Comparison of two peroxidases with high potential for biotechnology applications - HRP vs. APEX2.

Peroxidases are essential elements in many biotechnological applications. An especially interesting concept involves split enzymes, where the enzyme is separated into two smaller and inactive proteins that can dimerize into a fully active enzyme. Such split forms were developed for the horseradish peroxidase (HRP) and ascorbate peroxidase (APX) already. Both peroxidases have a high potential for biotechnology applications. In the present study, we performed biophysical comparisons of these two peroxidases and their split analogues. The active site availability is similar for all four structures. The split enzymes are comparable in stability with their native analogues, meaning that they can be used for further biotechnology applications. Also, the tertiary structures of the two peroxidases are similar. However, differences that might help in choosing one system over another for biotechnology applications were noticed. The main difference between the two systems is glycosylation which is not present in the case of APX/sAPEX2, while it has a high impact on the HRP/sHRP stability. Further differences are calcium ions and cysteine bridges that are present only in the case of HRP/sHRP. Finally, computational results identified sAPEX2 as the systems with the smallest structural variations during molecular dynamics simulations showing its dominant stability comparing to other simulated proteins. Taken all together, the sAPEX2 system has a high potential for biotechnological applications due to the lack of glycans and cysteines, as well as due to high stability.

Highly selective preparation of N-terminus Horseradish peroxidase-DNA conjugate with fully retained enzymatic activity: HRP-DNA structure - activity relation.

Within the last decade, the field of bio-nanoengineering has achieved significant advances allowing us to generate, e.g., nanoscaled molecular machineries with arbitrary shapes. To unleash the full potential of novel methods such as DNA origami technology, it is important to functionalise complex molecules and nanostructures precisely. Thus, considerable attention has been given to site-selective modifications of proteins allowing further incorporation of various functionalities. Here, we describe a method for the covalent attachment of oligonucleotides to the glycosylated horseradish peroxidase protein (HRP) with high N-terminus selectivity and significant yield while conserving the enzymatic activity. This two-step process includes a pH-controlled metal-free diazotransfer reaction using imidazole-1-sulfonyl azide hydrogen sulfate, which at pH 8.5 results in an N-terminal azide-functionalized protein, followed by the Cu-free click SPAAC reaction to dibenzocyclooctyne- (DBCO) modified oligonucleotides. The reaction conditions were optimised to achieve maximum yield and the best performance. The resulting protein-oligonucleotide conjugates (HRP-DNA) were characterised by electrophoresis and mass spectrometry (MS). Native-PAGE experiments demonstrated different migration patterns for HRP-DNA and the azido-modified protein allowing zymogram experiments. Structure-activity relationships of novel HRP-DNA conjugates were assessed using molecular dynamics simulations, characterising the molecular interactions that define the structural and dynamical properties of the obtained protein-oligonucleotide conjugates (POC).

Screening of Novel Antimicrobial Diastereomers of Azithromycin-Thiosemicarbazone Conjugates: A Combined LC-SPE/Cryo NMR, MS/MS and Molecular Modeling Approach.

A well-known class of antibacterials, 14- and 15-membered macrolides are widely prescribed to treat upper and lower respiratory tract infections. Azithromycin is a 15-membered macrolide antibiotic possessing a broad spectrum of antibacterial potency and favorable pharmacokinetics. Bacterial resistance to marketed antibiotics is growing rapidly and represents one of the major global hazards to human health. Today, there is a high need for discovery of new anti-infective agents to combat resistance. Recently discovered conjugates of azithromycin and thiosemicarbazones, the macrozones, represent one such class that exhibits promising activities against resistant pathogens. In this paper, we employed an approach which combined LC-SPE/cryo NMR, MS/MS and molecular modeling for rapid separation, identification and characterization of bioactive macrozones and their diastereomers. Multitrapping of the chromatographic peaks on SPE cartridges enabled sufficient sample quantities for structure elucidation and biological testing. Furthermore, two-dimensional NOESY NMR data and molecular dynamics simulations revealed stereogenic centers with inversion of chirality. Differences in biological activities among diastereomers were detected. These results should be considered in the process of designing new macrolide compounds with bioactivity. We have shown that this methodology can be used for a fast screening and identification of the macrolide reaction components, including stereoisomers, which can serve as a source of new antibacterials.

Effect of N-glycosylation on horseradish peroxidase structural and dynamical properties.

The effect of different branching types of glycosylation on the structure and dynamics of the horseradish peroxidase (HRP) and an engineered split horseradish peroxidase (sHRP) was studied using all-atom molecular dynamics (MD) simulations. Although tertiary structures of both proteins are stable in the presence, as well as in the absence of glycans, differences in the dynamical properties regarding the presence of glycans were noticed. Fluctuations in the protein structure along both proteins are decreased when glycosylation is introduced. We identified two main regions that are affected the most. The peripheral region is impacted directly by glycans and the central region within the active site with a propagated effect of glycans. Since the mentioned central region in the glycoprotein is not surrounded by glycans and is close to the heme, it is easily approachable to the solvent and substrate. An influence of the glycan presence on the electrostatic potential of the protein and on the heme cofactor was also observed. Altogether, this work presents a global and local analysis of the glycosylation influence on HRP protein's structural and dynamical properties at a molecular level.

Electrokinetic mobility, pH and conductance/conductivity data for aqueous silica and PTFE suspension of controlled composition for selected temperature ranges.

The Data in Brief contains data on the electrokinetic mobility of PTFE and silica particles in aqueous suspensions as a function of pH and temperature. Furthermore, the concomitant conductivities and pH values are reported both for systems in the absence and presence of PTFE particles as a function of temperature and are compatible with the associated research paper "The influence of temperature on the charging of Polytetrafluoroethylene surfaces in electrolyte solutions" (Barisic et al.). The trend of the electrokinetic charging with temperature can be inferred from this for both kinds of particles. The data on the evolution of the pH and the measured conductivities are valuable input for future models that simulate the charge of inert surfaces at variable temperature.