Olof Ramström

KTH Royal Institute of Technology, Tukholma, Stockholm, Sweden

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Publications (121)565.35 Total impact

  • Nanjing Hao · Kitjanit Neranon · Olof Ramström · Mingdi Yan
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    ABSTRACT: Nanomaterials constitute a class of structures that have unique physiochemical properties and are excellent scaffolds for presenting carbohydrates, important biomolecules that mediate a wide variety of important biological events. The fabrication of carbohydrate-presenting nanomaterials, glyconanomaterials, is of high interest and utility, combining the features of nanoscale objects with biomolecular recognition. The structures can also produce strong multivalent effects, where the nanomaterial scaffold greatly enhances the relatively weak affinities of single carbohydrate ligands to the corresponding receptors, and effectively amplifies the carbohydrate-mediated interactions. Glyconanomaterials are thus an appealing platform for biosensing applications. In this review, we discuss the chemistry for conjugation of carbohydrates to nanomaterials, summarize strategies, and tabulate examples of applying glyconanomaterials in in vitro and in vivo sensing applications of proteins, microbes, and cells. The limitations and future perspectives of these emerging glyconanomaterials sensing systems are furthermore discussed. Copyright © 2015 Elsevier B.V. All rights reserved.
    Biosensors & Bioelectronics 07/2015; DOI:10.1016/j.bios.2015.07.031 · 6.45 Impact Factor
  • Fredrik Schaufelberger · Olof Ramström
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    ABSTRACT: The first example of a bifunctional organocatalyst assembled through dynamic covalent chemistry (DCC) is described. The catalyst is based on reversible imine chemistry and can catalyze the Morita-Baylis-Hillman (MBH) reaction of enones with aldehydes or N-tosyl imines. Furthermore, these dynamic catalysts were shown to be optimizable through a systemic screening approach, in which large mixtures of catalyst structures were generated, and the optimal catalyst could be directly identified by using dynamic deconvolution. This strategy allowed one-pot synthesis and in situ evaluation of several potential catalysts without the need to separate, characterize, and purify each individual structure. The systems were furthermore shown to catalyze and re-equilibrate their own formation through a previously unknown thiourea-catalyzed transimination process. © 2015 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. This is an open access article under the terms of Creative Commons Attribution NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.
    Chemistry - A European Journal 07/2015; DOI:10.1002/chem.201502088 · 5.70 Impact Factor
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    Lei Hu · Yang Zhang · Olof Ramström
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    ABSTRACT: An organogelator was produced and identified from a dynamic imine system, resolved and amplified by selective gelation. The formation of the organogel was monitored in situ by (1)H NMR, showing the existence of multiple reversible reactions operating simultaneously, and the redistribution of the involved species during gelation. The formed organogelator proved effective with a range of organic solvents, including DMSO, toluene, and longer, linear alcohols.
    Scientific Reports 06/2015; 5:11065. DOI:10.1038/srep11065 · 5.58 Impact Factor
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    Fredrik Schaufelberger · Lei Hu · Olof Ramström
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    ABSTRACT: The development of chemical transaminations as a new type of dynamic covalent reaction is described. The key 1,3-proton shift is under complete catalytic control and can be conducted orthogonally to, or simultaneous with, transimination in the presence of an amine to rapidly yield two-dimensional dynamic systems with a high degree of complexity evolution. The transamination-transimination systems are proven to be fully reversible, stable over several days, compatible with a range of functional groups, and highly tunable. Kinetic studies show transamination to be the rate-limiting reaction in the network. Furthermore, it was discovered that readily available quinuclidine is a highly potent catalyst for aldimine transaminations. This study demonstrates how connected dynamic reactions give rise to significantly larger systems than the unconnected counterparts, and shows how reversible isomerizations can be utilized as an effective diversity-generating element. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    Chemistry - A European Journal 06/2015; 21(27). DOI:10.1002/chem.201500520 · 5.70 Impact Factor
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    Na Kong · Manishkumar R Shimpi · Olof Ramström · Mingdi Yan
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    ABSTRACT: Carbohydrate-functionalized single-walled carbon nanotubes (SWNTs) were synthesized using microwave-assisted reaction of perfluorophenyl azide with the nanotubes. The results showed that microwave radiation provides a rapid and effective means to covalently attach carbohydrates to SWNTs, producing carbohydrate-SWNT conjugates for biorecognition. The carbohydrate-functionalized SWNTs were furthermore shown to interact specifically with cognate carbohydrate-specific proteins (lectins), resulting in predicted recognition patterns. The carbohydrate-presenting SWNTs constitute a new platform for sensitive protein- or cell recognition, which pave the way for glycoconjugated carbon nanomaterials in biorecognition applications. Copyright © 2014 Elsevier Ltd. All rights reserved.
