Rapid and efficient screening of adsorbent for oligopeptide using molecular docking and isothermal titration calorimetry

Metal-Free C-C Coupling of an Allenyl Sulfone with Picolyl Amides to Access Vinyl Sulfones via Pyridine-Initiated In Situ Generation of Sulfinate Anion

Vinyl sulfones are privileged motifs known for their biological activity and synthetic utility. Synthetic transformations to efficiently access high-value compounds with these motifs are desired and sought after. Herein, a new procedure is described to form vinyl sulfone-containing compounds by selective functionalization of the C(sp³)-H bond adjacent to the pyridine ring of pharmacologically prevalent picolyl amides with an allenyl sulfone, 1-methyl-4-(propa-1,2-dien-1-ylsulfonyl)benzene. The reaction conditions are mild with no metal catalyst or additives required and display good functional group tolerance. Mechanistic studies for this unusual transformation suggest that the reaction operates via a rare pyridine-initiated and p-toluenesulfinate anion-mediated activation of the allenyl sulfone analogous to phosphine-triggered reactions.

New method for affinity adsorbent screening using gold colloids

A rapid, effective method for the screening of adsorbent ligands based on the unique optical properties of gold colloid has been developed. Different interactions between adsorbate and ligands induce different states of aggregation of the gold colloid, and the associated distinct color changes of the colloid have been utilized to estimate the affinity of the ligands toward the adsorbate. In this work, phosphorylated peptide CGGFGGpSG was appended to a gold colloid to obtain the adsorbate-modified gold colloid (CG8-AuNPs). Candidate ligands Dpa-Zn(2+), DMAPAA, and AAn were copolymerized with acrylamide to form linear polymers and cross-linked CG8-AuNPs to induce aggregation. Screening of the candidate ligands revealed that Dpa-Zn(2+) showed the highest affinity among those tested, inducing a color change of the gold colloid at a concentration of 10 μM, which is much lower than those of ligands DMAPAA (40 μM) and AAn (almost no color change could be observed). Subsequent statistical adsorption experiments confirmed these screening results, with the adsorbent A-AAm-Dpa-Zn(2+) showing the highest adsorption capacity (426 mg/g) for CG-8, almost twice that of adsorbent A-AAm-DMAPAA. This reported method has low sample consumption, and the screening may be simply monitored by the naked eye.

Adsorbents with high selectivity for uremic middle molecular peptides containing the Asp-Phe-Leu-Ala-Glu sequence

Asp-Phe-Leu-Ala-Glu (DE5) is a frequent sequence of many toxic middle molecular peptides that accumulate in uremic patients. To eliminate these peptides by hemoperfusion, three adsorbents (CP1-Zn(2+), CP2-Zn(2+), and CP3-Zn(2+)) were designed on the basis of coordination and hydrophobic interactions. Adsorption experiments indicated that CP2-Zn(2+) had the highest affinity for DE5 among these three adsorbents. Also, the adsorption capacity of CP2-Zn(2+) in DE5 and DE5-containing peptides was about 2-6 times higher than that of peptides without the DE5 sequence. Linear polymers bearing the same functional groups of the adsorbents were used as models to study the adsorption mechanism via isothermal titration calorimetry (ITC) and computer-aided analyses. The results indicated that coordination and hydrophobic interactions played the most important roles in their affinity. When two carboxyl moieties on Asp and Glu residues coordinated to CP2-Zn(2+), the hydrophobic interaction took place by the aggregation of the hydrophobic amino acid residues with phenyl group on CP2-Zn(2+). The optimal collaboration of these interactions led to the tight binding and selective adsorption of DE5-containing peptides onto CP2-Zn(2+). These results may provide new insight into the design of affinity adsorbents for peptides containing DE5-like sequences.