Structure of a glycerol-conducting channel and the basis for its selectivity

Membrane channel proteins of the aquaporin family are highly selective for permeation of specific small molecules, with absolute exclusion of ions and charged solutes and without dissipation of the electrochemical potential across the cell membrane. We report the crystal structure of the Escherichia coli glycerol facilitator (GlpF) with its primary permeant substrate glycerol at 2.2 angstrom resolution. Glycerol molecules line up in an amphipathic channel in single file. In the narrow selectivity filter of the channel the glycerol alkyl backbone is wedged against a hydrophobic corner, and successive hydroxyl groups form hydrogen bonds with a pair of acceptor, and donor atoms. Two conserved aspartic acid-proline-alanine motifs form a key interface between two gene-duplicated segments that each encode three-and-one-half membrane-spanning helices around the channel. This structure elucidates the mechanism of selective permeability for linear carbohydrates and suggests how ions and water are excluded.

The wheat and barley vernalization gene VRN3 is an orthologue of FT

Winter wheat and barley varieties require an extended exposure to low temperatures to accelerate flowering (vernalization), whereas spring varieties do not have this requirement. In this study, we show that in these species, the vernalization gene VRN3 is linked completely to a gene similar to Arabidopsis FLOWERING LOCUS T (FT). FT induction in the leaves results in a transmissible signal that promotes flowering. Transcript levels of the barley and wheat orthologues, designated as HvFT and TaFT, respectively, are significantly higher in plants homozygous for the dominant Vrn3 alleles (early flowering) than in plants homozygous for the recessive vrn3 alleles (late flowering). In wheat, the dominant Vrn3 allele is associated with the insertion of a retroelement in the TaFT promoter, whereas in barley, mutations in the HvFT first intron differentiate plants with dominant and recessive VRN3 alleles. Winter wheat plants transformed with the TaFT allele carrying the promoter retroelement insertion flowered significantly earlier than nontransgenic plants, supporting the identity between TaFT and VRN-B3. Statistical analyses of flowering times confirmed the presence of significant interactions between vernalization and FT allelic classes in both wheat and barley (P < 0.0001). These interactions were supported further by the observed up-regulation of HvFT transcript levels by vernalization in barley winter plants (P = 0.002). These results confirmed that the wheat and barley FT genes are responsible for natural allelic variation in vernalization requirement, providing additional sources of adaptive diversity to these economically important crops.

Dual functions of largest NURF subunit NURF301 in nucleosome sliding and transcription factor interactions

NURF is an ISWI complex of four proteins that uses the energy of ATP hydrolysis to catalyze nucleosome sliding. Three NURF components have been identified previously. We have cloned cDNA encoding the largest NURF subunit, revealing a 301 kDa polypeptide (NURF301) that shares structural motifs with ACF1. We have reconstituted full and partial NURF complexes from recombinant proteins and show that NURF301 and the ISWI ATPase are necessary and sufficient for accurate and efficient nucleosome sliding. An HMGA/HMGI(Y)-like domain of NURF301 that facilitates nucleosome sliding indicates the importance of DNA conformational changes in the sliding mechanism. NURF301 also shows interactions with sequence-specific transcription factors, providing a basis for targeted recruitment of the NURF complex to specific genes.

Inflammation-Responsive Drug-Loaded Hydrogels with Sequential Hemostasis, Antibacterial, and Anti-Inflammatory Behavior for Chronically Infected Diabetic Wound Treatment

Stimuli-responsive hydrogels possess unique advantages in drug delivery due to their variable performance and status based on the external environment. In the present study, a dual-responsive (pH and reactive oxygen species (ROS)) hydrogel was prepared to realize drug release properties under inflammatory stimulation. By grafting 3-carboxy-phenylboronic acid to the gelatin molecular backbone and cross-linking with poly(vinyl alcohol), we successfully synthesized the inflammation-responsive drug-loaded hydrogels after encapsulation with vancomycin-conjugated silver nanoclusters (VAN-AgNCs) and pH-sensitive micelles loaded with nimesulide (NIM). This novel design not only retained the dynamic functions of hydrogels, such as injectability, self-healing, and remodeling, but also realized sequential and on-demand drug delivery at diabetic-infected wound sites. In this work, we found that the hydrogel exhibited excellent biocompatibility and hemostasis properties owing to the enhanced cell-adhesive property of the gelatin component. The significant antibacterial and anti-inflammatory effect of the hydrogel was demonstrated in an in vitro experiment. Moreover, in the in vivo experiment, the hydrogel was found to play a role in promoting infected wound healing through sequential hemostasis and antibacterial and anti-inflammatory processes. Collectively, this inflammation-responsive hydrogel design containing VAN-AgNCs and NIM-loaded micelles has great potential in the application of chronically infected diabetic wound treatment, as well as in other inflammatory diseases.

