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ABSTRACT: Neutrophil recruitment to inflammation sites purportedly depends on sequential waves of chemoattractants. Current models propose that leukotriene B(4) (LTB(4)), a secondary chemoattractant secreted by neutrophils in response to primary chemoattractants such as formyl peptides, is important in initiating the inflammation process. In this study we demonstrate that LTB(4) plays a central role in neutrophil activation and migration to formyl peptides. We show that LTB(4) production dramatically amplifies formyl peptide-mediated neutrophil polarization and chemotaxis by regulating specific signaling pathways acting upstream of actin polymerization and MyoII phosphorylation. Importantly, by analyzing the migration of neutrophils isolated from wild-type mice and mice lacking the formyl peptide receptor 1, we demonstrate that LTB(4) acts as a signal to relay information from cell to cell over long distances. Together, our findings imply that LTB(4) is a signal-relay molecule that exquisitely regulates neutrophil chemotaxis to formyl peptides, which are produced at the core of inflammation sites.
Developmental cell 04/2012; 22(5):1079-91. · 13.36 Impact Factor
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ABSTRACT: We show that the short-time behavior of time-resolved fluorescence Stokes shifts (TRSS) are similar to that of the intermediate scattering function obtained from neutron scattering at q near the peak in the static structure factor for glycerol. This allows us to extract a Debye-Waller (DW) factor analog from TRSS data at times as short as 1 ps in a relatively simple way. Using the time-domain relaxation data obtained by this method we show that DW factors evaluated at times ≥ 40 ps can be directly influenced by α relaxation and thus should be used with caution when evaluating relationships between fast and slow dynamics in glassforming systems.
Journal of Physical Chemistry Letters 01/2011; 2(12):1464-1468. · 6.21 Impact Factor
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ABSTRACT: Raman microspectroscopy can provide the chemical contrast needed to characterize the complex intracellular environment and macromolecular organization in cells without exogenous labels. It has shown a remarkable ability to detect chemical changes underlying cell differentiation and pathology-related chemical changes in tissues but has not been widely adopted for imaging, largely due to low signal levels. Broadband coherent anti-Stokes Raman scattering (B-CARS) offers the same inherent chemical contrast as spontaneous Raman but with increased acquisition rates. To date, however, only spectrally resolved signals from the strong CH-related vibrations have been used for CARS imaging. Here, we obtain Raman spectral images of single cells with a spectral range of 600-3200 cm⁻¹, including signatures from weakly scattering modes as well as CH vibrations. We also show that B-CARS imaging can be used to measure spectral signatures of individual cells at least fivefold faster than spontaneous Raman microspectroscopy and can be used to generate maps of biochemical species in cells. This improved spectral range and signal intensity opens the door for more widespread use of vibrational spectroscopic imaging in biology and clinical diagnostics.
Biophysical Journal 10/2010; 99(8):2695-704. · 3.65 Impact Factor
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ABSTRACT: New and interesting properties can be obtained from macromolecular architectures functionalized with supramolecular moieties, particularly metal-ligand complexes. Self-assembly, based on the selective control of noncovalent interactions, guides the creation of hierarchically ordered materials providing access to novel structures and new properties. This field has expanded significantly in the last two decades, and one of the most ubiquitous functionalities is terpyridine. Despite its wide-spread use, much basic knowledge regarding the binding of terpyridine with metal ions remains unknown. Here, the binding constants of PEG-substituted terpyridine in relation to other literature reports are studied and a few examples of supramolecular materials from our laboratory are summarized.
Macromolecular Rapid Communications 05/2010; 31(9-10):784-93. · 4.60 Impact Factor
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ABSTRACT: Imaging of polymer implants during surgical implantations is challenging in that most materials lack sufficient X-ray contrast. Synthetic derivatization with iodine serves to increase the scattering contrast but results in distinct physicochemical properties in the material which influence subsequent protein adsorption and cell morphology behavior. Herein we report the impact of increasing iodine inclusion on the cell morphology (cell area and shape) of MC3T3-E1 osteoblasts on a series of homopolymers and discrete blend thin films of poly(desaminotyrosyl tyrosine ethyl ester carbonate), poly(DTE carbonate), and an iodinated analogue poly(I(2)-DTE carbonate). Cell morphology is correlated to film chemical composition via measuring fibronectin (FN) adhesion protein adsorption profile on these films. FN exhibits up to 2-fold greater adsorption affinity for poly(I(2)-DTE carbonate) than (poly(DTE carbonate)). A correlation was established between cell area, roundness, and the measured FN adsorption profile on the blend films up to 75% by mass poly(I(2)-DTE carbonate). Data suggest that incorporation of iodine within the polymer backbone has a distinct impact on the way FN proteins adsorb to the surface and within the studied blend systems; the effect is composition dependent.
