Catalytic Formation of Disulfide Bonds in Peptides by Molecularly Imprinted Microgels at Oil/Water Interfaces.

This work describes the preparation and investigation of molecularly imprinted polymer (MIP) microgel (MG) stabilized Pickering emulsions (PEs) for their ability to catalyze the formation of disulfide bonds in peptides at the O/W interface. The MIP MGs were synthesized via precipitation polymerization and a programmed initiator change strategy. The MIP MGs were characterized using DLS analysis, SEM measurement, and optical microscopy analysis. The dry and wet MIP MGs showed a hydrodynamic diameter of 100 and 280 nm, respectively. A template rebinding experiment showed that the MIP MGs bound over two times more template (24 mg g-1) compared to the uptake displayed by a nonimprinted reference polymer (NIP) MG (10 mg g-1) at saturation. Using the MIP MGs as stabilizers, catalytic oxidation systems were prepared by emulsifying the oil phase and water phase in the presence of different oxidizing agents. During the cyclization, the isolation of the thiol precursors and the oxidizing reagents nonselectively decreased the formation of the byproducts, while the imprinted cavities on the MIP MGs selectively promoted the intramolecular cyclization of peptides. When I2 was used as the oxidizing agent, the MIP-PE-I2 system showed a product yield of 50%, corresponding to a nearly 2-fold increase compared to that of the nonimprinted polymer NIP-PE-I2 system (26%). We believe the interfacial catalysis system presented in this work may offer significant benefits in synthetic peptide chemistry by raising productivity while suppressing the formation of byproducts.

Removal of potentially genotoxic acetamide and arylsulfonate impurities from crude drugs by molecular imprinting.

The present study describes the synthesis and preliminary testing of molecularly imprinted polymers (MIPs) as scavenger resins for removal of the genotoxic impurities (GTI) acetamide and arylsulfonates from active pharmaceutical ingredients (API). The MIPs were synthesized as monoliths using acetamide or methyl tosylate respectively as templates. The polymers were crushed and subsequently tested in the batch and chromatographic mode for template recognition and potential removal efficiency. Both the acetamide and the tosylate MIPs exhibited a strong memory effect for their templates and selectivity with respect to model APIs. For instance the MIP for acetamide preferentially retained acetamide over other amides, such as formamide, acrylamide, methacrylamide, benzamide and N-tert-butylacrylamide. Moreover, passing model API crude contaminated with the acetamide through the MIPs led to the quantitative removal of acetamide.

Light-induced structural changes in a photosynthetic reaction center caught by Laue diffraction.

Photosynthetic reaction centers convert the energy content of light into a transmembrane potential difference and so provide the major pathway for energy input into the biosphere. We applied time-resolved Laue diffraction to study light-induced conformational changes in the photosynthetic reaction center complex of Blastochloris viridis. The side chain of TyrL162, which lies adjacent to the special pair of bacteriochlorophyll molecules that are photooxidized in the primary light conversion event of photosynthesis, was observed to move 1.3 angstroms closer to the special pair after photoactivation. Free energy calculations suggest that this movement results from the deprotonation of this conserved tyrosine residue and provides a mechanism for stabilizing the primary charge separation reactions of photosynthesis.