Understanding the Two-Dimensional Mixing Behavior of 1-Naphthalenethiol and Octanethiol.

A two-dimensional (2D) mixture in the form of a self-assembled monolayer composed of two distinct organothiol compounds was created by sequentially depositing 1-naphthalenethiol (1NT) and octanethiol (OT) on a gold surface. By varying the sequence of deposition, two mixed surface systems were created. The surface structure of the resulting mixed monolayer was characterized with Scanning Tunneling Microscopy (STM) and showed surface disorder across all investigated domains. Elemental analysis was carried out with X-ray Photoelectron Spectroscopy (XPS) and indicated that the 1NT monolayer was prone to significant oxidation. Reductive desorption (RD) was used to characterize the binding strength and electrochemical environments of the molecular components in the mixture, and confirmed disordered molecular layers. Due to the presence of oxidized species in the 1NT monolayer, 1NT was displaced by OT resulting in a novel surface structure composed of either OT or 1NT. Monolayers of OT that were exposed to a solution of 1NT resulted in disordered surface structures with a significant amount of gold vacancy islands. To date, there is no experimental phase diagram explaining the chemical behavior of two-dimensional mixtures. This study addresses the need for an experimental understanding of the phase behavior of mixed organothiol self-assembled monolayers (SAMs).

Nitrogen-sparging assisted anoxic biological drinking water treatment system.

Existing heterotrophic denitrification reactors rely on microorganisms to consume dissolved oxygen (DO) and create conditions suitable for denitrification, but this practice leads to excessive microbial growth and increased organic carbon doses. An innovative reactor that uses nitrogen gas sparging through a contactor to strip DO was developed and tested in the lab. It reduced influent nitrate from 15 to <1 mg/L as N with nitrite accumulation <1 mg/L as N. It maintained a consistent flow rate and developed minimal headloss, making it easier to operate than the denitrifying dual-media filter that was operated in parallel. Gravel, polyvinyl chloride pieces, and no packing media were assessed as options for the nitrogen-sparged contactor, and gravel was found to support denitrification at the highest loading rate and was resilient to nitrogen-sparging shutoffs and intermittent operation. This innovative reactor appears promising for small drinking water systems.

Design and Testing of USEPA'S Flint Pipe Rig for Corrosion Control Evaluation.

The US Environmental Protection Agency's Office of Research and Development designed, fabricated, and installed four pipe rigs in Flint, Mich., to help the city optimize corrosion control. The lead service line (LSL) pipe loops were constructed of polyvinyl chloride pipe and fittings and welded steel channel frames. Each pipe rig consisted of four approximately 4 ft-long sections of 0.75 in. inside diameter lead pipe that were excavated from homes fed by the Flint distribution system. The rigs were operated on a set daily on/off schedule such that a specified amount of water passed through each pipe using a solenoid valve-operated timer system. Solenoid problems resulted in sporadic and enhanced daily flow volume (but no flow rate changes) that prevented restabilization of pipe scales. Lead levels were relatively sporadic and statistically different during this period. After the solenoids were replaced, the lead pipe rigs were successfully conditioned, and lead release with consistent influent water chemistry became relatively stable. Average lead levels across all 16 loops ranged between approximately 2 and 5 µg/L after the solenoid replacement. The lead results were consistent with levels measured from LSLs from homes in the city during sequential sampling efforts.

High-throughput screening system for inhibitors of human Heat Shock Factor 2.

Development of novel anti-cancer drug leads that target regulators of protein homeostasis is a formidable task in modern pharmacology. Finding specific inhibitors of human Heat Shock Factor 1 (hHSF1) has proven to be a challenging task, while screening for inhibitors of human Heat Shock Factor 2 (hHSF2) has never been described. We report the development of a novel system based on an in vivo cell growth restoration assay designed to identify specific inhibitors of human HSF2 in a high-throughput format. This system utilizes a humanized yeast strain in which the master regulator of molecular chaperone genes, yeast HSF, has been replaced with hHSF2 with no detrimental effect on cell growth. This replacement preserves the general regulatory patterns of genes encoding major molecular chaperones including Hsp70 and Hsp90. The controlled overexpression of hHSF2 creates a slow-growth phenotype, which is the basis of the growth restoration assay used for high-throughput screening. The phenotype is most robust when cells are cultured at 25 °C, while incubation at temperatures greater than 30 °C leads to compensation of the phenotype. Overexpression of hHSF2 causes overexpression of molecular chaperones which is a likely cause of the slowed growth. Our assay is characterized by two unique advantages. First, screening takes place in physiologically relevant, in vivo conditions. Second, hits in our screen will be of medically relevant potency, as compounds that completely inhibit hHSF2 function will further inhibit cell growth and therefore will not be scored as hits. This caveat biases our screening system for compounds capable of restoring hHSF2 activity to a physiologically normal level without completely inhibiting this essential system.

