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Thorson R.A.,University of Wisconsin - Stevens Point | Woller G.R.,University of Wisconsin - Stevens Point | Driscoll Z.L.,University of Wisconsin - Stevens Point | Geiger B.E.,University of Wisconsin - Stevens Point | And 7 more authors.
European Journal of Organic Chemistry | Year: 2015

A model system for the investigation of intramolecular halogen bonds is introduced. Two molecules capable of intramolecular halogen bonding have been studied in comparison with eight control compounds by 15N, 13C, and 19F NMR spectroscopy. Iodine- and bromine-centered halogen bonds are indicated by decreases in the 15N NMR chemical shifts of the halogen bond acceptor atom of approximately 6 and 1 ppm, respectively. 13C NMR chemical shifts of the alkynyl carbons in 2-ethynylpyridine systems are good indicators of halogen bonding, with differences of up to 2.4 ppm between halogen-bonded and related control compounds. Halogen bond strengths in different solvents, as indicated by 19F NMR chemical shifts, decrease in the following order: Cyclohexane > toluene > benzene > dichloromethane > acetone > pyridine. Chemical shift effects associated with the structural and electronic properties of intramolecular halogen-bonded systems are modeled well by calculations at the B3LYP/6-311+G(2d,p) level of theory. © 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Erdelyi M.,Gothenburg University | Erdelyi M.,Swedish Center
Chemical Society Reviews | Year: 2012

Halogen bonding is the electron density donation based weak interaction of halogens with Lewis bases. Its applicability for molecular recognition processes long remained unappreciated and has so far mostly been studied in silico and in solid state. As most physiological processes and chemical reactions take place in solution, investigations in solutions are of highest relevance for its use in the pharmaceutical and material scientific toolboxes. Following a short discussion of the phenomenon of halogen bonding, this tutorial review presents an overview of the methods hitherto applied for gaining an improved understanding of its behaviour in solutions and summarizes the gained knowledge in order to indicate the scope of the techniques and to facilitate exciting future developments. © The Royal Society of Chemistry 2012. Source

Carlsson A.-C.C.,Gothenburg University | Grafenstein J.,Gothenburg University | Budnjo A.,Gothenburg University | Budnjo A.,University of Bergen | And 8 more authors.
Journal of the American Chemical Society | Year: 2012

Halogen bonding is a recently rediscovered secondary interaction that shows potential to become a complementary molecular tool to hydrogen bonding in rational drug design and in material sciences. Whereas hydrogen bond symmetry has been the subject of systematic studies for decades, the understanding of the analogous three-center halogen bonds is yet in its infancy. The isotopic perturbation of equilibrium (IPE) technique with 13C NMR detection was applied to regioselectively deuterated pyridine complexes to investigate the symmetry of [N-I-N] + and [N-Br-N] + halogen bonding in solution. Preference for a symmetric arrangement was observed for both a freely adjustable and for a conformationally restricted [N-X-N] + model system, as also confirmed by computation on the DFT level. A closely attached counterion is shown to be compatible with the preferred symmetric arrangement. The experimental observations and computational predictions reveal a high energetic gain upon formation of symmetric, three-center four-electron halogen bonding. Whereas hydrogen bonds are generally asymmetric in solution and symmetric in the crystalline state, the analogous bromine and iodine centered halogen bonds prefer symmetric arrangement in solution. © 2012 American Chemical Society. Source

Nilsson J.,Gothenburg University | Halim A.,Gothenburg University | Moslemi A.-R.,Gothenburg University | Pedersen A.,Swedish Center | And 2 more authors.
Biochimica et Biophysica Acta - Molecular Basis of Disease | Year: 2012

Glycogenin-1 initiates the glycogen synthesis in skeletal muscle by the autocatalytic formation of a short oligosaccharide at tyrosine 195. Glycogenin-1 catalyzes both the glucose-O-tyrosine linkage and the α1,4 glucosidic bonds linking the glucose molecules in the oligosaccharide. We recently described a patient with glycogen depletion in skeletal muscle as a result of a non-functional glycogenin-1. The patient carried a Thr83Met substitution in glycogenin-1. In this study we have investigated the importance of threonine 83 for the catalytic activity of glycogenin-1. Non-glucosylated glycogenin-1 constructs, with various amino acid substitutions in position 83 and 195, were expressed in a cell-free expression system and autoglucosylated in vitro. The autoglucosylation was analyzed by gel-shift on western blot, incorporation of radiolabeled UDP- 14C-glucose and nano-liquid chromatography with tandem mass spectrometry (LC/MS/MS). We demonstrate that glycogenin-1 with the Thr83Met substitution is unable to form the glucose-O-tyrosine linkage at tyrosine 195 unless co-expressed with the catalytically active Tyr195Phe glycogenin-1. Our results explain the glycogen depletion in the patient expressing only Thr83Met glycogenin-1 and why heterozygous carriers without clinical symptoms show a small proportion of unglucosylated glycogenin-1. © 2011 Elsevier B.V. Source

Bedin M.,Gothenburg University | Karim A.,Gothenburg University | Reitti M.,Gothenburg University | Carlsson A.-C.C.,Gothenburg University | And 11 more authors.
Chemical Science | Year: 2015

A detailed investigation of the influence of counterions on the [N-I-N]+ halogen bond in solution, in the solid state and in silico is presented. Translational diffusion coefficients indicate close attachment of counterions to the cationic, three-center halogen bond in dichloromethane solution. Isotopic perturbation of equilibrium NMR studies performed on isotopologue mixtures of regioselectively deuterated and nondeuterated analogues of the model system showed that the counterion is incapable of altering the symmetry of the [N-I-N]+ halogen bond. This symmetry remains even in the presence of an unfavorable geometric restraint. A high preference for the symmetric geometry was found also in the solid state by single crystal X-ray crystallography. Molecular systems encompassing weakly coordinating counterions behave similarly to the corresponding silver(i) centered coordination complexes. In contrast, systems possessing moderately or strongly coordinating anions show a distinctly different behavior. Such silver(i) complexes are converted into multi-coordinate geometries with strong Ag-O bonds, whereas the iodine centered systems remain linear and lack direct charge transfer interaction with the counterion, as verified by 15N NMR and DFT computation. This suggests that the [N-I-N]+ halogen bond may not be satisfactorily described in terms of a pure coordination bond typical of transition metal complexes, but as a secondary bond with a substantial charge-transfer character. © The Royal Society of Chemistry 2015. Source

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