@article {2673, title = {Structures of Water Molecules at the Interfaces of Aqueous Salt Solutions and Silica: Cation Effects}, journal = {Journal of Physical Chemistry C}, volume = {113}, number = {19}, year = {2009}, note = {ISI Document Delivery No.: 443FLTimes Cited: 6Cited Reference Count: 53Yang, Zheng Li, Qifeng Chou, Keng C.}, month = {May}, pages = {8201-8205}, type = {Article}, abstract = {Structures of water molecules at water/silica interfaces, in the presence of alkali chloride. were investigated using infrared-visible sum frequency vibrational spectroscopy. Significant perturbations of the interfacial water structure were observed on silica surfaces with the NaCl concentration as low as 1 x 10(-4) M. The cations, which interact with the Silica Surface via electrostatic interaction, play key roles in Perturbing the hydrogen-bond network of water molecules at the water/silica interface. This cation effect becomes saturated at concentrations around 10(-2) to 10(-1) M, where the sum frequency generation peaks at 3200 and 3400 cm(-1) decrease by 75\%. Different alkali cation species (Li+, Na+, and K+) produce different magnitudes of perturbation, with K+ > Li+ > Na+. This order can be explained by considering the effective ionic radii of the hydrated cations and the electrostatic interactions between the hydrated cations and silica Surfaces. The interfacial water structure associated with the 3200 cm(-1) band is more vulnerable to the cation perturbation, Suggesting that the more ordered water structure on silica is likely associated with the vincinal silanol groups, which create a higher local surface electrical field on silica.}, keywords = {ADSORPTION, charge, DYNAMICS SIMULATIONS, ELECTROLYTE INTERFACE, hydration, INTERFACE, LIQUID WATER, SOLID/LIQUID, SUM-FREQUENCY SPECTROSCOPY, SURFACE, vibrational spectroscopy}, isbn = {1932-7447}, url = {://000265895500034}, author = {Yang, Z. and Li, Q. F. and Chou, K. C.} } @article {1469, title = {Surface characterization of polytetrafluoroethylene (PTFE) transfer films during rolling-sliding tribology tests using X-ray photoelectron spectroscopy}, journal = {Wear}, volume = {261}, number = {10}, year = {2006}, note = {ISI Document Delivery No.: 113XZTimes Cited: 4Cited Reference Count: 33Lu, X. Wong, K. C. Wong, P. C. Mitchell, K. A. R. Cotter, J. Eadie, D. T.}, month = {Nov}, pages = {1155-1162}, type = {Article}, abstract = {A disk-on-disk Amsler wear tester simulating the rolling-sliding motion and high pressure during wheel/rail contact, was used to study the wear performance of PTFE including its film transfer and material flow properties. The chemical composition of the transfer film formed on the wheel-disk surface at various test stages were analyzed by X-ray photoelectron spectroscopy (XPS). The friction curve of the PTFE films obtained on the Amsler can be divided into three regions, according to the friction level and disk surface morphology. Initially, there is a rapid increase of friction coefficient which is presumably accompanied by a fast material transfer from pre-coated rail-disk to the wheel-disk surfaces. In the second region, the friction remains stable throughout and the XPS results show the presence of PTFE on the wheel-disk surface which confirms a transfer of material between the two contact surfaces. In addition, the splitting of F 1s and C 1s photoelectron peaks of PTFE, as a result of a discrepancy in surface charging, suggests that the transfer film exists in two forms: thick patch and thin film. With an increase in rolling cycles, the thick patches become thinner, as well as its coverage reduces. By contrast, the thin film gains both in thickness and coverage. Using a simple model, the thin film is calculated to be only a few nanometers thick. At the beginning of the third region, only a thin film is left on the surface. Additional rolling leads to a rapid rise in friction and the transfer film thickness continues to decrease. The evidence supports the removal of PTFE out of the contact zone, and a high friction coefficient (mu = 0.6) is reached at the end of the test indicating an un-lubricated metal-metal contact. No major tribochemical reaction of PTFE is observed during this study. (c) 2006 Elsevier B.V. All rights reserved.}, keywords = {(XPS), COMPOSITES, CONTACT, friction, friction modifier, INTERFACE, LUBRICATION, MODIFIER, polytetrafluoroethylene (PTFE), SURFACE, third body, TOP, WEAR, WHEEL-RAIL ADHESION, wheel/rail contact, X-ray photoelectron spectroscopy}, isbn = {0043-1648}, url = {://000242632600012}, author = {Lu, X. and Wong, K. C. and Wong, P. C. and Mitchell, K. A. R. and Cotter, J. and Eadie, D. T.