Experimental comparison of a Shack-Hartmann sensor and a phase-shifting interferometer for large-optics metrology applications.

We performed a direct side-by-side comparison of a Shack-Hartmann wave-front sensor and a phase-shifting interferometer for the purpose of characterizing large optics. An expansion telescope of our own design allowed us to measure the surface figure of a 400-mm-square mirror with both instruments simultaneously. The Shack-Hartmann sensor produced data that closely matched the interferometer data over spatial scales appropriate for the lenslet spacing, and much of the <20-nm rms systematic difference between the two measurements was due to diffraction artifacts that were present in the interferometer data but not in the Shack-Hartmann sensor data. The results suggest that Shack-Hartmann sensors could replace phase-shifting interferometers for many applications, with particular advantages for large-optic metrology.

Identification of the synthetic surfactant nonylphenol ethoxylate: a P-glycoprotein substrate in human urine.

P-glycoprotein (Mdr1p) is an ATP-dependent drug efflux pump that is overexpressed in multidrug-resistant cells and some cancers. Mdr1p is also expressed in normal tissues like the kidney, where it can mediate transepithelial drug transport. A human urinary compound that reverses multidrug resistance and blocks [3H]azidopine photolabeling of P-glycoprotein was purified to homogeneity and identified by 1H-NMR and mass spectrometry as the synthetic surfactant nonylphenol ethoxylate (NPE). Multidrug-resistant Chinese hamster ovary (CHO) C5 cells accumulated less [3H]NPE than parental drug-sensitive Aux-B1 cells, and Mdr1p substrates, verapamil and cyclosporin A, increased this surfactant's accumulation in C5 cells. NPE blocked the net transepithelial transport (basolateral to apical) of [3H]cyclosporin A in epithelia formed by Madin-Darby canine kidney (MDCK) cells. Net transepithelial transport (basal to apical) of [3H]NPE was demonstrated in MDCK cells and was inhibited by cyclosporin A. These findings show NPE is a Mdr1p substrate excreted into urine by kidney P-glycoprotein. NPE is a widely used surfactant and a known hormone disrupter that is readily absorbed orally or topically. The current findings indicate the function of kidney Mdr1p may be to eliminate exogenous compounds from the body.

Rapid quantitation of thermal oxidation products in fats and oils by 1H-NMR spectroscopy.

This work describes the application of high-resolution proton nuclear magnetic resonance (1H-NMR) spectroscopy to the study of the thermal peroxidation of beef tallow and corn oil under standardized conditions. The approach provides a rapid, quantitative method for determining the degree of oxidation of unsaturated fatty acids in animal and vegetable fats and oils by quantitating the decreasing intensities of 1H-NMR peaks for allylic and olefinic protons in unsaturated fatty acid chains of triglycerides and the increasing peak intensities of hydroperoxide and saturated and alpha, beta-unsaturated aldehydic protons in relation to the less labile protons in the triglyceride molecule. Two-dimensional correlation spectroscopy analysis of highly oxidized beef tallow (180 degrees C for 24 h) suggested that the unsaturated aldehydes that persisted were apparently associated with carboxy groups.

Synthesis of pentasaccharide analogues of the N-glycan substrates of N-acetylglucosaminyltransferases III, IV and V using tetrasaccharide precursors and recombinant beta-(1-->2)-N-acetylglucosaminyltransferase II.

Recombinant human UDP-GlcNAc: alpha-Man-(1-->6)R beta-(1-->2)-N-acetylglucosaminyltransferase II (EC 2.4.1.143, GlcNAc-T II) was produced in the Sf9 insect cell/baculovirus expression system as a fusion protein with a (His)6 tag and partially purified by affinity chromatography on a metal chelating column. The partially purified enzyme was used to catalyze the transfer of GlcNAc from UDP-GlcNAc to R-alpha-Man(1-->6)(beta-GlcNAc(1-->2)alpha-Man(1-->3))beta-Man-O-octyl to form beta-GlcNAc(1-->2)R-alpha-Man(1-->6)(beta-GlcNAc(1-->2)alpha- Man(1-->3))beta-Man-O-octyl where there is either no modification of the alpha-Man(1-->6) residue (7), or where R is 3-deoxy (8), 4-deoxy (9) or 6-deoxy (10). The yields ranged from 64-80%. Products were characterized by 1H and 13C nuclear magnetic resonance spectroscopy and fast atom bombardment mass spectrometry. Compounds 7-10 are pentasaccharide analogues of the biantennary N-glycan substrates of N-acetylglucosaminyltransferases III, IV and V.

