China
Africa
Explore chapters and articles related to this topic
Methods for the Morphological Study of Tracheal and Bronchial Glands
Published in Joan Gil, Models of Lung Disease, 2020
Serous tubules in the human respiratory tract stain moderately for complex carbohydrate at the light microscopic level. With the AB-PAS method, some serous cells in human submucosal gland evidence red staining indicative of neutral mucosubstance and others blue-purple coloration demonstrative of acidic glycoconjugate. The acidic groups are identifiable as sulfate esters from their gray to black staining with the HID-AB sequence. The latter method rarely reveals blue staining demonstrative of neuraminic acid (sialic acid) in serous cells, in contrast with the abundant sialic acid demonstrable histochemically in mucous cells. Meanwhile, serous tubules in mouse trachea have been found to lack affinity for cationic reagents, including AB and iron diamine, and to stain red with the AB-PAS method; they are, therefore, uniformly judged to produce a neutral complex carbohydrate. The peanut lectin-horseradish peroxidase (Stoward et al., 1980) and galactose oxidase-Schiff methods concur in demonstrating terminal galactose in glycoprotein devoid of neuraninic acid (Spicer et al., 1983). Beyond an inconstant degree of affinity for HID, demonstrative of a variable content of sulfate esters in secretory mucosubstance, serous cells differ little from one another at the light microscopic level.
Pregnancy-Related Proteins Detected by Immunochemical or Physicochemical Methods
Published in Gábor N. Than, Hans Bohn, Dénes G. Szabó, Advances in Pregnancy-Related Protein Research, 2020
Thus far, no biological functions or structural relations to other proteins are known for PP25. Isolation and characterization of this soluble placental tissue protein were described in 1991.48 PP25 has a molecular weight of about 100,000 Da as determined by ultracentrifugation and a subunit molecular mass of around 20,000 as determined by SDS-polyacrylamide gel electrophoresis. Its electrophoretic mobility was found to be in the range between albumin and the α1-globulins. Treatment with neuraminidase did not change the electrophoretic mobility. This accords with the analytical findings that this protein does not contain detectable amounts of neuraminic acid.
Biocatalysts: The Different Classes and Applications for Synthesis of APIs
Published in Peter Grunwald, Pharmaceutical Biocatalysis, 2019
N-acetyl-D-neuraminic acid (NeuAc; sialic acid) that can mediate or modulate a wide variety of physiological and pathological processes (Varki, 2008; Tao et al., 2010) is the precursor of a variety of drugs (e.g., for treatment of rheumatoid arthritis, septic shock, gastric ulcers, and other diseases). Several (chemo)enzymatic routes for the two-step synthesis of NeuAc have been described. The first step is the alkali-orN-acetyl-D-glucosamine(GlcNAc)-epimerase-catalyzed epimerization of GlcNAc to N-acetyl-D-mannosamine (ManNAc), followed by the production of Neu5Ac from ManNAc in presence of N-acetyl-D-neuraminic acid aldolase (opposite scheme). For this purpose, Lee et al. (2007) cloned and expressed genes from Anabaena sp. (GlcNAc-epimerase) and Escherichia coli (Neu5Ac aldolase) in E. coli BL21 (DE3); with the transformed E. coli cells that could be reused for more than 8 cycles a maximal productivity of 10.2 g NeuAc L−1∙h−1 was achieved. Gao et al. (2011; see also literature cited therein) used spore surface-displayed Neu5Ac aldolase (spores of B. subtilis, also reusable and an alternative to Neu5Ac aldolase immobilization); the productivity of this process was 4.9 g NeuAc L−1∙h−1.
