IRMPD Spectroscopy Sheds New (Infrared) Light on the Sulfate Pattern of Carbohydrates.

IR spectroscopy of gas-phase ions is proposed to resolve positional isomers of sulfated carbohydrates. Mass spectrometric fingerprints and gas-phase vibrational spectra in the near and mid-IR regions were obtained for sulfated monosaccharides, yielding unambiguous signatures of sulfated isomers. We report the first systematic exploration of the biologically relevant but notoriously challenging deprotonated state in the near IR region. Remarkably, anions displayed very atypical vibrational profiles, which challenge the well-established DFT (Density Functionnal Theory) modeling. The proposed approach was used to elucidate the sulfate patterns in glycosaminoglycans, a ubiquitous class of mammalian carbohydrates, which is regarded as a major challenge in carbohydrate structural analysis. Isomeric glycosaminoglycan disaccharides from heparin and chondroitin sources were resolved, highlighting the potential of infrared multiple photon dissociation spectroscopy as a novel structural tool for carbohydrates.

Applications of ion mobility mass spectrometry for high throughput, high resolution glycan analysis.

BACKGROUND: Diverse varieties of often heterogeneous glycans are ubiquitous in nature. They play critical roles in recognition events, act as energy stores and provide structural stability at both molecular and cellular levels. Technologies capable of fully elucidating the structures of glycans are far behind the other '-omic' fields. Liquid chromatography (LC) and mass spectrometry (MS) are currently the most useful techniques for high-throughput analysis of glycans. However, these techniques do not provide full unambiguous structural information and instead the gap in full sequence assignment is frequently filled by a priori knowledge of the biosynthetic pathways and the assumption that these pathways are highly conserved. SCOPE OF THE REVIEW: This comprehensive review details the rise of the emerging analytical technique ion mobility spectrometry (IMS) (coupled to MS) to facilitate the determination of three-dimensional shape: the separation and characterization of isobaric glycans, glyco(peptides/proteins), glycolipids, glycosaminoglycans and other polysaccharides; localization of sites of glycosylation; or interpretation of the conformational change to proteins upon glycan binding. MAJOR CONCLUSIONS: IMS is a highly promising new analytical route, able to provide rapid isomeric separation (ms timescale) of either precursor or product ions facilitating MS characterization. This additional separation also enables the deconvolution of carbohydrate MS(/MS) information from contaminating ions, improving sensitivity and reducing chemical noise. Derivation of collision cross sections (CCS) from IM-MS(/MS) data and subsequent calculations validate putative structures of carbohydrates from ab initio derived candidates. IM-MS has demonstrated that amounts of specific glycan isomers vary between disease states, which would be challenging to detect using standard analytical approaches. GENERAL SIGNIFICANCE: IM-MS is a promising technique that fills an important gap within the Glycomics toolbox, namely identifying and differentiating the three-dimensional structure of chemically similar carbohydrates and glycoconjugates. This article is part of a Special Issue entitled "Glycans in personalised medicine" Guest Editor: Professor Gordan Lauc.

Discrimination of epimeric glycans and glycopeptides using IM-MS and its potential for carbohydrate sequencing.

Mass spectrometry is the primary analytical technique used to characterize the complex oligosaccharides that decorate cell surfaces. Monosaccharide building blocks are often simple epimers, which when combined produce diastereomeric glycoconjugates indistinguishable by mass spectrometry. Structure elucidation frequently relies on assumptions that biosynthetic pathways are highly conserved. Here, we show that biosynthetic enzymes can display unexpected promiscuity, with human glycosyltransferase pp-α-GanT2 able to utilize both uridine diphosphate N-acetylglucosamine and uridine diphosphate N-acetylgalactosamine, leading to the synthesis of epimeric glycopeptides in vitro. Ion-mobility mass spectrometry (IM-MS) was used to separate these structures and, significantly, enabled characterization of the attached glycan based on the drift times of the monosaccharide product ions generated following collision-induced dissociation. Finally, ion-mobility mass spectrometry following fragmentation was used to determine the nature of both the reducing and non-reducing glycans of a series of epimeric disaccharides and the branched pentasaccharide Man3 glycan, demonstrating that this technique may prove useful for the sequencing of complex oligosaccharides.

Isolation and characterization of Francisella novicida mutants defective in lipopolysaccharide biosynthesis.

In order to identify genes involved in LPS biosynthesis we isolated random mutants generated by transposon insertion in Francisella novicida. The resulting mutant bank yielded mutants with three distinct LPS phenotypes, and three representative mutants were chosen for further study. One mutant that had short O-antigen chains was sensitive to serum; this mutant and one other were more sensitive to killing by deoxycholate than control strains. The third mutant was resistant to deoxycholate killing but slightly sensitive to serum. The three mutants varied in their ability to grow in macrophages. The DNA sequences interrupted by the transposon in two of the three mutants showed similarity to known LPS biosynthetic genes at the deduced amino acid level.

