IntroductionBiomedical applications of nanoparticles (NPs) as enzyme inhibitors have recently come to light. Oxides of metals native to the physiological environment (eg, Fe, Zn, Mg, etc.) are of particular interest—especially the functional consequences of their enzyme interaction.Materials and methodsHere, Fe2O3, zinc oxide (ZnO), magnesium oxide (MgO) and nickel oxide (NiO) NPs are compared to copper (Cu) and boron carbide (B4C) NPs. The functional impact of NP interaction to the model enzyme luciferase is determined by 2-dimensional fluorescence difference spectroscopy (2-D FDS) and 2-dimensional photoluminescence difference spectroscopy (2-D PLDS). By 2-D FDS analysis, the change in maximal intensity and in 2-D FDS area under the curve (AUC) is in the order Cu~B4C>ZnO>NiO>>Fe2O3>MgO. The induced changes in protein conformation are confirmed by tryptic digests and gel electrophoresis.ResultsAnalysis of possible trypsin cleavage sites suggest that cleavage mostly occurs in the range of residues 112–155 and 372–439, giving a major 45 kDa band. By 2-D PLDS, it is found that B4C NPs completely ablate bioluminescence, while Cu and Fe2O3 NPs yield a unique bimodal negative decay rate, −7.67×103 and −3.50×101 relative light units respectively. Cu NPs, in particular, give a remarkable 271% change in enzyme activity. Molecular dynamics simulations in water predicted that the surfaces of metal oxide NPs become capped with metal hydroxide groups under physiological conditions, while the surface of B4C becomes populated with boronic acid or borinic acid groups. These predictions are supported by the experimentally determined zeta potential. Thin layer chromatography patterns further support this conception of the NP surfaces, where stabilizing interactions were in the order ionic>polar>non-polar for the series tested.ConclusionOverall the results suggest that B4C and Cu NP functional dynamics on enzyme biochemistry are unique and should be examined further for potential ramifications on other model, physiological or disease-relevant enzymes.
A 5 yr old indoor–outdoor domestic longhair red tabby cat presented for evaluation of a 1-day history of hiding, urinating and defecating outside the litterbox, and vocalizing when picked up. Physical examination revealed significant pain on palpation of the caudal sternum where an approximately 8 × 6 cm contusion was noted. Sedated thoracic radiographs revealed a luxated fifth intersternebral joint with the sixth sternebra being cranioventrally displaced (along with the seventh and eight sternebrae) to the level of the mid fourth sternebra. There were sharply marginated, short oblique fractures of the distal sixth costal cartilages bilaterally with mild dorsal displacement of the distal segment. The sternal luxation was palpated more aggressively once the patient was sedated and deemed to be stable. Because of the stability of the luxation and absence of sternebral fractures, conservative medical management in the form of analgesics and rest was instituted. Repeat thoracic radiographs 2 wk after presentation revealed an unchanged sternal luxation. Twelve months after presentation, the patient presented for an unrelated lameness and, in that timeframe, has exhibited no sequelae to the sternal luxation, which still palpates stable and is radiographically unchanged.
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