Monosaccharide composition analysis of oligosaccharides and glycoproteins by high-performance liquid chromatography

A simple and sensitive high-performance liquid chromatography (HPLC)-based method for complete monosaccharide composition analysis of oligosaccharides and glycoproteins is described. In this method, an oligosaccharide or glycoprotein is first hydrolyzed using an optimized method to give the constituent monosaccharides, which are subsequently labeled with 1-phenyl-3-methyl-5-pyrazolone (PMP) as previously described by Honda et al. (Anal, Biochem. 180, 351-357, (1989)). The labeled monosaccharides are separated by reverse-phase HPLC using a column developed especially for this purpose, monitored by uv absorbance at 245 nm, and quantitated by their integration values relative to standards. Sialic acids are acid-labile keto-sugars. They are, therefore, released with neuraminidases or by mild acid hydrolysis and then converted with neuraminic acid aldolase to their corresponding mannosamine derivatives, which are then PMP-labeled, separated, and quantitated as described above. Individual sialic acids including N-acetyl and N-glycolyl neuraminic acids are well resolved and quantitated by this method. This method has proven to be highly sensitive, requiring only 1 pmol for reliable detection. Quantitative analysis of neutral and amino sugars from both oligosaccharide and glycoprotein samples can be achieved using one acid hydrolysis and a set of equal molar monosaccharide standards. Similarly, quantitation of sialic acids works equally well with both free oligosaccharide and glycoprotein samples. Monosaccharide compositions of oligosaccharides and glycoproteins determined by this method were found to be highly accurate.

A detailed structural characterization of ribonuclease B oligosaccharides by 1H NMR spectroscopy and mass spectrometry

The structures of ribonuclease B oligosaccharides have previously been shown to be high mannose type by methylation analyses and sequential exoglycosidase digestion. Due to the unique nature of these oligosaccharides, in that all mannosyl residues are attached by alpha-(1-->2)-linkages beyond the branch points, methylation analysis fails to solve the exact structures beyond Man5. Therefore, we have undertaken this study using 1H nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry. In this study, bovine pancreatic ribonuclease B was first reduced and carboxymethylated, and was then deglycosylated by peptide/N-glycosidase F (PNGase F). The released oligosaccharides were fractionated by Bio-Gel P-4 chromatography to give five pools, Man5 through Man9. The structures of the oligosaccharide pools were then studied by laser desorption time of flight mass spectrometry and 1H NMR spectroscopy at 300 MHz. For Man5, Man-A and Man-B are attached in alpha-(1-->3)- and alpha-(1-->6)-linkages to the alpha-(1-->6)-linked Man-4' of the pentasaccharide core structure. For Man6, Man-C is linked alpha-(1-->2) to the alpha-(1-->3)-linked Man-4. Man7 exists as three structural isomers, and has the additional mannosyl residue (Man-D) linked alpha-(1-->2) to Man-A, Man-B, and Man-C is linked alpha-(1-->2) to the alpha-(1-->3)-linked Man-4. Man-7 exists as three structural isomers, with the additional two mannosyl residues linked alpha-(1-->2) to Man-A, Man-B, and Man-C. For each position, Man-A, Man-B, and Man-C, the extent of occupancy by one of the additional alpha-(-->)-linked mannosyl residues was 15, 94, and 91%, respectively. Man9 is a single component, with the three additional mannosyl residues linked alpha-(1-->2) to Man-A, Man-B, and Man-C, respectively. The relative molar proportions of Man5 to Man9 are 57, 31, 4, 7, and 1%, respectively. This report presents for the first time the complete structural characterization of the oligosaccharides from ribonuclease B.