Synthesis of azaalanine peptides using the solid phase method.

The methodology for the incorporation of azaamino-acid residues into peptides synthesised by a solid-phase method has been extended to allow azaalanine peptides to be prepared. In this way, Ac-Leu-Ser-Gly-azaAla-Gly-Phe-Ser-Leu-NH2 H-Ala-Ala-Lys-Glu-Ala-Ala-Glu-Ala -Ala-Glu-Lys-Ala-azaAla-Glu-Leu-Ala-Leu-N2H3, and H-Ala-azaAla-Lys-Glu-Ala-Ala-Glu-Ala-Ala-Glu-Lys-Ala-Ala-Glu-Leu-A la-Leu-N2H3 have been prepared. A new analogue of the Ala-Gly sequence, 3-azaalanylpropionic acid has been prepared and used to prepare the peptide analogue acetyl-Leu-Ser-Gly-azaAla-3-Prop-Phe-Ser-Leu-NH2.

A real-time gesture recognizer based on dynamic programming.

Coded gestures are physical movements to which precise meanings have been attached. Their use with an electronic pointing device potentially increases the power of the pointer by allowing several distinct control functions to be incorporated. The formation of a coded gesture is invariably subject to distortions which make its automatic recognition difficult. After particular consideration of three techniques, a dynamic programming algorithm was developed and was used in the design of a real-time gesture recognizer that allows mouse-driven software to be operated purely by means of an electronic pointer. The decision was taken to implement the gesture recognizer using a widely available, obsolescent microcomputer in order to keep down costs. Despite the inevitable technical compromises in this approach, results of preliminary trials using 10 normal subjects show an average gesture recognition rate of 98.3% and a gesture confusion rate of only 0.4%.

Incorporation of azaglutamine residues into peptides synthesised by the ultra-high load solid (gel)-phase technique.

The solid (gel)-phase peptide synthesis of peptides, each containing an azaglutamine residue, has been examined. Procedures using various mono-, di- and tripeptide and carbazate fragments containing or relating to an azaglutamine (1) residue have been evaluated. N-Activation of the amino-terminus of a resin-bound peptide with bis-(2,4-dinitrophenyl)carbonate (2) yielded the terminal isocyanate species, which reacted with protected carbazates to give resin-bound protected peptides containing the aza-residue. By contrast, coupling of activated amino-acid derivates to the free amino-group of a resin-bound peptide with an aza-residue at the N-terminus was a slow and unsatisfactory process. It is concluded that the route yielding the best results involves the reaction of a protected amino-acyl carbazate to a resin-bound isocyanate-activated peptide.

Prostaglandins in the kidney, urinary bladder and gills of the rainbow trout and European eel adapted to fresh water and seawater.

Prostaglandins in kidney, gills, and urinary bladder of freshwater-adapted and seawater-adapted rainbow trout, Oncorhynchus mykiss (= Salmo gairdneri), and European eel, Anguilla anguilla, were determined by solid-phase extraction of tissue homogenates and high-pressure liquid chromatography. Prostaglandins E2, E1, F1 alpha, F2 alpha, and D2 and the more stable metabolite of prostacyclin, 6-keto F1 alpha, occurred in these osmoregulatory tissues. In gill filaments and kidneys of both eel and trout, prostaglandins D2 and 6-keto F1 alpha were major prostaglandins. Concentrations of these prostaglandins were significantly lower in the eel after seawater adaptation, but not in the trout. The urinary bladder of the trout contained the highest levels of prostaglandins; bladders of seawater-adapted trout contained prostaglandin D2 at 6.7 ng/mg wet tissue, the highest level of any prostaglandin determined in the present studies. Prostaglandin D2 was not detected in bladders of freshwater-adapted trout.

Inhibition of trypsin by t-butyloxycarbonyl-alpha-aza-(4-aminophenyl)alanine phenyl ester.

t-Butyloxycarbonyl-alpha-aza-(4-aminophenyl)alanine phenyl ester (III: R = NH2) has been synthesized. The rate of inhibition of trypsin (EC 3.4.21.4) by this compound (due to acylation followed by slower deacylation) shows a marked pH maximum at approximately 6. The shape of the pH-rate curve is discussed in terms of (i) the normal pH-activity curve of trypsin reacting with a charged substrate, i.e. the protonated form of the amino compound, (ii) the deprotonation of the 4-amino group with pKa 4.3, and (iii) the lower rate of reaction of the enzyme with the uncharged, deprotonated form of the ester.

Immobilization of lipase from Candida cylindraceae and its use in the synthesis of menthol esters by transesterification.

Lipase (EC 3.1.1.3) from Candida cylindraceae has been immobilized by the cellulose-titanium chloride method, and on EP-400 polyethylene, with and without glutaraldehyde crosslinking, to give active preparations when assessed by their ability to catalyse the hydrolysis of tributyrin. In both cases, the use of glutaraldehyde crosslinking was shown to improve the stability of the preparations for repeated use. The lipase immobilized on EP-400 polyethylene was found to be effective in transesterification using tributyrin or triacetin as acyl donors with l-menthol as acceptor. The production of methyl butanoate and of methyl acetate using this immobilized preparation was in each case enhanced in the presence of Amberlite IR 47 Anion exchange resin (OH form).

