A Facile and Mild Synthesis of 1-D ZnO, CuO, and α-Fe₂O₃ Nanostructures and Nanostructured Arrays

ZnO nanowires, CuO nanowires, and α-Fe2O3 nanotubes as well as their corresponding arrays have been successfully synthesized via a low cost, generalizable, and simplistic template method. Diameters of one-dimensional (1-D) metal oxide nanostructures (∼60−260 nm), measuring micrometers in length, can be reliably and reproducibly controlled by the template pore channel dimensions. Associated vertically aligned arrays have been attached to the surfaces of a number of geometrically significant substrates, such as curved plastic and glass rod motifs. The methodology reported herein relies on the initial formation of an insoluble metal hydroxide precursor, initially resulting from the reaction of the corresponding metal solution and sodium hydroxide, and its subsequent transformation under mild conditions into the desired metal oxide nanostructures. Size- and shape-dependent optical, magnetic, and catalytic properties of as-prepared 1-D metal oxides were investigated and noted to be mainly comparable to or better than the associated properties of the corresponding bulk oxides. A plausible mechanism for as-observed wire and tube-like motifs is also discussed

Determining DNA Global Structure and DNA Bending by Application of NMR Residual Dipolar Couplings

The local structure of nucleic acids can be determined from traditional solution NMR techniques, but it is usually not possible to uniquely define the global conformation of DNA or RNA double helices. This results from the short-range nature of the NOE-distance and torsion angle constraints used in generating the solution structures. However, new alignment techniques make it possible to readily measure residual dipolar couplings, which provide information on the relative orientation of individual bond vectors in the molecule. To determine the effects of incorporating dipolar couplings in the structure determinations of nucleic acids, molecular dynamics calculations were performed with simulated constraints derived from two DNA duplex target molecules. Refinements that included NOE, torsion angle, and dipolar coupling constraints were compared to refinements without dipolar couplings. These results show that dipolar couplings significantly improved the local structure while also dramatically improving the global structure of DNA duplexes. The model simulations also illustrate that molecular dynamics calculations induce changes in the local structure before the global structure, which can have important implications for refinements with dipolar coupling constraints. Results are presented that show that the inclusion of dipolar coupling constraints makes it possible to accurately and precisely reproduce the overall helical bend in a DNA duplex. The implications of including dipolar coupling constraints in defining DNA global structure and DNA bending in solution will be discussed

Probing Structure−Parameter Correlations in the Molten Salt Synthesis of BaZrO₃ Perovskite Submicrometer-Sized Particles

Single-crystalline perovskite BaZrO3 submicrometer-sized particles were synthesized using a simple, scaleable molten salt method. In this paper, in addition to a time-dependent particle evolution study, we explored primarily the effects of different experimental processing parameters, such as the identity of the salt, annealing temperatures, overall reaction times, cooling rates, and the chemical nature of the precursor in determining their impact upon the purity, size, shape, and morphology of the as-obtained products. We also discuss the role of additional experimentally controllable factors such as the heating rate applied, the amount of salt used, the molar ratios of precursors involved, and the use of surfactant. By a judicious choice of experimental parameters and conditions, we describe herein a rational means of producing pure products with a reproducible composition and morphology

Structural Insights into the Interaction between the Bacterial Flagellar Motor Proteins FliF and FliG

The binding of the soluble cytoplasmic protein FliG to the transmembrane protein FliF is one of the first interactions in the assembly of the bacterial flagellum. Once established, this interaction is integral in keeping the flagellar cytoplasmic ring, responsible for both transmission of torque and control of the rotational direction of the flagellum, anchored to the central transmembrane ring on which the flagellum is assembled. Here we isolate and characterize the interaction between the N-terminal domain of Thermotoga maritima FliG (FliGN) and peptides corresponding to the conserved C-terminal portion of T. maritima FliF. Using nuclear magnetic resonance (NMR) and other techniques, we show that the last ∼40 amino acids of FliF (FliFC) interact strongly (upper bound Kd in the low nanomolar range) with FliGN. The formation of this complex causes extensive conformational changes in FliGN. We find that T. maritima FliGN is homodimeric in the absence of the FliFC peptide but forms a heterodimeric complex with the peptide, and we show that this same change in oligomeric state occurs in full-length T. maritima FliG, as well. We relate previously observed phenotypic effects of FliFC mutations to our direct observation of binding. Lastly, on the basis of NMR data, we propose that the primary interaction site for FliFC is located on a conserved hydrophobic patch centered along helix 1 of FliGN. These results provide new detailed information about the bacterial flagellar motor and support efforts to understand the cytoplasmic ring’s precise molecular structure and mechanism of rotational switching

Supplemental material for Design of First-Order 121.6 nm Minus Filters

<p>Supplemental Material for Design of First-Order 121.6 nm Minus Filters by Xiaodong Wang, Bo Chen, Tonglin Huo and Hongjun Zhou in Applied Spectroscopy</p

<i>C</i>‑Diazeniumdiolate Graminine in the Siderophore Gramibactin Is Photoreactive and Originates from Arginine

