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Zhang W, Moore JS. Shape-Persistent Macrocycles: Structures and Synthetic Approaches from Arylene and Ethynylene Building Blocks. Angew Chem Int Ed Engl 2006; 45:4416-39. [PMID: 16770818 DOI: 10.1002/anie.200503988] [Citation(s) in RCA: 449] [Impact Index Per Article: 24.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Shape-persistent arylene ethynylene macrocycles have attracted much attention in supramolecular chemistry and materials science because of their unique structures and novel properties. In this Review we describe recent examples of macrocycle synthesis by cross-coupling (Sonogashira: aryl acetylene macrocycle or Glaser: aryl diacetylene macrocycle) and dynamic covalent chemistry. The primary disadvantage of the coupling methods is the kinetically determined product distribution, since a significant portion of oligomers grow beyond the length of the cyclic targets ("overshooting"). Better results have been obtained recently by a dynamic covalent approach involving reversible metathesis reactions that afford macrocycles in one step. Mechanistic studies demonstrate that macrocycle formation is thermodynamically controlled by this route. Remaining synthetic challenges include the efficient preparation of site-specifically functionalized structures and larger, more complex two- and three-dimensional molecules.
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Zhang W, Moore JS. Formtreue Makrocyclen: Strukturen und Synthesen aus Arylen- und Ethinylen-Bausteinen. Angew Chem Int Ed Engl 2006. [DOI: 10.1002/ange.200503988] [Citation(s) in RCA: 124] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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253
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Elliott EL, Ray CR, Kraft S, Atkins JR, Moore JS. Solid-Phase Synthesis of m-Phenylene Ethynylene Heterosequence Oligomers. J Org Chem 2006; 71:5282-90. [PMID: 16808517 DOI: 10.1021/jo0607212] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Both homo- and heterosequence m-phenylene ethynylene oligomers are synthesized using a conceptually simple iterative solid-phase strategy. Oligomers are attached to Merrifield's resin through a known triazene-type linkage. The phenylene ethynylene molecular backbone is constructed through a series of palladium-mediated cross-coupling reactions. The strategy employs two types of monomers that bear orthogonal reactivity, one being a monoprotected bisethynyl arene and the other being a 3-bromo-5-iodo arene. The catalyst conditions are tailored to the requirements of each monomer type. The monoprotected bisethynyl arene is coupled to the growing chain in 2 h at room temperature using a Pd(I) dimer precatalyst ((t)Bu3P(Pd(mu-Cl)(mu-2-methyl allyl)Pd)P(t)Bu3) in conjunction with ZnBr2 and diisopropylamine. In alternate steps, the resin is deprotected in situ with TBAF and coupled to the 3-bromo-5-iodo arene using the iodo selective Pd(tri-2-furylphosphine)4 catalyst in conjunction with CuI and piperidine; this reaction is also completed in 2 h at room temperature. These cross-coupling events are alternated until an oligomer of the desired length is achieved. The oligomer is then cleaved from the resin using CH(2)I(2)/I(2) at 110 degrees C and purified using preparatory GPC. Using this method, a series of homo- and heterosequence oligomers up to 12 units in length in excellent yield and purity were synthesized on the 100 mg scale. Longer oligomers were attempted; however, deletion sequences were found in oligomers longer than 12 units.
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Balakrishnan K, Datar A, Zhang W, Yang X, Naddo T, Huang J, Zuo J, Yen M, Moore JS, Zang L. Nanofibril Self-Assembly of an Arylene Ethynylene Macrocycle. J Am Chem Soc 2006; 128:6576-7. [PMID: 16704255 DOI: 10.1021/ja0618550] [Citation(s) in RCA: 135] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Nanofibril structures have been fabricated from an arylene ethynylene macrocycle (AEM), which consists of a square frame corner-joined by four carbazole moieties. The fabrication was performed through a gelating process by cooling a warm, homogeneous solution in cyclohexane at high temperature (e.g., 100 degrees C) to room temperature. During the gelation, the molecules become organized, with optimal pi-pi stacking in cooperation with the side-chain association. The favorable pi-pi stacking facilitates the 1D growth of molecular assembly.
