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排序方式: 共有335条查询结果,搜索用时 46 毫秒
1.
Stability of XGCGCp, GCGCYp, and XGCGCYp helixes: an empirical estimate of the energetics of hydrogen bonds in nucleic acids 总被引:8,自引:0,他引:8
S M Freier N Sugimoto A Sinclair D Alkema T Neilson R Kierzek M H Caruthers D H Turner 《Biochemistry》1986,25(11):3214-3219
The stabilizing effects of dangling ends and terminal base pairs on the core helix GCGC are reported. Enthalpy and entropy changes of helix formation were measured spectrophotometrically for AGCGCU, UGCGCA, GGCGCCp, CGCGCGp, and the corresponding pentamers XGCGCp and GCGCYp containing the GCGC core plus a dangling end. Each 5' dangling end increases helix stability at 37 degrees C roughly 0.2 kcal/mol and each 3' end from 0.8 to 1.7 kcal/mol. The free energy increments for dangling ends on GCGC are similar to the corresponding increments reported for the GGCC core [Freier, S. M., Alkema, D., Sinclair, A., Neilson, T., & Turner, D. H. (1985) Biochemistry 24, 4533-4539], indicating a nearest-neighbor model is adequate for prediction of stabilization due to dangling ends. Nearest-neighbor parameters for prediction of the free energy effects of adding dangling ends and terminal base pairs next to G.C pairs are presented. Comparison of these free energy changes is used to partition the free energy of base pair formation into contributions of "stacking" and "pairing". If pairing contributions are due to hydrogen bonding, the results suggest stacking and hydrogen bonding make roughly comparable favorable contributions to the stability of a terminal base pair. The free energy increment associated with forming a hydrogen bond is estimated to be -1 kcal/mol of hydrogen bond. 相似文献
2.
Polymer-supported RNA synthesis and its application to test the nearest-neighbor model for duplex stability 总被引:19,自引:0,他引:19
R Kierzek M H Caruthers C E Longfellow D Swinton D H Turner S M Freier 《Biochemistry》1986,25(24):7840-7846
A solid-phase method using a phosphoramidite approach is described for synthesis of oligoribonucleotides. The method was used to synthesize pairs of oligomers with identical nearest neighbors but different sequences. Comparison of thermodynamic parameters for these pairs provides a test of the nearest-neighbor hypothesis for prediction of helix stability. In general, pairs of sequences with identical nearest neighbors have enthalpy and entropy changes for helix formation that differ by 8% on average, delta Go37 that differ by 6% on average, and melting temperatures within 0-5 degrees C of each other. These limits are typical of the accuracy that should be expected from nearest-neighbor predictions of RNA helix stability. UCAUGA and UGAUCA have the same nearest neighbors but melting temperatures that differ by 7 degrees C. This suggests some sequences will not be approximated well by the nearest-neighbor model. 相似文献
3.
The effect of neurotensin on submaximally-stimulated hepatobiliary and pancreatic secretion was studied in 6 healthy subjects. An intravenous infusion of neurotensin 1.4 ± 0.3 pmol/kg/min, designed to reproduce plasma neurotensin immunoreactivity levels within the physiological range, produced a significant increase in pancreatic bicarbonate output. Plasma concentrations of pancreatic polypeptide rose by 83 ± 16 pmol/l and were associated with a small reduction in trypsin, but no significant change in bilirubin outputs. 相似文献
4.
R. Kierzek 《Nucleosides, nucleotides & nucleic acids》2013,32(8):1757-1768
Abstract The effect of eleven different phosphoryl center protecting groups on the stability of trisubstituted internucleotide bond of the dimers (1a-k), in the presence of the vicinal 2′-hydroxyl, was examined. It has been found that electronic properties of the phosphoryl center protecting groups are essential for the reactivity of the trisubstituted internucleotide bond. Those observations were applied to the chemical synthesis of the uridyl(2′-phosphate)-(3′-5′)-uridine, a useful model for further pre-tRNA splicing studies. 相似文献
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Ryszard Kierzek Wojciech T. Markiewicz 《Nucleosides, nucleotides & nucleic acids》2013,32(1-2):403-405
Abstract 5′3′-O-protected 4-N-tosyl-2′-deoxycyt id ine was converted with 1,6-diaminohexane to 4-N-/6-ami nohexyl/-2′-deoxycyt id i ne and then into 5′-0-d imethoxytr i ty 1 -k-N-/(-tr if luoroacetamidohexyl 1–2 ′-deoxycyt id ine, The latter was used to prepare oligonucleotides by the phosphoramidite approach. Deprotected oligomers were labeled with biotin. 相似文献
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AB Zarafi AM Emechebe AD Akpa O Alabi 《Archives Of Phytopathology And Plant Protection》2013,46(4):261-268
Pearl millet downy mildew (DM) incidence, severity and yield losses of two pearl millet varieties (local and improved) due to the disease were determined in the field. Significant differences in the disease incidence and severity were recorded in the plots sown with metalaxyl-treated seeds and those sown with non-treated seeds, indicating the efficacy of the fungicide on the fungus. Yield losses due to non-treatment of seeds with metalaxyl was 40.88 and 45.39% in a local variety and 43.00 and 18.60% in an improved variety in the 2000 and 2001 cropping seasons respectively. Significant differences between plots sown with metalaxyl-treated and those sown with non-treated seeds were obtained for other yield components such as 1000-grains weight, panicle length and weight. 相似文献
10.
Kayigan Wilson d’Almeida Dominique Pateron Gérald Kierzek Bertrand Renaud Caroline Semaille Pierre de Truchis Fran?ois Simon Judith Leblanc France Lert Stéphane Le Vu Anne-Claude Crémieux 《PloS one》2013,8(4)