A novel human tocopherol-associated protein: cloning, in vitro expression, and characterization.

Vitamin E (alpha-tocopherol) is an essential dietary nutrient for humans and animals. The mechanisms involved in cellular regulation as well as in the preferential cellular and tissue accumulation of alpha-tocopherol are not yet well established. We previously reported (Stocker, A., Zimmer, S., Spycher, S. E., and Azzi, A. (1999) IUBMB Life 48, 49-55) the identification of a novel 46-kDa tocopherol-associated protein (TAP) in the cytosol of bovine liver. Here, we describe the identification, the molecular cloning into Escherichia coli, and the in vitro expression of the human homologue of bovine TAP, hTAP. This protein appears to belong to a family of hydrophobic ligand binding proteins, which have the CRAL (cis-retinal binding motif) sequence in common. By using a biotinylated alpha-tocopherol derivative and the IASys resonant mirror biosensor, the purified recombinant protein was shown to bind tocopherol at a specific binding site with K(d) 4.6 x 10(-7) m. Northern analyses showed that hTAP mRNA has a size of approximately 2800 base pairs and is ubiquitously expressed. The highest amounts of hTAP message are found in liver, brain, and prostate. In conclusion, hTAP has sequence homology to proteins containing the CRAL_TRIO structural motif. TAP binds to alpha-tocopherol and biotinylated tocopherol, suggesting the existence of a hydrophobic pocket, possibly analogous to that of SEC14

Adsorptive removal of humic acid by zirconia embedded in a poly(ether sulfone) membrane

The presence of humic acid (HA) in groundwater threatens aquatic life and human health; for the effective treatment of such pollutants, an advanced/hybrid method is essential. In this work, zirconia embedded in poly(ether sulfone) (ZrePES) mixed matrix membranes (MMMs) has been studied for the removal of HA. Chemical precipitation method was utilized to prepare nano zirconia (ZrO2). The modified PES membrane with nano ZrO2 of 2.5 and 5 wt % were studied. Contact angle measurement and protein rejection studies showed an enhanced hydrophilicity with increase in pore radius for ZrePES membranes. Also, the addition of nano ZrO2 altered the membrane morphology and improved pure water permeability. Batch adsorption experiments revealed that HA adsorption efficiency was higher at pH 2 for ZrePES membranes. The HA uptake capacity of 50.5 mg/g was observed for the 5 wt % ZrePES membrane. Experimental adsorption results showed good agreement with adsorption kinetics model. Ultrafiltration studies showed HA rejection was up to 97% for 5 wt % ZrePES membrane. The effects of natural substances and their impact on HA rejection in ZrePES membrane were also analyzed and discusse