Constitutive activation of the beta2 adrenergic receptor alters the orientation of its sixth membrane-spanning segment

The binding site of the beta2 adrenergic receptor, like that of other homologous G-protein-coupled receptors, is contained within a water-accessible crevice formed among its seven membrane-spanning segments. Methanethiosulfonate ethylammonium (MTSEA), a charged, hydrophilic, lipophobic, sulfhydryl-specific reagent, had no effect on the binding of agonist or antagonist to wild-type beta2 receptor expressed in HEK 293 cells. This suggested that no endogenous cysteines are accessible in the binding site crevice. In contrast, in a constitutively active beta2 receptor, MTSEA significantly inhibited antagonist binding, and isoproterenol slowed the rate of reaction of MTSEA. This implies that at least one endogenous cysteine becomes accessible in the binding site crevice of the constitutively active beta2 receptor. Cys-285, in the sixth membrane-spanning segment, is responsible for the inhibitory effect of MTSEA on ligand binding to the constitutively active mutant. The acquired accessibility of Cys-285 in the constitutively active mutant may result from a rotation and/or tilting of the sixth membrane-spanning segment associated with activation of the receptor. This rearrangement could bring Cys-285 to the margin of the binding site crevice where it becomes accessible to MTSEA.

Decreased SLIM1 expression and increased gelsolin expression in failing human hearts measured by high-density oligonucleotide arrays

BACKGROUND

Failing human hearts are characterized by altered cytoskeletal and myofibrillar organization, impaired signal transduction, abnormal protein turnover, and impaired energy metabolism. Thus, expression of multiple classes of genes is likely to be altered in human heart failure.

METHODS AND RESULTS

We used high-density oligonucleotide arrays to explore changes in expression of approximately 7000 genes in 2 nonfailing and 2 failing human hearts with diagnoses of end-stage ischemic and dilated cardiomyopathy, respectively. We report altered expression of (1) cytoskeletal and myofibrillar genes (striated muscle LIM protein-1 [SLIM1], myomesin, nonsarcomeric myosin regulatory light chain-2 [MLC(2)], and ss-actin); (2) genes responsible for degradation and disassembly of myocardial proteins (alpha(1)-antichymotrypsin, ubiquitin, and gelsolin); (3) genes involved in metabolism (ATP synthase alpha-subunit, succinate dehydrogenase flavoprotein [SDH Fp] subunit, aldose reductase, and TIM17 preprotein translocase); (4) genes responsible for protein synthesis (elongation factor-2 [EF-2], eukaryotic initiation factor-4AII, and transcription factor homologue-HBZ17); and (5) genes encoding stress proteins (alphaB-crystallin and mu-crystallin). In 5 additional failing hearts and 4 additional nonfailing controls, we then compared expression of proteins encoded by the differentially expressed genes, alphaB-crystallin, SLIM1, gelsolin, alpha(1)-antichymotrypsin, and ubiquitin. In each case, changes in protein expression were consistent with changes in transcript measured by microarray analysis. Gelsolin protein expression was also increased in cardiomyopathic hearts from tropomodulin-overexpressing (TOT) mice and rac1-expressing (racET) mice.

CONCLUSIONS

Altered expression of the genes identified in this study may contribute to development of the heart failure phenotype and/or represent compensatory mechanisms to sustain cardiac function in failing human hearts.

Mapping the binding-site crevice of the dopamine D2 receptor by the substituted-cysteine accessibility method

The binding site of the dopamine D2 receptor, like that of other homologous G protein-coupled receptors, is contained within a water-accessible crevice formed among its seven membrane-spanning segments. We have developed a method to map systematically all the residues forming the surface of this binding-site crevice, and we have applied this method to the third membrane-spanning segment (M3). We mutated, one at a time, 23 residues in and flanking M3 to cysteine and expressed the mutant receptors heterologously. Ten of these mutants reacted with charged, hydrophilic, lipophobic, sulfhydryl-specific reagents, added extracellularly, and were protected from reaction by a reversible dopamine antagonist. Thus, the side chains of these residues are exposed in the binding-site crevice, which like M3 extends from the extracellular to the intracellular side of the membrane. The pattern of exposure is consistent with a short loop followed by six turns of an alpha helix.