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Long TM, Prakash S, Shannon MA, Moore JS. Water-vapor plasma-based surface activation for trichlorosilane modification of PMMA. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2006; 22:4104-9. [PMID: 16618151 DOI: 10.1021/la052977t] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Separation rates and resolutions within capillary electrophoretic (CE) systems can be enhanced when surface zeta potentials are uniform with minimum deviations from ideal pluglike flow. Microfluidic CE devices based on poly(methyl methacrylate) (PMMA) are being developed due to the optical clarity, availability, stability, and reproducible electroosmotic flow (EOF) rates displayed by this polymer. Control of EOF in polymer-based CE systems can be achieved by surface zeta potential alteration through chemical modification. Herein, a method will be presented for the surface functionalization of PMMA with chemistry analogous to formation of trichlorosilane self-assembled monolayers on SiO2. The current method involves two separate steps. First, surface activation with water-vapor plasma introduces surface hydroxylation. Second, treatment of the plasma-treated PMMA with a substituted trichlorosilane solution forms the functional surface layer. The modified surfaces were characterized using several analytical techniques, including water contact angle, X-ray photoelectron spectroscopy, Fourier transform infrared-attenuated total reflection, secondary ion mass spectroscopy, and measurement of EOF velocities within PMMA microchannels.
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256
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Plunkett KN, Zhu X, Moore JS, Leckband DE. PNIPAM chain collapse depends on the molecular weight and grafting density. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2006; 22:4259-66. [PMID: 16618173 DOI: 10.1021/la0531502] [Citation(s) in RCA: 201] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
This study demonstrates that the thermally induced collapse of end-grafted poly(N-isopropylacrylamide) (PNIPAM) above the lower critical solution temperature (LCST) of 32 degrees C depends on the chain grafting density and molecular weight. The polymer was grafted from the surface of a self-assembled monolayer containing the initiator (BrC(CH3)2COO(CH2)11S)2, using surface-initiated atom transfer radical polymerization. Varying the reaction time and monomer concentration controlled the molecular weight, and diluting the initiator in the monolayer altered the grafting density. Surface force measurements of the polymer films showed that the chain collapse above the LCST decreases with decreasing grafting density and molecular weight. At T > LCST, the advancing water contact angle increases sharply on PNIPAM films of high molecular weight and grafting density, but the change is less pronounced with films of low-molecular-weight chains at lower densities. Below the LCST, the force-distance profiles exhibit nonideal polymer behavior and suggest that the brush architecture comprises dilute outer chains and much denser chains adjacent to the surface.
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257
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Goto K, Moore JS. Sequence-specific binding of m-phenylene ethynylene foldamers to a piperazinium dihydrochloride salt. Org Lett 2006; 7:1683-6. [PMID: 15844880 DOI: 10.1021/ol0500721] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
[reaction: see text] Binding properties of a series of isomeric m-phenylene ethynylene oligomers containing short amide sequences to a piperazinium dihydrochloride salt were investigated by using circular dichroism (CD) measurements. Although these isomeric oligomers exhibited similar helical conformations, high affinity was observed only for one oligomer. This behavior is presumably controlled by the orientation of amino groups of the amide sequence and the folded conformation of the oligomer.
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Moore JS, Zhang J. Effiziente Synthese makrocyclischer Kohlenwasserstoffe mit Durchmessern im Nanometerbereich. Angew Chem Int Ed Engl 2006. [DOI: 10.1002/ange.19921040715] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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259
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Weissman H, Plunkett KN, Moore JS. A Highly Active, Heterogeneous Catalyst for Alkyne Metathesis. Angew Chem Int Ed Engl 2006. [DOI: 10.1002/ange.200502840] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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260
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Weissman H, Plunkett KN, Moore JS. A Highly Active, Heterogeneous Catalyst for Alkyne Metathesis. Angew Chem Int Ed Engl 2006; 45:585-8. [PMID: 16355427 DOI: 10.1002/anie.200502840] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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261
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Abstract
Trends obtained from systematic studies based on chain-length variation have provided valuable insight and understanding into the behavior of m-phenylene ethynylene foldamers. The generalization of this experimental approach, the chain-length dependence test, is useful for studying solution conformation, packing in the solid state, specific intrachain interactions, and the contributions of end groups to a particular property.
