The role of imidazole in peptide cyclization by transesterification: parallels to the catalytic triads of serine proteases

TEMPO mediated oxidative annulation of aryl methyl ketones with amines/ammonium acetate for imidazole synthesis

A facile synthesis of 1H-imidazoles by direct oxidative annulation of aryl methyl ketones and primary amines has been developed in the presence of TEMPO under weakly acidic conditions. By replacing amines with ammonium acetate, 2H-imidazole skeletons were achieved for the first time from ketones. Substrates containing various functional groups, such as alkyl, aryl, naphthyl, halogen (F, Cl, Br, I), nitro, trifluoromethyl, sulfonyl ester, furyl, thienyl, and pyridyl groups, were readily transformed into the desired products. The application potential of this method was verified by the scale-up synthesis and Sonogashira coupling functionalization of imidazoles. Mechanistically, the α-TEMPO-enamine adduct may serve as the key reaction intermediate.

Construction, expression, and in vitro assembly of virus-like particles of L1 protein of human papillomavirus type 52 in Escherichia coli BL21 DE3

Background

A major discovery in human etiology recognized that cervical cancer is a consequence of an infection caused by some mucosatropic types of human papillomavirus (HPV). Since L1 protein of HPV is able to induce the formation of neutralizing antibodies, it becomes a protein target to develop HPV vaccines. Therefore, this study aims to obtain and analyze the expression of HPV subunit recombinant protein, namely L1 HPV 52 in E. coli BL21 DE3. The raw material used was L1 HPV 52 protein, while the synthetic gene, which is measured at 1473 bp in pD451-MR plasmid, was codon-optimized (ATUM) and successfully integrated into 5643 base pairs (bps) of pETSUMO. Bioinformatic studies were also conducted to analyze B cell epitope, T cell epitope, and immunogenicity prediction for L1HPV52 protein.

Results

The pETSUMO-L1HPV52 construct was successfully obtained in a correct ligation size when it was cut with EcoRI. Digestion by EcoRI revealed a size of 5953 and 1160 bps for both TA cloning petSUMO vector and gene of interest, respectively. Furthermore, the right direction of construct pETSUMO-L1HPV52 was proven by PCR techniques using specific primer pairs then followed by sequencing, which shows 147 base pairs. Characterization of L1 HPV 52 by SDS-PAGE analysis confirms the presence of a protein band at a size of ~55 kDa with 6.12 mg/L of total protein concentration. Observation under by transmission electron microscope demonstrates the formation of VLP-L1 at a size between 30 and 40 nm in assembly buffer under the condition of pH 5.4. Based on bioinformatics studies, we found that there are three B cell epitopes (GFPDTSFYNPET, DYLQMASEPY, KEKFSADLDQFP) and four T cell epitopes (YLQMASEPY, PYGDSLFFF, DSLFFFLRR, MFVRHFFNR). Moreover, an immunogenicity study shows that among all the T cell epitopes, the one that has the highest affinity value is DSLFFFLRR for Indonesian HLAs.

Conclusion

Regarding the achievement on successful formation of L1 HPV52-VLPs, followed by some possibilities found from bioinformatics studies, this study suggests promising results for future development of L1 HPV type 52 vaccine in Indonesia.

Molecular Dynamics Simulations of a Catalytic Multivalent Peptide-Nanoparticle Complex

Molecular modeling of a supramolecular catalytic system is conducted resulting from the assembling between a small peptide and the surface of cationic self-assembled monolayers on gold nanoparticles, through a multiscale iterative approach including atomistic force field development, flexible docking with Brownian Dynamics and µs-long Molecular Dynamics simulations. Self-assembly is a prerequisite for the catalysis, since the catalytic peptides do not display any activity in the absence of the gold nanocluster. Atomistic simulations reveal details of the association dynamics as regulated by defined conformational changes of the peptide due to peptide length and sequence. Our results show the importance of a rational design of the peptide to enhance the catalytic activity of peptide-nanoparticle conjugates and present a viable computational approach toward the design of enzyme mimics having a complex structure-function relationship, for technological and nanomedical applications.

Degradation of polysorbates 20 and 80 catalysed by histidine chloride buffer

Polysorbates are amphiphilic, non-ionic surfactants, and they represent one of the key components of biopharmaceuticals. They serve as stabilisers, and their degradation can cause particle formation, which has been an industry-wide issue over the past decade. To determine the influence of the buffers most frequently used in biopharmaceuticals on polysorbate degradation, an accelerated stability study was carried out using placebo formulations containing 0.02% polysorbates and 20 mM buffers (pH 5.5, 6.5). These included histidine chloride, sodium citrate, sodium succinate and sodium phosphate buffers. The rate of polysorbate degradation was highest in histidine chloride buffer, and therefore we further focused on the mechanism here. The predominant degradation pathway of polysorbates in this buffer was ester hydrolysis, catalysed by the imidazole moiety of the histidine. Interestingly, the presence of therapeutic proteins in the formulations slowed histidine-catalysed degradation of polysorbates in 50% of cases, with negligible degradation seen otherwise. This emphasises the complex nature of the interactions between the components of biopharmaceutical drug products. Nonetheless, there are disadvantages of using histidine chloride buffers in biopharmaceuticals that contain polysorbates. Careful consideration should be given to selection of excipients used in parenteral formulations, whereby compatibility between buffer and surfactant is of key importance.