Effect of Ionic Strength on Freeze–Thaw Stability of Glycosylated Soy Protein Emulsion

This study used Soy Protein Isolate (SPI), Soy Protein Isolate Hydrolysates (SPH) and Dextran (D) as raw materials. Covalent compounds were prepared by grafting soy protein isolate and soy protein isolate hydrolysate with dextran by water-heating method, which were SPI-D and SPH-D, respectively. The effect of ionic strength (0–500 mM) on the freeze–thaw stability of SPI, SPI-D, and SPH-D emulsions was investigated. Fourier transform infrared analysis and Fluorescence emission spectroscopy analysis indicated that the structure of the protein changed. In this study, it was found that with the increase of ionic strength, the zeta potential of the three samples presented a downward trend and the surface hydrophobicity first decreased and then increased. The addition of ions effectively improved the freeze–thaw stability of the emulsions. The particle size of the emulsions changed little after freeze–thaw cycles, and coalescence degree, creaming index, and oiling off significantly decreased. Especially when the ionic strength reached 300 mM, the degree of coalescence was 248.46%, 170.92%, and 167.77%, respectively, and the oiling off was also reduced by 68.52%, 68.25%, and 59.92%, respectively. The creaming index of the SPI emulsion was 48.49% lower than the creaming index without ions. However, when the ionic strength exceeded 300 mM, the coalescence degree, creaming index, and oiling off of the emulsions increased. Optical microstructures also found that at ionic strength of 300 mM, the oil droplets produced by the three kinds of emulsion after freeze–thaw were smaller than those without ions.     

Impact of milieu conditions on the α-lactalbumin glycosylation in the dry state

Maillard reaction is influenced by protein and sugar properties, water activity (a_w) as well as the glycosylation time and temperature. The aim of this work was to investigate the influence of environmental parameters on the glycosylation reaction kinetics and to develop a technology platform for protein glycosylation as a possible substrate pre-treatment. The glycosylation reaction of bovine α-lactalbumin (α-La) was performed with lactose and maltodextrin in the dry-state at 40, 50 or 60 °C performed at a_w of 0.33, 0.44 or 0.58 for reaction times of 8, 24 or 48 h. The degree of glycosylation (DG) was determined as the loss of lysine using the ortho-phthalaldehyde (OPA) method. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS–PAGE) with Coomassie and glycoprotein staining was also performed. The reaction with lactose reached higher DG values in all cases as compared to reactions with maltodextrin (maximum DG of 85% and 31%, respectively, at a_w = 0.58 after 48 h). Lactosylation kinetics showed that the second order rate constants increased with increasing temperature and were highest at a_w = 0.58 in all cases. The activation energies were determined as 97.1 ± 37.7, 193.9 ± 9.1 and 136.6 ± 15.6 kJ/mol for a_w = 0.33, 0.44 and 0.58, respectively and showed an increasing trend with increasing temperature. Glycosylation of α-La offers a new process for improvement of functional properties as well as being a substrate pre-treatment process to control enzymatic digestion in order to generate tailor-made peptides as food additives with important health benefits like probiotics due to glycoprotein resistance to further enzyme hydrolysis.     

N -linked oligosaccharide in MSP-1 and its implication for scallop calcification

We speculated the structure of the N-linked oligosaccharides enzymatically released from the organic matrix (OM) component in the foliated layer of Patinopecten yessoensis. The 80 kDa component of the soluble OM was detected by lectin blotting and was identified as MSP-1 using liquid chromatography/mass spectrometry (LC/MS/MS). LC/MS/MS analysis of the N-glycan liberated from MSP-1 detected a hybrid-type N-glycan, which contained sulfite and sialic acid at its terminus based on the characteristic Y ions. The data strongly imply that MSP-1, a sulfated OM glycoprotein, participates in molluscan biomineralization by creating a favorable environment for calcium ion uptake through sulfite acid and sialic acid. Further analyses of oligosaccharides linked to the OM components in wide variety of species and shell microstructures may definitely contribute in elucidation of molluscan biomineralization at the molecular level.     

Using lectins in biomarker research: Addressing the limitations of sensitivity and availability

Carbohydrates have fundamental roles throughout biology, yet they have not been as well studied as proteins and nucleic acids, in part due to limitations in the experimental tools. Improved methods for studying glycans could spur significant advances in the understanding and application of glycobiology. The use of affinity reagents, such as lectins and glycan-binding antibodies, is a valuable complement to methods involving mass spectrometry and chromatography. This article addresses two limitations that have prevented the broader experimental use of glycan-binding proteins: sensitivity and availability. The sensitivity limitation stems from the poor affinity that many glycan-binding proteins have as isolated analytical reagents. To address this problem, I propose making use of multivalent interactions between lectins and glycans, mimicking those frequently found in the biological setting. Recent experiments show that a practical technique for producing lectin multimers can significantly improve detection sensitivity. The second limitation, availability, is the difficulty of finding and obtaining glycan-binding proteins that recognize less common or arbitrarily defined glycan structures. To address this problem, I propose translating the wealth of existing glycan array data into a quantitative, searchable database of the specificities of glycan-binding proteins. Such a resource would allow us to more easily identify proteins with defined specificities and perform detailed comparisons between reagents. Solutions to these two limitations could lead to the more effective use of, and a broader range of, glycan-binding reagents.     

