Does deprotonated benzoic acid lose carbon monoxide in collision-induced dissociation?

Decarboxylation is known to be the major fragmentation pathway for the deprotonated carboxylic acids in collision-induced dissociation (CID). However, in the CID mass spectrum of deprotonated benzoic acid (m/z 121) recorded on a Q-orbitrap mass spectrometer, the dominant peak was found to be m/z 93 instead of the anticipated m/z 77. Based on theoretical calculations, ¹⁸O-isotope labeling and MS³ experiments, we demonstrated that the fragmentation of benzoate anion begins with decarboxylation, but the initial phenide anion (m/z 77) can react with trace O₂ in the mass analyzer to produce phenolate anion (m/z 93) and other oxygen-containing ions. Thus oxygen adducts should be considered when annotating the MS/MS spectra of benzoic acids.     

Flow structure of water in carbon nanotubes: poiseuille type or plug-like?

We have conducted molecular dynamics simulations of water flow in carbon nanotubes (CNTs) for (6,6) to (20,20) CNTs at a streaming velocity of 100 ms. The fluidized piston model (FPM) and the ice piston model (IPM) are employed to drive flow through the CNTs. The results show that the single-file water flow inside (6,6) CNT has a convex upward streaming velocity profile, whereas the velocity profiles in (10,10) to (20,20) CNTs are flat except near the tube wall. The flow structure of cylindrical water in the (8,8) CNT is intermediate between that for the (6,6) CNT and the larger CNTs. The flow parameters are found not to exhibit any dependence on streaming velocity at up to 300 ms in the (12,12) CNT. The hydrogen bond lifetimes of water flowing in CNTs tend to be longer than for the corresponding equilibrium states, and nonzero flow does not reduce the microscopic structure or structural robustness (hydrogen bond lifetime). Although the atomic density profile varies with tube diameter, reflecting the change in static microscopic structure of flow from single file to cylindrical, tube diameter does not induce a clear transition in streaming velocity, temperature, or hydrogen bond lifetime over this diameter range. The results suggest that water flow in CNTs of this size is more pluglike than Poiseuille type, although the flow structure does not strictly accord with either definition.     

Does magnetic treatment of water change its properties?

Some properties and functions of water treated under magnetic field were examined. No change in properties of pure water distilled from ultrapure water in vacuum was observed by magnetic treatment. However, when the same magnetic treatment was carried out after the distilled water was exposed to O2, water properties such as vibration modes and electrolytic potential were changed. The degree of magnetic treatment effect on water was quantitatively evaluated by contact angle.     

Do probe molecules influence water in confinement?

The water inside reverse micelles can differ dramatically from bulk water. Some changes in properties can be attributed to the interaction of water molecules with the micellar interface, forming a layer of shell water inside the reverse micelle. The work reported here monitors changes in intramicellar water through chemical shifts and signal line widths in 51V NMR spectra of a large polyoxometalate probe, decavanadate, and from infrared spectroscopy of isotopically labeled water, to obtain information on the water in the water pool in AOT reverse micelles formed in isooctane. The studies reveal several things about the reverse micellar water pool. First, in agreement with our previous measurements, the proton equilibrium of the decavanadate solubilized within the reverse micelles differs from that in bulk aqueous solution, indicating a more basic environment compared to the starting stock solutions from which the reverse micelles were formed. Below a certain size, reverse micelles do not form when the polyoxometalate is present; this indicates that the polyanionic probe requires a layer of water to solvate it in addition to the water that solvates the surfactant headgroups. Finally, the polyoxometalate probe appears to perturb the water hydrogen-bonding network in a fashion similar to that in the interior surface of the reverse micelles. These measurements demonstrate the dramatic differences possible for water environments in confined spaces.     

Does Fluorine Participate in Halogen Bonding?

When R is sufficiently electron withdrawing, the fluorine in the R?F molecules could interact with electron donors (e.g., ammonia) and form a noncovalent bond (F ??? N). Although these interactions are usually categorized as halogen bonding, our studies show that there are fundamental differences between these interactions and halogen bonds. Although the anisotropic distribution of electronic charge around a halogen is responsible for halogen bond formations, the electronic charge around the fluorine in these molecules is spherical. According to source function analysis, F is the sink of electron density at the F ??? N BCP, whereas other halogens are the source. In contrast to halogen bonds, the F ??? N interactions cannot be regarded as lump–hole interactions; there is no hole in the valence shell charge concentration (VSCC) of fluorine. Although the quadruple moment of Cl and Br is mainly responsible for the existence of σ‐holes, it is negligibly small in the fluorine. Here, the atomic dipole moment of F plays a stabilizing role in the formation of F ??? N bonds. Interacting quantum atoms (IQA) analysis indicates that the interaction between halogen and nitrogen in the halogen bonds is attractive, whereas it is repulsive in the F ??? N interactions. Virial‐based atomic energies show that the fluorine, in contrast to Cl and Br, stabilize upon complex formation. According to these differences, it seems that the F ??? N interactions should be referred to as “fluorine bond” instead of halogen bond.     

