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Abstract: Sigma-1 receptors are associated with Alzheimer''s disease, major depressive disorders, and schizophrenia. These receptors show progrowth/antiapoptotic properties via their chaperoning functions to counteract ER (endoplasmic reticulum) stress, to block neurodegeneration, and to regulate neuritogenesis. The sigma-1 receptor knock out mouse offered an opportunity to assess possible mechanisms by which the sigma-1 receptor modulates cellular oxidative stress. Nuclear magnetic resonance (NMR) metabolomic screening of the WT (wild type) and sigma-1 KO (knockout) livers was performed to investigate major changes in metabolites that are linked to oxidative stress. Significant changes in protein levels were also identified by two-dimensional (2D) gel electrophoresis and mass spectrometry. Increased levels of the antioxidant protein peroxiredoxin 6 (Prdx6), and the ER chaperone BiP (GRP78) compared to WT littermates were detected. Oxidative stress was measured in WT and sigma-1 KO mouse liver homogenates, in primary hepatocytes and in lung homogenates. Furthermore, sigma-1 receptor mediated activation of the antioxidant response element (ARE) to upregulate NAD(P)H quinone oxidoreductase 1 (NQO1) and superoxide dismutase 1 (SOD1) mRNA expression in COS cells was shown by RT PCR. These novel functions of the sigma-1 receptor were sensitive to well-known sigma ligands via their antagonist/agonist properties. [Copyright &y& Elsevier]

σ-1 receptors represent unique binding sites that are capable of interacting with a wide range of compounds to mediate different cellular events. The composition of the ligand binding site of this receptor is unclear, since no NMR or crystal structures are available. Recent studies in our laboratory using radiolabeled photoreactive ligands suggested that the steroid binding domain-like I (SBDLI) (amino acids 91-109) and the steroid binding domain-like II (SBDLII) (amino acids 176-194) regions are involved in forming the ligand binding site(s) (Chen, Y., Hajipour, A. R., Sievert, M. K., Arbabian, M., and Ruoho, A. E. (2007) Biochemistry 46, 3532-3542; Pal, A., Hajipour, A. R., Fontanilla, D., Ramachandran, S., Chu, U. B., Mavlyutov, T., and Ruoho, A. E. (2007) Mol. Pharmacol. 72, 921-933). In this report, we have further addressed this issue by utilizing our previously developed sulthydryl-reactive, cleavable, radioiodinated photocross-linking reagent: methanesulfonothioic acid, S-((4-(4-amino-3-[125I]iodobenzoyl) phenyl)methyl) ester (Guo, L. W., Hajipour, A. R., Gavala, M. L., Arbabian, M., Martemyanov, K. A., Arshavsky, V. Y., and Ruoho, A. E. (2005) Bioconjugate Chem. 16, 685-693). This photoprobe was shown to derivatize the single cysteine residues as mixed disulfides at position 94 in the SBDLI region of the wild type guinea pig σ-1 receptor (Cys94) and at position 190 in the SBDLII region of a mutant guinea pig σ-1 receptor (C94A,V190C), both in a σ-ligand (haloperidol or (+ )-pentazocine)-sensitive manner. Significantly, photocross-linking followed by Endo Lys-C cleavage under reducing conditions and intramolecular radiolabel transfer from the SBDLI to the SBDLII region in the wild type receptor and, conversely, from the SBDLII to the SBDLI region in the mutant receptor were observed. These data support a model in which the SBDLI and SBDLII regions are juxtaposed to form, at least in part, a ligand binding site of the σ-1 receptor. [ABSTRACT FROM AUTHOR]

A strategy for rapid in situ elimination of interfering substances that are present in extracts of food samples during assay is described in this article. The novel feature of this method is that the sample purification is carried out as a part of the assay, and a separate sample cleanup step is not required. The assay procedure involves the sequential addition of standard or sample, cleaning solutions, and aflatoxin B1r-horseradish peroxidase conjugate (AFBI-HRP) over antibody-spotted zones of a membrane, and 3,3′-diaminobenzidine was used as the substrate for visualization. We have determined that trifluoroacetic acid and propionic acids at concentrations of 100 mM are highly effective for cleaning groundnut, wheat, corn, and poultry feed samples and that NaHCO3 (100 mM) is successful in cleaning processed soybean. In all cases, subsequent washing was performed with phosphate-buffered saline solution to facilitate the removal of traces of adhering interfering substances. A batch of 12 samples can be analyzed within 8 min either by visual comparison of the color intensity (inversely related to the analyte concentration) of a sample spot with those of reference standards or, more precisely, by densitometry. The method was tested for the analysis of AFB1 in groundnut, wheat, corn, processed soybean, chili, and poultry feed. The detection limit obtained was 5 μg/kg, except for chili, where it was 10 μg/kg. The average recoveries from different noninfected food samples spiked with AFB1 at concentrations of 5 to 100 μg/kg were between 99 and 105%. The values obtained for infected corn and groundnut samples correlated well with the estimates obtained by high-pressure liquid chromatography. The absence of a sample extraction step reduces the cost and labor involved in the assay. The method may be potentially applicable to the assay of other mycotoxins and environmental pollutants. [ABSTRACT FROM AUTHOR]

Abstract: The sigma-2 (σ2) receptor has been suggested to be a promising target for pharmacological interventions to curb tumor progression. Development of σ2-specific ligands, however, has been hindered by lack of understanding of molecular determinants that underlie selective ligand-σ2 interactions. Here we have explored effects of electron donating and withdrawing groups on ligand selectivity for the σ2 versus σ1 receptor using new benzamide-isoquinoline derivatives. The electron-donating methoxy group increased but the electron-withdrawing nitro group decreased σ2 affinity. In particular, an extra methoxy added to the para-position (5e) of the benzamide phenyl ring of 5f dramatically improved (631 fold) the σ2 selectivity relative to the σ1 receptor. This para-position provided a sensitive site for effective manipulation of the sigma receptor subtype selectivity using either the methoxy or nitro substituent. Our study provides a useful guide for further improving the σ2-over-σ1 selectivity of new ligands. [Copyright &y& Elsevier]

The growth of Ge on Si(111)/Ge-(√3 × √3)Ag substrates was investigated for Ge coverages up to 1 monolayer (ML). The √3Ag substrate was obtained by depositing 0.2 ML Ag on Si(111)/Ge(111)-5 × 5 surfaces. Because of the low Ag coverage, three types of regions – √3Ag ‘island’, √3Ag ‘hole’ and exposed Ge(111)-5 × 5 – are produced. This has allowed investigation of Ge growth simultaneously on these three types of surface features by scanning tunneling microscopy. Ge has been found to grow as bilayers almost exclusively on the √3Ag ‘hole’ regions, with its surface terminated by a √3Ag structure. This indicates that Ag behaves like a surfactant and segregates to the top of the deposited Ge via Ag-Ge exchange. At higher Ge coverages the √3Ag surface undergoes a transformation to a (3 × 1) Ag phase. The deposited Ge hardly grows on the exposed Si/Ge-5 × 5 regions, in contrast to the expected growth behavior on bare Si/Ge-5 × 5 surface. [ABSTRACT FROM AUTHOR]