Spirochetes from termite hindguts and freshwater sediments possessed homologs of a nitrogenase gene (nifH) and exhibited nitrogenase activity, a previously unrecognized metabolic capability in spirochetes. Fixation of 15-dinitrogen was demonstrated with termite gut Treponema ZAS-9 and free-livingSpirochaeta aurantia. Homologs of nifH were also present in human oral and bovine ruminal treponemes. Results implicate spirochetes in the nitrogen nutrition of termites, whose food is typically low in nitrogen, and in global nitrogen cycling. These results also proffer spirochetes as a likely origin of certainnifHs observed in termite guts and other environments that were not previously attributable to known microbes.

STM based kinetic and thermodynamic studies of ordered organic adlayer formation at the solution–solid interface.

Implication of dispersion interactions on geometric, adsorption and electronic properties of porphyrin monolayer on conductive surfaces using density functional theory.

Mechanical and structural properties of ionically self-assembled nanostructures of meso-tetra(4-sulfonatophenyl)porphyrin (TSPP) and meso-tetra(4-pyridyl)porphyrin (TPyP) are presented. This is the first time that elastic modulus of an ionic porphyrin nanostructure has been reported. X-ray photoelectron spectroscopy (XPS), UV-visible spectra, and elemental analysis all support a stoichiometric 1 : 1 TSPP to TPyP composition. Atomic force microscopy (AFM) revealed that the porphyrin nanostructure is composed of stacked ribbons about 20 nm tall, 70 nm wide, and several microns in length. High resolution transmission electron microscopy (HRTEM) images showed clear lattice fringes 1.5 ± 0.2 nm in width aligned along the length of the nanorod. Selected area electron diffraction (SAED) and powder X-ray diffraction patterns of TSPP:TPyP are consistent with an orthorhombic system and space group Imm2 with lattice parameters a = 26.71 Å, b = 20.16 Å, and c = 8.61 Å. Crystallographic data is consistent with an arrangement of alternating face-to-face TSPP and TPyP molecules forming ordered columns along the length of the nanorods. The structural integrity of the solid is attributed to combined noncovalent interactions that include ionic, hydrogen bonding, and π–π interactions. The values of Young's modulus obtained for the crystalline TSPP:TPyP nanorods averaged 6.5 ± 1.3 GPa. This modulus is comparable to those reported for covalently bonded flexible polymeric systems. The robust bonding character of the TSPP:TPyP nanostructures combined with their mechanical properties makes them excellent candidates for flexible optoelectronic devices.