Two-potential electrochemical probe for study of DNA immobilization

A two-potential electrochemical method is applied to study DNA immobilization, by the simultaneous characterization of capture probe DNA self-assembled monolayers and hybridized target DNA molecules on a given gold electrode surface. Capture probe and target DNA strands are labeled with ferrocenes composed of differing chemical environments, to permit their simultaneous, yet independent signaling at different formal potentials, so that their respective signals may be de-convoluted and assessed for relative surface concentration. Some special attributes of the nondestructive two-potential electrochemical probe described herein include surface sensitivity, chemical and orientation specificity, and the ability to provide a real-time, in situ probe that does not need any wash steps for stringency. This electrochemical probe is applied to study the kinetics, surface architecture, coverage, and orientation of DNA during its immobilization on gold. On the basis of our results primarily from this electrochemical probe, and validated by N(1s) core-level X-ray photoelectron spectra, we judge significant DNA deposition within 5 min of incubation in the deposition solutions, with the capture probe DNA anchored predominantly via the thiol end, even at low coverages. Surface coverage for DNA immobilization plateaus within 30 min of incubation time to approximately 2 x 10(13) molecules/cm(2) and the immobilization kinetics as determined from this electrochemical method are consistent with surface re-organization as the rate-determining step.     

Phase transfer of oleic acid capped Ni(core)Ag(shell) nanoparticles assisted by the flexibility of oleic acid on the surface of silver

The phase transfer protocols in vogue for the oleic acid capped silver nanoparticles, viz., salt-induced precipitation and redispersion or phosphoric acid-induced method, are examined and compared thoroughly. A comprehensive evaluation with respect to the mechanistic aspects involved is made and the merits and demerits of the different procedures are delineated. It is found that the salt-induced precipitation and redispersion is more versatile in that the precipitate can actually be redispersed in both aqueous and organic media. However, in terms of mechanism both the routes seem to be very similar wherein the orientational change of oleic acid on the silver surface in the two different environments-organic and aqueous-plays a crucial role in the adaptability of the system to the different environments. Subsequently, this change of orientation of oleic acid on silver surface in aqueous and organic media has been utilized to phase transfer Ni-based nanoparticulate systems. The nascent oleic acid-capped Ni nanoparticles, which were synthesized by a foam-based protocol, were dispersible in water but not in nonpolar organic media such as cyclohexane or toluene. Then, just by coating a thin shell of silver on them we could achieve complete phase transfer of the Ni(core)Ag(shell) from aqueous to organic media following similar procedures used for oleic acid-capped silver nanoparticles. Here, the phase transfer seems to be facilitated by the orientational flexibility of oleic acid on the silver surface as opposed to other metal surfaces as evidenced from the infrared and thermogravimetric analyses of oleic acid-capped Ni and Ni(core)Ag(shell) nanoparticles. This orientation-assisted phase transfer method could be generalized and can be adapted to other systems where, if the nascent nanoparticles cannot be phase transferred as is, they can be coated by a silver shell and oleic acid making them suitable for dispersion in both aqueous and organic media.     

Coordination chemistry of palladium(II) and platinum(II) complexes with bioactive Schiff bases: Synthetic,spectral, and biocidal aspects

The Schiff bases, 5-nitro-indol-2,3-dionehydrazinecarboxamide (HSCZ¹) and 7-nitro-indol-2,3- dionehydrazinecarboxamide (HSCZ²), have been synthesized by the condensation of 5-nitro-indol-2,3-dione and 7-nitro-1H-indol-2,3-dione with semicarbazide hydrochloride, respectively. The palladium(II) and platinum( II) complexes have been prepared by mixing palladium chloride and platinum chloride in 1: 2 molar ratios with monobasic bidentate Schiff bases. The ligands and complexes of palladium and platinum have been characterized by elemental analyses, melting point determinations, conductance measurements, molecular weight determinations, and IR, ¹H NMR, and UV spectral studies. These studies showed that the ligands coordinate to the metal atoms in a monobasic bidentate mode, coordinating through oxygen and nitrogen donor systems. Thus, a tetracoordinated environment around the metal atom has been proposed. Both the ligands and their complexes have been screened for their biological activity on several pathogenic fungi and bacteria and were found to possess appreciable fungicidal and bactericidal properties. Plant growth regulating activity of one of the ligands and its complexes has also been recorded on gram plant, and results have been discussed. The article is published in the original.     