} } @article {865, title = {Evaluation of an atomic force microscopy pull-off method for measuring molecular weight and polydispersity of polymer brushes: Effect of grafting density}, journal = {Langmuir}, volume = {20}, number = {15}, year = {2004}, note = {ISI Document Delivery No.: 837VSTimes Cited: 16Cited Reference Count: 31}, month = {Jul}, pages = {6238-6245}, type = {Article}, abstract = {The accuracy of the molecular weights M-n and polydispersities of polymer brushes, determined by stretching the grafted chains using atomic force microscopy (AFM) and measuring the contour length distribution, was evaluated as a function of grafting density sigma. Poly(NN-dimethylacrvlamide) brushes were prepared by surface initiated atom transfer radical polymerization on latex particles with a ranging between 0.17 and 0.0059 chains/nm(2) and constant M-n. The polymer, which could be cleaved from the grafting surface by hydrolysis and characterized by gel permeation chromatography (GPC), had a M-n of 30 600 and polydispersity (PDI) of 1.35. The M-n determined by the AFM technique for the higher density brushes agreed quite well with the GPC results but was significantly underestimated for the lower sigma. At high grafting density in good solvent, the extended structure of the brush increases the probability of forming segment-tip contacts located at the chain end. When the distance between chains approached twice the radius of gyration of the polymer, the transition from brush to mushroom structure presumably enabled the formation of a larger number of segment-tip contacts having separations smaller than the contour length, which explains the discrepancy between the two methods at low sigma. The PDI was typically higher than that obtained by GPC, suggesting that sampling of chains with above average contour length occurs at sigma frequency that is greater than their spatial distribution.}, keywords = {CHAIN, DETACHMENT, DIBLOCK COPOLYMER MONOLAYERS, DYNAMICS, INTERFACE, LAYERS, NEUTRON REFLECTIVITY, SURFACE}, isbn = {0743-7463}, url = {://000222669800025}, author = {Goodman, D. and Kizhakkedathu, J. N. and Brooks, D. E.} } @article {1040, title = {Laser-light-scattering study of internal motions of polymer chains grafted on spherical latex particles}, journal = {Journal of Physical Chemistry B}, volume = {108}, number = {48}, year = {2004}, note = {ISI Document Delivery No.: 875JUTimes Cited: 6Cited Reference Count: 35}, month = {Dec}, pages = {18479-18484}, type = {Article}, abstract = {Using atom-transfer radical polymerization, we have prepared core-shell particles by grafting thermally sensitive poly(N-isopropylacrylamide) (PNIPAM) chains on a spherical polystyrene latex core (with a radius of similar to287 nm) via the "grafting-from" approach. As the temperature increases from 25 degreesC to 35 degreesC, the PNIPAM shell shrinks from a thickness of 625 nm to 110 nm and the chain density near the core increases from 7.3 x 10(-3) g/cm(3) to 7.2 x 10(-2) g/cm(3). Using such core-shell particles, we have, for the first time, been able to study dynamics of long chains anchored on a particle in dilute dispersion by laser-light scattering. Our results showed that, besides the translational diffusion of the particle as a whole, there also exists an additional slow relaxation mode that is only observable at larger scattering vectors (q),which are presumably related to internal motions of the shell. In the fully swollen state, the relaxation rate of the slow motion ((slow)) is insensitive to the observation length (1/q); however, its contribution to the scattering intensity (A(slow)) increases as q increases. In the shrunken state, (slow) slightly decreases as q increases. (slow) can be scaled to the shell thickness ((brush)) as (slow) proportional to (alpha)(brush), with alpha = -2.5 +/- 0.2, which is smaller than the predicated value of 3.}, keywords = {AQUEOUS ATRP, BRUSHES, CONFORMATION, DYNAMICS, GLOBULE TYPE TRANSITIONS, INTERFACE, LAYERS, MODEL, POLY(N-ISOPROPYLACRYLAMIDE), SIMULATION}, isbn = {1520-6106}, url = {://000225417200015}, author = {Yang, C. and Kizhakkedathu, J. N. and Brooks, D. E. and Jin, F. and Wu, C.