Molecular properties and myocardial salvage effects of morin hydrate.

Morin hydrate is a bioactive pigment found in yellow Brazil wood. Recently, we reported that morin hydrate prolongs the survival of three types of cells from the human circulatory system against oxyradicals generated in vitro. The protection excels that given by equimolar concentrations of ascorbate, mannitol, and Trolox. Here, we demonstrate that, in vivo, morin hydrate at 5 mumol/kg actually reduced by > 50% the tissue necrosis in post-ischemic and reperfused rabbit hearts. Mechanistically, morin hydrate not only scavenges oxyradicals, but also moderately inhibits xanthine oxidase, a free-radical generating enzyme from the ischemic endothelium. Among other possibilities, morin hydrate appears to chelate some metal ions (e.g. Fe2+) in oxyradical formation, although this needs to be examined further. Nuclear magnetic resonance (at 500 mHz) and electron-impact mass spectrometry also supported a molecular formula of C15H10O7 for morin hydrate. Only by X-ray crystallography was it clearly revealed that there are two water molecules attached by intermolecular hydrogen bonds to a morin molecule. Also, the three rings of morin hydrate approach coplanarity. This conformation favours a delocalization of electrons after oxyradical reduction, making morin an effective antioxidant. Thus, we have documented some of the molecular properties and myocardial salvage effects of morin hydrate.

Synthesis of di- and tri-saccharides with intramolecular NH-glycosidic linkages: molecules with flexible and rigid glycosidic bonds for conformational studies.

Attempted dephthalimidation of the trisaccharide 1-O-acetyl-3,4-di-O-benzyl- 2,6-di-O-(3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-beta-D-glucopyranosyl )-alpha-D-mannopyranose (1) and its derivatives 2 and 3, as well as the disaccharide 1-O-acetyl-3,4,6-tri-O-benzyl-2-O-(3,4,6-tri-O-acetyl- 2-deoxy-2-phthalimido-beta-D-glucopyranosyl)-alpha-D-mannopyranose (13), with hydrazine hydrate in ethanol at 80 degrees C, produced the trisaccharide-6-O-(2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-beta-D- glucopyranosyl)-3,4-di-O-benzyl-beta-D-mannopyranose-3',4',6'-tri-O-a cet yl- beta-D-glucopyranose 1,2'-N:1',2-O-dianhydride (4) and 3,4,6-tri-O-benzyl-beta-D-mannopyranose 3',4',6'-tri-O-acetyl-beta-D-glucopyranose 1,2'-N:1',2-O-dianhydride (14), respectively, containing an intramolecular NH-glycosidic linkage. The conventional deblocking of compounds 4 and 14 gave the completely deblocked trisaccharide 6-O-(2-acetamido-2-deoxy-beta-D-glucopyranosyl)-beta-D-mannopyranose beta-D-glucopyranose 1,2'-N:1',2-O-dianhydride (6) and the disaccharide beta-D-mannopyranose beta-D-glucopyranose 1,2'-N:1',2-O-dianhydride (16), respectively, containing an intact intramolecular NH-glycosidic bond. The unusual intra NH-glycosyl character makes the linkage rigid, and therefore these compounds should not only be useful for NMR studies but also as substrates or inhibitors of GlcNAc-transferases.

Effect of sodium tanshinone IIA sulfonate in the rabbit myocardium and on human cardiomyocytes and vascular endothelial cells.

Sodium tanshinone IIA sulfonate (STS) is a derivative of tanshinone IIA. The latter is a pharmacologically active component isolated from the rhizome of the Chinese herb Salvia miltiorrhiza. Liquid chromatographically pure STS was found to reduce myocardial infarct size by 53.14 +/- 22.79% relative to that in the saline control in a rabbit 1 hr-ischemia and 3 hr-reperfusion model. This effect was comparable to that of Trolox (a better characterized antioxidant serving as a reference cytoprotector), which salvaged the myocardium in the same infarct model by 62.13 +/- 18.91%. Also, like Trolox, STS did not inhibit oxygen uptake by xanthine oxidase (XO), a key enzyme in free radical generation. However, in contrast to Trolox, STS significantly prolonged the survival of cultured human saphenous vein endothelial cells but not human ventricular myocytes in vitro when these cells were separately exposed to XO-generated oxyradicals. Note that the endothelium is recognized to be a key site of oxidant generation and attack. Our findings in vitro and in vivo support the interpretation that STS is a cardioprotective substance, and that it may exert a beneficial effect on the clinically important vascular endothelium.