Sequence, mapping and disruption of CCC2, a gene that cross-complements the Ca(2+)-sensitive phenotype of csg1 mutants and encodes a P-type ATPase belonging to the Cu(2+)-ATPase subfamily

We have isolated, sequenced, mapped and disrupted a gene, CCC2, from Saccharomyces cerevisiae. This gene displays non-allelic complementation of the Ca(2+)-sensitive phenotype conferred by the csg1 mutation. Analysis of the CCC2p amino acid sequence reveals that it encodes a member of the P-type ATPase family and is most similar to a subfamily thought to consist of Cu2+ transporters, including the human genes that mutate to cause Wilson disease and Menkes disease. The ability of this gene, in two or more copies, to reverse the csg1 defect suggests that Ca(2+)-induced death of csg1 mutant cells is related to Cu2+ metabolism. Cells without CCC2 require increased Cu2+ concentrations for growth. Therefore CCC2p may function to provide Cu2+ to a cellular compartment rather than in removal of excess Cu2+.

Synthesis and biological activity of highly potent octapeptide analogs of somatostatin

In the search for selective and long-acting analogs of somatostatin, nearly 200 compounds were synthesized by solid-phase methods, purified, and tested biologically. Among these octapeptides, some contained N-terminal (Formula: see text) were 177 times and 113 times more potent, respectively, than somatostatin in tests for inhibition of growth hormone release. These two octapeptides containing tyrosine and valine in positions 3 and 6, respectively, were more active and more selective than their Phe-3 and Thr-6 counterparts, D-Phe-Cys-Phe-D-Trp-Lys-Thr-Cys-Thr-NH2 and D-Phe-Cys-Phe-D-Trp-Lys-Thr-Cys-Trp-NH2. D-Phe-Cys-Tyr-D-Trp-Lys-Val-Cys-Thr-NH2 was also about 6 times more potent than its L-Trp-4 diastereoisomer. The analogs D-Phe-Cys-Tyr-Lys-Val-Cys-Thr-NH2 and D-Phe-Cys-Tyr-D-Trp-Lys-Val-Cys-Trp-NH2 showed a prolonged duration of action and were able to inhibit growth hormone release for at least 3 hr. Analogs of both Phe-3/Thr-6 and Tyr-3/Val-6 classes also suppressed the release of insulin and glucagon in rats and pentagastrin-induced secretion of gastric acid in dogs, but their potencies in these tests were much smaller than the growth-hormone-release inhibitory activity. Some of these analogs possessed antitumor activities as shown by the inhibition of growth of animal models of prostate, mammary, and ductal pancreatic tumors.

Potentiation of the D2 mutant motor phenotype in mice lacking dopamine D2 and D3 receptors

Within the D2-class of dopamine receptors, the D2 and D3 subtypes share the highest degree of similarity in their primary structure. However, the extent to which these two receptor subtypes have similar or different functional properties is unclear. The present study used gene targeting to generate mice deficient for D2, D3, and D2/D3 receptors. A comparative analysis of D2 and D3 single mutants and D2/D3 double mutants revealed that D2/D3 double mutants develop motor phenotypes that, although qualitatively similar to those seen in D2 single mutants, are significantly more severe. Furthermore, increased levels of the dopamine metabolites dihydroxyphenyl acetic acid and homovanillic acid are found in the dorsal striatum of D2 single mutants. The levels of these metabolites, however, are significantly higher in mice lacking D2 and D3 receptors. In addition, results of immunoprecipitation experiments revealed that D2 single mutants express higher levels of D3 receptor proteins during later stages of their postnatal development. These results suggest that D3 receptors compensate for some of the lacking D2 receptor functions and that these functional properties of D3 receptors, detected in mice with a D2 mutant genetic background, remain masked when the abundant D2 receptor is expressed.

SUR1 (CSG1/BCL21), a gene necessary for growth of Saccharomyces cerevisiae in the presence of high Ca2+ concentrations at 37 degrees C, is required for mannosylation of inositolphosphorylceramide

Saccharomyces cerevisiae cells require two genes, CSG1/SUR1 and CSG2, for growth in 50 mM Ca2+, but not 50 mM Sr2+. CSG2 was previously shown to be required for the mannosylation of inositolphosphorylceramide (IPC) to form mannosylinositolphosphorylceramide (MIPC). Here we demonstrate that SUR1/CSG1 is both genetically and biochemically related to CSG2. Like CSG2, SUR1/CSG1 is required for IPC mannosylation. A 93-amino acid stretch of Csg1p shows 29% identity with the alpha-1, 6-mannosyltransferase encoded by OCH1. The SUR1/CSG1 gene is a dose-dependent suppressor of the Ca(2+)-sensitive phenotype of the csg2 mutant, but overexpression of CSG2 does not suppress the Ca2+ sensitivity of the csg1 mutant. The csg1 and csg2 mutants display normal growth in YPD, indicating that mannosylation of sphingolipids is not essential. Increased osmolarity of the growth medium increases the Ca2+ tolerance of csg1 and csg2 mutant cells, suggesting that altered cell wall synthesis causes Ca(2+)-induced death. Hydroxylation of IPC-C to form IPC-D requires CCC2, a gene encoding an intracellular Cu2+ transporter. Increased expression of CCC2 or increased Cu2+ concentration in the growth medium enhances the Ca2+ tolerance of csg1 mutants, suggesting that accumulation of IPC-C renders csg1 cells Ca2+ sensitive.