} } @article {1019, title = {Mutations in the SAM domain of the ETV6-NTRK3 chimeric tyrosine kinase block polymerization and transformation activity}, journal = {Molecular and Cellular Biology}, volume = {24}, number = {11}, year = {2004}, note = {ISI Document Delivery No.: 822JXTimes Cited: 12Cited Reference Count: 53}, month = {Jun}, pages = {4636-4650}, type = {Article}, abstract = {The 12p13 ETV6 (TEL) gene is frequently targeted by chromosomal translocations in human malignancies, resulting in the formation of oncogenic ETV6 gene fusions. Many of the known partner genes encode protein tyrosine kinases (PTKs), generating fusion proteins that function as chimeric PTKs. ETV6-NTRK3 (EN), comprised of the ETV6 SAM domain fused to the NTRK3 PTK, is unique among ETV6 chimeric oncoproteins, as it is expressed in cancers of multiple lineages. We initially hypothesized that, similar to other ETV6-PTK chimeras, SAM-mediated dimerization of EN leads to constitutive activation of the PTK and downstream signaling cascades. However, when the EN SAM domain was replaced with an inducible FK506 binding protein (FKBP) dimerization system, resulting FKBP-NTRK3 chimeras failed to transform NIH 3T3 cells even though PTK activation was preserved. It was recently shown that the ETV6 SAM domain has two potential interacting surfaces, raising the possibility that this domain can mediate protein polymerization. We therefore mutated each EN SAM binding interface in a manner shown previously to abolish self-association of wild-type ETV6. Each mutation completely blocked the ability of EN to polymerize, to activate its PTK, and to transform NIH 3T3 cells. Furthermore, EN itself formed large polymeric structures within cells while mutant EN proteins were present only as monomers. Finally, we observed a dominant negative effect on the transformation of isolated SAM domains coexpressed in EN-transformed cells. Taken together, our results suggest that higher-order polymerization may be a critical requirement for the transformation activity of EN and possibly other ETV6-PTK fusion proteins.}, keywords = {ABL-RELATED GENE, ACUTE LYMPHOBLASTIC-LEUKEMIA, BCR-ABL, CHROMOSOMAL TRANSLOCATION, CHRONIC MYELOMONOCYTIC LEUKEMIA, CONGENITAL FIBROSARCOMA, FUSION PROTEIN, INTERFACE, MYELOID-LEUKEMIA, OLIGOMERIZATION, PROTEIN-KINASE}, isbn = {0270-7306}, url = {://000221536600004}, author = {Tognon, C. E. and Mackereth, C. D. and Somasiri, A. M. and McIntosh, L. P. and Sorensen, P. H. B.} } @article {498, title = {An atmospheric pressure ion lens that improves nebulizer assisted electrospray ion sources}, journal = {Journal of the American Society for Mass Spectrometry}, volume = {13}, number = {8}, year = {2002}, note = {ISI Document Delivery No.: 588METimes Cited: 7Cited Reference Count: 27}, month = {Aug}, pages = {906-913}, type = {Article}, abstract = {An atmospheric pressure ion lens improves the performance and ease of use of a nebulizer assisted electrospray (ion spray) ion source. The lens is comprised of an oblong-shaped stainless steel ring attached to an external high voltage power supply. The lens is located near the tip of the conductive sprayer, and is maintained at a potential less than that of the sprayer. The ion lens improves the shape of the equipotential lines in the vicinity of the sprayer tip. This lens gives approximately a 2-fold reduction in the signal RSD, a 2-fold increase in the ion signal, an increase in the number of multiply charged ions, and a much broader range of usable sprayer positions. (C) 2002 American Society for Mass Spectrometry.}, keywords = {CAPILLARY-ZONE-ELECTROPHORESIS, DISSOCIATION, EVAPORATION, IDENTIFICATION, INDUCED, INTERFACE, IONIZATION MASS-SPECTROMETRY, JUNCTION, MECHANISM, PROTEIN-ANALYSIS, SHEATHLESS}, isbn = {1044-0305}, url = {://000177704600002}, author = {Schneider, B. B. and Douglas, D. J. and Chen, D. D. Y.} } @article {497, title = {Multiple sprayer system for high-throughput electrospray ionization mass spectrometry}, journal = {Rapid Communications in Mass Spectrometry}, volume = {16}, number = {20}, year = {2002}, note = {ISI Document Delivery No.: 604ADTimes Cited: 13Cited Reference Count: 32}, pages = {1982-1990}, type = {Article}, abstract = {

A multiple sprayer electrospray ion source for high-throughput analysis is described. The ion source is comprised of multiple electrospray capillaries, each with an ion lens located near the tip. The electric potentials applied to the ion lenses are used to control the sprayers. The use of ion lenses eliminates the need for mechanical blocking devices to selectively enable or disable the sprayers, and results in a less expensive and more reliable set-up. Sprayers can be enabled or disabled within approximately 50-250 ms when the lens potentials are controlled manually. For simultaneous operation of multiple electrospray capillaries, it is advantageous to orient the capillaries so that the spray from each passes directly in front of the entrance aperture of the mass spectrometer. Copyright (C) 2002 John Wiley Sons, Ltd.

