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Kouwijzer MLCE, van Eijck BP, Kooijman H, Kroon J. An extension of the GROMOS force field for carbohydrates, resulting in improvement of the crystal structure determination of α-D-galactose. ACTA CRYSTALLOGRAPHICA SECTION B: STRUCTURAL SCIENCE 1995. [DOI: 10.1107/s0108768194011262] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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127
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van Eijck BP, Mooij WTM, Kroon J. Attempted prediction of the crystal structures of six monosaccharides. ACTA CRYSTALLOGRAPHICA SECTION B: STRUCTURAL SCIENCE 1995. [DOI: 10.1107/s0108768194009651] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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128
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Verdonk ML, Tjerkstra RW, Ridder IS, Kanters JA, Kroon J, van der Kemp WJM. ToBaD: A method for the estimation of torsion barriers from crystal structure data; conformational analysis ofN,N-dimethylaniline and derivatives. J Comput Chem 1994. [DOI: 10.1002/jcc.540151212] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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129
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Matholouthi M, Angiboust J, Kacurakova M, Hooft R, Kanters J, Kroon J. Structural studies on sweet taste inhibitors: lactisole, dl-2(4-methoxyphenoxy)-propanoic acid. J Mol Struct 1994. [DOI: 10.1016/0022-2860(94)08328-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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130
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van Wyk PJ, Kroon J, Cleaton-Jones PE. Geographical distribution of dental operators in South Africa over the period 1972-1992. THE JOURNAL OF THE DENTAL ASSOCIATION OF SOUTH AFRICA = DIE TYDSKRIF VAN DIE TANDHEELKUNDIGE VERENIGING VAN SUID-AFRIKA 1994; 49:457-62. [PMID: 9508980] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Using data available on dentists for 1972, 1982 and 1992 and on dental therapists for 1992 the geographical distribution of dental operators (dentists/dental therapists) in South Africa was determined and the dental operator to population ratios were calculated. Over a period of 20 years the number of dentists in South Africa has increased by 135,6 per cent while the total population of the area has increased by 59,8 per cent. The lowest operator to population ratio was 1:4517 found in the PWV region, and the highest ratio was 1:48730, recorded in the Northern Transvaal. The greatest decrease in dental operator to population ratios occurred in Natal and Transvaal. The study shows that there is an imbalance in the geographic distribution of dental operators favouring large urban areas.
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Verhoeven J, Wegewijs B, Kroon J, Rettschnick R, Paddon-Row M, Oliver A. Rigid donor—bridge—acceptor systems: photoinduced charge transfer in solution and in a supersonic jet. J Photochem Photobiol A Chem 1994. [DOI: 10.1016/1010-6030(94)87011-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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132
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Kroon J, Kroon-Batenburg L, Leeflang B, Vliegenthart J. Intramolecular versus intermolecular hydrogen bonding in solution. J Mol Struct 1994. [DOI: 10.1016/0022-2860(94)87018-7] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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133
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Schouten A, Kanters JA, Kroon J, Plate R, Kelder J. Structure of Org 32763: 3-methoxyiminoquinuclidinium chloride. Acta Crystallogr C 1994. [DOI: 10.1107/s0108270193007504] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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134
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Kroon J, Souer E, de Graaff A, Xue Y, Mol J, Koes R. Cloning and structural analysis of the anthocyanin pigmentation locus Rt of Petunia hybrida: characterization of insertion sequences in two mutant alleles. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 1994; 5:69-80. [PMID: 8130799 DOI: 10.1046/j.1365-313x.1994.5010069.x] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Anthocyanin biosynthesis in flowers of Petunia hybrida is controlled by the regulatory genes an1, an2 and an11. Seven classes of cDNA clones homologous to transcripts that are down-regulated in an1-, an2- and an11- mutants were isolated via differential cDNA cloning. Genetic mapping, antisense RNA experiments and analyses of mutant alleles demonstrated that one class of clones originated from the Rt locus. The rt gene has no introns and encodes a protein with homology to mammalian glucuronosyl transferases and flavonoid 3-O-glucosyltransferase (UF3GT) encoded by the bz1 gene from Zea mays. As the Rt locus controls the rhamnosylation of reddish anthocyanin-3-O-glucosides which is the first in a series of modifications that finally yield magenta or blue/purple coloured anthocyanins, this suggests that rt encodes an anthocyanin rhamnosyl transferase. Molecular analysis of two mutant rt alleles showed that their expression is blocked by different DNA insertion elements. Mutability of the rt-vu15 allele results from the presence of a 284 bp transposable element (dTph1) in the rt promoter region, causing a block in transcription. The protein coding region of the rt-r27 allele contains a 442 bp insertion (dTph3) resulting in premature polyadenylation of rt transcripts. Although dTph3 cannot transpose, it has sequence characteristics of transposable elements, suggesting that it is a defective member of a new family of transposable elements.