Control of glycoprotein synthesis. Characterization of (1-->4)-N-acetyl-beta-D-glucosaminyltransferases acting on the alpha-D-(1-->3)- and alpha-D-(1-->6)-linked arms of N-linked oligosaccharides.

Hen oviduct membranes contain at least three N-acetyl-beta-D-glucosaminyltransferases (GlcNAc-T) that attach a beta GlcNAc residue in (1-4)-linkage to a D-Man p residue of the N-linked oligosaccharide core, i.e., (1-->4)-beta-D-GlcNAc-T III which adds a "bisecting" GlcNAc group to form the beta-D-GlcpNAc-(1-->4)-beta-D-Man p-(1-->4)-D-GlcNAc moiety; (1-->2)-beta-D-GlcNAc-T IV which adds a GlcNAc group to the (1-->3)-alpha-D-Man arm to form the beta-D-GlcpNAc-(1-->4)-[beta-D- GlcpNAc-(1-->2)]-alpha-D-Man p-(1-->3)-beta-D-Man p-(1-->4)-D-GlcpNAc component; and (1-->4)-beta-D-GlcNAc-T VI which adds a GlcNAc group to the alpha-D-Man p residue of beta-D-GlcpNAc-(1-->6)-[beta-D-GlcpNAc- (1-->2)]-alpha-D-Man p-R to form beta-D-GlcpNAc-(1-->6)-[beta-D-GlcpNAc-(1-->4)]-[beta-D-GlcpNAc- (1-->2)]-alpha-D-Man p-R. We now report a novel (1-->4)-beta-D-GlcNAc-T activity (GlcNAc-T VI') in hen oviduct membranes that transfers GlcNAc to beta-D-GlcpNAc-(1-->2)-alpha-D-Man p-(1-->6)-beta-D-Man p-R to form beta-D-GlcpNAc-(1-->4)-[beta-D-GlcpNAc-(1-->2)]-alpha-D-Man p-(1-->6)- beta-D-Man p-R. The structure of the enzyme product was confirmed by 1H NMR spectroscopy, FAB-mass spectrometry and methylation analysis. Previous work with GlcNAc-T IV was carried out with biantennary substrates; we now show that hen oviduct membrane GlcNAc-T IV can also transfer GlcNAc to monoantennary beta-D-GlcpNAc-(1-->2)-alpha-D-Manp-(1-->3)-beta-D-Man p-R to form beta-D-GlcpNAc-(1-->4)-[beta-D-GlcpNAc-(1-->2)]-alpha-D-Man p- (1-->3)-beta-D-Man p-R. The findings that GlcNAc-T VI' and IV have similar kinetic characteristics and that hen oviduct membranes can convert methyl beta-D-GlcpNAc-(1-->2)-alpha-D-Man p to methyl beta-D-GlcpNAc-(1-->4)-[beta-D-GlcpNAc-(1-->2)]-alpha-D-Man p suggest that these two activities may be due to the same enzyme. The R-group of the beta-D-GlcpNAc-(1-->2)-alpha-D-Man p-(1-->6)-beta-D-Man p (or Glcp)-R substrate has an important influence on GlcNAc-T VI' enzyme activity.(ABSTRACT TRUNCATED AT 400 WORDS)

Tryptophanyl-tRNA synthetase from Bacillus subtilis. Characterization and role of hydrophobicity in substrate recognition.

The tryptophanyl-tRNA synthetase from Bacillus subtilis was purified to homogeneity and characterized. It has an alpha 2 subunit structure and a molecular weight of 77,000. Tryptophanyl-tRNA synthetase does not catalyze any significant proofreading. It activates tryptophan as well as the three fluorinated analogues, DL-4-fluoro-, DL-5-fluoro-, or DL-6-fluorotryptophan (4F-, 5F-, and 6F-Trp), in the ATP-pyrophosphate exchange reaction. In the aminoacylation reaction, the fluorotryptophans act as competitive inhibitors of Trp. Their relative activities follow the same order in both reactions: Trp greater than 4F-Trp greater than 6F-Trp greater than 5F-Trp. This order is the inverse of the order of relative hydrophobicities of these compounds, pointing to the importance of hydrophobic interactions in the selective recognition by tryptophanyl-tRNA synthetase among this group of substrates. To define the physical basis of the relative hydrophobicities, the crystallographic structure of 4F-Trp was determined and compared to that of trptophan. Charge distributions calculated for tryptophan and its different fluoroanalogues on the basis of molecular structures were supported by their carbon-13 NMR spectra. Correlations between charge distributions and relative hydrophobicities suggest that the polarity of the C-F bond represents an underlying factor determining the hydrophobicities of 4F-, 5F-, and 6F-Trp, thus relating tryptophanyl-tRNA synthetase selectivity toward tryptophan and its fluoroanalogues directly to their electronic configurations.