}, keywords = {ARRAYS, capillary electrophoresis, INTERFACE, LIBRARIES, LIQUID CHROMATOGRAPHY/MASS SPECTROMETRY, SEPARATE SAMPLE}, isbn = {0951-4198}, doi = {10.1002/rcm.806}, url = {https://onlinelibrary.wiley.com/doi/full/10.1002/rcm.806}, author = {Schneider, B. B. and Douglas, D. J. and Chen, D. D. Y.} } @article {5188, title = {An atmospheric pressure ion lens to improve electrospray ionization at low solution flow-rates}, journal = {Rapid Communications in Mass Spectrometry}, volume = {15}, number = {22}, year = {2001}, note = {ISI Document Delivery No.: 492XYTimes Cited: 14Cited Reference Count: 20}, pages = {2168-2175}, type = {Article}, abstract = {The performance of a reduced flow-rate electrospray ion source is substantially improved by the addition of an atmospheric pressure ion lens near the tip of the tapered sprayer. The magnitude and stability of ion signals, detected within a mass spectrometer, are significantly improved. In addition, the ion lens decreased the dependence of the ion signals on the sprayer position. These benefits are believed to be due to an improvement in the shape of the equipotential lines near the tip of the electrospray ion source. Copyright (C) 2001 John Wiley \& Sons, Ltd.}, keywords = {CAPILLARY ZONE ELECTROPHORESIS, INTERFACE, MASS-SPECTROMETRY}, isbn = {0951-4198}, url = {://000172193900014}, author = {Schneider, B. B. and Douglas, D. J. and Chen, D. D. Y.} } @article {5040, title = {A combined linear ion trap time-of-flight system with improved performance and MSn capabilities}, journal = {Rapid Communications in Mass Spectrometry}, volume = {15}, number = {19}, year = {2001}, note = {ISI Document Delivery No.: 477JFTimes Cited: 47Cited Reference Count: 28}, pages = {1777-1795}, type = {Article}, abstract = {A detailed description of a linear ion trap time-of-flight (TOF) mass spectrometer system, capable of sequential mass spectrometry (MS{\textquoteright}), is given. Many improvements have been incorporated since the initial description of this system (Rapid Commun. Mass Spectrom. 1998; 12:1463-1474). The pressure in the trap has been lowered from 7.0 to 1.8 mTorr, resulting in an increase in the mass resolution of ion excitation from 75 to 240. Use of the system for MS3 is demonstrated. Dipole excitation of the n = I harmonic, instead of the n = 0 fundamental frequency of ion motion, is shown to have a higher frequency resolution, f/Deltaf, but lower mass resolution, m/Deltam. Both experiments and modeling demonstrate that at the lower pressure there is less collisional cooling of ions in the axial and radial directions of the trap. The efficiency of trapping is shown to be nearly 100\% for periods up to 5 s. The demonstrated mass range for mass analysis has been extended to greater than m/z 16 250. To avoid the formation of adduct ions when trapping protein ions for extended times requires ultra-high vacuum cleanliness conditions, even though the trap operates in the mTorr-pressure range. Upgrading the TOF to a reflectron with higher quality ion optics results in an increase in the mass resolution of the TOF mass spectrometer to about 5000 at m/z 750. Copyright (C) 2001 John Wiley \& Sons, Ltd.}, keywords = {COLLISION CELL, EXCITATION, GUIDE, INTERFACE, MOLECULE, QUADRUPOLE MASS-SPECTROMETER, reaction, STORAGE ASSISTED DISSOCIATION}, isbn = {0951-4198}, url = {://000171279800001}, author = {Collings, B. A. and Campbell, J. M. and Mao, D. M. and Douglas, D. J.