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135
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Kouwijzer M, Van Eijck B, Kroes S, Kroon J. Comparison of two force fields by molecular dynamics simulations of glucose crystals: Effect of using ewald sums. J Comput Chem 1993. [DOI: 10.1002/jcc.540141104] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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136
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Verwer P, Ravelli RBG, Krabbendam H, Kroon J. Application of the sparse density principle: a statistical evaluation of the phase ambiguity in the single-wavelength anomalous scattering method (SAS). Z KRIST-CRYST MATER 1993. [DOI: 10.1524/zkri.1993.206.12.45] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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137
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Kroon-Batenburg LM, Kroon J, Leeflang BR. Conformational analysis of methyl beta-cellobioside by ROESY NMR spectroscopy and MD simulations in combination with the CROSREL method. Carbohydr Res 1993; 245:21-42. [PMID: 8358749 DOI: 10.1016/0008-6215(93)80057-l] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Methyl beta-cellobioside has been studied extensively by molecular dynamics (MD) simulations in water and by ROESY NMR spectroscopy in order to establish its solution structure. The MD simulations were started with four significantly different minimal energy conformations. The MD trajectories were analysed with respect to interproton distances and mobility, in order to find models for application in the analysis of NMR data. The ROESY spectra were analysed by using the CROSREL method, which allows quantitative analysis of ROESY spectra through correction for the offset dependence and incorporation of HOHAHA transfer estimates. These results were compared with data obtained from an initial rate analysis of the ROESY data and with the MD data. It is concluded that methyl beta-cellobioside in aqueous solution is in the same extended conformation that is also found in the solid state.
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Verdonk ML, Boks GJ, Kooijman H, Kanters JA, Kroon J. Stereochemistry of charged nitrogen-aromatic interactions and its involvement in ligand-receptor binding. J Comput Aided Mol Des 1993; 7:173-82. [PMID: 8320555 DOI: 10.1007/bf00126443] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Recently, new evidence was found for the involvement of charged nitrogen-aromatic interactions in ligand-receptor binding. In this study we report two favourable orientations of a phenyl ring with respect to a R-N+(CH3)3 group, based on crystal structure statistics from the Cambridge Structural Database. In the first orientation, the phenyl ring is situated in between the substituents at about 4.5 A from the nitrogen atom, and the ring is approximately oriented on the sphere around the nitrogen atom. In the second orientation, the phenyl ring is situated in the same direction as one of the N-C bonds at about 6.0 A from the nitrogen atom, and the ring is tilted with respect to the sphere around the nitrogen atom. The same two orientations were also found in the crystal structures of three ligand-receptor complexes, which implies that these orientations probably play a major role in molecular recognition mechanisms.