What are carbon nanotubes’ roles in anti-tumor therapies?

Since their discovery, carbon nanotubes (CNTs) have become one of the most promising nanomaterials in many industrial and biomedical applications. Due to their unique physicochemical properties, CNTs have been proposed and actively exploited as multipurpose innovative carriers for cancer therapy. The aim of this article is to provide an overview of the status of applications, advantages, and up-to-date research and development of carbon nanotubes in cancer therapy with an emphasis on drug delivery, photothermal therapy, gene therapy, RNAi, and immune therapy. In addition, the issues of risk and safety of CNTs in cancer nanotechnology are discussed briefly.     

Test of the water adsorption model of organic electrocatalysis in the carbon monoxide–silver system in alkaline medium

A test has been carried out of the model of T. Iwasita, X.H. Xia, H.-D. Liess, W. Vielstich [J. Phys. Chem. B. 101 (1997) 7542], according to which the maximum at about the same potential in both the positive and negative sweeps in cyclic voltammograms (CVs) of small organic molecules on Pt is due to the concurrence of two processes with opposite potential dependences, adsorption of the organic compound and electrooxidation of its intermediates, which decrease and increase, respectively, with increasing potential. In turn, the decrease with increasing potential of the adsorption of the undissociated organic is due to its increasing displacement by molecular water, this competition occurring because the two molecular compounds have similar, low values of the adsorption energy. According to the model of T. Iwasita, X.H. Xia, H.-D. Liess, W. Vielstich [J. Phys. Chem. B. 101 (1997) 7542], with CO on Pt no anodic currents are observed in the negative sweep because of the high adsorption energy of CO on Pt, which precludes its displacement by water. Therefore, the model has been tested with the CO–Ag system, for which anodic currents should be observed in the negative sweep, since the adsorption energy of CO on Ag is very low. Effectively, this has been found to be the case, which indicates that the model is indeed applicable to the CO–Ag system over the tested pH range, 10–14. At pH⩽11 adsorbed CO was displaced from the surface of Ag by N₂ bubbling, while it was not at pH⩾12. However, even at pH⩾12 the adsorption energy of CO on Ag should be rather weak, since anodic currents appeared in the negative sweep in CO-saturated solution over the whole pH range tested, 10–14.     

When is water not water? Exploring water confined in large reverse micelles using a highly charged inorganic molecular probe

The interior water pool of aerosol OT (AOT) reverse micelles tends toward bulk water properties as the micelle size increases. Thus, deviations from bulk water behavior in large reverse micelles are less expected than in small reverse micelles. Probing the interior water pool of AOT reverse micelles with a highly charged decavanadate (V(10)) oligomer using (51)V NMR spectroscopy shows distinct changes in solute environment. For example, when an acidic stock solution of protonated V(10) is placed in a reverse micelle, the (51)V chemical shifts show that the V(10) is deprotonated consistent with a decreased proton concentration in the intramicellar water pool. Results indicate that a proton gradient exists inside the reverse micelles, leaving the interior neutral while the interfacial region is acidic.     

Does Li4Ti5O12 need carbon in lithium ion batteries? Carbon-free electrode with exceptionally high electrode capacity

A carbon-free Li(4)Ti(5)O(12) electrode has shown excellent electrochemical performance without any effort to enhance the electrical conductivity. Partial reduction of Ti(4+) and a metallic Li(7)Ti(5)O(12) phase are suggested to be possible origins of the exceptional behavior.     

Does Chemistry Have a Future in Therapeutic Innovations?

A bright future for small molecules: Drugs based on molecules made by chemists are far from old-fashioned. Although biopharmaceuticals developed during the last two decades may have caught the public's imagination, traditional drugs remain a strong force in the pharmaceutical industry. Effective, inexpensive small-molecule drugs are crucial in fighting diseases and maintaining cost-effective health care.     

Dispersion of carbon nanotubes by the branched block copolymer Tetronic 1107 in an alcohol–water solution

The dispersion of carbon nanotubes (CNTs) by the branched block copolymer Tetronic 1107 was investigated in mixed solvents consisting of water and one of the following alcohols: ethanol, n-propanol, ethylene glycol (EG), or glycerol (GLY). The maximum concentration of dispersed CNTs (C _limit) and the optimum T1107 concentration (C _opt) to disperse the maximum amount of CNTs in different solvents were obtained from UV–vis–NIR absorbance spectra. The addition of ethanol or n-propanol to water dramatically increases the C _limit. The value of C _opt follows the order: n-propanol–water?>?ethanol–water?>?EG–water?≈?GLY–water mixtures. I _D/I _G was used to characterize the defect density of CNTs dispersed in the mixed solvents, which was investigated by Raman spectroscopy. The I _D/I _G values in n-propanol–water and ethanol–water mixtures are higher than those in EG–water and GLY–water mixtures. High-resolution transmission electron microscopy is used to confirm a favorable dispersion in the presence of different alcohols.     

