@article {2695, title = {Modulating the Mechanical Stability of Extracellular Matrix Protein Tenascin-C in a Controlled and Reversible Fashion}, journal = {Journal of Molecular Biology}, volume = {390}, number = {4}, year = {2009}, note = {ISI Document Delivery No.: 477KYTimes Cited: 2Cited Reference Count: 45Zhuang, Shulin Peng, Qing Cao, Yi Li, Hongbin}, month = {Jul}, pages = {820-829}, type = {Article}, abstract = {Stretching force can induce conformational changes of proteins and is believed to be an important biological signal in the mechanotransduction network. Tenascin-C is a large extracellular matrix protein and is subject to stretching force under its physiological condition. Regulating the mechanical properties of the fibronectin type III domains of tenascin-C will alter its response to mechanical stretching force and thus may provide the possibility of regulating the biological activities of tenascin-C in living cells. However, tuning the mechanical stability of proteins in a rational and systematic fashion remains challenging. Using the third fibronectin type III domain (TNfn3) of tenascin-C as a model system, here we report a successful engineering of a mechanically stronger extracellular matrix protein via engineered metal chelation. Combining steered molecular dynamics simulations, protein engineering and single-molecule atomic force microscopy, we have rationally engineered a bihistidine-based metal chelation site into TNfn3. We used its metal chelation capability to selectively increase the unfolding energy barrier for the rate-limiting step during the mechanical unfolding of TNfn3. The resultant TNfn3 mutant exhibits enhanced mechanical stability. Using a stronger metal chelator, one can convert TNfn3 back to a state of lower mechanical stability. This is the first step toward engineering extracellular matrix proteins with defined mechanical properties, which can be modulated reversibly by external stimuli, and will provide the possibility of using external stimuli to regulate the biological functions of extracellular matrix proteins. (C) 2009 Elsevier Ltd. All rights reserved.}, keywords = {DYNAMICS, ELASTICITY, ENGINEERING PROTEINS, FNIII DOMAIN, FRAGMENTS, MECHANICAL STABILITY, mechanical unfolding, microscopy, MOLECULE FORCE SPECTROSCOPY, MUSCLE, rational design, recombination, SINGLE PROTEIN, single-molecule force spectroscopy, tenascin}, isbn = {0022-2836}, url = {://000268519200019}, author = {Zhuang, S. L. and Peng, Q. and Cao, Y. and Li, H. B.} } @article {2456, title = {Nanomechanical Properties of Tenascin-X Revealed by Single-Molecule Force Spectroscopy}, journal = {Journal of Molecular Biology}, volume = {385}, number = {4}, year = {2009}, note = {ISI Document Delivery No.: 403HJTimes Cited: 4Cited Reference Count: 35Jollymore, Ashlee Lethias, Claire Peng, Qing Cao, Yi Li, Hongbin}, month = {Jan}, pages = {1277-1286}, type = {Article}, abstract = {Tenascin-X is an extracellular matrix protein and binds a variety of molecules in extracellular matrix and on cell membrane. Tenascin-X plays important roles in regulating the structure and mechanical properties of connective tissues. Using single-molecule atomic force microscopy, we have investigated the mechanical properties of bovine tenascin-X in detail. Our results indicated that tenascin-X is an elastic protein and the fibronectin type III (FnIII) domains can unfold under a stretching force and refold to regain their mechanical stability upon the removal of the stretching force. All the 30 FnIII domains of tenascin-X show similar mechanical stability, mechanical unfolding kinetics, and contour length increment upon domain unfolding, despite their large sequence diversity. In contrast to the homogeneity in their mechanical unfolding behaviors, FnIII domains fold at different rates. Using the 10th FnIII domain of tenascin-X (TNXfn10) as a model system, we constructed a polyprotein chimera