One of the possible mechanisms for the inhibition effect of Tb(III) on peroxidase activity in horseradish (Armoracia rusticana) treated with Tb(III) was investigated using some biophysical and biochemical methods. Firstly, it was found that a large amount of Tb(III) can be distributed on the cell wall, that some Tb(III) can enter into the horseradish cell, indicating that peroxidase was mainly distributed on cell wall, and thus that Tb(III) would interact with horseradish peroxidase (HRP) in the plant. In addition, peroxidase bioactivity was decreased in the presence of Tb(III). Secondly, a new peroxidase-containing Tb(III) complex (Tb-HRP) was obtained from horseradish after treatment with Tb(III); the molecular mass of Tb-HRP is near 44 kDa and the pI is about 8.80. Thirdly, the electrocatalytic activity of Tb-HRP is much lower than that of HRP obtained from horseradish without treatment with Tb(III). The decrease in the activity of Tb-HRP is due to the destruction (unfolding) of the conformation in Tb-HRP. The planarity of the heme active center in the Tb-HRP molecule was increased and the extent of exposure of Fe(III) in heme was decreased, leading to inhibition of the electron transfer. The microstructure change in Tb-HRP might be the result of the inhibition effect of Tb(III) on peroxidase activity in horseradish.
An ultrasensitive and rapid electrochemical detection of trace Hg(II) sensor was developed. The significantly amplified electrochemical signals were caused by the high specific surface area of the electrochemical sensor. Scanning electron microscopy showed that the gold nanospikes were 200-300 nm in length and 50 nm in diameter. The electrochemical properties of sensor were characterized by square wave voltammetry. Experimental parameters were optimized using square wave stripping voltammetry. The linear range of sensor for Hg(II) is 3×10-10 mol l-1 ~ 7×10-7 mol l-1 and the limit of detection is 1×10-10 mol l-1. Hg(II) was successfully quantified in river water and cosmetics. The original Hg(II) in loose powder, sunblock, and whitening lotion using the high ratio surface area electrochemical sensor determination were found to be 2.234, 2.056, and 2.347 mg kg-1, respectively. The results are within the range of standard values, the RSD are 1.7 %, 1.5 %, and 2.1 %, respectively. The HRSA Au electrode sensor displays high sensitivity, excellent stability, reproducibility, and is more convenient than ICP-MS and AFS verification methods. We look forward to the possibility that the HRSA Au electrode sensor can be used for real-time monitoring of mercury ions in water and cosmetics in the future.
Emerging evidence suggests that donor/recipient matching in non-HLA (human leukocyte antigen) regions of the genome may impact transplant outcomes and recognizing these matching effects may increase the power of transplant genetics studies. Most available matching scores account for either single-nucleotide polymorphism (SNP) matching only or sum these SNP matching scores across multiple gene-coding regions, which makes it challenging to interpret the association findings. We propose a multi-marker Joint Score Test (JST) to jointly test for association between recipient genotype SNP effects and a gene-based matching score with transplant outcomes. This method utilizes Eigen decomposition as a dimension reduction technique to potentially increase statistical power by decreasing the degrees of freedom for the test. In addition, JST allows for the matching effect and the recipient genotype effect to follow different biological mechanisms, which is not the case for other multi-marker methods. Extensive simulation studies show that JST is competitive when compared with existing methods, such as the sequence kernel association test (SKAT), especially under scenarios where associated SNPs are in low linkage disequilibrium with non-associated SNPs or in gene regions containing a large number of SNPs. Applying the method to paired donor/recipient genetic data from kidney transplant studies yields various gene regions that are potentially associated with incidence of acute rejection after transplant.
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