} } @article {4924, title = {Collision-induced dissociation of ions within the orifice-skimmer region of an electrospray mass spectrometer}, journal = {Analytical Chemistry}, volume = {72}, number = {4}, year = {2000}, note = {ISI Document Delivery No.: 285HETimes Cited: 38Cited Reference Count: 33}, month = {Feb}, pages = {791-799}, type = {Article}, abstract = {An equation was derived to describe the variation of the gas number density within the region between the orifice and the skimmer of an electrospray ionization mass spectrometer. The equation was used to develop a semiquantitative model to predict the value of orifice voltages that lead to ion fragmentation within this region. This model made it possible to predict the types of solvent adducts observed for analytes at various orifice voltages. In addition, it is shown that a small number of high-energy collisions is equally effective for collision-induced dissociation as compared to a large number of low-energy collisions. Finally, this model is tested with different background electrolyte solutions and a different electrospray mass spectrometer. It is demonstrated that controlled fragmentation studies can be performed on single-quadrupole mass spectrometers, and the proposed model gives a reasonable description of the fragmentation process in both spectrometers.}, keywords = {capillary electrophoresis, CYTOCHROME-C, DYNAMICS, IDENTIFICATION, INTERFACE, IONIZATION, LIQUID-CHROMATOGRAPHY, PROTEINS, SENSITIVITY, SEPARATION}, isbn = {0003-2700}, url = {://000085383000019}, author = {Schneider, B. B. and Chen, D. D. Y.} } @article {4128, title = {Modeling and structure of mercury-water interfaces}, journal = {Journal of Chemical Physics}, volume = {107}, number = {6}, year = {1997}, note = {ISI Document Delivery No.: XP280Times Cited: 37Cited Reference Count: 78}, month = {Aug}, pages = {2122-2141}, type = {Article}, abstract = {The modeling and nature of the physisorption of water at the metal (Hg)-water interface is explored in this paper. We have evaluated potential models that fit into three general classes that are employed in the literature. These classes are distinguished by the manner in which the isotropic interactions between the metal and the water are modeled: namely, as non-attractive, weakly attractive, and strongly attractive. In the present studies the metal is described by a jellium model. In our model, in addition to the isotropic water potential there is an interaction between the jellium and the water molecules which depends on the orientation of the water molecule with respect to the metal surface. We find that hard potentials without isotropic attractive terms dewet. The density of water near hydrocarbon-like potentials remains close to the bulk value but the interaction isn{\textquoteright}t strong enough to structure the water near the interface, nor are the adsorption energies sufficiently high. The strongly attractive potentials seem to be the most appropriate. For such models we have checked the sensitivity of the results to the parameters in our model including surface corrugation. We find that the structural results are insensitive to the parameters employed suggesting that they not only provide a good classical description of the Hg-water interface but may be readily adaptable to describe the physisorption of water on metals in general. Although we find the layering of water molecules and the pattern of hydrogen bonding near these surfaces, which have been described as ice-like in previous studies, the actual arrangement of the water molecules near these surfaces is distinctly different from the structure of ice. (C) 1997 American Institute of Physics.}, keywords = {CHARGED ELECTRODES, COMPUTER-SIMULATION, DOUBLE-LAYER, ELECTROLYTE, HALIDE-IONS, INTERFACE, LIQUID WATER, METAL INTERFACE, MOLECULAR-DYNAMICS SIMULATION, SURFACE, TIP4P WATER}, isbn = {0021-9606}, url = {://A1997XP28000045}, author = {Shelley, J. C. and Patey, G. N. and Berard, D. R. and Torrie, G. M.} }