Relative versus absolute quantitation in disease glycomics

The glycome of a diagnostic biological material such as blood, urine, saliva, tissue, or cell cultures comprises of a vast array of structurally distinct glycans attached to the protein complement. Aberrant glycan structures and distributions result from changes in specific glycosyltransferase activities and have different biological significance, making proper quantitation of glycans highly important. In this review, common HPLC/CE and LC-MS/MS-based methods for glycomics, their advantages and disadvantages, will be discussed with respect to the main quantitative strategies. With the increasing interest in absolute quantitation for glycomics, we discuss absolute and relative glycome quantitation and how it affects the resulting conclusions drawn from glycomics studies. We argue that while absolute quantitation of glycomes may be attractive for some areas of clinical glycomics, relative quantitation of glycans remains the most informative and time/cost-effective method to obtain biological insight into the regulation of the cellular glycosylation machinery and the synthesis of the resultant glycan structures in most research questions due to the enzymatic relatedness of the biosynthesized glycans. Recent developments in multiplexing of glycomes by the introduction of stable isotopic labeling of glycans show promise for providing another level of information to the existing benefits of relative quantitation.     

Soluble amyloid precursor protein 770 is a novel biomarker candidate for acute coronary syndrome

Most Alzheimer disease patients show deposition of amyloid β (Aβ) peptide in blood vessels as well as the brain parenchyma. We previously found that vascular endothelial cells express amyloid β precursor protein (APP) 770, a different APP isoform from neuronal APP695, and that they produce amyloid β peptide. We analyzed the glycosylation of APP770 and found that O-glycosylated sAPP770 is preferentially processed by proteases for Aβ production. Because the soluble APP cleavage product sAPP is considered to be a possible marker for Alzheimer disease diagnosis, sAPP, consisting of a mixture of these variants, has been widely measured. We hypothesized that measurement of the endothelial APP770 cleavage product in patients separately from that of neuronal APP695 would enable us to discriminate between endothelial and neurological dysfunctions. Our recent findings, showing that the level of plasma sAPP770 is significantly higher in patients with acute coronary syndrome, raise the possibility that sAPP770 could be an indicator of endothelial dysfunction. In this review, we first describe the expression, glycosylation, and processing of APP770, and then discuss sAPP770 as a novel biomarker candidate of acute coronary syndrome.     

Changes of serum‐associated fucosylated glycoproteins and changes in glycosylation of IgA in human cirrhosis

Many modifications in N‐glycosylation have been demonstrated in hepatic cirrhosis. These modifications correspond to an increase of a bisecting core alpha(1,6)‐fucosylated biantennary glycan, an increase in core fucosylation, and the presence of an important population of neutral oligosaccharides in human serum of cirrhotic patients. In this study, a glycoproteomic approach which consists of lectin affinity chromatography, MALDI‐TOF MS for the characterization of N‐glycans released from glycoproteins, one‐ and 2‐D PAGE, electrospray ionization quadrupole ion trap (ESI‐QIT) MS was used to identify serum fucosylated glycoproteins related to cirrhosis. Employing this method, we have shown that IgA is one of the major proteins that is responsible of the glycosylation modifications observed in the serum N‐glycome of cirrhotic patients. To our knowledge, this is the first time that aberrant N‐glycosylation of IgA in cirrhosis is described.     

Glycosylation of Fluorophenols by Plant Cell Cultures

Fluoroaromatic compounds are used as agrochemicals and released into environment as pollutants. Glycosylation of 2-, 3-, and 4-fluorophenols using plant cell cultures of Nicotiana tabacum was investigated to elucidate their potential to metabolize these compounds. Cultured N. tabacum cells converted 2-fluorophenol into its β-glucoside (60%) and β-gentiobioside (10%). 4-Fluorophenol was also glycosylated to its β-glucoside (32%) and β-gentiobioside (6%) by N. tabacum cells. On the other hand, N. tabacum glycosylated 3-fluorophenol to β-glucoside (17%).     

Use of Furandicarboxylic Acid and Its Decyl Ester as Additives in the Fischer’s Glycosylation of Decanol by d-Glucose: Physicochemical Properties of the Surfactant Compositions Obtained

2,5-Furandicarboxylic acid is a promising bio-based platform chemical that may serve as a ‘green’ substitute for terephthalate in polyesters. In the present work, straightforward glycosylation of decanol with unprotected and non-activated d-glucose was performed under reduced quantities of sulfuric acid as catalyst (down to 0.9 mol%) in the presence of 2,5-furandicarboxylic acid or its n-decyl ester as additive. Yield of decyl monoglucosides was highly improved by the use of the additives. Moreover, the presence of additive also limited the colouration of the reaction. The physical and chemical properties of the surfactant composition produced were studied and compared to reference compositions. The ultimate biodegradability of furan-2,5-dicarboxylic acid (FDCA) and its n-decyl ester formed or produced in the bulk reaction medium was also studied in order to assess its potential use in surfactant industry.