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Zhang W, Brombosz SM, Mendoza JL, Moore JS. A High-Yield, One-Step Synthesis of o-Phenylene Ethynylene Cyclic Trimer via Precipitation-Driven Alkyne Metathesis. J Org Chem 2005; 70:10198-201. [PMID: 16292873 DOI: 10.1021/jo0517803] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
[reaction: see text] A shape-persistent, conjugated o-phenylene ethynylene cyclic trimer was prepared in one step from tetrasubstituted benzene monomer 4 in 86% isolated yield through precipitation-driven alkyne metathesis. The template-free, selective generation of the molecular triangle 5 is a thermodynamically favored process and under equilibrium control. A novel tetrameric macrocycle 7 was generated via scrambling metathesis between tricycle 5 and hexacycle 6 using this dynamic covalent chemistry.
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Plunkett KN, Mohraz A, Haasch RT, Lewis JA, Moore JS. Light-Regulated Electrostatic Interactions in Colloidal Suspensions. J Am Chem Soc 2005; 127:14574-5. [PMID: 16231901 DOI: 10.1021/ja054666a] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The net charge of a colloidal particle was controlled using light and a new photocleavable self-assembled monolayer (SAM). The SAM contained a terminal ammonium group and a centrally located carboxylic acid group that was masked with an ortho-nitrobenzyl functionality. Once exposed to UV light, the 2-nitrobenzyl group was cleaved, therefore transforming the colloidal particle from a net positive (silica-SAM-NH3+) to a net negative (silica-SAM-COO-) charge. By varying the UV exposure time, their zeta potential could be tailored between +26 and -60 mV at neutral pH. To demonstrate a photoinduced gel-to-fluid phase transition, a binary colloidal suspension composed of silica-SAM-NH3+ and negatively charged, rhodamine-labeled silica particles was mixed to form a gel. Exposure to UV light rendered all of the particles negative and therefore converted the system into a colloidal fluid that settles to form a dense sediment.
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Berkowski KL, Potisek SL, Hickenboth CR, Moore JS. Ultrasound-Induced Site-Specific Cleavage of Azo-Functionalized Poly(ethylene glycol). Macromolecules 2005. [DOI: 10.1021/ma051394n] [Citation(s) in RCA: 193] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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265
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Plunkett KN, Berkowski KL, Moore JS. Chymotrypsin responsive hydrogel: application of a disulfide exchange protocol for the preparation of methacrylamide containing peptides. Biomacromolecules 2005; 6:632-7. [PMID: 15762623 DOI: 10.1021/bm049349v] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Methacrylamide groups were selectively coupled to cysteine residues in the presence of amines and alcohols by utilizing a disulfide exchange reaction in aqueous, acidic buffer. The tetrapeptide sequence, CYKC, was used as a cross-linker to create poly(acrylamide) hydrogels that dissolved when subjected to either a flowing or stationary solution of alpha-chymotrypsin. Control hydrogels that were cross-linked with the tetrapeptide, CSKC, were not affected by the same protease solution. In contrast, dissolution of both the CYKC and CSKC cross-linked hydrogel structures was accomplished by using the disulfide reducing agent tris(2-carboxyethyl) phosphine (TCEP). The chemoselective conjugation technique described could have utility for more advanced protease-responsive hydrogels as well as other hybrid materials composed of synthetic and biomacromolecules.