composed of alternating TNXfn10 and GB1 domains and used. atomic force microscopy to confirm that the mechanical properties of TNXfn10 are consistent with those of the FnIII domains of tenascin-X These results lay the foundation to further study the mechanical properties of individual FnIII domains and establish the relationship between point mutations and mechanical phenotypic effect on tenascin-X Moreover, our results provided the opportunity to compare the mechanical properties and design of different forms of tenascins. The comparison between tenascin-X and tenascin-C revealed interesting common as well as distinguishing features for mechanical unfolding and folding of tenascin-C and tenascin-X and will open up new avenues to investigate the mechanical. functions and architectural design of different forms of tenascins. (C) 2008 Elsevier Ltd. All rights reserved.}, keywords = {AFM, BINDING, DEFICIENCY, DOMAINS, FAMILY, FnIII domains, IDENTIFICATION, III MODULES, MECHANICAL STABILITY, mechanical unfolding, microscopy, PROTEIN, single molecule force spectroscopy, tenascin}, isbn = {0022-2836}, url = {://000263073400022}, author = {Jollymore, A. and Lethias, C. and Peng, Q. and Cao, Y. and Li, H. B.} } @article {2479, title = {Narrowband spectroscopy by an all-optical correlation of broadband laser pulses}, journal = {Physical Review A}, volume = {79}, number = {3}, year = {2009}, note = {ISI Document Delivery No.: 427HKTimes Cited: 0Cited Reference Count: 29Konorov, Stanislav O. Xu, Xiaoji G. Hepburn, John W. Milner, Valery}, month = {Mar}, pages = {4}, type = {Article}, abstract = {High-peak-power ultrafast lasers are widely used in nonlinear spectroscopy, but often limit its spectral resolution because of the broad frequency bandwidth of ultrashort laser pulses. Improving the resolution by achieving spectrally narrow excitation of, or emission from, the resonant medium by means of multiphoton interferences has been the focus of many recent developments in ultrafast spectroscopy. We demonstrate an alternative approach in which high resolution is exercised by detecting narrow spectral correlations between broadband excitation and emission optical fields. All-optical correlation analysis, easily incorporated into a traditional spectroscopic setup, enables direct, robust, and simultaneous detection of multiple narrow resonances in a single measurement.}, keywords = {2-PHOTON, 2ND-HARMONIC GENERATION, CARS, COHERENT, DYNAMICS, FEMTOSECOND PULSES, high-speed optical techniques, laser beams, measurement by laser beam, microscopy, MULTIPHOTON INTRAPULSE INTERFERENCE, multiphoton processes, optical correlation, STOKES-RAMAN SCATTERING}, isbn = {1050-2947}, url = {://000264770200011}, author = {Konorov, S. O. and Xu, X. J. G. and Hepburn, J. W. and Milner, V.} } @article {2617, title = {Observation of coexistence of 1D and 2D nanostructures in cobalt dipyrromethene trimer complexes adsorbed on a graphite surface}, journal = {Applied Surface Science}, volume = {256}, number = {4}, year = {2009}, note = {ISI Document Delivery No.: 527BXTimes Cited: 0Cited Reference Count: 24Son, S. B. Lee, S. J. Hahn, J. R. Ma, L. Shin, J-Y. Dolphin, D.4th Vacuum and Surface Science Conference of Asia and AustraliaOCT 28-31, 2008Matsue City, JAPAN}, month = {Nov}, pages = {1176-1179}, type = {Proceedings Paper}, abstract = {We report the direct observation of 1D and 2D nanostructures of cobalt dipyrromethene trimer complexes adsorbed on a highly oriented pyrolytic graphite surface using scanning tunneling microscopy (STM). STM images showed two types of ordered structures coexisting on the surface: long 1D molecular chains isolated on the terraces, and 2D hexagonal patterns confined by a 1D chain and/or a graphite step edge. These 1D and 2D structures are attributed to {\textquoteright}edge-on{\textquoteright} and {\textquoteright}face-on{\textquoteright} complex alignments on the surface, respectively. In both configurations, substrate-mediated molecule-molecule interactions may play a significant role in stabilizing the nanostructures. (C) 2009 Elsevier B. V. All rights reserved.