Structural characterization by chromatographic profiling of the oligosaccharides of human immunodeficiency virus (HIV) recombinant envelope glycoprotein gp120 produced in Chinese hamster ovary cells

This report together with the paper by T. Mizuochi, M. W. Spellman, M. Larkin, J. Solomon, L. J. Basa and T. Feizi (1988) Biochem. J. 254, 599-603 describes the structural elucidation of the N-linked oligosaccharides of the HIV envelope glycoprotein, gp120 (cloned from the HTLV-III B isolate and expressed as a secreted fusion protein after transfection of Chinese hamster ovary cells), which is known to bind with high affinity to human T4 lymphocytes. Oligosaccharides were released from peptide by hydrazinolysis, fractionated by paper electrophoresis, high performance lectin affinity chromatography and Bio-Gel P-4 column chromatography, and their structures determined by sequential exoglycosidase digestions in conjunction with methylation analysis. The glycoprotein was found to be unique in its diversity of oligosaccharide structures. These include high-mannose type and hybrid type, as well as four categories of complex type chains: mono-, bi-, tri- and tetra-antennary, with or without N-acetyllactosamine repeats, and with or without a core region fucose residue. Among the sialidase-treated oligosaccharides no less than 29 structures were identified as follows: (formula; see text) where G = galactose; GN = N-acetylglucosamine; M = mannose; F = fucose; +/- = residues present in a proportion of chains. The actual number of oligosaccharide structures is much greater since before desialylation there was evidence that among the hybrid and complex type chains all but 6% contained sialic acid at the C-3 position of terminal galactose residues, and partially sialylated forms of the bi- and multiantennary chains were present.     

Study of the primary structure of recombinant tissue plasminogen activator by reversed-phase high-performance liquid chromatographic tryptic mapping

Two high-resolution tryptic maps have been developed for recombinant tissue plasminogen activator (rt-PA) that separate the expected 51 tryptic peptides. The trypsin digestion was performed after reduction and S-carboxymethylation of the protein. The high-performance liquid chromatographic separation of the tryptic peptides used a Nova-Pak C18 (5 microns) column with a mobile phase that contained 0.1% aqueous trifluoroacetic acid (TFA) or 50 mM sodium phosphate (pH 2.85) and a linear gradient of acetonitrile. A TFA solvent system was also used for re-purification and for characterization of the peptides isolated from the phosphate-based separation. All of the isolated peptides had compositions consistent with the sequence proposed for rt-PA. The identities of the glycopeptides were confirmed by lectin chromatography on concanavalin A-Sepharose. The mixture of tryptic peptides was also treated with endo-beta-N-acetylglucosaminidase H and peptide:N-glycosidase F to locate the position of either high mannose or complex oligosaccharides. These studies demonstrated that a high mannose oligosaccharide is attached to Asn-117 while complex carbohydrate side-chains are attached to Asn-184 and Asn-448. The residue Asn-184 is the site of optional glycosylation that results in the formation of two rt-PA variants that contain either two or three oligosaccharides.     

Effect of Pr-Ca substitution on the transport and magnetic behavior of LaMnO3 perovskite

The effect of simultaneous substitution of a fluctuating cation and a divalent cation in LaMnO₃ perovskite modifies the properties of the material to exhibit large valence colossal magnetoresistance (CMR) effect. A good example of these properties is (La_1−2x Pr _x Ca _x )MnO₃ (LPCMO) type CMR material. In this communication it is reported that, with the increase in x (for x=0.1, 0.15, 0.2), the T _c varies between 100 and 120 K with improvisation in metal-insulator transition. Interestingly, resistance increases with x from few hundred ohms to few kilo ohms with corresponding decrease in the unit cell volume. The results of the studies using X-ray diffraction (XRD), electrical resistivity, magnetoresistance and ac susceptibility measurements on LPCMO samples for understanding the structural, transport and magnetic properties are discussed in detail.     

