| | 2 | Author
| GlennH. Penner3, Baiyi Zhaoa, KennethR. Jeffrey0 | Requires cookie* | | | Title
|  | | | | Abstract
| The molecular dynamics of solid (CH3)3NBH3 is investigated by deuterium NMR spectroscopy. Variable temperature lineshape analyses yield activation energies of 27 + 3, 19 + 2, and 12.5 ± 2 kJ/mol for -CH3, -N(CH3)3 and -BH3 rotation, respectively. Analysis of the temperature depen dence of the spin-lattice relaxation times, Tt , gives activation energies of 33 + 3, 15 + 1.5, and 14 + 1.5 kJ/mol, respectively. Direct comparison of rotational exchange rates (from lineshape simu lations) an of rotational correlation times (from Tx analyses) for -N(CH3)3 and -BH3 rotation indicate that the two motions are correlated in solid (CH3)3NBH3 and together constitute a whole molecule reorientation about the N-B bond. This is supported by an internal rotational barrier of 18.0 kJ/mol for-BH3 rotation, obtained from ab initio molecular orbital calculations at the MP2/6-31G* level. | | | |
Reference
| Z. Naturforsch. 50a, 81—89 (1995); received September 22 1994 | | | |
Published
| 1995 | | | |
Keywords
| NMR spectroscopy, Molecular dynamics, NMR relaxation | | | |
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| | | | | TEI-XML for
| default:Reihe_A/50/ZNA-1995-50a-0081.pdf | | | | Identifier
| ZNA-1995-50a-0081 | | | | Volume
| 50 | |
| 3 | Author
| Jürgen Schiller, Jürgen Arnhold, Klaus Arnold | Requires cookie* | | | Title
| Nuclear Magnetic Resonance and Mass Spectrometric Studies on the Action of Proteases on Pig Articular Cartilage | | | | Abstract
| Rheumatic diseases are accompanied by a progradient diminution of the cartilage layer. Unfortunately, degradation mechanisms (role of different enzymes and reactive oxygen spe cies) are not yet understood. Since nuclear magnetic resonance (NM R) spectroscopy was often used for the investigation of synovial fluids, the aim of the present work was to detect cartilage degradation products upon proteolytic digest of cartilage. Cartilage samples were incubated at 37 °C with phosphate buffer in the absence or pres ence of different proteases (collagenase, trypsin and papain). Supernatants were subsequently assayed towards their content of carbohydrate and protein degradation products by NMR ('H-and 13C-) and M ALD I-TOF mass spectrometry. Intense resonances of relatively mobile N-acetyl side chains (ca. 2.01 ppm) of polysaccha rides of cartilage were only detectable on digestion with papain. The appearance of these resonances indicates intense degradation of the core protein of proteoglycan aggregate of cartilage, whereby polysaccharides are released. Additionally, broad resonances at 0.85 ppm arising from collagen degradation products were observed upon the action of all applied proteases. However, glycine as a m arker of exhaustive collagen degradation was only ob served, if cartilage was digested by collagenase. Using more vigorous incubation conditions, additionally high-abundant amino acids of collagen (proline, hydroxyproline) could be de tected in the 13C-NMR-and the M ALDI spectra. The observed differences are correlated with the different selectivities of the applied enzymes. It is concluded that NMR allows the detection of characteristic protein and polysaccharide degradation products. The observed differences may be of some relevance for the diagnosis of rheumatic diseases. | | | |
Reference
| Z. Naturforsch. 53c, 1072—1080 (1998); received July 17/August 21 1998 | | | |
Published
| 1998 | | | |
Keywords
| Pig A rticular Cartilage, NMR Spectroscopy, Papain, Trypsin, Collagenase | | | |
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| default:Reihe_C/53/ZNC-1998-53c-1072.pdf | | | | Identifier
| ZNC-1998-53c-1072 | | | | Volume
| 53 | |
| 4 | Author
| Lech Dudycz, Ryszard Stolarski, Reynaldo Pless, David Shugar | Requires cookie* | | | Title
| A 1H NM R Study of the Syn-Anti Dynamic Equilibrium in Adenine Nucleosides and Nucleotides with the Aid of Some Synthetic Model Analogues with Fixed Conformations | | | | Abstract
| The syn-anti equilibrium about the glycosidic bond in adenosine and some related analogues was studied by means of *H NMR spectroscopy, with the aid of several model analogues fixed in given conformations either by intramolecular bonding, or by introduction of a bulky substituent. A model unambiguously and exclusively in the syn conformation is 8-(a-hydroxyisopropyl) adenosine; while one fixed in the a n ti conformation is 8,5'-anhydro-8-oxoadenosine. A new analogue, fixed in the high an ti conformation, is 8,2'-0-isopropylidenearabinofuranosyladenine. Several additional new model compounds were synthesized and their properties are described. With the aid of these models, the syn-anti dynamic equilibrium was examined for adenosine and some related compounds in different solvent systems, and the conformer populations evaluated quantitatively. The validity of the procedure applied, and the accuracy of the results, are critically examined, and compared with findings obtained by other procedures. Available literature data on the syn-anti equilibrium in other 8-substituted adenosines are re analyzed in the light of the present results. An analysis is also presented of the interdependence of the various conformational parameters, i. e. conformation about the glycosidic bond and those of the sugar ring and exocyclic carbinol group, in adenosine and 2',3'-0-isopropylideneadenosine. | | | |
Reference
| Z. Naturforsch. 34c, 359 (1979); received November 21 1978 | | | |
Published
| 1979 | | | |
Keywords
| NMR Spectroscopy, Conformation, S yn -A n ti Equilibrium, Purine Nucleosides and Nucleotides, Chemical Syntheses | | | |
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| default:Reihe_C/34/ZNC-1979-34c-0359.pdf | | | | Identifier
| ZNC-1979-34c-0359 | | | | Volume
| 34 | |
| 5 | Author
| Reynaldo Pless, Lech Dudycz, Ryszard Stolarski, David Shugar | Requires cookie* | | | Title
| Purine Nucleosides and Nucleotides Unequivocally in the Syn Conformation' .Guanosine and 5-GM P with 8-ter/-Butyl and 8-( ß-Hydroxyisopropyl) Substituents | | | |
Reference
| Z. Naturforsch. 33c, 902 (1978); received July 3 1978 | | | |
Published
| 1978 | | | |
Keywords
| 8 -Substituted Purines, Purine Nucleosides, Nucleotides, NMR Spectroscopy, Conformation, S yn -A n ti E quilibrium, 5'-Nucleotidase | | | |
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| default:Reihe_C/33/ZNC-1978-33c-0902.pdf | | | | Identifier
| ZNC-1978-33c-0902 | | | | Volume
| 33 | |
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