Siderophores are synthesized by microbes to facilitate iron acquisition required for growth. Catecholate, hydroxamate, and α-hydroxycarboxylate groups comprise well-established ligands coordinating Fe(III) in siderophores. Recently, a C-type diazeniumdiolate ligand in the newly identified amino acid graminine (Gra) was found in the siderophore gramibactin (Gbt) produced by Paraburkholderia graminis DSM 17151. The N–N bond in the diazeniumdiolate is a distinguishing feature of Gra, yet the origin and reactivity of this C-type diazeniumdiolate group has remained elusive until now. Here, we identify l-arginine as the direct precursor to l-Gra through the isotopic labeling of l-Arg, l-ornithine, and l-citrulline. Furthermore, these isotopic labeling studies establish that the N–N bond in Gra must be formed between the Nδ and Nω of the guanidinium group in l-Arg. We also show the diazeniumdiolate groups in apo-Gbt are photoreactive, with loss of nitric oxide (NO) and H+ from each d-Gra yielding E/Z oxime isomers in the photoproduct. With the loss of Gbt’s ability to chelate Fe(III) upon exposure to UV light, our results hint at this siderophore playing a larger ecological role. Not only are NO and oximes important in plant biology for communication and defense, but so too are NO-releasing compounds and oximes attractive in medicinal applications

FT-IR raw data from Highly efficient triazolone/metal ion/polydopamine/MCM-41 sustained release system with pH sensitive for pesticide delivery

MCM-41 was prepared through the sol–gel method and encapsulated by polydopamine (PDA) before coordinated with metal ion to form a highly efficient sustained release system (M-PDA–MCM-41) for triazolone delivery. The characterization results confirmed the existence of the coordination bond between the PDA layer and triazolone through the bridge effect from metal ion, which enhanced the interaction between PDA–MCM-41 and triazolone. The adsorption capacity (AC) of Fe-PDA–MCM-41 increased up to 173 mg g^–1, which was 160% more than that of MCM-41. The sustained release performance of M-PDA–MCM-41 in different pH values was investigated. Under the conditions of pH ≤7, the release speed of triazolone increased with pH decreasing. Whereas its release speed in the weak base condition was slower than in the neutral condition. Therefore, the as-synthesized system showed significant pH-sensitivity in the sustained release process, indicating that the sustained release system can be well stored in the neutral or basic environment and activated in the acid environment. Their sustained release curves described by Korsmeyer–Peppas equation at pH 7 showed the same behaviour, indicating that PDA decoration or metal ion coordination only increases the steric hindrance and the interaction between carrier and triazolone instead of changing the original structure of the pure MCM material in accordance with XRD and BET analysis results

BET raw data from Highly efficient triazolone/metal ion/polydopamine/MCM-41 sustained release system with pH sensitive for pesticide delivery

MCM-41 was prepared through the sol–gel method and encapsulated by polydopamine (PDA) before coordinated with metal ion to form a highly efficient sustained release system (M-PDA–MCM-41) for triazolone delivery. The characterization results confirmed the existence of the coordination bond between the PDA layer and triazolone through the bridge effect from metal ion, which enhanced the interaction between PDA–MCM-41 and triazolone. The adsorption capacity (AC) of Fe-PDA–MCM-41 increased up to 173 mg g–1, which was 160% more than that of MCM-41. The sustained release performance of M-PDA–MCM-41 in different pH values was investigated. Under the conditions of pH ≤7, the release speed of triazolone increased with pH decreasing. Whereas its release speed in the weak base condition was slower than in the neutral condition. Therefore, the as-synthesized system showed significant pH-sensitivity in the sustained release process, indicating that the sustained release system can be well stored in the neutral or basic environment and activated in the acid environment. Their sustained release curves described by Korsmeyer–Peppas equation at pH 7 showed the same behaviour, indicating that PDA decoration or metal ion coordination only increases the steric hindrance and the interaction between carrier and triazolone instead of changing the original structure of the pure MCM material in accordance with XRD and BET analysis results

Enhanced Electrocatalytic Performance of One-Dimensional Metal Nanowires and Arrays Generated via an Ambient, Surfactantless Synthesis

One-dimensional (1-D) metal (Ag, Au, and Pt) nanowires and their corresponding arrays have been synthesized using an ambient, surfactantless synthesis technique. The potential applicability of such crystalline, highly purified 1-D samples for practical uses was specifically demonstrated in their manifestation as electrocatalysts for an oxygen reduction reaction (ORR). Specifically, Pt 1-D nanostructures possessed a higher ORR activity as compared with that of Pt nanoparticles alone. Ag and Au nanowires also evinced reasonable ORR activity in alkaline solution

Observation of Discrete Au Nanoparticle Collisions by Electrocatalytic Amplification Using Pt Ultramicroelectrode Surface Modification

After growing a thin layer of oxide (PtO_<i>x</i>) by anodization of a Pt electrode, it changed from catalytically active for electrochemical NaBH₄ oxidation into an inactive electrode. When held at a potential where the oxide film was maintained, collisions of individual 14 nm diameter Au nanoparticles (NPs) that catalyzed NaBH₄ oxidation were successfully observed as discrete current pulses (spikes or blips) for each NP interaction with the modified Pt electrode via amplification from NaBH₄ oxidation. The current response is affected by NP concentration and the applied potential