Synthesis of cytidine ribonucleotides by stepwise assembly of the heterocycle on a sugar phosphate

Although various syntheses of the nucleic acid bases exist and ribose is a product of the formose reaction, no prebiotically plausible methods for attaching pyrimidine bases to ribose to give nucleosides have been described. Kinetic and thermodynamic factors are thought to mitigate against such condensation reactions in aqueous solution. This inability to produce pyrimidine nucleosides and hence nucleotides is a major stumbling block of the "RNA World" hypothesis and has led to suggestions of alternative nucleic acids as evolutionary precursors to RNA. Here, we show that a process in which the base is assembled in stages on a sugar phosphate can produce cytidine nucleotides. The sequential action of cyanamide and cyanoacetylene on arabinose-3-phosphate produces cytidine-2',3'-cyclophosphate and arabinocytidine-3'-phosphate.     

5',6'-nucleoside phosphonate analogues architecture: synthesis and comparative evaluation towards metabolic enzymes

Nucleoside phosphonates have been designed as stable 5'-mononucleotide mimics and are nowadays considered a potent class of antiviral agents. Within cells, they must be metabolised to the corresponding diphosphate to exert their biological activity. In this process, the first phosphorylation step, catalysed by nucleoside monophosphate kinases (NMP kinases), has been proposed as a bottleneck. Herein, we report the synthesis of a series of ribonucleoside phosphonate derivatives isosteric to 5'-mononucleotides, with different degrees of flexibility within the 5',6'-C-C bond, as well as different polarities, through the introduction of hydroxy groups. The influence of these modifications on the capacity of the compounds to act as substrates for appropriate human NMP kinases, involved in nucleic acids metabolism, has been investigated. Low flexibility, as well as an absence of hydroxy groups within the ribose-phosphorus architecture, is critical for efficient phosphotransfer. Among the series of pyrimidine analogues, one derivative was shown to be phosphorylated by human UMP-CMP kinase, with rates similar to those of dUMP and even better than dCMP.     

应用响应面法优化虫草发酵核苷类物质

采用响应面法(RSM)对冬虫夏草茵(Cordycepssinensis)CS-wx液态发酵生产核苷类物质的3种主要培养基成分——麦芽糖、葡萄糖和蛋白胨进行优化，采用多元二次回归方程拟合3种因素与核苷类物质含量为响应值之间的函数关系。经回归分析表明，上述3种因素对核苷类物质的含量有显著影响。通过岭脊分析获得对核苷类物质含量有显著影响的因素最佳浓度为：麦芽糖2.17％，葡萄糖2.95％，蛋白胨2.74％，通过HPLC法检测腺苷含量为1.02mg／g，较原始培养基腺苷含量0.85mg／g提高了20％。     

Polymerase Synthesis of DNAs Bearing Vinyl Groups in the Major Groove and their Cleavage by Restriction Endonucleases

DNA molecules containing 5‐vinyluracil, 5‐vinylcytosine, or 7‐deaza‐7‐vinyladenine were prepared by polymerase incorporation of the corresponding vinyl‐modified 2′‐deoxyribonucleoside triphosphates, and the influence of the vinyl group in the major groove of DNA on the cleavage by diverse type II restriction endonucleases (REs) was studied. The presence of 5‐vinyluracil was tolerated by most of the REs, whereas only some REs were able to cleave sequences containing 7‐deaza‐7‐vinyladenine. The enzyme ScaI was found to cleave DNA containing 5‐vinylcytosine efficiently but not DNA containing the related 5‐ethynylcytosine. All other REs failed to cleave sequences containing any cytosine modifications.     

Quality Changes of Deepwater Pink Shrimp (Parapenaeus longirostris) Packed in Modified Atmosphere

ABSTRACT: The storage of deepwater pink shrimp ( Parapenaeus longirostris ) in modified atmosphere was studied. Two gas mixtures were tested (40% CO₂/30% O₂/30% N₂ and 45% CO₂/5% O₂/50% N₂), combined with sulfites-based pretreatment, in comparison with air storage. The quality of shrimp was evaluated by sensory (black spot presence) and chemical analyses (pH value and nucleotides breakdown products). Generally, both atmospheres preserved the shrimp quality up to 9 d compared with 4 to 7 d of ice storage (only with pretreatment), although it seems that atmosphere containing 45% CO₂/5% O₂/50% N₂ was the most effective.     

