Intrinsic Degradation of the Type-II Antitoxin ParD from Pseudomonas aeruginosa

Type-II Toxin Antitoxin (TA) systems are regulated by differential half-lives of the resulting non-secreted proteins, such that the neutralizing antitoxin undergoes continual degradation and replenishment to maintain neutralization of its cognate toxin. Antitoxin proteins are widely reported as labile, including upon purification and in vitro storage. During the course of studies on a ParDE TA system we noted a prevalent in vitro degradation of the ParD antitoxin. In efforts to combat this for practical use in assays, we characterized parameters impacting the degradation as well as the resulting products. These revealed a mechanism likely mediated by a serine or metal-dependent protease. Using Direct Infusion Mass Spectrometry, the cleavage products were identified as an essentially intact DNA binding region of the antitoxin and with the toxin binding domain completely removed. No other species were identified in the solution, such as a contaminant that may mediate such cleavage. Therefore, while our studies revealed viable strategies to mitigate the in vitro degradation they did not identify any protease, leaving open the possibility of a potential auto-catalytic proteolytic activity of the antitoxin proteins.

The Degradation Kinetics Study of Aromatic Organics with Different Functional Compounds on Anatase 001 Surface

Anatase TiO2 photocatalysts with exposed (001) facets have attracted great attention for environmental protection technology due to their high reactivity for degradation of organic species. In this work, potassium hydrogen phthalate (denoted as KHP), as the most commonly used reference standard solution for calibrating photoelectrochemical chemical oxygen demand (denoted as PeCOD) instrument, was selected as the study sample. The intrinsic degradation kinetics of KHP on (001) surface was investigated by a photoelectrochemical (denoted as PEC) method with a purposely (001) faceted double-layered structure TiO2 photoanode. The high kinetics constants of fast process of KHP and other acids indicate that the (001) surface possesses a higher reactivity of aromatic carboxylic acid as theoretically predicted. Meanwhile, the investigation of the KHP adsorption properties on A001 photoanode provides the possibility of using this photoanode as a sensor in a new type of PeCOD instrument for organic acid determination.

Hollow NiAl(OH)x Nanocapsules to Enable Effective Glucose Oxidase Delivery and Synergistic Therapy

Cellular starvation induced by glucose oxidase (GOx) had been extensively explored as a potential approach for tumor therapy. However, the therapeutic efficacy suffers daunting challenges due to the unsatisfactory intracellular transportation of GOx molecules. Herein for the first time, hydroxide nanoparticles with unique hollow microstructure (denoted as H-NiAl(OH)x) were designed and synthesized for GOx delivery. In this system, despite its intrinsic degradation properties in acidic tumor microenvironment, Ni2+ ions released during degradation may catalyze a Fenton reaction to induce considerable production of cytotoxic hydroxyl radicals (OH). The cavity of hollow nanocapsules provides large surface area, and favors GOx capsulation and delivery. The findings indicate the intracellular glucose can be effectively consumed by GOx transported, and the reaction products consisting of acid and H2O2 facilitate the OH induction of nanocapsules in a synergistic manner. Both in vitro and in vivo antitumor properties have been consequently achieved by H-NiAl(OH)x/GOx systems. This study offering catalytic nanocapsules based on Ni2+ ions may spark a series of follow-on explorations in constructing drug delivery and therapeutic systems for synergistic tumor treatment.