    Carbohydrate Research 03/2015; 405:33-8. DOI:10.1016/j.carres.2014.09.006 · 1.92 Impact Factor
  • Suji Uppalapati · Na Kong · Oscar Norberg · Olof Ramström · Mingdi Yan
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    ABSTRACT: Covalently immobilized poly(4-vinylphenol) (PVP) monolayer films were fabricated by spin coating PVP on perfluorophenyl azide (PFPA)-functionalized surface followed by UV irradiation. The pH-responsive behavior of these PVP ultrathin films was evaluated by ellipsometry, quartz crystal microbalance (QCM) and surface plasmon resonance (SPR). By monitoring the responses of these films to pH in situ, the ionization constant of the monolayer thin films was obtained. The apparent pKa value of these covalently immobilized PVP monolayers, 13.4 by SPR, was 3 units higher than that of the free polymer in aqueous solution.
    Applied Surface Science 03/2015; 343. DOI:10.1016/j.apsusc.2015.03.014 · 2.54 Impact Factor
  • Sheng Xie · Olof Ramström · Mingdi Yan
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    ABSTRACT: Urea structures, of which N,N-diethylurea (DEU) proved to be the most efficient, were discovered to catalyze amidation reactions between electron-deficient aryl azides and phenylacetaldehydes. Experimental data support 1,3-dipolar cycloaddition between DEU-activated enols and electrophilic phenyl azides, especially perfluoroaryl azides, followed by rearrangement of the triazoline intermediate. The activation of the aldehyde under near-neutral conditions was of special importance in inhibiting dehydration/aromatization of the triazoline intermediate, thus promoting the rearrangement to form aryl amides.
    Organic Letters 01/2015; 17(3). DOI:10.1021/ol503655a · 6.32 Impact Factor
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    Xuan Chen · Olof Ramström · Mingdi Yan
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    ABSTRACT: Carbohydrates constitute the most abundant organic matter in nature, serving as structural components and energy sources, and mediating a wide range of cellular activities. The emergence of nanomaterials with distinct optical, magnetic, and electronic properties has witnessed a rapid adoption of these materials for biomedical research and applications. Nanomaterials of various shapes and sizes having large specific surface areas can be used as multivalent scaffolds to present carbohydrate ligands. The resulting glyconanomaterials effectively amplify the glycan-mediated interactions, making it possible to use these materials for sensing, imaging, diagnosis, and therapy. In this review, we summarize the synthetic strategies for the preparation of various glyconanomaterials. Examples are given where these glyconanomaterials have been used in sensing and differentiation of proteins and cells, as well as in imaging glycan-medicated cellular responses.
    Nano Research 10/2014; 7(10):1381-1403. DOI:10.1007/s12274-014-0507-y · 6.96 Impact Factor
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    ABSTRACT: Dual promiscuous racemization/amidation activities of lipases leading to efficient dynamic kinetic resolution protocols of racemic α-aminonitrile compounds are described. α-Amidonitrile products of high enantiomeric purity could be formed in high yields. Several lipases from different sources were shown to exhibit the dual catalytic activities, where opposite enantioselectivities could be recorded for certain substrates. Dynamic chemistry: Dual promiscuous racemization/amidation activities of lipases leading to efficient dynamic kinetic resolution protocols of racemic α-aminonitrile compounds are described. α-Amidonitrile products of high enantiomeric purity could be formed in high yields. Several lipases from different sources were shown to exhibit the dual catalytic activities, in which opposite enantioselectivities could be recorded for certain substrates (see scheme). © 2014 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. This is an open access article under the terms of Creative Commons Attribution NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.
    Chemistry - A European Journal 09/2014; 20(36). DOI:10.1002/chem.201402615 · 5.70 Impact Factor
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    ABSTRACT: Dynamic systems based on consecutive thia-Michael and Henry reactions were generated and transformed using lipase-catalyzed asymmetric transformation. Substituted thiolane structures with three contiguous stereocenters were resolved in the process in high yields and high enantiomeric excesses. © 2014 The authors. Published by Wiley-VCH Verlag GmbH &Co. KGaA. This is an open access article under the terms of the Creative Commons Attribution- NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.
    Advanced Synthesis & Catalysis 08/2014; 356(5). DOI:10.1002/adsc.201301033 · 5.54 Impact Factor
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    ABSTRACT: The asymmetric synthesis of 1,3-oxathiolan-5-one derivatives through an enzyme-catalyzed, dynamic covalent kinetic resolution strategy is presented. Dynamic hemithioacetal formation combined with intramolecular, lipase-catalyzed lactonization resulted in good conversions with moderate to good enantiomeric excess (ee) for the final products. The process was evaluated for different lipase preparations, solvents, bases, and reaction temperatures, where lipase B from Candida antarctica (CAL-B) proved most efficient. The substrate scope was furthermore explored for a range of aldehyde structures, together with the potential access to nucleoside analog inhibitor core structures.