The impact of temperature on the performance of anaerobic biological treatment of perchlorate in drinking water.

A 20-month pilot-scale study was conducted to examine the impact of temperature on the performance of an anaerobic biological contractor used to treat perchlorate-contaminated water. The contractor was successfully acclimated with indigenous microorganisms. Influent temperatures varied from 1.4 to 30 degrees C. The objectives of the study were to investigate the effects of temperature on perchlorate removal, nitrate removal, nitrite formation, dissolved oxygen consumption, sulfide production, and nutrient acetate consumption. The results confirmed that consistent biological perchlorate removal to 2 microg /L is feasible at temperatures above 10 degrees C. Effluent concentrations of perchlorate, nitrate, and dissolved oxygen varied inversely with temperature, while sulfide varied positively with temperature. Under the conditions that prevailed during this study, 10 degrees C was a threshold temperature below which microbial activity, including perchlorate reduction, decreased dramatically.

Multiplexed DNA sequencing-by-synthesis.

We report a new DNA sequencing-by-synthesis method in which the sequences of DNA templates, hybridized to a surface-immobilized array of DNA primers, are determined by sensing the number of nucleotides by which the primers in each array spot are extended in sequential DNA polymerase-catalyzed nucleotide incorporation reactions, each with a single fluorescein-labeled deoxyribonucleoside triphosphate (dNTP) species. The fluorescein label is destroyed after each readout by a photostimulated reaction with diphenyliodonium chloride. A DNA polymerase with enhanced ability to incorporate, and to extend beyond, modified nucleotides is used. Self-quenching of adjacent fluorescein labels, which impedes readout of homopolymeric runs, is avoided by diluting the labeled dNTP with unlabeled reagent. Misincorporation effects have been quantified and are small; however, low-level contamination of dNTPs with other nucleotides mimics misincorporation and can produce significant false-positive signals. These impurities are removed by polymerase-catalyzed incorporation into complementary "cleaning duplexes." Here, we demonstrate the accurate sequence readout for a small array of known DNA templates, the ability to quantify homopolymeric runs, and a short sequencing example of sections of the wild-type and mutant BRCA1 gene. For a 20,000-spot array, readout rates in excess of 6000 bases per minute are projected.

Stereochemical Consequences of the Bismuth Atom Electron Lone Pair, a Comparison between MX(6)E and MX(6) Systems. Crystal and Molecular Structures of Tris[N-(P,P-diphenylphosphinoyl)-P,P-diphenylphosphinimidato]bismuth(III), [Bi{(OPPh(2))(2)N}(3)], -indium(III), [In{(OPPh(2))(2)N}(3)].C(6)H(6), and -gallium(III), [Ga{(OPPh(2))(2)N}(3)].CH(2)Cl(2).

The tetraphenylimidodiphosphinate [N-(P,P-diphenylphosphinoyl)-P,P-diphenylphosphinimidate] ion forms stable tris-chelates with the Bi(III), In(III), and Ga(III) cations. The crystal and molecular structures of [M{(OPPh(2))(2)N}(3)] (M = Ga, In, Bi) were determined by X-ray diffractometry. The geometry around the bismuth atom in compound 3 displays an approximately C(3)(v)() symmetry. This arrangement suggests the presence of a stereoactive lone pair of electrons, which is located in one of the triangular octahedral faces. Derivative 3 crystallizes in the triclinic space group P&onemacr; with Z = 2, a = 14.006(6) Å, b = 14.185(4) Å, c = 17.609(8) Å, alpha = 88.45(2) degrees, beta = 79.34(2) degrees, and gamma = 78.23(2) degrees. The structures of the gallium(III) and indium(III) tris-chelate oxygen-based complexes (1 and 2, respectively) were compared with the bismuth analogue in order to determine the ligand steric bulk influence on the coordination sphere in the absence of the electron lone pair. Complex 1 crystallizes as the [Ga{(OPPh(2))(2)N}(3)].CH(2)Cl(2) solvate in the triclinic space group P&onemacr;; Z = 2, a = 13.534(4) Å, b = 13.855(4) Å, c = 18.732(7) Å, alpha = 95.48(2) degrees, beta = 98.26(2) degrees, and gamma = 97.84(2) degrees. Crystal data for the benzene solvate of 2, [In{(OPPh(2))(2)N}(3)].C(6)H(6): triclinic space group P&onemacr;, Z = 2, a = 13.542(9) Å, b = 15.622(3) Å, c = 18.063(5) Å, alpha = 98.21(1) degrees, beta = 104.77(0) degrees, and gamma = 92.260(0) degrees.