Biomacromolecules 08/2009; 10(9):2418-26. · 5.48 Impact Factor
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ABSTRACT: The integrity, function, and performance of biomedical devices having thin polymeric coatings are critically dependent on the mechanical properties of the film, including the elastic modulus. In this report, the elastic moduli of several tyrosine-derived polycarbonate thin films, specifically desaminotyrosyl ethyl tyrosine polycarbonates p(DTE carbonate), an iodinated derivative p(I(2)-DTE carbonate), and several discrete blends are measured using a method based on surface wrinkling. The data shows that the elastic modulus does not vary significantly with the blend composition as the weight percentage of p(I(2)-DTE carbonate) increases for films of uniform thickness in the range of 67 to 200 nm. As a function of film thickness, the observed elastic moduli of p(DTE carbonate), p(I(2)-DTE carbonate) and their 50:50 by mass blend show little variation over the range 30 to 200 nm.
Macromolecules 01/2009; 42(4):1212-1218. · 5.17 Impact Factor
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ABSTRACT: The synthesis of novel block copolymers with metal complexes in the side chain of the polymer and their bulk self-assembly are described. Atom transfer radical polymerization plus postpolymerization chemistry were used to synthesize these novel diblock and four-arm star diblock copolymers. One block was functionalized with an asymmetric ruthenium(II) bisterpyridine complex containing a C16 alkyl chain in the 4‘ position. 1H NMR and FT-IR were used to monitor the postpolymerization chemistry, while polarized optical microscopy, small angle X-ray scattering (SAXS), and wide-angle X-ray diffraction were used to characterize the self-assembled structures. The diblock copolymer microphase separated in the bulk to form a structure-within-structure morphology “cylinders in a sea of rods” that have spacings of 38 and 5.7 nm, respectively, and the C16 chains were crystalline. The star copolymer was birefringent in the bulk, gave a SAXS signal corresponding to 38 nm, and had crystalline C16 side chains; however, no evidence for structure-within-structure could be found in the SAXS experiments. This could be due to slow relaxation times, since the molecular weight was three times larger than the linear diblock copolymer, or frustrated packing due to the star architecture.
02/2008;
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02/2008: pages 169 - 189; , ISBN: 9783527610570
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ABSTRACT: A new colorimetric mercury sensor is reported based on binding to terpyridine derivatives. It is able to selectively detect Hg II ions over a number of environmentally relevant ions including Ca II, Pb II, Zn II, Cd II, Ni II, Cu II, and others. The response time upon exposure to Hg II is instantaneous. By the "naked eye," the detection limit of Hg II is 2 ppm (25 microM) in solution. With a spectrometer, this detection limit is increased down to 2 ppb (25 nM), which is the current EPA standard for drinking water. The significant problem of mercury poisoning requires new methods of detection that are sensitive and selective. Here we report a new simple system that takes advantage of the unique optical properties generated by terpyiridine-Hg complexes.
Chemistry 02/2008; 14(13):3904-7. · 5.93 Impact Factor
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Journal of Polymer Science Part A Polymer Chemistry 10/2007; 45(23):5618 - 5625. · 3.92 Impact Factor
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ABSTRACT: The synthesis of supramolecular polymers containing metal complexes in the side chain is described. Atom transfer radical polymerization (ATRP) was used to synthesize the macromolecular backbone, and the metal complex was attached via postpolymerization chemistry. Homopolymers containing [Ru(terpy)2]2+ in the side chain were prepared in which the complex contained either a long hydrophobic C16 alkyl group or only hydrogen at the 4‘-position. The homopolymers containing the long C16 alkyl groups showed lyotropic liquid crystalline (LC) behavior in chloroform solutions from room temperature to 60 °C and self-assembled in the bulk to form hexagonal arrays of cylinders. In addition, this alkyl side chain was observed to crystallize in the solid state. Homopolymers without the C16 alkyl group showed no lyotropic LC or any crystallization behavior. The material design emphasizes the relationship between the molecular structure and supramolecular organization of these polymers. It demonstrates that terpy complexes remain a versatile functionality for constructing supramolecular assemblies.