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266
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Zhang W, Moore JS. Reaction Pathways Leading to Arylene Ethynylene Macrocycles via Alkyne Metathesis. J Am Chem Soc 2005; 127:11863-70. [PMID: 16104765 DOI: 10.1021/ja053466w] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Mechanistic studies on the direct formation of arylene ethynylene macrocycles via alkyne metathesis catalyzed by a molybdenum complex are reported. Gel permeation chromatography (GPC) and matrix-assisted laser desorption ionization (MALDI) mass spectrometry on the products from metathesis of monomer 1 show the initial formation of linear oligomers and large macrocycles (n > 6), followed by their transformation into the thermodynamically most stable product distribution-mainly the cyclic hexamer. Variable temperature and scrambling experiments reveal the reversibility of macrocycle formation. Nearly identical product distributions are observed from the cross metathesis of hexacycle 2 with diphenylacetylene and from the metathesis of bis(phenylethynyl) substituted monomer 4, demonstrating that macrocycle formation is thermodynamically rather than kinetically controlled. The metathesis byproduct, 3-hexyne, is shown to inhibit the catalyst. It is suggested that the relative metathesis rates of dialkylalkynes versus diarylalkynes trap the catalyst in a nonproductive manifold, rendering it unavailable for the productive metathesis of aryl alkylalkyne substrates. This finding indicates that dialkyl-substituted alkyne byproducts should be avoided (or efficiently removed) if the metatheses of aryl substrates, especially those with electron-withdrawing groups, are to proceed to high conversion.
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267
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Rule JD, Moore JS. Polymerizations Initiated by Diradicals from Cycloaromatization Reactions. Macromolecules 2005. [DOI: 10.1021/ma050750z] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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268
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Zhang W, Moore JS. Arylene ethynylene macrocycles prepared by precipitation-driven alkyne metathesis. J Am Chem Soc 2005; 126:12796. [PMID: 15469273 DOI: 10.1021/ja046531v] [Citation(s) in RCA: 130] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A convenient, multigram-scale synthesis of arylene ethynylene macrocycles near room temperature is described. Driven by the precipitation of a diarylacetylene byproduct, alkyne metathesis produces the desired macrocycles in one step from monomers in high yields.
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Abstract
Crystallographic analysis revealed that pyridine-palladium complexation is a good geometric match to the m-phenylene ethynylene (mPE) repeat unit and thus could serve as a reversible linking group to join oligomer segments together. A series of pyridine-terminated mPE oligomers were then synthesized and found to coordinate with palladium dichloride to give complexes effectively twice the length of the free oligomers. A quantitative analysis of these coordination equilibria by isothermal calorimetry found the ability of the pyridine end-group to form a coordination complex corresponded with their ability to fold. Oligomers that were able to form complexes of sufficient length to fold showed positive cooperativity based on experimental determination of their association constants with a palladium ion. We suggest that the additional free energy of complexation for the folded oligomers is analogous to chelation by multidentate ligands, but here the "multidentate ligand" is held together by supramolecular rather than covalent bonds.
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270
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Boelaert K, Yu R, Tannahill LA, Stratford AL, Khanim FL, Eggo MC, Moore JS, Young LS, Gittoes NJL, Franklyn JA, Melmed S, McCabe CJ. PTTG's C-terminal PXXP motifs modulate critical cellular processes in vitro. J Mol Endocrinol 2004; 33:663-77. [PMID: 15591026 DOI: 10.1677/jme.1.01606] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Human pituitary tumor-transforming gene (PTTG), known also as securin, is a multifunctional protein implicated in the control of mitosis and the pathogenesis of thyroid, colon, oesophageal and other tumour types. Critical to PTTG function is a C-terminal double PXXP motif, forming a putative SH3-interacting domain and housing the gene's sole reported phosphorylation site. The exact role of phosphorylation and PXXP structure in the modulation of PTTG action in vitro remains poorly understood. We therefore examined the mitotic, transformation, proliferation and transactivation function of the C-terminal PXXP motifs of human PTTG. Live-cell imaging studies using an EGFP-PTTG construct indicated that PTTG's regulation of mitosis is retained regardless of phosphorylation status. Colony-formation assays demonstrated that phosphorylation of PTTG may act as a potent inhibitor of cell transformation. In proliferation assays, NIH-3T3 cells stable transfected and overexpressing mutations preventing PTTG phosphorylation (Phos-) showed significantly increased [3H]thymidine incorporation compared with WT, whereas mutants mimicking constitutive phosphorylation of PTTG (Phos+) exhibited reduced cell proliferation. We demonstrated that PTTG transactivation of FGF-2 in primary thyroid and PTTG-null cell lines was not affected by PTTG phosphorylation but was prevented by a mutant disrupting the PXXP motifs (SH3-). Taken together, our data suggest that PXXP structure and phosphorylation are likely to exert independent and critical influences upon PTTG's diverse actions in vitro.