Solution conformation of the branch points of N-linked glycans: synthetic model compounds for tri'-antennary and tetraantennary glycans.

The solution conformation of model compounds for the tri'-antennary and tetraantennary (six-arm) branch point of N-linked glycans has been determined through the use of chemical shift, relaxation, and nuclear Overhauser enhancement data. The object was to establish the conformation about the glycosidic linkages in the N-linked substructure GlcNAc(beta 1,6) [GlcNAc(beta 1,2)] Man(alpha)- by estimation of values for the appropriate glycosidic torsional angles. The GlcNAc(beta 1,6) linkage in a trisaccharide model compound was found to be constrained to a narrow rotameric subpopulation about the substituted Man C5-C6 bond (omega = -60 degrees) and a narrow range of possible phi - psi values. Free rotation about the Man C5-C6 bond was obstructed by unfavorable steric interactions between the GlcNAc(beta 1,6) and GlcNAc(beta 1,2) residues. A phi, psi value of 55 degrees, 190 degrees was found to be consistent with the NMR data for the GlcNAc(beta 1,6) linkage. However, the value of psi appears to be "virtual" in that the molecule is in equilibrium between two different values (90 degrees and 252 degrees). For the GlcNAc(beta 1,2) linkage, complete agreement between all the observed NMR parameters and all the calculated ensemble average values could only be obtained with a set of potential energy functions which included hydrogen bonding. Other choices of potentials yielded calculated values that disagreed with at least two of the observed quantities. As a result, we infer that an interresidue hydrogen bond is formed, and we find it to be between the GlcNAc(beta 1,2) ring oxygen and the Man C3 hydroxyl.(ABSTRACT TRUNCATED AT 250 WORDS)

Specific deuteration of a trimannoside confirms the existence of a disputed interresidue nuclear Overhauser enhancement.

The relative orientation of the 3-arm of N-linked glycans in solution can be determined, in part, by two interresidue nuclear Overhauser enhancements. The existence of one of these enhancements, that observed to the H5 proton of the (alpha 1,3)-linked mannose (attached to the core beta-linked mannose) upon irradiation of the beta-linked mannose H2 proton, has been disputed by other investigators (Homans, S. W., Dwek, R. A., Fernandes, D. L., and Rademacher, T. W. (1983) FEBS Lett. 164, 231-235). To demonstrate unequivocally the existence of this interresidue enhancement, we have synthesized a mannotrioside to model the corresponding moiety in N-linked glycans. Just as in N-linked glycans, the disputed enhancement cannot be directly observed due to spectral overlap with other enhancements but is detectable by careful quantitative analysis. By employing specifically deuterated derivatives of the mannotrioside, however, the disputed enhancement can be directly visualized.

Possible role for peptide-oligosaccharide interactions in differential oligosaccharide processing at asparagine-107 of the light chain and asparagine-297 of the heavy chain in a monoclonal IgG1 kappa.

The carbohydrate attached at Asn-107 of the light chain of a human myeloma IgG1 kappa (Hom) was isolated and the structure determined by 1H NMR. Two oligosaccharides were found corresponding to mono- and disialylated forms of the bisected biantennary class of glycopeptides. Both structures had Fuc alpha 1-6 linked to the GlcNAc residue attached to Asn and NeuNAc residues linked alpha 2-6. Because of the unusual nature of these structures, the Asn-297 oligosaccharides of the same IgG were prepared from Fc fragments and heavy chains. Comparison of the structures of the latter glycopeptides with structures from the same site on a second human myeloma IgG1 kappa (Tem) showed them to be quite similar in that the majority of the structures were biantennary but not bisected. We suggest that the completely bisected nature of the light-chain oligosaccharides comes from a high level of activity of GlcNAc-T-III (the enzyme responsible for the attachment of the bisecting GlcNAc) in the cells producing the IgG. We suggest a mechanism for differential glycosylation between the Asn-107 and Asn-297 sites based on the stabilization of the Asn-297 oligosaccharide in a conformation with the torsional angle omega about the C5-C6 bond of the Man alpha 1-6 linkage equal to -60 degrees. It has previously been postulated that this conformation is not a substrate for GlcNAc-T-III [Brisson, J.-R., & Carver, J. P. (1983) Can. J. Biochem. 61, 1067-1078].(ABSTRACT TRUNCATED AT 250 WORDS)

Structure of the glycopeptides of a human gamma 1-immunoglobulin G (Tem) myeloma protein as determined by 360-megahertz nuclear magnetic resonance spectroscopy.

