Interaction of nitrogen and oxygen with C60

Evidence is presented for the strong interaction of nitrogen and oxygen with buckminsterfullerene.

Interaction of single-walled carbon nanotubes with poly(propyl ether imine) dendrimers

We study the complexation of nontoxic, native poly(propyl ether imine) dendrimers with single-walled carbon nanotubes (SWNTs). The interaction was monitored by measuring the quenching of inherent fluorescence of the dendrimer. The dendrimer-nanotube binding also resulted in the increased electrical resistance of the hole doped SWNT, due to charge-transfer interaction between dendrimer and nanotube. This charge-transfer interaction was further corroborated by observing a shift in frequency of the tangential Raman modes of SWNT. We also report the effect of acidic and neutral pH conditions on the binding affinities. Experimental studies were supplemented by all atom molecular dynamics simulations to provide a microscopic picture of the dendrimer-nanotube complex. The complexation was achieved through charge transfer and hydrophobic interactions, aided by multitude of oxygen, nitrogen, and n-propyl moieties of the dendrimer. (C) 2011 American Institute of Physics. doi:10.1063/1.3561308]

Nitrogen Derivatives Of C-60 And C-70 - Interaction Of Fullerenes With Nitrogen In Gas-Phase

Mass spectrometric studies show that contact-arc vaporization of graphite in a partial atmosphere of N2 or NH3 yields nitrogenous products tentatively assigned to species such as C70N2, C59N6, C59N4 and C59N2 involving addition of or substitution by nitrogen along with the species due to C2 and C4 losses. Mass spectrometry and other techniques have been employed to identify products of the nucleophilic addition of aliphatic amines to C60 and C70 in solution phase.

Interaction analysis of strip footing resting on a non-homogeneous elastic medium

In this paper, a plane stress solution for the interaction analysis of strip footing resting on (i) a non-homogeneous elastic half-plane and (ii) a non-homogeneous elastic layer resting on a rigid stratum has been presented. The analysis has been done using a combined analytical and FEM method in which the discretization of the half-plane is not required and thereby minimizes the computational efforts considerably. The contact pressure distribution and the settlement profile for the selected cases of varying modulus half-plane, which has more relevance to foundation engineering, have been given. Experimental verification through a photoelastic method of stress analysis has been carried out for the case of footing on Gibson elastic half-plane, and the contact pressure distribution thus obtained has been compared with the theoretical results. Copyright (C) 1996 Elsevier Science Ltd

Interaction of sheep liver apo-serine hydroxymethyltransferase with pyridoxal-5'-phosphate: A physicochemical, kinetic, and thermodynamic study

Sheep liver serine hydroxymethyltransferase (EC 2.1.2.1) is a homotetramer of M(r) 213,000 requiring pyridoxal-5'-phosphate (PLP) as cofactor, Removal of PLP from the holoenzyme converted the enzyme to the apo form which, in addition to being inactive, was devoid of the characteristic absorption spectrum. Upon the addition of PLP to the apoenzyme, complete activity was restored and the visible absorption spectrum with a maximum at 425 nm was regained. The interaction of PLP with the apoenzyme revealed two phases of reaction with pseudo-first-order rate constants of 20 +/- 5 s(-1) and 12.2 +/- 2.0 x 10(-3) s(-1), respectively. However, addition of PLP to the apoenzyme did not cause gross conformational changes as evidenced by circular dichroic and fluorescence spectroscopy. Although conformationally apoenzyme and holoenzyme were indistinguishable, they had distinct apparent melting temperatures of 51 +/- 2 and 58 +/- 2 degrees C, respectively, and the reconstituted holoenzyme was thermally as stable as the native holoenzyme. These results suggested that there was no apparent difference in the secondary structure of holoenzyme, apoenzyme, and reconstituted holoenzyme, However, sedimentation analysis of the apoenzyme revealed the presence of two peaks of S-20,S-w values of 8.7 +/- 0.5 and 5.7 +/- 0.3 S, respectively. A similar pattern was observed when the apoenzyme was chromatographed on a calibrated Sephadex G-150 column. The first peak corresponded to the tetrameric form (M(r) 200,000 +/- 15,000) while the second peak had a M(r) of 130,000 +/- 10,000. Reconstitution experiments revealed that only the tetrameric form of the apoenzyme could be converted into an active holoenzyme while the dimeric form could not be reconstituted into an active enzyme. These results demonstrate that PLP plays an important role in maintaining the structural integrity of the enzyme by preventing the dissociation of the enzyme into subunits, in addition to its function in catalysis. (C) 1996 Academic Press, Inc.

Preparation, Characterization And Properties Of C-60 And C-70 - Spectroscopy, Structure, Anions, Interaction With Electron-Donors And Superconductivity

Preparation and characterization of the fullerenes, C60 and C70, are described in detail, including the design of the generators fabricated locally. The characterization techniques employed are UV-visible, IR, Raman and C-13 NMR spectroscopies, scanning as well as transmission electron microscopy and mass spectrometry. The electron energy level diagram of C60 as well as the one-electron reductions of C60 and C70 leading to various anions are discussed. Electronic absorption spectra of C60- and C60(2-) are reported. Phase transitions from the plastic to the crystalline states of C60 and C70 are examined. Based on a C-13 NMR study in a mixture of nematic liquid crystals, it has been demonstrated that C60 retains its extraordinary symmetry in solution phase as well. Interaction of C60 and C70 with strong electron-donor molecules has been investigated employing cyclic voltammetry. Superconductivity of K(x)C60 has been studied by non-resonant microwave absorption; Na(x)C60 as well as K(c)C70 are shown to be non-superconducting. Doping C60 with iodine does not make it superconducting. Interaction of C60 with SbCl5 and liquid Br2 gives rise to halogenated products.