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271
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Goto H, Heemstra JM, Hill DJ, Moore JS. Single-site modifications and their effect on the folding stability of m-phenylene ethynylene oligomers. Org Lett 2004; 6:889-92. [PMID: 15012057 DOI: 10.1021/ol036376+] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
[reaction: see text] The folded structure of a m-phenylene ethynylene oligomer is tolerant to single-site modifications to both the backbone sequence and end groups. The helical structure is reinforced by multiple noncovalent interactions, allowing the oligomer sequence to be customized without a significant change in stability in most cases. The small changes that are observed are consistent with the expected behavior of pi-stacked systems and demonstrate subtle control over folding through single-site modifications.
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272
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Heemstra JM, Moore JS. Enhanced Methylation Rate within a Foldable Molecular Receptor. J Org Chem 2004; 69:9234-7. [PMID: 15609960 DOI: 10.1021/jo048506d] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A N,N-(dimethylamino)pyridine monomer is incorporated into the backbone of a m-phenyleneethynylene oligomer such that the pyridine nitrogen is located on the interior surface of the binding cavity in the folded structure of the oligomer. For an oligomer having a chain length of 13 monomer units, competitive inhibition experiments reveal that methyl iodide binds weakly within the oligomer cavity with an association constant K(a) = 2 M(-1), and the oligomer-methyl iodide complex reacts with unimolecular rate constant k(u) = 0.082 s(-1) to provide the methylated product. The effective molarity is calculated to be 230 M by comparison of k(u) for the 13-mer with the second-order rate constant for a 3-mer that is too short to fold and thus unable to bind methyl iodide.
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273
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Stone MT, Fox JM, Moore JS. A Helicene-Containing Foldamer Displaying Highly Solvent-Dependent CD Spectra. Org Lett 2004; 6:3317-20. [PMID: 15355041 DOI: 10.1021/ol048770t] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
[structure: see text] A m-phenylene ethynylene oligomer containing a helicene unit was synthesized to bias the twist sense of the folded helical conformation. The CD spectra of the helicene oligomer exhibited large Cotton effects that varied greatly with the solvent composition, including three separate conformational transitions.
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274
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Plunkett KN, Moore JS. Patterned dual pH-responsive core-shell hydrogels with controllable swelling kinetics and volumes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2004; 20:6535-6537. [PMID: 15274549 DOI: 10.1021/la049453y] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Dual pH-responsive core-shell hydrogels containing both a vinyl pyridine component and a 2-dimethylaminoethyl methacrylate component were prepared using an in situ photopolymerization process. Complementary photomasks were utilized to prepare hydrogels with core/shell volume ratios of 2:1, 1:1, and 1:2. Depending on the location of each polymer component, dramatically different swelling profiles were achieved. Selective swelling of the shell followed by the core components allowed the hydrogel to expand with the usual kinetics; however, by switching the location of each polymer component and swelling the core first, swelling rates decreased by over 1 order of magnitude and were dependent on the shell component's volume. The ability to pattern core/shell volumes also provided the ability to fabricate hydrogels that possess a constant maximum diameter but different cutoff points between its first and its second transition volumes. These materials may be of interest for controlled release applications.
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