Mechanisms of modified LDL-induced pericyte loss and retinal injury in diabetic retinopathy

AIMS/HYPOTHESIS

In previous studies we have shown that extravasated, modified LDL is associated with pericyte loss, an early feature of diabetic retinopathy (DR). Here we sought to determine detailed mechanisms of this LDL-induced pericyte loss.

METHODS

Human retinal capillary pericytes (HRCP) were exposed to 'highly-oxidised glycated' LDL (HOG-LDL) (a model of extravasated and modified LDL) and to 4-hydroxynonenal or 7-ketocholesterol (components of oxidised LDL), or to native LDL for 1 to 24 h with or without 1 h of pretreatment with inhibitors of the following: (1) the scavenger receptor (polyinosinic acid); (2) oxidative stress (N-acetyl cysteine); (3) endoplasmic reticulum (ER) stress (4-phenyl butyric acid); and (4) mitochondrial dysfunction (cyclosporin A). Oxidative stress, ER stress, mitochondrial dysfunction, apoptosis and autophagy were assessed using techniques including western blotting, immunofluorescence, RT-PCR, flow cytometry and TUNEL assay. To assess the relevance of the results in vivo, immunohistochemistry was used to detect the ER stress chaperon, 78 kDa glucose-regulated protein, and the ER sensor, activating transcription factor 6, in retinas from a mouse model of DR that mimics exposure of the retina to elevated glucose and elevated LDL levels, and in retinas from human participants with and without diabetes and DR.

RESULTS

Compared with native LDL, HOG-LDL activated oxidative and ER stress in HRCP, resulting in mitochondrial dysfunction, apoptosis and autophagy. In a mouse model of diabetes and hyperlipidaemia (vs mouse models of either condition alone), retinal ER stress was enhanced. ER stress was also enhanced in diabetic human retina and correlated with the severity of DR.

CONCLUSIONS/INTERPRETATION

Cell culture, animal, and human data suggest that oxidative stress and ER stress are induced by modified LDL, and are implicated in pericyte loss in DR.

Residues in the seventh membrane-spanning segment of the dopamine D2 receptor accessible in the binding-site crevice

The binding site of the dopamine D2 receptor, like that of other homologous G-protein-coupled receptors, is contained within a water-accessible crevice formed among its seven membrane-spanning segments. Using the substituted-cysteine accessibility method, we previously mapped the residues that form the surface of the binding-site crevice in the third and fifth membrane-spanning segments (M3 and M5). We have now mutated to cysteine, one at a time, 26 consecutive residues in and flanking the seventh membrane-spanning segment (M7) and expressed the mutant receptors in HEK 293 cells. Nine of these mutants reacted with charged, hydrophilic, lipophobic, sulfhydryl-specific reagents, added extracellularly, and were protected from reaction by a reversible dopamine antagonist, sulpiride. Thus, we infer that the side chains of these residues are in the water-accessible surface of the binding-site crevice. The pattern of accessibility of the cysteine-substitution mutants is consistent with M7 being a kinked alpha-helix.