}, keywords = {CHEMISTRY, dipyrromethene, Graphite, MANIPULATION, microscopy, MONOLAYER, PHTHALOCYANINES, PORPHYRIN, porphyrins, SCANNING TUNNELING MICROSCOPY, STM, Supramolecules, VACANCY}, isbn = {0169-4332}, url = {://000272342300062}, author = {Son, S. B. and Lee, S. J. and Hahn, J. R. and Ma, L. and Shin, J. Y. and Dolphin, D.} } @article {1349, title = {Nonmechanical protein can have significant mechanical stability}, journal = {Angewandte Chemie-International Edition}, volume = {45}, number = {4}, year = {2006}, note = {ISI Document Delivery No.: 004RFTimes Cited: 30Cited Reference Count: 44}, pages = {642-645}, type = {Article}, keywords = {ADHESION, cell, DISULFIDE BONDS, DYNAMICS, ELASTICITY, mechanical properties, microscopy, MOLECULE FORCE-SPECTROSCOPY, protein unfolding, resistance, scanning probe microscopy, SIMULATION, SINGLE PROTEIN, single-molecule studies, TITIN IMMUNOGLOBULIN DOMAINS}, isbn = {1433-7851}, url = {://000234769200026}, author = {Cao, Y. and Lam, C. and Wang, M. J. and Li, H. B.} } @article {1350, title = {Single molecule force spectroscopy reveals a weakly populated microstate of the FnIII domains of tenascin}, journal = {Journal of Molecular Biology}, volume = {361}, number = {2}, year = {2006}, note = {ISI Document Delivery No.: 074WPTimes Cited: 8Cited Reference Count: 48Cao, Y. Li, Hongbin}, month = {Aug}, pages = {372-381}, type = {Article}, abstract = {The native states of proteins exist as an ensemble of conformationally similar microstates. The fluctuations among different microstates are of great importance for the functions and structural stability of proteins. Here, we demonstrate that single molecule atomic force microscopy (AFM) can be used to directly probe the existence of multiple folded microstates. We used the AFM to repeatedly stretch and relax a recombinant tenascin fragment TNfnALL to allow the fibronectin type III (FnIII) domains to undergo repeated unfolding/refolding cycles. In addition to the native state, we discovered that some FnIII domains can refold from the unfolded state into a previously unrecognized microstate, N* state. This novel state is conformationally similar to the native state, but mechanically less stable. The native state unfolds at similar to 120 pN, while the N* state unfolds at similar to 50 pN. These two distinct populations of microstates constitute the ensemble of the folded states for some FnIII domains. An unfolded FnIII domain can fold into either one of the two microstates via two distinct folding routes. These results reveal the dynamic and heterogeneous picture of the folded ensemble for some FnIII domains of tenascin, which may carry important implications for the mechanical functions of tenascins in vivo. (c) 2006 Elsevier Ltd. All rights reserved.}, keywords = {DYNAMICS, fluctuations, FnIII domains, HYDROGEN-EXCHANGE, IMMUNOGLOBULIN, MECHANICAL STABILITY, mechanical unfolding, microscopy, MODULES, PROTEIN-STRUCTURE, scanning probe, single-molecule force spectroscopy, tenascin, TITIN, UNFOLDING PATHWAYS}, isbn = {0022-2836}, url = {://000239842800014}, author = {Cao, Y. and Li, H. B.} } @article {1621, title = {The unfolding and folding dynamics of TNfnALL probed by single molecule force-ramp spectroscopy}, journal = {Polymer}, volume = {47}, number = {7}, year = {2006}, note = {ISI Document Delivery No.: 030JETimes Cited: 10Cited Reference Count: 53}, month = {Mar}, pages = {2548-2554}, type = {Article}, abstract = {Tenascin, an important extracellular matrix protein, is subject to stretching force under physiological conditions and plays important roles in regulating the cell-matrix interactions. Using the recently developed single molecule force-ramp spectroscopy, we investigated