Enzymatic Hydrolysis of Tertiary Amide Bonds by anti Nucleophilic Attack and Protonation

Effect of multi arm-PEG-NHS (polyethylene glycol n-hydroxysuccinimide) branching on cell adhesion to modified decellularized bovine and porcine pericardium

Implanting physical barrier materials to separate wounds from their surroundings is a promising strategy for preventing postoperative adhesions. Herein, we develop a material that switches from an anti-adhesive surface to an adhesive surface, preventing adhesion in the early stage of transplantation and then promoting recellularization. In this study, 2-arm, 4-arm, and 8-arm poly(ethylene glycol) succinimidyl glutarate (2-, 4-, 8-arm PEG-NHS) were used to modify the surface of decellularized porcine and bovine pericardium. The number of free amines on the surface of each material significantly decreased following modification regardless of the reaction molar ratio of NH2 and NHS, the number of PEG molecule branches, and the animal species of the decellularized tissue. The structure and mechanical properties of the pericardium were maintained after modification with PEG molecules. The time taken for the PEG molecules to detach through hydrolysis of the ester bonds differed between the samples, which resulted in different cell repulsion periods. By adjusting the reaction molar ratio, the number of PEG molecule branches, and the animal species of the decellularized pericardium, the duration of cell repulsion can be controlled and is expected to provide an anti-adhesion material for a variety of surgical procedures.

The design, synthesis, and inhibition of Clostridioides difficile spore germination by acyclic and bicyclic tertiary amide analogs of cholate

Clostridioides difficile infection (CDI) is a major identifiable cause of antibiotic-associated diarrhea. In our previous study (J. Med. Chem., 2018, 61, 6759-6778), we have identified N-phenyl-cholan-24-amide as a potent inhibitor of spore germination. The most potent compounds in our previous work are N-arylamides. We were interested in the role that the conformation of the amide plays in activity. Previous research has shown that secondary N-arylamides exist exclusively in the coplanar trans conformation while tertiary N-methyl-N-arylamides exist in a non-planar, cis conformation. The N-methyl-N-phenyl-cholan-24-amide was 17-fold less active compared to the parent compounds suggesting the importance of the orientation of the phenyl ring. To lock the phenyl ring into a trans conformation, cyclic tertiary amides were prepared. Indoline and quinoline cholan-24-amides were both inhibitors of spore germination; however, the indoline analogs were most potent. Isoindoline and isoquinoline amides were inactive. We found that the simple indoline derivative gave an IC50 value of 1 μM, while the 5'-fluoro-substituted compound (5d) possessed an IC50 of 400 nM. To our knowledge, 5d is the most potent known spore germination inhibitor described to date. Taken together, our results indicate that the trans, coplanar conformation of the phenyl ring is required for potent inhibition.

Optimization of physicochemical properties is a strategy to improve drug-likeness associated with activity: novel active and selective compounds against Trypanosoma cruzi

Trypanosoma cruzi is the causing agent of Chagas disease, a parasitic infection without efficient treatment for chronic patients. Despite the efforts, no new drugs have been approved for this disease in the last 60 years. Molecular modifications based on a natural product led to the development of a series of compounds (LINS03 series) with promising antitrypanosomal activity, however previous chemometric analysis revealed a significant impact of excessive lipophilicity and low aqueous solubility on potency of amine and amide derivatives. Therefore, this work reports different modifications in the core structure to achieve adequate balance of the physicochemical properties along with biological activity. A set of 34 analogues were designed considering predicted properties related to lipophilicity/hydrosolubility and synthesized to assess their activity and selective toxicity towards the parasite. Results showed that this strategy contributed to improve the drug-likeness of the series while considerable impacts on potency were observed. The rational analysis of the obtained data led to the identification of seven active piperazine amides (28-34, IC₅₀ 8.7 to 35.3 µM against intracellular amastigotes), devoid of significant cytotoxicity to mammalian cells. The addition of water-solubilizing groups and privileged substructures such as piperazines improved the physicochemical properties and overall drug-likeness of these compounds, increased potency and maintained selectivity towards the parasite. The obtained results brought important structure-activity relationship (SAR) data and new lead structures for further modifications were identified to achieve improved antitrypanosoma compounds.

Peptide Backbone Modifications for the Assessment of Cleavage Site Relevance in Precursors of Signaling Peptides

The physiological relevance of site-specific precursor processing for the biogenesis of peptide hormones and growth factors can be demonstrated in genetic complementation experiments, in which a gain of function is observed for the cleavable wild-type precursor, but not for a non-cleavable precursor mutant. Similarly, cleavable and non-cleavable synthetic peptides can be used in bioassays to test whether processing is required for bioactivity. In genetic complementation experiments, site-directed mutagenesis has to be used to mask a processing site against proteolysis. Peptide-based bioassays have the distinctive advantage that peptides can be protected against proteolytic cleavage by backbone modifications, i.e., without changing the amino acid sequence. Peptide backbone modifications have been employed to increase the metabolic stability of peptide drugs, and in basic research, to investigate whether processing at a certain site is required for precursor maturation and formation of the bioactive peptide. For this approach, it is important to show that modification of the peptide backbone has the desired effect and does indeed protect the respective peptide bond against proteolysis. This can be accomplished with the MALDI-TOF mass spectrometry-based assay we describe here.

Metalloaminopeptidases of the Protozoan Parasite Plasmodium falciparum as Targets for the Discovery of Novel Antimalarial Drugs

Malaria poses a significant threat to approximately half of the world's population with an annual death toll close to half a million. The emergence of resistance to front-line antimalarials in the most lethal human parasite species, Plasmodium falciparum (Pf), threatens progress made in malaria control. The prospect of losing the efficacy of antimalarial drugs is driving the search for small molecules with new modes of action. Asexual reproduction of the parasite is critically dependent on the recycling of amino acids through catabolism of hemoglobin (Hb), which makes metalloaminopeptidases (MAPs) attractive targets for the development of new drugs. The Pf genome encodes eight MAPs, some of which have been found to be essential for parasite survival. In this article, we discuss the biological structure and function of each MAP within the Pf genome, along with the drug discovery efforts that have been undertaken to identify novel antimalarial candidates of therapeutic value.