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Despite the large number of peptidomimetics with incorporated heteroannularly functionalized ferrocenes, few studies have investigated their bioactivity. Here, we report the biological evaluation and conformational analysis of enantiomeric dipeptides derived from 1′-aminoferrocene-1-carboxylic acid (Fca) and hydrophobic amino acids (AA = Val, Leu, Phe). The conformational properties of Y-AA-Fca-OMe (Y = Ac, Boc) were elucidated by experimental (IR, NMR, CD, and X-ray) and theoretical (DFT) methods. The prepared dipeptides were screened for their antimicrobial activity against selected Gram-positive and Gram-negative bacteria, lactic acid bacteria and yeasts, while their antioxidant activity was tested by DPPH and FRAP methods. Of all compounds tested, dipeptide d-2a showed the best antibacterial properties against S. aureus, B. subtilis, and P. aeruginosa at a concentration of 2 mM. The time–kill curves showed that antibacterial activity was concentration- and time-dependent. Chirality (d-) and a more polar-protecting group (Ac) were found to affect the biological activity, both antimicrobial and antioxidant. All investigated peptides are considered to be highly hydrophobic and chemically stable in both acidic and buffer media. Dipeptides d-1a–3a, which showed biological activity, were subjected to the determination of proteolytic activity, revealing very good resistance to proteolysis in the presence of chymotrypsin. [ABSTRACT FROM AUTHOR]

Trypsin is by far the most commonly used protease in proteomics. Even though the amount of protease used in each experiment is very small, digestion of large amounts of protein prior to enrichment can be rather costly. The price of commercial trypsin is highly dependent on the quality of the enzyme, which is determined by its purity, activity, and chemical modifications. In this study we evaluated several strategies for improving the quality of crude trypsin by reductive methylation and affinity purification. We present a protocol applicable to most proteomics laboratories for obtaining a highly stable and pure trypsin preparation using reductive methylation and purification by benzamidine-sepharose. The entire workflow can be performed within a day and yields ~4 mg per batch but is completely scalable. The methylated product was benchmarked against sequencing grade trypsin from Promega and they were found to be comparable for one hour digestions at elevated temperatures, where residual chymotryptic activity was found to be negligible. [ABSTRACT FROM AUTHOR]

Peptides constructed with the 20 natural amino acids are generally considered to have little therapeutic potential because they are unstable in the presence of proteases and peptidases. However, proteolysis cleavage can be idiosyncratic, and it is possible that natural analogues of functional sequences exist that are highly resistant to cleavage. Here, we explored this idea in the context of peptides that bind to the signaling protein Gai1. To do this, we used a two-step in vitro selection process to simultaneously select for protease resistance while retaining function-first by degrading the starting library with protease (chymotrypsin), followed by positive selection for binding via mRNA display. Starting from a pool of functional sequences, these experiments revealed peptides with 100-400 fold increases in protease resistance compared to the parental library. Surprisingly, selection for chymotrypsin resistance also resulted in similarly improved stability in human serum (~100 fold). Mechanistically, the decreases in cleavage results from both a lower rate of cleavage (kcat) and a weaker interaction with the protease (Km). Overall, our results demonstrate that the hydrolytic stability of functional, natural peptide sequences can be improved by two orders of magnitude simply by optimizing the primary sequence. [ABSTRACT FROM AUTHOR]