Residues in the fifth membrane-spanning segment of the dopamine D2 receptor exposed in the binding-site crevice

The binding site of the dopamine D2 receptor, like that of other homologous G-protein-coupled receptors, is contained within a water-accessible crevice formed among its seven membrane-spanning segments. Using the substituted-cysteine accessibility method, we previously mapped the residues in the third membrane-spanning segment (M3) that are exposed in the biding site crevice [Javitch et al. (1995) Neuron 14, 825]. We have now mutated, one at a time, 24 consecutive residues in and flanking the fifth membrane-spanning segment (M5) to cysteine and expressed the mutant receptors in HEK 293 cells. Thirteen of these mutants reacted with charged, hydrophilic, lipophobic, sulfhydryl-specific reagents, added extracellularly, and were protected from reaction by another reversible dopamine antagonist, sulpiride. Thus, the side chains of these residues are exposed in the binding-site crevice. Of the 13 exposed residues, 10 are consecutive, from Phe189 to Phe198. This pattern of exposure is inconsistent with the expectation that M5, like M3, forms a fixed alpha-helix, one side of which is exposed in the binding-site crevice. The exposed region of M5, which contains the serines likely to bind agonist [Strader et al. (1989) J. Biol. Chem. 264, 13752], might loop out into the lumen of the binding-site crevice and be completely accessible to water and thus to MTSEA. Alternatively, the exposed region of M5 might be embedded in the membrane and also in contact with other membrane-spanning segments. At any instant, only a limited set of residues might be exposed in the binding-site crevice; however, M5 might move rapidly to expose different sets of residues.

Vibration sonoelastography and the detectability of lesions

Vibration sonoelastography has been developed for the detection of hard lesions in relatively soft tissue. The basic concept is to propagate low-amplitude and low-frequency shear waves (with displacements below 0.1 mm and frequencies typically below 1000 Hz) through deep organs, and displaying the vibration response in real-time using advanced color Doppler imaging techniques. A hard inhomogeneity, such as a tumor, will produce a localized disturbance in the vibration pattern, forming the basis for detection even when the tumor is isoechoic on B-scan images. This paper focuses on the important quantitative issues concerning the detectability or inherent contrast of lesions. The specific factors of lesion size, relative stiffness and vibration frequency are studied using theoretical models, finite element methods and experimental measurements on tissue-mimicking materials. The results indicate that detectability increases with vibration (shear wave) frequency; however, loss mechanisms ultimately limit the penetration of higher vibration frequencies (in the kHz range).

Effects of modified LDL and HDL on retinal pigment epithelial cells: a role in diabetic retinopathy?

AIMS/HYPOTHESIS

Blood-retina barrier leakage in diabetes results in extravasation of plasma lipoproteins. Intra-retinal modified LDLs have been implicated in diabetic retinopathy (DR), but their effects on retinal pigment epithelial (RPE) cells and the added effects of extravasated modified HDLs are unknown.

METHODS

In human retinas from individuals with and without diabetes and DR, immunohistochemistry was used to detect ApoB, ApoA1 and endoplasmic reticulum (ER) stress markers. In cell culture, human RPE cells were treated with native LDL (N-LDL) or heavily-oxidised glycated LDL (HOG-LDL) with or without pretreatment with native HDL (N-HDL) or heavily-oxidised glycated HDL (HOG-HDL). Cell viability, oxidative stress, ER stress, apoptosis and autophagy were assessed by Cell Counting Kit-8 assay, dichlorofluorescein assay, western blotting, immunofluorescence and TUNEL assay. In separate experiments, RPE cells were treated with lipid oxidation products, 7-ketocholesterol (7-KC, 5-40 μmol/l) or 4-hydroxynonenal (4-HNE, 5-80 μmol/l), with or without pretreatment with N-HDL or HOG-HDL.

RESULTS

ApoB, ApoA1 staining and RPE ER stress were increased in the presence of DR. HOG-LDL but not N-LDL significantly decreased RPE cell viability and increased reactive oxygen species generation, ER stress, apoptosis and autophagy. Similarly, 4-HNE and 7-KC decreased viability and induced ER stress. Pretreatment with N-HDL mitigated these effects, whereas HOG-HDL was less effective by most, but not all, measures.

CONCLUSIONS/INTERPRETATION

In DR, extravascular modified LDL may promote RPE injury through oxidative stress, ER stress, autophagy and apoptosis. N-HDL has protective effects, but HOG-HDL is less effective. Extravasation and modification of HDL may modulate the injurious effects of extravasated modified LDL on the retinal pigment epithelium.