Surface charge, glycocalyx, and blood-brain barrier function
Published in Tissue Barriers, 2021
Fruzsina R. Walter, Ana R. Santa-Maria, Mária Mészáros, Szilvia Veszelka, András Dér, Mária A. Deli
The surface charge density of brain endothelial cells can be made more positive by using specific enzymes to digest off negatively charged residues from the glycocalyx (Figure 2). This observation was already made in the 1980s by electron microscopy, when neuraminidase, heparinase III and other enzymes were used to remove sialic acid and heparan sulfate from the luminal side of brain endothelial cells.22,43,44 Treatment with neuraminidase lowered the endothelial glycocalyx thickness while increasing the permeability to albumin in rat mesenteric microvessels.45 Recently, it was shown, that treatment with neuraminidase elevates the surface potential and decreases the sialic acid and N-acetyl neuraminic acid coverage on a human brain endothelial cell line.46 Neuraminidase treatment did not change the electrical resistance and permeability of the BBB culture model for hydrophilic markers dextran (4 and 10 kDa) and albumin (67.5 kDa),46 suggesting that BBB models can behave differently from other vascular endothelial models. In contrast, intravenously injected hyaluronidase increased BBB permeability for Evans blue in rats and aggravated brain edema following cardiac arrest,47 indicating a different role for hyaluronic acid within the glycocalyx in pathological conditions.
Human carbonic anhydrases and post-translational modifications: a hidden world possibly affecting protein properties and functions
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2020
Anna Di Fiore, Claudiu T. Supuran, Andrea Scaloni, Giuseppina De Simone
In CA IX, O-linked glycosylation occurs at accessible residues present in the highly disordered PG domain84. Interestingly, T115 is present within a region having a high sequence similarity with the keratan sulphate attachment domain of the large aggregating proteoglycan, aggrecan85. Mass spectrometry experiments identified di-, tri- and tetra-saccharides containing N-acetyl-neuraminic Acid (NeuAc) or N-glycolylneuraminic acid (NeuGc), and having or not a sulphate moiety, which were O-linked at this site55. Some of these oligosaccharides highly resemble the keratan sulphate unit that was already described to occur in the proteoglycan domain of other proteins involved in cell adhesion processes and tumour progression86. Studies aimed at elucidating the functional role of this modification on CA IX are currently not available. On the other hand, more complex O-linked glycosaminoglycan (GAG)-like structures87 were detected at S54, which accounted for a mass shift of 20–50 kDa with respect to the non-modified protein88. Their nature was ascertained as chondroitin and heparan sulphate simply based on the specificity of enzymes (chondroitin ABC lyase and heparanase III) used for protein digestion. Novel and more informative studies are requested to fully characterise this CA IX modification.
Charge variant native mass spectrometry benefits mass precision and dynamic range of monoclonal antibody intact mass analysis
Published in mAbs, 2018
Aaron O. Bailey, Guanghui Han, Wilson Phung, Paul Gazis, Jennifer Sutton, Jonathan L. Josephs, Wendy Sandoval
Sialic acids are monosaccharides that include a carboxylic acid group, which imparts a net decrease in protein pI, causing a shift to earlier RT. Neuraminic acid is a type of sialic acid that may be added to N-glycan structures of mAbs. Two neuraminic acid N-glycans, S1G0F and S1G1F, were identified in combinations with the abundant glycans G0F and G1F on isoforms that eluted early relative to the main peak (Figure 6a,d). By comparing the top three sialic acid-containing glycoforms to the top three main peak glycoforms, we estimated 2.47% relative abundance. We also identified the corresponding sialic acid-containing glycoforms that were also deamidated. These species were detected at approximately 0.45% abundance, but were easily identified due to the further decreased RT, owing to the decreased pI resulting from contributions from both deamidation and sialic acid (Figure 6b,e). Multiple species were identified containing two sialylated glycoforms (S1G0F/S1G0F, S1G0F/S1G1F, S1G1F/S1G1F), observed at approximately 0.49% relative abundance (Figure 6c,f). This species demonstrated a decreased RT compared to the moieties containing only one sialic acid glycan, consistent with the presence of an additional sialic acid relative to main peak glycoforms.