    ChemInform 06/2014; 70(24):3826–3831. DOI:10.1002/chin.201428119
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    Bo Ren · Hai Dong · Olof Ramström
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    ABSTRACT: A carbohydrate-anion recognition system in nonpolar solvents is reported, in which complexes form at the B-faces of β-D-pyranosides with H1-, H3-, and H5-cis patterns similar to carbohydrate-π interactions. The complexation effect was evaluated for a range of carbohydrate structures; it resulted in either 1:1 carbohydrate-anion complexes, or 1:2 complex formation depending on the protection pattern of the carbohydrate. The interaction was also evaluated with different anions and solvents. In both cases it resulted in significant binding differences. The results indicate that complexation originates from van der Waals interactions or weak CH⋅⋅⋅A(-) hydrogen bonds between the binding partners and is related to electron-withdrawing groups of the carbohydrates as well as increased hydrogen-bond-accepting capability of the anions.
    Chemistry - An Asian Journal 05/2014; 9(5). DOI:10.1002/asia.201301617 · 3.94 Impact Factor
  • Lei Hu · Yan Zhang · Olof Ramström
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    ABSTRACT: A domino addition-lactonization pathway has been applied to a dynamic covalent resolution protocol, leading to efficient oxathiazinanone formation as well as chiral discrimination. A new, double biocatalytic pathway has furthermore been proposed and evaluated where the initial product inhibition could be efficiently circumvented.
    Organic & Biomolecular Chemistry 04/2014; 12(22). DOI:10.1039/c4ob00365a · 3.49 Impact Factor
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    Yan Zhang · Olof Ramström
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    ABSTRACT: A complex dynamic system based on a network of multiple reversible reactions has been established. The network was applied to a dynamic systemic resolution protocol based on kinetically controlled lipase-catalyzed transformations. This resulted in the formation of cyclized products, where two thiazolidinone compounds were efficiently produced from a range of potential transformations.
    Chemistry - A European Journal 03/2014; 20(12). DOI:10.1002/chem.201304690 · 5.70 Impact Factor
  • Lei Hu · Olof Ramström
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    ABSTRACT: A dynamic azomethine ylide system was established using Sc(OTf)3 and Ag/Taniaphos as catalysts. The system was subsequently kinetically resolved in a tandem 1,3-dipolar cycloaddition process where the silver complex acted as both a reaction catalyst and an external selector, resulting in the formation of an exclusive pyrrolidine product in good yield and enantiopurity.
    Chemical Communications 02/2014; 50(29). DOI:10.1039/c4cc00944d · 6.83 Impact Factor
  • Lei Hu · Fredrik Schaufelberger · Yan Zhang · Olof Ramström
    15th Brazilian Meeting on Organic Synthesis; 12/2013
  • Lei Hu · Fredrik Schaufelberger · Yan Zhang · Olof Ramström
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    ABSTRACT: The anti-HIV nucleoside lamivudine was asymmetrically synthesized in only three steps via a novel surfactant-treated subtilisin Carlsberg-catalyzed dynamic kinetic resolution protocol. The enantiomer of lamivudine could also be accessed using the same protocol catalyzed by Candida antarctica lipase B.
    Chemical Communications 09/2013; 45(12). DOI:10.1039/c3cc45551c · 6.83 Impact Factor
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    ABSTRACT: A new microarray platform, based on lectin super-microarrays and glycans labeled with dye-doped nanoparticles, has been developed to study glycan-lectin interactions. Glycan ligands were conjugated onto fluorescein-doped silica nanoparticles (FSNPs) using a general photocoupling chemistry to afford FSNP-labeled glycan probes. Lectins were printed on epoxy slides in duplicate sets to generate lectin super-microarrays where multiple assays could be carried out simultaneously in each lectin microarray. Thus, the lectin super-microarray was treated with FSNP-labeled glycans to screen for specific binding pairs. Furthermore, a series of ligand competition assays were carried out on a single lectin super-microarray to generate the dose-response curve for each glycan-lectin pair, from which the apparent affinity constants were obtained. Results showed 4-7 orders of magnitude increase in affinity over the free glycans with the corresponding lectins. Thus, the glycan epitope structures having weaker affinity than the parent glycans could be readily identified and analyzed from the lectin super-microarrays.
    Biosensors & Bioelectronics 03/2013; 47C:258-264. DOI:10.1016/j.bios.2013.03.014 · 6.45 Impact Factor
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    Xin Wang · Oscar Norberg · Lingquan Deng · Olof Ramström · Mingdi Yan
    03/2013;

Publication Stats

3k Citations
565.35 Total Impact Points

Institutions

  • 2002–2015
    • KTH Royal Institute of Technology
      • • Department of Chemistry
      • • Division of Organic Chemistry
      Tukholma, Stockholm, Sweden
  • 2009–2013
    • Portland State University
      • Department of Chemistry
      Portland, Oregon, United States
  • 2012
    • Huazhong University of Science and Technology
      • Department of Chemical Engineering
      Wu-han-shih, Hubei, China
  • 2000–2011
    • University of Strasbourg
      Strasburg, Alsace, France
  • 1993–2002
    • Lund University
      • Division of Pure and Applied Biochemistry
      Lund, Skåne, Sweden