Neutral oligosaccharide content of preterm human milk

Human milk oligosaccharides are known to play a role in protection against certain infectious diseases. Previous reports indicate that the content of human milk oligosaccharides varies widely among individuals at term but such information on preterm milk is lacking. After removal of the fat, protein and most of the lactose from non-pooled human milk samples, a total neutral oligosaccharide fraction was isolated by ion-exchange chromatography followed by gel filtration. A Dionex high-performance anion-exchange chromatography system equipped with a pulsed electrometric detector was then employed to measure the levels of ten neutral oligosaccharides in the individual milk samples. Twenty-three milk samples from thirteen mothers who delivered at a mean gestational age of 29.5 (SD 3.1) weeks were collected between days 0 and 33 of lactation, and compared with three samples of term milk from two mothers. The ranges of the total and individual levels of the ten neutral oligosaccharides in preterm milk were similar to those in term milk. Further, as previously described in term milk, preterm milk exhibited a quantitative individual variation. This variation was independent of the gestational age, day of lactation, and postconceptional age. In conclusion, levels of ten neutral oligosaccharides did not differ between preterm and term human milk.

Matrix-assisted laser desorption/ionization mass spectrometry of immobilized duplex DNA probes

Matrix-assisted laser desorption/ionization (MALDI) time-of-flight (TOF) mass spectrometry was used to analyze short DNA duplex probes with one strand immobilized on solid supports (straptavidin-coated magnetic beads or controlled pore glass beads). Only the non-immobilized strand could be detected. Partial denaturation was found when the duplex probes were mixed with 3-hydroxypicolinic acid, ammonium citrate matrix. The strategy has several applications, such as fast DNA sequence analysis and DNA diagnostics.

N-glycosylation site mapping of human serotransferrin by serial lectin affinity chromatography, fast atom bombardment-mass spectrometry, and 1H nuclear magnetic resonance spectroscopy

This report describes the N-glycosylation site mapping of human serotransferrin (h-STF). Reduced and S-carboxymethylated h-STF was digested with trypsin or chymotrypsin. Glycopeptides in the proteolytic digests were isolated by serial concanavalin A (Con A), Sambucus nigra agglutinin (SNA), and Phaseolus vulgaris leukoagglutinin (LPHA) affinity chromatography and subjected to preliminary analysis by 1H NMR spectroscopy. The glycopeptide fractions were then individually digested with N-glycanase. One part of the digest of each fraction was analyzed by fast atom bombardment-mass spectrometry (FAB-MS) to identify the peptide sequences of the glycosylation sites. The other part was used to isolate the oligosaccharide by the corresponding lectin affinity chromatography and to characterize the structures of the isolated oligosaccharides by 1H NMR spectroscopy and FAB-MS. The oligosaccharides in the Con A-bound fraction were shown to have bi-alpha(2-->6)-sialyl, diantennary structures. The SNA-bound fraction was shown to contain trisialyl, triantennary structures. Di- and triantennary oligosaccharides were found to occur on each of the two N-glycosylation sites of h-STF (Asn413 and Asn611) in the ratio of approximately 85:15. The SNA-bound glycopeptides were further fractionated by LPHA affinity chromatography. Two different oligosaccharides were characterized, namely, a trisialyl 2,4-triantennary and a trisialyl 2,6-triantennary glycan. The ratio of 2,4-triantennary vs 2,6-triantennary oligosaccharides attached to glycosylation site Asn413 was found to be approximately 5:1, whereas the two isomeric triantennary oligosaccharides were found to be attached to glycosylation site Asn611 in the ratio approximately 1:1.

Evaluation of the safety, reactogenicity and immunogenicity of three recombinant outer surface protein (OspA) lyme vaccines in healthy adults

The safety, reactogenicity and immunogenicity of three candidate Lyme vaccines based on recombinant outer surface protein (OspA) presented in either lipidated or unlipidated forms, were assessed in 300 seronegative volunteers. Subjects received three doses of one of the three formulations at monthly intervals and were evaluated for antibody levels and the presence of symptoms after each dose. All formulations proved to be safe, the majority of local reactions being reported as mild, and all general symptoms were perceived to be either-mild or moderate in intensity. No subject refused a subsequent vaccine dose. All subjects were tested for both anti-OspA IgG and LA-2 equivalent antibodies up until day 84. All three vaccines induced an immune response but subjects who received lipoprotein OspA had the highest anti-OspA IgG and LA-2 equivalent GMTs after each dose and this was also true for the subset of subjects tested on day 180. The lipoprotein OspA group also had the largest number of subjects who remained seropositive for anti-OspA IgG antibodies. As the lipoprotein formulation produced the strongest immune response, with symptoms which were acceptable to all the vaccinees, we suggest further development of this vaccine.