Shape of the vapor—liquid interface in narrow slit-shaped pores

The shape of the meniscus (vapor—liquid interface) and the transient region in narrow slit-shaped pores of different width were studied. The adsorbate was modeled by spherical particles, the interaction between them being described by the Lennard-Jones potential model. The calculation was carried out on the basis of the lattice-gas model in the quasichemical approximation for accounting the intermolecular interactions between the nearest neighbors. The greatest meniscus curvature was found for narrow pores. As the pore width increases, the meniscus curvature decreases. The effect of the surface potential on the meniscus shape in narrow pores was discussed. Dedicated to the 90th anniversary of the L. Ya. Karpov Institute of Physical Chemistry. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1118–1129, June, 2008.     

How does surface modification aid in the dispersion of carbon nanofibers?

Small-angle light scattering is used to assess the dispersion behavior of vapor-grown carbon nanofibers suspended in water. These data provide the first insights into the mechanism by which surface treatment promotes dispersion. Both acid-treated and untreated nanofibers exhibit hierarchical morphology consisting of small-scale aggregates (small bundles) that agglomerate to form fractal clusters that eventually precipitate. Although the morphology of the aggregates and agglomerates is nearly independent of surface treatment, their time evolution is quite different. The time evolution of the small-scale bundles is studied by extracting the size distribution from the angle-dependence of the scattered intensity, using the maximum entropy method in conjunction with a simplified tube form factor. The bundles consist of multiple tubes possibly aggregated side-by-side. Acid oxidation has little effect on this bundle morphology. Rather acid treatment inhibits agglomeration of the bundles. The time evolution of agglomeration is followed by fitting the scattering data to a generalized fractal model. Agglomerates appear immediately after cessation of sonication for untreated fibers but only after hours for treated fibers. Eventually, however, both systems precipitate.     

Does transparent nematic phase exist in 5CB∕DDAB∕water microemulsions? From the viewpoint of temperature dependent dielectric spectroscopy

Liquid crystal colloids have received tremendous attention because of its great potential both in the understanding of the liquid crystalline phase and in searching for new application of liquid crystals. Inverse microemulsion composed of 4-cyano-4-n-pentylbiphenyl (5CB), didodecyl dimethyl ammonium bromide, and water was investigated by means of broadband dielectric spectroscopy in this study. Based on the understanding of previous investigations on the same system, the isotropic phase was taken into account to quantitatively characterize the bulklike relaxations after the isotropic-to-nematic phase transition. Analogous results concerning the phase transition and phase composition to other investigations were obtained. In addition to bulklike relaxations, a new relaxation was observed at the frequency range about two orders lower than bulklike relaxations. This new relaxation shows abnormal temperature dependence, suggesting that superstructures composed of water droplets and confined 5CB molecules exist. This superstructure possibly possesses a confined nanoscaled liquid crystal ordering and may correspond to the notion of the transparent nematic phase.     

Water-mediated interactions in the CRP–cAMP–DNA complex: Does water mediate sequence-specific binding at the DNA primary-kink site?

The cyclic AMP receptor protein (CRP) of Escherichia coli binds preferentially to DNA sequences possessing a T:A base pair at position 6 (at which the DNA becomes kinked), but with which it does not form any direct interactions. It has been proposed that indirect readout is involved in CRP-DNA binding, in which specificity for this base pair is primarily related to sequence effects on the energetic susceptibility of the DNA to kink formation. In the current study, the possibility of contributions to indirect readout by water-mediated hydrogen bonding of CRP with the T:A base pair was investigated. A 1.0 ns molecular dynamics simulation of the CRP-cAMP-DNA complex in explicit solvent was performed, and assessed for water-mediated CRP-DNA hydrogen bonds; results were compared to several X-ray crystal structures of comparable complexes. While several water-mediated CRP-DNA hydrogen bonds were identified, none of these involved the T:A base pair at position 6. Therefore, the sequence specificity for this base pair is not likely enhanced by water-mediated hydrogen bonding with the CRP.     

Selective synthesis of carbon monoxide via formates in reverse water–gas shift reaction over alumina-supported gold catalyst

Thermal decomposition of formic acid on SiO_2, CeO_2 and γ-Al_2O_3 was studied as an elementary step of reverse water–gas shit reaction(RWGS) over supported Au catalysts. γ-Al_2O_3 showed the highest CO selectivity among the tested oxides in the decomposition of formic acid. Infrared spectroscopy showed the formation of four formate species on γ-Al_2O_3: three η~1-type and one μ~2-type species, and these formates decomposed to CO at 473 K or higher. Au-loaded γ-Al_2O_3 samples were prepared by a depositionprecipitation method and used as catalysts for RWGS. The supported Au catalyst gave CO with high selectivity over 99% from CO_2 and H_2, which is attributed to the formation of formates on Au and subsequent decomposition to CO on γ-Al_2O_3.