the unfolding-folding kinetics of a recombinant tenascin fragment TNfnALL. Our results showed that all the 15 FnIII domains in TNfnALL have similar spontaneous unfolding rate constant at zero force, but show great difference in their folding rate constants. Our results demonstrated that single molecule force-ramp spectroscopy is a powerful tool for accurate determination of the kinetic parameters that characterize the unfolding and folding reactions. We anticipate that single molecule force-ramp spectroscopy will become a versatile addition to the single molecule manipulation tool box and greatly expand the scope of single molecule force spectroscopy. (c) 2006 Elsevier Ltd. All rights reserved.}, keywords = {ADHESION, DOMAIN, EXPRESSION, III, IMMUNOGLOBULIN, MATRIX PROTEINS, MECHANICAL STABILITY, microscopy, MUSCLE PROTEIN TITIN, tenascin, UBIQUITIN}, isbn = {0032-3861}, url = {://000236629900037}, author = {Wang, M. J. and Cao, Y. and Li, H. B.} } @inbook {4741, title = {Can cytoplasm exist without undergoing phase separation?}, booktitle = {International Review of Cytology - a Survey of Cell Biology, Vol 192}, series = {International Review of Cytology-a Survey of Cell Biology}, volume = {192}, year = {2000}, note = {ISI Document Delivery No.: BP32STimes Cited: 6Cited Reference Count: 10Review525 B STREET, SUITE 1900, SAN DIEGO, CA 92101-4495 USA}, pages = {321-330}, publisher = {Academic Press Inc}, organization = {Academic Press Inc}, address = {San Diego}, keywords = {BOUND WATER, confocal, microscopy, PHASE SEPARATION, scanning probe microscopy}, isbn = {0074-7696}, url = {://000084720600013}, author = {Brooks, D. E.} } @article {3978, title = {Investigation of hydrogel formation from hydroxypropylmethylcellulose (HPMC) by NMR spectroscopy and NMR imaging techniques}, journal = {Macromolecules}, volume = {30}, number = {20}, year = {1997}, note = {ISI Document Delivery No.: YA289Times Cited: 54Cited Reference Count: 21}, month = {Oct}, pages = {6230-6237}, type = {Article}, abstract = {NMR imaging has been used to investigate the in situ swelling behavior of 2-hydroxypropylmethylcellulose (HPMC) tablets in a sample geometry chosen for the simplicity of its diffusion behavior. Preliminary H-1 NMR spectroscopy experiments were performed on equilibrated mixtures of HPMC and water. From these, the dependence of the H-1 T-1 and T-2 relaxation parameters of the water protons with respect to HPMC weight percent were obtained. Further analysis of the T-2 values and H-1 z-spectroscopic data revealed that as the polymer concentration was increased from 10\% to 20\% w/w HPMC, the polymer mobility decreased substantially. One-dimensional NMR imaging of H-1 in the swelling tablet system was used to monitor the movement of water into the polymer and to calculate the T-2 parameters across the system. HPMC weight percents were calculated from these T-2 values using the previously determined calibration. HPMC distributions were determined for two tablet thicknesses. Similar swelling behavior was observed for both thicknesses at early times prior to the thinner tablet becoming completely hydrated.}, keywords = {ABSORPTION, BEHAVIOR, DIFFUSION, DRUG-RELEASE, GEL LAYER, MECHANISMS, microscopy, PENETRATION, RELEASE DOSAGE FORMS, TABLETS}, isbn = {0024-9297}, url = {://A1997YA28900036}, author = {Fyfe, C. A. and Blazek, A. I.