptosis.     

High-performance chromatographic assay for the sulphoxide metabolite of 2′-deoxy-3′-thiacytidine in human urine

A high-performance liquid chromatographic method is described for the determination in human urine of GI138870X, the sulphoxide metabolite of a novel dideoxynucleoside analogue, 2′-deoxy-3′-thiacytidine (lamivudine). GI138870X was extracted from human urine using Empore SDB RPS solid-phase extraction disks prior to reversed-phase chromatography with UV detection. The method has shown to be valid over the concentration range 0.5–100 μg/ml using a 0.5-ml sample volume.     

Some properties of the nickel-containing hydrogenase of chemolithotrophically grown Rhizobium japonicum.

The uptake hydrogenase of chemolithotrophically grown Rhizobium japonicum was purified to apparent homogeneity with a final specific activity of 69 mumol of H2 oxidized per min per mg of protein. The procedure included Triton extraction of broken membranes and DEAE-cellulose and Sephacryl S-200 chromatographies. The purified protein contained two polypeptides separable only by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. They comigrated on native polyacrylamide gels and sucrose density gradients. The molecular weights were ca. 60,000 and 30,000. Densitometric scans of the sodium dodecyl sulfate gels indicated a molar ratio of 1.03 +/- 0.03. Antiserum was developed against the 60-kilodalton polypeptide for use in hydrogenase detection by an enzyme-linked immunosorbent assay. The antiserum did not cross-react with the 30-kilodalton polypeptide. Native gel electrophoresis of Triton-extracted cells grown in the presence of 63Ni showed comigration of the hydrogenase and radioactive Ni.     

NONCONFIRMATION OF NODULATION IN ARTEMISIA LUDOVICIANA

Reports of nodulation and nitrogen fixation specifically associated with nodules or insect galls of Artemisia ludoviciana were not confirmed.     

Resolution of two subunits from the molybdenum-iron protein of Azotobacter vinelandii nitrogenase

The Mo-Fe protein of Azotobacter vinelandii nitrogenase was fractionated on 9.5 M urea isoelectric focusing gels and gave three distinct bands (alpha', alpha", beta'). Protein focused on nondenaturing gels gave a single brown band, which when excised and refocused on a denaturing gel gave the three-band pattern. Partial trypsin digestion of the subunits and fractionation of the peptides by sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicated that the alpha' and alpha" polypeptide moieties were the same. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the alpha' and beta' proteins with appropriate molecular weight standards indicated Mr = 61,000 and 57,000, respectively. This is consistent with an overall alpha 2 beta 2 mass of 236,000 daltons.     

On the multiplicity of platelet prostaglandin receptors. I. Evaluation of competitive antagonism by aggregometry

Methods for the evaluation of competitive interactions at receptors associated with platelet activation and inhibition using aggregometry of human PRP have been developed. The evidence supports the suggestion that PGE1 and PGI2 share a common receptor for inhibition of platelet reactivity, but only a portion (if any) of the aggregation stimulation associated with PGE2 is the result of PGE2 binding (without efficacy) to this receptor. PGE2 (at .3-20 microM) is an effective antagonist of PGE1, PGI2, and PGD2 producing a shift of about one order of magnitude in the IC50-values obtained from complete aggregation inhibition dose response curves. The antagonism of PGD2 inhibition is particularly notable, 80 nM PGE2 levels are detectable. This and other actions of PGE2 indicate another platelet receptor for PGE2. PGE1 acts at both the PGE2 and PGI2 receptor. Other substances showing PGI2-like actions only at high doses (1-30 microM), display additive responses with PGI2 indicative of decreased affinity for the I2/E1 receptor and the absence of PGE2-like aggregation stimulation activity. PGI2 methyl ester has intrinsic inhibitory action not associated with in situ ester hydrolysis. The methyl ester is dissaggregatory showing particular specificity for inhibition of release and second wave aggregation.     

