Nanopores can serve as high throughput, single-molecule sensing devices that provide insight into the distribution of static and dynamic molecular activities, properties, or interactions. We have studied double stranded DNA electrophoretic transport dynamics through fabricated nanopores in silicon nitride. A fabricated pore enables us to interrogate a broader range of molecules with a wider range of conditions than can be investigated in a self-assembled protein pore in a lipid membrane.

Background: Biclustering of gene expression data searches for local patterns of gene expression. A bicluster (or a two-way cluster) is defined as a set of genes whose expression profiles are mutually similar within a subset of experimental conditions/samples. Although several biclustering algorithms have been studied, few are based on rigorous statistical models.

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Crystal structures for [Pd(16Se4)][BF 4 ] 2 (1) (16Se4 ) 1,5,9,13-tetraselenacyclohexadecane) and [Pd(16Se4)]- [BF 4 ]Cl (2) both contain the [Pd(16Se4)] 2+ ion which has square-planar coordination about Pd and a stereochemistry (denoted c,c,c) in which all of the selenium nonbonding valence electron pairs are mutually cis with respect to the coordination plane. In both structures the conformation adopted by the cation deviates slightly but significantly from molecular mm (C 2V ) symmetry. The asymmetry is most clearly resolved for 2, in which the Pd-Se bond lengths vary significantly (2.444(1)-2.463(1) Å). For 1: T ) 295 K; fw ) 764.2; space group Pnma; Z ) 4; a ) 12.356(1) Å; b ) 10.397(1) Å; c ) 16.233(2) Å; V ) 2193.7 Å 3 ; R F ) 0.036 for 997 data (I o g 2.5σ(I o )) and 131 variables. For 2: T ) 295 K; fw ) 712.8; space group P1 h; Z ) 2; a ) 7.2377(4) Å; b ) 10.7784(7) Å; c ) 12.9523(9) Å; R ) 76.607(6)°; β ) 86.020(6)°; γ ) 85.186(5)°; V ) 978.17 Å 3 ; R F ) 0.023 for 2134 data (I o g 2.5σ(I o )) and 214 variables. The 77 Se, 1 H, 13 C, and 1 H-13 C correlated NMR spectra for 1 in D 2 O solution were fully assigned. At room temperature, [Pd(16Se4)] 2+ occurs in D 2 O solution predominantly as the c,t,c and c,c,c stereoisomers. Variable temperature NMR spectroscopic results demonstrate that at an elevated temperature (389 K) configurational interconversion is rapid on the 1 H-NMR time scale. Cyclic voltammetry of 1 and 2, in MeCN solution with Pt electrodes, shows that the redox reaction of the pair Pd(II)/Pd(I) is irreversible with cathodic peak potentials at -0.56 and -0.47 V vs SCE, respectively. The crystal structure of [(PdCl) 2 (24Se6)]-[BF 4 ] 2 ‚2CH 2 Cl 2 (3‚2CH 2 Cl 2 ) reveals a complex dication in which two individual palladium(II) centers are each bound by three adjacent selenium atoms. Both palladium centers display square planar coordination with a chlorine atom occupying the fourth site. The complex exhibits trans relationships between adjacent pyramidal selenium centers and adopts a conformation which has only approximate m (C s ) symmetry. The mutually trans Pd-Se bond lengths range from 2.421(1) to 2.428(1) Å. The Pd-Se bond lengths trans to the chlorine atom are 2.372-(1) and 2.364(1) Å, and the corresponding Pd-Cl bond lengths are 2.343(2) and 2.351(3) Å. For 3‚2CH 2 Cl 2 : T ) 195 K; monoclinic, space group P2 1 /c; Z ) 4; a ) 16.421(2) Å; b ) 19.353(2) Å; c ) 12.397(3) Å; β ) 91.16(2)°; V ) 3938.9 Å 2 ; R F ) 0.037 for 3793 data (I o g 2.5σ(I o )) and 409 variables. Cyclic voltammetry of 3 in MeCN solution with Pt electrodes shows an irreversible cathodic peak potential at -0.58 V vs SCE corresponding to a Pd(II)/Pd(I) pair. Electrolysis in MeCN confirms that this is a two-electron reduction for the complex.