03/2007;
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Journal of Polymer Science Part A Polymer Chemistry 02/2007; 45(6):1109 - 1121. · 3.92 Impact Factor
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ABSTRACT: Polymer architectures containing metal–ligands in their side chain represent a diverse approach to generating multi-functional materials. The ability to define a versatile synthetic platform will enable many chemistries and architectures to be studied. This report describes our latest efforts to prepare these unique polymers by either a direct polymerization of functionalized monomers or a post-polymerization attachment. Random and block copolymers have been successfully prepared. Subsequent functionalization with metal ions leads to a variety of properties including metal induced gelation and solvochromic sensors.
08/2005;
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ABSTRACT: Poly(l-lactic acid-b-ethylene oxide-b-l-lactic acid) (PLLA-b-PEO-b-PLLA) triblock copolymers were synthesized by a ring-opening polymerization. PLLA and PEO sequentially crystallized by slowly cooling (−2 °C/min) from the melt. In the resultant spherulitic morphology, the retardation of polarized light was additive, and the sign of the spherulite (negative) was preserved when the PEO crystallized within the framework established by the PLLA crystals. Homopolymer blends of PLLA and PEO having the same composition as the block copolymer showed similar optical behavior. However, the change in the optical retardation upon crystallization of the PEO was much greater for the triblock copolymer than for the blend. Upon heating, the small-angle X-ray scattering from both the triblock copolymer and homopolymer mixture showed a stepwise increase in the long period at 60 °C, i.e., when the PEO crystals melted. For comparable volume fractions (φPLLA = 0.57), the increase in long period was greater for the triblock copolymer than for the blend. Wide-angle X-ray diffraction studies on shear aligned triblock copolymers indicate that the PLLA and PEO crystals adopt the same average orientation; though, in the case of the copolymer, the orientation is more strongly coupled.
12/2004;
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ABSTRACT: We report detailed rheological data on aqueous gels formed from triblock copolymers of L-lactide and ethylene oxide including the dependence of the viscoelastic moduli on frequency and applied stress of these systems for the first time. We are able to create strong gels with elastic moduli greater than 10,000 Pa, which is an order of magnitude higher than previously achieved with related biocompatible physically associated gels of similar chemistry. Moreover, the value of the elastic modulus strongly depends on PLLA block length, offering a mechanism to control the mechanical properties as desired for particular applications. At the gel point, we observe scaling that is characteristic of a percolated network, G' approximately G" approximately omega(Delta), but with an exponent that is lower than predicted by percolation, Delta=0.36. Our results have implications for the design of new materials for soft tissue engineering, where native tissues have moduli in the kPa range.
Biomaterials 04/2004; 25(6):1087-93. · 7.40 Impact Factor
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02/2004;
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ABSTRACT: Parallel fibers can be rapidly created by manually brushing solvated polymer solutions over arrays of microfabricated pillars. Recently, this technique has been utilized to produce suspended arrays of micron and sub-micron scale fibers consisting of a new triblock copolymer composed of a hydrophilic mid-block of polyethylene oxide (PEO) surrounded by two hydrophobic end groups of poly-L-lactic acid (PLLA). A solution of this polymer in chloroform has been used to fabricate fibers with diameters ranging from 125 nm to >50 μm. Annealing these fibers in water induces the formation of ultrastructural nanoscale pores that can be selectively oriented through variation of the surface treatment. Because the PLLA-PEO-PLLA triblock copolymer is both biocompatible and biodegradable, these arrays of fibers are excellent candidates for biomimetic extracellular matrix (ECM) structures. Additionally, the porous ultrastructure of the fibers may provide a platform for the in situ delivery of growth factors to stimulate endothelial cell proliferation, migration, and lumen formation.