Binding of the snake venom-derived proteins applaggin and echistatin to the arginine-glycine-aspartic acid recognition site(s) on platelet glycoprotein IIb.IIIa complex inhibits receptor function

In the present report we describe the platelet-binding characteristics of applaggin and echistatin, potent inhibitors of fibrinogen-dependent platelet aggregation derived from Agkistrodon piscivorus piscivorus and Echis carinatus snake venoms, respectively. Both molecules bound to unstimulated platelets in a specific and saturable manner. At saturation there were 37,100 +/- 3,150 (mean, +/- S.D.) molecules of applaggin and 27,200 +/- 2,816 molecules of echistatin bound/platelet, with dissociation constants (Kd) of 1.4 +/- 0.6 x 10(-7) M and 4.9 +/- 1.2 x 10(-7) M, respectively. Stimulation of platelets with ADP (10 microM) + epinephrine (2 microM) resulted in an increase in the number of molecules bound at saturation to 42,300 +/- 2,105 for applaggin and 32,185 +/- 3,180 for echistatin, with a Kd of 5.6 +/- 0.3 x 10(-8) M and 1.8 +/- 0.6 x 10(-7) M, respectively. The synthetic peptide (Arg)8-Gly-Asp-Val was a competitive antagonist of applaggin and echistatin binding to unstimulated platelets (Ki = 25 and 36 microM, respectively). Applaggin and echistatin inhibited the binding of fibrinogen to stimulated platelets in a dose-dependent manner, with an IC50 of 9 and 25 nM, respectively. In concert with inhibition of platelet aggregation, applaggin and echistatin inhibited platelet secretion and synthesis of thromboxane A2 induced by ADP, collagen, and human gamma-thrombin. The monclonal antibody, LJ-CP3, which inhibits the binding of Arg-Gly-Asp containing ligands to platelet GPIIb.IIIa, also inhibited applaggin binding to unstimulated platelets in a competitive manner (Ki = 4.5 microM). Thus, applaggin and echistatin bind to the platelet GPIIb.IIIa complex, and the Arg-Gly-Asp sequence plays a central role in mediating this interaction.     

Phylogenetic relationships within the Alcidae (Charadriiformes: Aves) inferred from total molecular evidence

The Alcidae is a unique assemblage of Northern Hemisphere seabirds that forage by "flying" underwater. Despite obvious affinities among the species, their evolutionary relationships are unclear. We analyzed nucleotide sequences of 1,045 base pairs of the mitochondrial cytochrome b gene and allelic profiles for 37 allozyme loci in all 22 extant species. Trees were constructed on independent and combined data sets using maximum parsimony and distance methods that correct for superimposed changes. Alternative methods of analysis produced only minor differences in relationships that were supported strongly by bootstrapping or standard error tests. Combining sequence and allozyme data into a single analysis provided the greatest number of relationships receiving strong support. Addition of published morphological and ecological data did not improve support for any additional relationship. All analyses grouped species into six distinct lineages: (1) the dovekie (Alle alle) and auks, (2) guillemots, (3) brachyramphine murrelets, (4) synthliboramphine murrelets, (5) true auklets, and (6) the rhinoceros auklet (Cerorhinca monocerata) and puffins. The two murres (genus Uria) were sister taxa, and the black guillemot (Cepphus grylle) was basal to the other guillemots. The Asian subspecies of the marbled murrelet (Brachyramphus marmoratus perdix) was the most divergent brachyramphine murrelet, and two distinct lineages occurred within the synthliboramphine murrelets. Cassin's auklet (Ptychoramphus aleuticus) and the rhinoceros auklet were basal to the other auklets and puffins, respectively, and the Atlantic (Fratercula arctica) and horned (Fratercula corniculata) puffins were sister taxa. Several relationships among tribes, among the dovekie and auks, and among the auklets could not be resolved but resembled "star" phylogenies indicative of adaptive radiations at different depths within the trees.