Sigma receptors once considered as a class of opioid receptors are now regarded as unique orphan receptors, distinguished by the ability to bind various pharmacological agents such as the progesterone (steroid), haloperidol (anti-psychotic), and drugs of abuse such as cocaine and methamphetamine. The sigma-1 receptor is a 223 amino acid protein, proposed to have two transmembrane segments. We have developed a scheme for the purification of the guinea pig sigma-1 receptor following overexpression in Escherichia coli as a maltose binding protein (MBP) fusion and extraction with Triton X-100. Affinity chromatography using an amylose column and Ni2+ affinity column was used to purify the sigma-1 receptor. The sigma-1 receptor purified by this method is a 26 kDa polypeptide as assessed by SDS-PAGE, binds sigma ligands with high affinity and can be specifically photoaffinity labeled with the sigma-1 receptor photoprobe, [125I]-iodoazidococaine. Ligand binding using [3H]-(+)-pentazocine indicated that approximately half of the purified protein in Triton X-100 bound to radioligand. The MBP-sigma-1 receptor and the sigma-1 receptor in 0.5% triton were maximally stable for approximately two weeks at -20 degrees C in buffer containing 30% glycerol.

Al 2 O 3 thin films were deposited by atomic layer deposition on HF-cleaned and NH3 plasma-treated GaAs surfaces, respectively. The precursors used for Al2O3 films are trimethylaluminum and water. Effects of NH3 plasma pretreatment on the electrical and structural properties of Al2O3∕GaAs interface were investigated by C-V measurements, high-resolution transmission electron microscopy, and x-ray photoelectron spectroscopy measurements. The C-V measurements showed that the electrical property is improved after NH3 plasma pretreatment. X-ray photo electron spectroscopy analyses confirmed that GaAs oxides and elemental As are greatly decreased and the GaAs surface can be efficiently protected during NH3 plasma pretreatment and atomic layer deposition of Al2O3.

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