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Kooijman H, Kanters JA, Kroon J, Kelder J. Structure and conformation of the muscarinic agonists 3-(3-amino-1,2,4-oxadiazol-5-yl)-1-azabicyclo[2.2.2]octane and 1,2,5,6-tetrahydro-1-methyl-3-pyridinecarboxaldehyde oxime and related tertiary amine, quaternary ammonium and sulfonium analogues. ACTA CRYSTALLOGRAPHICA SECTION B: STRUCTURAL SCIENCE 1993. [DOI: 10.1107/s0108768192008383] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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140
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141
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Kanters JA, Schouten A, Kroon J, Grech E. Complexes of the `proton sponge' 1,8-bis(dimethylamino)naphthalene (DMAN). IV. Structure of [DMANH]2+.[squarate]2− tetrahydrate at 100 K. Acta Crystallogr C 1992. [DOI: 10.1107/s0108270191014348] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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142
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Leeflang BR, Vliegenthart JF, Kroon-Batenburg LM, van Eijck BP, Kroon J. A 1H-NMR and MD study of intramolecular hydrogen bonds in methyl beta-cellobioside. Carbohydr Res 1992; 230:41-61. [PMID: 1511454 DOI: 10.1016/s0008-6215(00)90512-3] [Citation(s) in RCA: 90] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The existence of an HO-3...O-5' intramolecular hydrogen bond in methyl beta-cellobioside in solution in Me2SO-d6 and H2O-CD3OD (4:1 w/w) was studied by 500-MHz 1H-NMR spectroscopy and MD simulations. Temperature coefficients for the chemical shift of the hydroxyl resonances in these solvents were determined and the rates of proton exchange in the latter solvent were obtained from NOE data. With H2O-CD3OD as the solvent, the HO-3...O-5' hydrogen bond was insignificant, but its presence in Me2SO-d6 was confirmed.
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Cafarelli E, Lelbesman J, Kroon J. ADAPTATION IN FORCE SENSATION AFTER ENDURANCE TRAINING. Med Sci Sports Exerc 1992. [DOI: 10.1249/00005768-199205001-00681] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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144
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Kooijman H, van Eijck B, Kroon J. Molecular dynamics simulations of crystal structure containing charged molecules. J Mol Struct 1992. [DOI: 10.1016/0022-2860(92)85077-t] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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145
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Kanters JA, ter Horst EH, Kroon J, Grech E. Complexes of the `proton sponge' 1,8-bis(dimethylamino)naphthalene (DMAN). III. Structure of [DMANH]+.[pentachlorophenolate]−.[pentachlorophenol]2 at 100 K. Acta Crystallogr C 1992. [DOI: 10.1107/s0108270191009459] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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146
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Kanters JA, Schouten A, Kroon J, Grech E. Structure of 8-dimethylamino-1-dimethylammonionaphthalene hydrogen squarate. Acta Crystallogr C 1991. [DOI: 10.1107/s0108270190008988] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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147
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Verwer P, Krabbendam H, Kroon J. The concept of sparse electron density as a tool in structure-factor phase determination. Acta Crystallogr A 1991. [DOI: 10.1107/s0108767391000661] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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148
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van der Sluis P, Kroon J. Conformation of the Xyl-β-(1⇒2)-Man glycosidic linkage. Structure of 3,4,6-tri-O-acetyl-1-O-methyl-2-O-(2,3,4-tri-O-acetyl-β-D-xylopyranosyl)-β-D-mannopyranose. Acta Crystallogr C 1990. [DOI: 10.1107/s0108270190002827] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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149
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Stouten PFW, Kroon J. Computation Confirms Contraction: A Molecular Dynamics Study of Liquid Methanol, Water and a Methanol-Water Mixture. MOLECULAR SIMULATION 1990. [DOI: 10.1080/08927029008022129] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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150
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Van Eijck B, Kroon-Batenburg L, Kroon J. Hydrogen-bond geometry around sugar molecules: comparison of crystal statistics with simulated aqueous solutions. J Mol Struct 1990. [DOI: 10.1016/0022-2860(90)80149-e] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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