Thermal analysis of iron(II) sulphate heptahydrate in air

Iron(II) sulphate hydrates (hexa- through mono-) have been prepared and their thermal decomposition behaviours have been studied in air by isothermal and dynamic thermal analysis methods. The results show that their behaviours are similar to that of the heptahydrate. The stepwise loss of water molecules is accompanied by oxidation. Under a restricted supply of oxygen, the anhydrous sulphate is oxidized directly to Fe₂O(SO₄)₂ without the formation of Fe(OH)SO₄. When free exchange with oxygen is allowed, Fe(OH)SO₄ is formed, which in turn decomposes to Fe₂O(SO₄)₂. The decomposition of Fe₂(SO₄)₂ to iron(III) oxide and sulphur oxides appears to occur via two independent paths — one direct and other through iron(III) sulphate.     

The spin dependence of an weak interaction in the decay of hypernuclei

From an analysis of 468 hypernuclei (HFs) with ranges > 120 μm, the non-mesic to π^?-mesic ratio (Q^?) for_ΛHe and_ΛHe⁵ HFs was found to be 1.37 ±0.17 and 1.58± 0.20 respectively. This data, together with results on_ΛHe⁴ and heavy hypernuclei, has been used to deduce spin dependences for Λⁿ and ΛP weak interactions in decay of hypernuclei. It is found that the rates for triplet and singlet interactions between Λ and neutron are 22 Γ_Λ and 11 Γ_Λ and for Λ and proton are 8.2 Γ_Λ and 5.5 Γ_Λ respectively, where Γ_Λ is the decay rate of Λ. The total decay rates for ΛHe⁴ and_ΛHe⁵ are 1.28 Γ_Λ and 0.99 Γ_Λ and the non-mesic decay rates are 0.17 Γ_Λ and 0.51 Γ_Λ respectively.     

Liesegang rings of copper chromate in gelatin gel

Summary DistinctLiesegang Rings of Copper chromate in gelatin gel are not formed as the salt forms a very stable colloid in this medium. As this sol is coagulated by KH₂PO₄, well defined rings of Copper chromate in gelatin gel are formed in the presence of this electrolyte.

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Zusammenfassung DeutlicheLiesegang-Ringe werden in Kupfer-Chromat und Gelatine-Gel nicht gebildet, da das Salz ein sehr stabiles Kolloid in diesem Medium darstellt. Wenn dieses Sol durch KH₂PO₄ koaguliert wird, entstehen definierte Ringe von Kupfer-Chromat im Gelatine-Gel bei Gegenwart dieses Elektrolyten.

     

In Vitro Antibacterial and Antifungal Activities of Some Sulfur–Nitrogen–Oxygen and Oxygen–Nitrogen–Oxygen Donor Bifunctional Tridentate Schiff Bases and Their Boron(III) Complexes

Antimicrobial properties of sulfur, nitrogen, and oxygen bonded organoboron (III) complexes with biologically potent ligands viz., 2-hydroxy-N-phenyl benzamide hydrazine carboxamide(HO^∩N^∩OH), 2-hydroxy-N-phenyl benzamide hydrazine carbothioamide (HO^∩N^∩SH), and 2-hydroxy-N-phenyl benzamide hydrazine carbodithioic acid (HO^∩N^∩SH), have been studied. The unimolar and bimolar reactions of triisopropoxy borane with dibasic tridentate ligands resulted in the formation of colored solids, which have been characterized by elemental analysis, molecular weight determinations, and conductance measurements. The UV, IR, and NMR (¹H, ¹³C, and ¹¹B) spectral studies indicate a tetra-coordinated geometry for the resulting complexes. The ligands and their complexes have been screened for their fungicidal and bactericidal activities, and the results indicate that they exhibit significant antimicrobial properties.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.