Characterization by tandem mass spectrometry of stable cysteine sulfenic acid in a cysteine switch peptide of matrix metalloproteinases

Cysteine sulfenic acid (Cys-SOH) is an elusive intermediate in reactive oxygen species-induced oxidation reactions of many proteins such as peroxiredoxins and tyrosine phosphatases. Cys-SOH is proposed to play a vital role in catalytic and signaling functions. The formation of cysteine sulfinic acid (Cys-SO(2)H) and cysteine sulfonic acid (Cys-SO(3)H) has been implicated in the activation of matrix metalloproteinase-7 (MMP-7) and oxidation of thiol to cysteine sulfinic acid has been associated with the autolytic cleavage of MMP-7. We have examined the formation of cysteine sulfenic acid in a synthetic peptide PRCGVPDVA, which is a cysteine switch domain of MMP-7 and other matrix metalloproteases. We have prepared the cysteine sulfenic acid containing peptide, PRC(SOH)GVPDVA, by reaction with hydroxyl radicals generated by the Fenton reaction (Fe(+2)/H(2)O(2)). We characterized this modified peptide by tandem mass spectrometry and accurate mass measurement experiments. In addition, we used 7-chloro-4-nitrobenzo-2-oxa-1,3-diazol (NBD-Cl) reagent to form an adduct with PRC(SOH)GVPDVA to provide additional evidence for the viability of PRC(SOH)GVPDVA in solution. We also characterized an intramolecular cysteine sulfinamide cross-link product PRC[S(O)N]GVPDVA based on tandem mass spectrometry and accurate mass measurement experiments. These results contribute to the understanding of a proteolytic cleavage mechanism that is traditionally associated with MMP activation.     

A Classification of Fully Residually Free Groups of Rank Three or Less

A groupGisfully residually freeprovided to every finite setS ⊂ G\{1} of non-trivial elements ofGthere is a free groupF_Sand an epimorphismh_S:G → F_Ssuch thath_S(g) ≠ 1 for allg ∈ S. Ifnis a positive integer, then a groupGisn-freeprovided every subgroup ofGgenerated bynor fewer distinct elements is free. Our main result shows that a fully residually free group of rank at most 3 is either abelian, free, or a free rank one extension of centralizers of a rank two free group. To prove this we prove that every 2-free, fully residually free group is actually 3-free. There are fully residually free groups which are not 2-free and there are 3-free, fully residually free groups which are not 4-free.     

Notions of Discrimination

As an outgrowth of the study of algebraic geometry over groups, discriminating groups were introduced. Many important universal type groups such as Higman's universal group and Thompson's group F were shown to be discriminating. Squarelike groups were then introduced to better capture axiomatic properties of discrimination. In the present article squarelike groups are reinterpreted in terms of discrimination of quasi varieties, and the relationship with an older version of discrimination, termed varietal discrimination here, is studied.     

Analysis of a non-contact magnetoelastic torque transducer

Results are presented for the performance of a magnetoelastic torque transducer that converts a torque-induced strain in a non-magnetic shaft into changes in a measurable magnetic field. The magnetic field is generated by a thin magnetostrictive layer that is coated onto the circumference of the shaft. The layer is magnetized and has an initial residual strain. The magnetization within the layer rotates in response to changes in the strain which occur when the shaft is torqued. The magnetic field produced by the layer changes with the magnetization and this can be sensed by a magnetometer to monitor the torque on the shaft. In this paper, a phenomenological theory is developed for predicting the performance of the transducer. The theory can be used to predict the magnetic field distribution of the transducer as a function of the physical properties of the magnetic coating, its residual strain, and the applied torque. It enables rapid parametric analysis of transducer performance, which is useful for the development and optimization of novel non-contact torque sensors.     

Minimum-weight two-connected spanning networks

We consider the problem of constructing a minimum-weight, two-connected network spanning all the points in a setV. We assume a symmetric, nonnegative distance functiond(·) defined onV × V which satisfies the triangle inequality. We obtain a structural characterization of optimal solutions. Specifically, there exists an optimal two-connected solution whose vertices all have degree 2 or 3, and such that the removal of any edge or pair of edges leaves a bridge in the resulting connected components. These are the strongest possible conditions on the structure of an optimal solution since we also show thatany two-connected graph satisfying these conditions is theunique optimal solution for a particular choice of canonical distances satisfying the triangle inequality. We use these properties to show that the weight of an optimal traveling salesman cycle is at most 4/3 times the weight of an optimal two-connected solution; examples are provided which approach this bound arbitrarily closely. In addition, we obtain similar results for the variation of this problem where the network need only span a prespecified subset of the points.     

Generalizations of free groups: some questions

This paper poses ten questions about groups which in some way resemble free groups