Realtime kinetic analysis of antigen-antibody interaction using solid phase binding: Transformation of hCG-monoclonal antibody complex

Kinetic constants of MAb-hCG interactions have been determined using solid phase binding of I-125[hCG] to immobilized MAb. While association has been shown to follow the expected pattern, dissociation consists of at least two reversible steps, one with a rate constant of 0.0025 min(-1), and a second with a rate constant of 0.00023 min(-1). Validity of affinity constant measurements in the light of the complex reaction kinetics is discussed, A comparison between the method of surface plasmon resonance technology (BIAcore) and solid phase binding (SPB) for determination of kinetic parameters shows that SPB provides not only a cost-effective approach for determination of realtime kinetic parameters of macromolecular ligand-ligate interaction but also a method with several advantages over the BIAcore system in investigating the mechanism of antigen-antibody interaction.

Derivation and consistency of the partial functions of the ternary system involving interaction coefficients

The logarithm of activity coefficients of the components of the ternary system is derived based on the Maclaurin infinite series, which is expressed in terms of the integral property of the system and subjected to appropriate boundary conditions. The derivation of the functions involves extensive summation of various infinite series pertaining to the first-order interaction coefficients that have been shown completely to remove any truncational error. Since the conventional equations involving interaction coefficients are internally inconsistent, a consistent form of the partial functions is developed in the article using the technique just described. The thermodynamic consistency of the functions based on the Maxwell and the Gibbs-Duhem relations has been established. The derived values of the logarithmic activity coefficients of the components have been found to be in agreement with the thermodynamic data of the Fe-Cr-Ni system at 1873 K and have been found to be independent of the compositional paths.

Quinazoline�iodine interaction as studied by NMR in nematic solutions

The results of an NMR study of the interaction of quinazoline with iodine in the nematic phase indicate the formation of at least two different types of charge-transfer complexes. Significant changes in the molecular geometry of the quinazoline moiety were observed as a result of complexation with iodine. Detailed information on the formation of the charge-transfer complexes was derived from the changes in the molecular structure, order parameters and chemical shifts as functions of iodine concentration. The observed changes in the order parameters are interpreted in terms of bond interaction tensors.

The sputtering temperature of a cooling cylindrical rod without and with an insulated core in a two-fluid medium

Utilising Jones' method associated with the Wiener-Hopf technique, explicit solutions are obtained for the temperature distributions on the surface of a cylindrical rod without an insulated core as well as that inside a cylindrical rod with an insulated inner core when the rod, in either of the two cases, is allowed to enter, with a uniform speed, into two different layers of fluid with different cooling abilities. Simple expressions are derived for the values of the sputtering temperatures of the rod at the points of entry into the respective layers, assuming the upper layer of the fluid to be of finite depth and the lower of infinite extent. Both the problems are solved through a three-part Wiener-Hopf problem of special type and the numerical results under certain special circumstances are obtained and presented in tabular forms.

Mutations in beta ` subunit of Escherichia coli RNA polymerase perturb the activator polymerase functional interaction required for promoter clearance

P>Transcription activator C employs a unique mechanism to activate mom gene of bacteriophage Mu. The activation process involves, facilitating the recruitment of RNA polymerase (RNAP) by altering the topology of the promoter and enhancing the promoter clearance by reducing the abortive transcription. To understand the basis of this multi-step activation mechanism, we investigated the nature of the physical interaction between C and RNAP during the process. A variety of assays revealed that only DNA-bound C contacts the beta' subunit of RNAP. Consistent to these results, we have also isolated RNAP mutants having mutations in the beta' subunit which were compromised in C-mediated activation. Mutant RNAPs show reduced productive transcription and increased abortive initiation specifically at the C-dependent mom promoter. Positive control (pc) mutants of C, defective in interaction with RNAP, retained the property of recruiting RNAP to the promoter but were unable to enhance promoter clearance. These results strongly suggest that the recruitment of RNAP to the mom promoter does not require physical interaction with C, whereas a contact between the beta' subunit and the activator, and the subsequent allosteric changes in the active site of the enzyme are essential for the enhancement of promoter clearance.

Interaction of Bacillus polymyxa with some oxide minerals with reference to mineral beneficiation and environmental control

Interaction of Bacillus polymyxa with calcite, hematite, corundum and quartz resulted in significant surface chemical changes not only of the cells but also in the minerals. Both the cell surfaces as well as quartz particles were rendered more hydrophobic after mutual interaction, whilst the rest of the minerals exhibited enhanced hydrophilicity after interaction with the bacteria. The bacteria were also observed to be capable of dissolving calcite, hematite and corundum and biosorbing the dissolved metal ions to varying extents. An excess of polysaccharides could be observed on biotreated calcite, hematite and corundum while the predominance of a protein-based metabolic product was evident on quartz surfaces. The utility of bioprocessing in the beneficiation of the above minerals through bioflotation and bioflocculation is demonstrated. (C) 1997 Elsevier Science Ltd.