Glycoprotein gonadotropins. Structure and synthesis.

The four human glycoprotein hormones FSH, LH, CG and TSH are closely related in structure, each consisting of a common alpha-subunit and a specific beta-subunit. Amino acid sequences have been established by standard methods of protein sequencing and confirmed by base sequencing of the cDNAs encoding for the polypeptide units. Speculation on the structures involved in the binding of subunits and binding to receptors has been based on examination of these sequences for common or similar regions. There are asparagine-linked carbohydrate chains attached to the subunits and in addition O-glycosidically linked carbohydrate chains in beta-CG attached to serine molecules. The carbohydrates are essential for full biological activity. The progress so far and future possibilities for the synthesis of these glycoprotein hormones by the technique of genetic engineering are discussed.

Glomerular ultrastructure of the trout, Salmo gairdneri: effects of angiotensin II and adaptation to seawater.

The effect of angiotensin infusion on the glomerular ultrastructure of freshwater- and seawater-adapted rainbow trout. Salmo gairdneri, has been examined by scanning and transmission electron microscopy. Adaptation of trout to seawater resulted in epithelial podocyte flattening, primary process broadening and apparent loss of foot processes in almost all glomeruli, features which were uncommon in freshwater-adapted trout. Similar changes were induced by infusion of freshwater-adapted animals with angiotensin, suggesting that the renin-angiotensin system plays a role in the modification of glomerular epithelial ultrastructure. Adaptation of trout to seawater also reduced glomerular diameter, but infusion of freshwater-adapted animals with angiotensin did not mirror this effect. Infusion of angiotensin into seawater-adapted animals increased the overall thickness of glomerular basement membrane by increasing the lamina rara interna and lamina densa. This did not occur when freshwater-adapted fish were either infused with angiotensin or adapted to seawater. These findings suggest that other humoral systems are involved in the control of glomerular diameter and basement membrane thickness as part of an integrated response to increased environmental salinity.

Assay of the high-alkaline proteinase from alkalophilic bacillus PB92 using a chromogenic tripeptide substrate.

The chromogenic tripeptide substrate, benzyloxycarbonylglycyl-L-prolyl-L-citrulline p-nitroanilide, is proposed for the assay of the high-alkaline proteinase, HAP-PB92, from an alkalophilic Bacillus. The assay method is sensitive, reproducible, and may be adapted for an automatic system.

Renal and cardiovascular effects of angiotensin II in the rainbow trout, Salmo gairdneri.

The renal and cardiovascular effects of an intravenous infusion of angiotensin II in the freshwater anaesthetised rainbow trout, Salmo gairdneri, have been reappraised, without the infusion of noradrenaline. In these fish the previously reported antidiuretic response to angiotensin II was not maintained although a systemic pressor response persisted and the tubular transport maximum for glucose remained depressed. The data suggest that angiotensin has an intrarenal action which may play a role in renal adaptation to increased environmental salinities.

Benzyloxycarbonylphenylalanylcitrulline p-nitroanilide as a substrate for papain and other plant cysteine proteinases.

After preliminary assays, with papain, bromelain and ficin, on a range of citrulline p-nitroanilides, values of Km and kcat. for the papain-catalysed hydrolysis of three derivatives, N alpha- benzyloxycarbonylcitrulline p-nitroanilide, benzyloxycarbonylphenylalanylcitrulline p-nitroanilide and benzyloxycarbonylglycylphenylalanylcitrulline p-nitroanilide, were obtained. It is concluded that benzyloxycarbonylphenylalanylcitrulline p-nitroanilide is a highly selective substrate for the sensitive detection and assay of the plant cysteine proteinases.

Glomerular ultrastructure of the trout, Salmo gairdneri. Glomerular capillary epithelium and the effects of environmental salinity.

The epithelial ultrastructure of the glomerulus of fresh- and sea-water adapted rainbow trout, Salmo gairdneri was examined by scanning and transmission electron microscopy after in vivo-perfusion fixation. Adaptation to seawater for a period of up to 9 weeks was not associated with a change in glomerular size, although after one year in seawater both glomeruli and their capsules were significantly smaller than the glomeruli of freshwater adapted fish. In freshwater adapted trout the epithelial ultrastructure conformed to the general vertebrate pattern, with rounded podocytes, well-defined primary processes and interdigitating pedicels. Adaptation to seawater was associated with a marked increase in the frequency of cytoplasmic microprojections. In many glomeruli there was a flattening of the podocytes, broadening of the primary processes, and areas of closely-packed pedicels were common. These observations are discussed in the light of previous studies on the mammalian kidney and the changes of single nephron function known to be associated with adaptation of trout to increased environmental salinities.