EVALUATION OF ANOMERICRECOGNITION IN GALACTOSE BINDING LECTINS USING CROSSLINKED HEMICELLULOSE: A COMPARATIVE STUDY THROUGH AFFINITY CHROMATOGRAPHY

The isolation of lectins by affinity chromatography with crosslinked hemicelluloses has been a common practice because of the variety of glycosides that they present, improving the isolation of different kinds of lectins, such as the galactose ligands.Lectins affinity for carbohydrates is so specific that a simple configuration of the chiral carbon can affect affinity, and there are lectins that are more related to alfa-galactosidic than beta-galactosidic residues, setting up that way, an anomeric recognition.The anomeric configuration of galactose residuesseems to have biological importance related to the behavior of some diseases and physiological processes. This work aimed to assess the anomeric recognition of two lectins reported as β-galactose ligands (PNA and ricin) and two lectins reported as α-galactose ligands (frutalin and jacalin) in two types of hemicellulose (xyloglucan of Tamarindus indica and galactomannan of Caesalpinia pulcherrima), subsequently crosslinked and used as chromatographic matrices. As a result,chromatographic profiles and retained fractions suggested preferential anomeric recognition by lectins for the hemicelluloses crosslinked. The galactomannan matrix retained 0,5mg of PNA lectin and 2,3mg of ricin lectin; meanwhile, the xyloglucan matrix retained 3,4mg of PNA and 3,2mg of ricin; results obtained by applying 5 mg of lectin. Ricin expresses a visible flexibility in anomeric recognition, while PNA shows a restricted recognition of β-galactose residues.Frutalin and jacalin did not show recognition of the xyloglucan matrix. This work proposes using hemicellulose reticles with epichlorohydrin as affinity chromatographic matrices for anomeric studies on recognizing galactose binding lectins.

Collision-induced dissociation of xylose and its applications in linkage and anomericity identification

Different dehydration barrier heights result in different branching ratio, a simple and fast anomeric configuration identification for xylose.

Selective Anomeric Deacetylation of Per-Acetylated Carbohydrates Using (i-Pr)3Sn(OEt) and Synthesis of New Derivatives

In this study natural carbohydrates such as glucose, galactose, xylose, fructose andlactose, are acetylated by acetic anhydride and sodium acetate catalyst. Anomeric configuration is deacetylated by (i-Pr)3Sn(OEt)as a catalyst, an easy synthetic regioselective deacetylation of full acetylated carbohydrates using (i--Pr)3Sn(OEt) is described. The acetylated carbohydrates reacted with HBr (solution in AcOH, 32 wt.%) for the bromination of anomeric position. The synthesis oxazaphosphorine, and bromo hexa alkyl Methylsulfonate derivatives from anomeric position of carbohydrates was reacted. FT IR, 1H, 13C NMR, 31PNMR spectroscopy techniques were employed to examine the synthesized compounds.

Chiral evasion and stereospecific antifolate resistance in Staphylococcus aureus

Antimicrobial resistance is a health care crisis. The resistance-conferring mutation F98Y in Staphylococcus aureus dihydrofolate reductase (SaDHFR) reduces effectiveness of antifolates, e.g., trimethoprim (TMP). Although propargyl-linked antifolates (PLAs) are much more resilient than TMP towards F98Y, this substitution still vitiates their inhibition potency. Surprisingly, differences in the enantiomeric configuration at the stereogenic center of PLAs influence the isomeric state of NADPH cofactor. Is resistance correlated with chiral evasion? A mechanism of action underpinning this coupling is unknown. To understand the molecular basis of F98Y-mediated resistance and how PLAs’ inhibition drives NADPH isomeric states, we used OSPREY to analyze a comprehensive suite of structural, biophysical, biochemical, and computational data. We present a model showing how F98Y SaDHFR exploits a different anomeric configuration of NADPH to evade certain PLAs’ inhibition, while other PLAs remain resilient to resistance. Our model should enable general design of inhibitors that are resilient to chiral evasion.