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1.  Synthesis and electrical characterization of intrinsic and in situ doped Si nanowires using a novel precursor 
Summary
Perchlorinated polysilanes were synthesized by polymerization of tetrachlorosilane under cold plasma conditions with hydrogen as a reducing agent. Subsequent selective cleavage of the resulting polymer yielded oligochlorosilanes SinCl2 n +2 (n = 2, 3) from which the octachlorotrisilane (n = 3, Cl8Si3, OCTS) was used as a novel precursor for the synthesis of single-crystalline Si nanowires (NW) by the well-established vapor–liquid–solid (VLS) mechanism. By adding doping agents, specifically BBr3 and PCl3, we achieved highly p- and n-type doped Si-NWs by means of atmospheric-pressure chemical vapor deposition (APCVD). These as grown NWs were investigated by means of scanning electron microscopy (SEM) and transmission electron microscopy (TEM), as well as electrical measurements of the NWs integrated in four-terminal and back-gated MOSFET modules. The intrinsic NWs appeared to be highly crystalline, with a preferred growth direction of [111] and a specific resistivity of ρ = 6 kΩ·cm. The doped NWs appeared to be [112] oriented with a specific resistivity of ρ = 198 mΩ·cm for p-type Si-NWs and ρ = 2.7 mΩ·cm for n-doped Si-NWs, revealing excellent dopant activation.
doi:10.3762/bjnano.3.65
PMCID: PMC3458602  PMID: 23019552
chemical vapour deposition; field-effect transistor; oligosilanes; radiation-induced nanostructures; silicon nanowires; vapor–liquid–solid mechanism
2.  Mercuric Conjugates of Cysteine Are Transported by the Amino Acid Transporter System b0,+: Implications of Molecular Mimicry 
Humans and other mammals continue to be exposed to various forms of mercury in the environment. The kidneys, specifically the epithelial cells lining the proximal tubules, are the primary targets where mercuric ions accumulate and exert their toxic effects. Although the actual mechanisms involved in the transport of mercuric ions along the proximal tubule have not been defined, current evidence implicates mercuric conjugates of cysteine, primarily 2-amino-3-(2-amino-2-carboxyethylsulfanylmercuricsulfanyl)propionic acid (Cys-S-Hg-S-Cys), as the most likely transportable species of inorganic mercury (Hg2+). Because Cys-S-Hg-S-Cys and the amino acid cystine (Cys-S-S-Cys) are structurally similar, it was hypothesized that Cys-S-Hg-S-Cys might act as a molecular mimic of cystine at one or more of the amino acid transporters involved in the luminal absorption of this amino acid. One such candidate is the Na+-independent heterodimeric transporter system b0,+. Therefore, the transport of Cys-S-Hg-S-Cys and cystine was studied in MDCK II cells that were or were not stably transfected with b0,+AT-rBAT. Transport of Cys-S-Hg-S-Cys and cystine across the luminal plasma membrane was similar in the transfected cells, indicating that Cys-S-Hg-S-Cys can behave as a molecular mimic of cystine at the site of system b0,+. Moreover, only the b0,+AT-rBAT transfectants became selectively intoxicated during exposure to Cys-S-Hg-S-Cys. These findings indicate that system b0,+ likely contributes to the nephropathy induced by Hg2+ in vivo. These data represent the first direct molecular evidence for the participation of a specific transporter in the luminal uptake of a large divalent metal cation in proximal tubular cells.
doi:10.1097/01.ASN.0000113553.62380.F5
PMCID: PMC2587250  PMID: 14978168
3.  Luminal Heterodimeric Amino Acid Transporter Defective in Cystinuria 
Molecular Biology of the Cell  1999;10(12):4135-4147.
Mutations of the glycoprotein rBAT cause cystinuria type I, an autosomal recessive failure of dibasic amino acid transport (b0,+ type) across luminal membranes of intestine and kidney cells. Here we identify the permease-like protein b0,+AT as the catalytic subunit that associates by a disulfide bond with rBAT to form a hetero-oligomeric b0,+ amino acid transporter complex. We demonstrate its b0,+-type amino acid transport kinetics using a heterodimeric fusion construct and show its luminal brush border localization in kidney proximal tubule. These biochemical, transport, and localization characteristics as well as the chromosomal localization on 19q support the notion that the b0,+AT protein is the product of the gene defective in non-type I cystinuria.
PMCID: PMC25748  PMID: 10588648

Results 1-3 (3)