High field magnetic resonance spectroscopy has been utilized to deduce the primary structure of the glycopeptides from a human myeloma gamma 1-immunoglobulin G (Tem). The major structures found belong to the biantennary complex class of glycopeptides, with a minor (5%) fraction belonging to the bisected biantennary complex class. In the biantennary class, three structures were present with different residues at the termini of the alpha Man(1-6) and alpha Man(1-3) arms: (i) with beta Gal(1-4) and alpha NeuNAc(2-6), respectively (33%); (ii) with beta Gal(1-4) and beta Gal(1-4), respectively (45%); and (iii) beta Gal(1-4) and beta GlcNAc(1-2), respectively (17%). In the bisected biantennary class only the latter termini were found for the two arms. These results suggest that the galactosyl transferase in these cells has a preference for the beta GlcNAc(1-2) of the alpha Man(1-6) arm and that the sialyltransferase has a preference for the beta Gal(1-4) of the alpha Man(1-3) arm.

Determination of glycopeptide primary structure by 360-MHz proton magnetic resonance spectroscopy.

A detailed analysis of the proton magnetic resonance spectral parameters for the anomeric and C2 hydrogen resonances of 63 different glycopeptides and oligosaccharides of known structure reveals a general method for the determination of the primary structure of glycopeptides for most currently known classes of structures. In particular, a two-dimensional display formed by plotting mannosyl C1-H vs. C2-H chemical shifts demonstrates that these pairs of values are sensitive to long-range perturbation by remote substitution by hexoses as well as to direct substitution effects. A total of 41 Cl-H/C2-H chemical shift clusters have been defined which characterize unique structural microenvironments. On the basis, the sequence and branching pattern for most structures can be derived. Corroborative evidence is obtained from an examination of the chemical shifts of the galactosyl and N-acetylglucosaminyl anomeric hydrogens as well as other features of the spectrum.

Determination of the Structure of four glycopeptides from hen ovalbumin using 360-MHz proton magnetic resonance spectroscopy.

Four glycopeptides have been purified by Dowex and Bio-Gel P2 chromatography from Pronase digests of hen ovalbumin. The high-resolution proton magnetic resonance spectra of these glycopeptides and various products of their enzymatic digestion have been obtained at 360 MHz. By use of information derived from the spectra of a number of model compounds, an unambiguous assignment of all C1-H and Man C2-H resonances in the spectra can be made. On this basis structures are proposed for the four glycopeptides which are identical with those structures previously deduced from destructive chemical methods.

The location and nature of calcium-binding sites in salivary acidic proline-rich phosphoproteins.

The location of the calcium-binding sites in the human acidic proline-rich proteins, salivary proteins A and C, were determined by equilibrium dialysis of the tryptic peptides with buffers containing 45Ca. All the calcium-binding sites are located in the NH2-terminal tryptic peptide (TX peptide). The nature of the calcium binding sites in the TX peptide and native salivary proteins A and C, as well as dephosphorylated proteins were compared. Two types of sites can be distinguished in peptide TX. Type I sites have an apparent dissociation constant (K) of 38 microM and are responsible for the binding of 2.6 mol of Ca/mol of peptide. The corresponding figures for Type II sites are 780 microM and 5.3 mol of Ca/mol of peptide. In the native proteins, the amount of calcium bound at the type II sites decreases to 3.9 mol of Ca/mol of proteins A and C and K increases to 1100 microM. The amount of calcium bound at type I sites decreases to 1.5 mol/mol of protein A and 0.6 mol/mol of protein C, but there is no change in K. Dephosphorylation affects the calcium binding at both types of sites. The experiments indicate that the COOH-terminal parts of the native proteins affect the number and the nature of the protein calcium-binding sites. Proton and phosphorous NMR data demonstrate that beta-COOH in aspartic acid, as well as phosphoserine, are part of the calcium-binding sites. The difference in calcium binding to salivary proteins A and C may be due at least partially to differences in the environment of one or more aspartic acids.