排序方式: 共有61条查询结果,搜索用时 15 毫秒
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Matulic-Adamic J Daniher AT Karpeisky A Haeberli P Sweedler D Beigelman L 《Nucleosides, nucleotides & nucleic acids》2001,20(4-7):1113-1115
2'-Modified pyrimidine nucleoside 5'-triphosphates comprising amino, imidazole and carboxylate functionality attached to the 5-position of the base were synthesized. Two different phosphorylation methods were used to optimize the yields of these highly modified triphosphates. 相似文献
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Earnshaw DJ Hamm ML Piccirilli JA Karpeisky A Beigelman L Ross BS Manoharan M Gait MJ 《Biochemistry》2000,39(21):6410-6421
The hairpin ribozyme achieves catalytic cleavage through interaction of essential nucleotides located in two distinct helical domains that include internal loops. Initial docking of the two domains is ion dependent and appears to be followed by a structural rearrangement that allows the ribozyme to achieve a catalytically active state that can undergo cleavage. The proposed structural rearrangement may also be ion dependent and is now of increased importance due to recent evidence that docking is not rate limiting and that metal ions are unlikely to be involved in the chemical cleavage step. An initial structural model of the docked hairpin ribozyme included a proposal for a ribose zipper motif that involves two pairs of hydroxyl groups at A(10) and G(11) in domain A pairing with C(25) and A(24) in domain B, respectively. We have used a chemical functional group substitution technique to study whether this proposed ribose zipper is likely to be present in the active, conformationally rearranged ribozyme that is fit for cleavage. We have chemically synthesized a series of individually modified hairpin ribozymes containing 2'-analogues of nucleosides, that include 2'-deoxy and 2'-deoxy-2'-fluoro at each of the four nucleoside positions, 2'-amino-2'-deoxy, 2'-deoxy-2'-thio, and 2'-arabino at position C(25), and 2'-oxyamino at position A(10), as well as some double substitutions, and we studied their cleavage rates under both single- and multiple-turnover conditions. We conclude that at least some of the hydrogen-bonding interactions in the ribose zipper motif, either as originally proposed or in a recently suggested structural variation, are unlikely to be present in the active rearranged form of the ribozyme that undergoes cleavage. Instead, we provide strong evidence for a very precise conformational positioning for the residue C(25) in the active hairpin. A precise conformational requirement would be expected for C(25) if it rearranges to form a base-triple with A(9) and the essential residue neighboring the cleavage site G(+1), as recently proposed by another laboratory. Our results provide further support for conformational rearrangement as an important step in hairpin ribozyme cleavage. 相似文献
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Effects of divalent cations on beta-cell electrical activity 总被引:1,自引:0,他引:1
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Jasenka Matulic-Adamic Peter Haeberli Anthony B. DiRenzo Victor R. Mokler Lara Maloney Leonid Beigelman 《Nucleosides, nucleotides & nucleic acids》2013,32(10-11):1933-1950
Abstract Novel 5′-amino-5′-deoxy-2′-O-methyl uridine, guanosine and adenosine 3′-O-phosphoramidites 5, 11, and 20, as well as protected 5′-mercapto-5′-deoxy-2′-O-methyl uridine 3′-O-phosphoramidite 23 were synthesized from 2′-O-methyl nucleosides. These analogs were incorporated at the 5′-ends of hammerhead ribozymes to evaluate achiral bridging 5′-N- phosphoramidates and 5′-S-phosphorothioates as alternatives for non- bridging phosphorothioates commonly used for end stabilization against nucleases. Oligonucleotide synthesis and deprotection conditions were optimized for better yields of these modified ribozymes. 相似文献
25.
Leonid Beigelman Alexander Karpeisky Jasenka Matulic-Adamic Nassim Usman 《Nucleosides, nucleotides & nucleic acids》2013,32(3-5):421-425
Abstract Three different approaches to the synthesis of 2′-O-methyl nucleosides starting from the corresponding nucleoside or commercially available 1,2:5,6-di-O-isopropylidene-α-D-allofuranose 1 are described. 相似文献
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Insulin from individual isolated mouse islets of Langerhans 总被引:1,自引:0,他引:1
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