} } @article {4062, title = {LEED crystallographic analysis for the Rh(111)-(root 7x root 7)R19.1 degrees-P surface structure}, journal = {Surface Science}, volume = {372}, number = {1-3}, year = {1997}, note = {ISI Document Delivery No.: WF207Times Cited: 7Cited Reference Count: 32}, month = {Feb}, pages = {312-322}, type = {Article}, abstract = {A recent communication [11] reported a novel structure for the (root 7 x root 7)R19.1 degrees reconstruction formed by P on the Rh(111) surface, and the present paper details the associated tensor LEED analysis. This reconstruction involves a packed arrangement of Rh pentagons and triangles for the topmost layer, with P atoms at 3/7 monolayer coverage occupying eight-coordinate sites created by the Rh pentagons. The nearly flat, densely packed Rh-P mixed layer (density of five Rh and three P atoms per seven Rh atoms in the substrate unit mesh) appears to provide a major stabilizing effect on this surface. The average P-Rh bond distance is indicated to be 2.52 Angstrom, slightly longer than that (2.38 A) in bulk Rh2P where the P atoms are also eight-coordinate. Some similarities are noted with the corresponding (rv (7) over bar x root 7)R19.1 degrees structures formed by S on the Pd(111), Cu(111) and Ag(111) surfaces.}, keywords = {chemisorption, ENERGY ELECTRON-DIFFRACTION, HETEROCYCLIZATION SITES, low energy electron diffraction, low index single crystal surface, METAL-SURFACES, microscopy, PHOSPHORUS, rhodium, SULFIDED PD(111) SURFACE, SURFACE RELAXATION AND RECONSTRUCTION, TENSOR LEED}, isbn = {0039-6028}, url = {://A1997WF20700043}, author = {Liu, W. and Wong, K. C. and Mitchell, K. A. R.} } @article {3618, title = {Structure and biodistribution relationships of photodynamic sensitizers}, journal = {Photochemistry and Photobiology}, volume = {64}, number = {3}, year = {1996}, note = {ISI Document Delivery No.: VG533Times Cited: 269Cited Reference Count: 77}, month = {Sep}, pages = {469-485}, type = {Review}, abstract = {Photodynamic therapy (PDT) has, during the last quarter century, developed into a fully fledged biomedical field with its own association, the International Photodynamic Association (TPA) and regular conferences devoted solely to this topic, Recent approval of the first PDT sensitizer, Photofrin(R) (porfiner sodium), by health boards in Canada, Japan, the Netherlands and United States for use against certain types of solid tumors represents, perhaps, the single most significant indicator of the progress of PDT from a laboratory research concept to clinical reality. The approval of Photofrin(R) will undoubtedly encourage the accelerated development of second-generation photosensitizers, which have recently been the subject of intense study, Many of these second-generation drugs show significant differences, when compared to Photofrin(R), in terms of treatment times postinjection, light doses and drug doses required for optimal results, These differences can ultimately be attributed to variations in either the quantum efficiency of the photosensitizer in situ, which is in turn affected by aggregation state, localized concentration of endogenous quenchers and primary photophysics of the dye, or the intratumoral and intracellular localization of the photosensitizer at the time of activation with light, The purpose of this review is to bring together data relating to the biodistribution and pharmacokinetics of second-generation sensitizers and attempt to correlate this with structural and electronic features of these molecules, As this requires a clear knowledge of photosensitizer structure, only chemically well-characterized compounds are included, e,g. Photofrin(R) and crude sulfonated phthalocyanines have been excluded as they are known to be complex mixtures, Nonporphyrin-based photosensitizers, e,g, rose bengal and the hypericins, have also been omitted to allow meaningful comparisons to be made between different compounds, As the intracellular distribution of photosensitizers to organelles and other subcellular structures can have a large effect on PDT efficacy, a section will be devoted to this topic.}, keywords = {CHLORIN-E6, HUMAN-MALIGNANT TUMOR, IN-VIVO FLUORESCENCE, L-ASPARTYL, LASER SCANNING, LIPOSOME-DELIVERED SI(IV)-NAPHTHALOCYANINE, microscopy, MOUSE-TUMOR MODEL, PHOTOSENSITIZING PROPERTIES, RING-A BPD, SULFONATED ALUMINUM PHTHALOCYANINES, TISSUE DISTRIBUTION}, isbn = {0031-8655}, url = {://A1996VG53300012}, author = {Boyle, R. W. and Dolphin, D.} }