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Analytical Chemistry Jun 2020Understanding molecular mechanisms governing interactions of glycosaminoglycans (such as heparin) with proteins remains challenging due to their enormous structural...
Understanding molecular mechanisms governing interactions of glycosaminoglycans (such as heparin) with proteins remains challenging due to their enormous structural heterogeneity. Commonly accepted approaches seek to reduce the structural complexity by searching for "binding epitopes" within the limited subsets of short heparin oligomers produced either enzymatically or synthetically. A top-down approach presented in this work seeks to preserve the chemical diversity displayed by heparin by allowing the longer and structurally diverse chains to interact with the client protein. Enzymatic lysis of the protein-bound heparin chains followed by the product analysis using size exclusion chromatography with online mass spectrometry detection (SEC/MS) reveals the oligomers that are protected from lysis due to their tight association with the protein, and enables their characterization (both the oligomer length, and the number of incorporated sulfate and acetyl groups). When applied to a paradigmatic heparin/antithrombin system, the new method generates a series of oligomers with surprisingly distinct sulfation levels. The extent of sulfation of the minimal-length binder (hexamer) is relatively modest yet persistent, consistent with the notion of six sulfate groups being both essential and sufficient for antithrombin binding. However, the masses of longer surviving chains indicate complete sulfation of disaccharides beyond the hexasaccharide core. Molecular dynamics simulations confirm the existence of favorable electrostatic interactions between the high charge-density saccharide residues flanking the "canonical" antithrombin-binding hexasaccharide and the positive patch on the surface of the overall negatively charged protein. Furthermore, electrostatics may rescue the heparin/protein interaction in the absence of the canonical binding element.
Topics: Antithrombins; Bacteroides; Chromatography, Gel; Heparin; Humans; Mass Spectrometry; Molecular Dynamics Simulation; Polysaccharide-Lyases; Printing, Three-Dimensional; Solutions
PubMed: 32347711
DOI: 10.1021/acs.analchem.0c00115 -
IDCases 2023is an obligately anaerobic, catalase-positive, motile, non-sporulating, gram-positive coccobacillus. Human infections are rare and have not been previously reported in...
BACKGROUND
is an obligately anaerobic, catalase-positive, motile, non-sporulating, gram-positive coccobacillus. Human infections are rare and have not been previously reported in Japan. Herein, we report the first case of perforated peritonitis with bacteremia in Japan.
CASE PRESENTATION
A 61-year-old Japanese man with advanced colorectal adenocarcinoma presented with fever and abdominal pain. Abdominal computed tomography revealed a low-density area with thinning of the sigmoid colon wall and air outside the intestinal tract, which was diagnosed as perforated peritonitis. Cultures of the ascitic fluid isolated , , , , and . Gram-positive rods were detected in the blood culture on admission after 4 days. The isolate was identified as via 16S ribosomal RNA (16S rRNA) sequencing. The patient underwent open abdominal washout and drainage via a transverse colon bifurcation colostomy. Intravenous meropenem (3 g/day) was administered for 5 days, followed by intravenous piperacillin-tazobactam (9 g/day) for 6 days, and then levofloxacin (500 mg/day) and metronidazole (1500 mg/day) intravenously for 15 days. Postoperatively, the patient gradually recovered. He was transferred to another palliative care hospital on day 38 after admission for worsening advanced colorectal cancer condition.
CONCLUSION
Bacteremia caused by is rare. 16S rRNA sequencing should be considered for the identification of gram-positive anaerobic rods that are difficult to diagnose by conventional methods.
PubMed: 37214185
DOI: 10.1016/j.idcr.2023.e01797