不同剂量60Co-γ射线辐照对烟鸡胸肉贮藏过程中滋味的影响

目的 研究60Co-γ 辐照对烟鸡胸肉菌落总数、感官和滋味成分的影响,探讨其在烟鸡胸肉保鲜中的可行性。方法 采用食品中菌落总数测量烟鸡胸肉的菌落总数,全自动氨基酸分析仪测量游离氨基酸,高效液相法测量呈味核苷酸、有机酸,并结合感官评定法分析辐照处理对烟鸡胸肉滋味和质量的影响。结果 辐照能够有效杀菌并延长烟鸡胸肉的货架期,促进鲜味和甜味游离氨基酸的增加,减少苦味游离氨基酸。辐照处理后2~4 kGy的呈味核苷酸腺苷-5′-二磷酸(ADP)和腺苷-5′-一磷酸(AMP)减少,但肌苷-5′-一磷酸(IMP)无显著变化,6 kGy则显著增加IMP,辐照对烟鸡胸肉的鲜味具有提升作用。2~4 kGy辐照处理,丙酮酸含量有所减少。贮藏过程中,对照组和辐照组的感官评价均显著下降(P<0.05)。3和4 kGy的鲜味和甜味游离氨基酸含量维持较好,4和6 kGy的呈甜味和鲜味核苷酸下降最少,3和4 kGy的丙酮酸含量下降最少,2和6 kGy的苹果酸含量下降较少。结论 3和4 kGy剂量的60Co-γ 辐照对烟鸡胸肉滋味成分和感官评价没有明显的负面影响,并能有效延缓烟鸡胸肉的货架期。     

Fluorescent N2,N3-epsilon-adenine nucleoside and nucleotide probes: synthesis, spectroscopic properties, and biochemical evaluation

N1,N(6)-ethenoadenine, epsilon-A, nucleos(t)ides have been previously applied as fluorescent probes in numerous biochemical systems. However, these epsilon-A analogues lack the H-bonding capability of adenine. To improve the fluorescence characteristics while preserving the H-bonding pattern required for molecular recognition, we designed a novel probe: N(2),N3-etheno-adenosine, (N(2),N3-epsilon-A). Here, we describe four novel syntheses of the target epsilon-nucleoside and related analogues. These methods are short, facile, and provide the product regiospecifically. In addition, we report the absorption and emission spectra of N(2),N3-epsilon-A and the dependence of the spectral features on the pH and polarity of the medium. Specifically, maximum emission of N(2),N3-epsilon-A in water is observed at 420 nm (phi=0.03, excitation at 290 nm). The biochemical relevance of the new probe was evaluated with respect to the P2Y(1) receptor and NTPDases 1 and 2. N(2),N3-epsilon-ATP was found to be almost equipotent with ATP at the P2Y(1) receptor and was hydrolyzed by NTPDases 1 and 2 at about 80 % of the rate of ATP. Furthermore, protein binding does not seem to shift the fluorescence of N(2),N3-epsilon-ATP. Based on the fluorescence and full recognition by ATP-binding proteins, we propose N(2),N3-epsilon-ATP and related nucleo(s)tides as unique probes for the investigation of adenine nucleo(s)tide-binding proteins as well as for other biochemical applications.     

核苷酸营养功能研究进展及应用现状

近年来的研究表明,核苷酸是一种无毒、无害的安全型饲料添加剂,它在动物的营养方面有着重要的作用。近年来,国内外学者对核苷酸在营养功能方面的研究越来越多。本文主要是从促进动物生长发育、肠胃道发育以及改善免疫系统等方面对核苷酸在动物营养方面的研究进展和应用做一综述。