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用于通过毛细管电泳/质谱法检测苯并[a]芘二醇环氧化物-DNA加合物的选择性消化和新型净化技术。

Selective digestion and novel cleanup techniques for detection of benzo[a]pyrene diol epoxide-DNA adducts by capillary electrophoresis/mass spectrometry.

作者信息

Gennaro Lynn A, Vadhanam Manicka, Gupta Ramesh C, Vouros Paul

机构信息

Department of Chemistry and Chemical Biology and Barnett Institute, Northeastern University, Boston, MA 02115, USA.

出版信息

Rapid Commun Mass Spectrom. 2004;18(14):1541-7. doi: 10.1002/rcm.1516.

Abstract

Benzo[a]pyrene (BP) is a ubiquitous environmental polycyclic aromatic hydrocarbon (PAH) which, upon metabolic conversion to reactive benzo[a]pyrene-7,8-diol-9,10-epoxide (BPDE), has been found to attach covalently to DNA. Given the low level of DNA adducts typically present in vivo or in vitro, an essential first step prior to capillary electrophoresis/mass spectrometry (CE/MS) (or liquid chromatography/mass spectrometry (LC/MS)) analysis of the DNA digests is the removal of the bulk non-adducted nucleotides, enzymes or salts, and isolation of enriched adducts. This report focuses on the development of novel sample handling methods aimed at facilitating the analysis of BPDE-DNA adducts by CE/MS. This approach involves a simple variation on the digestion procedure, in combination with the use of metal affinity ZipTips for the more efficient cleanup of BPDE-DNA adducts formed in vitro for subsequent CE/MS analysis. The previously described digestion procedure, consisting of micrococcal nuclease, spleen phosphodiesterase and nuclease P1, allows for selective dephosphorylation of normal nucleotides, while leaving adducted nucleotides intact. Metal affinity ZipTips, typically used for selective extraction of phosphopeptides, were used here for extraction of adducted nucleotides. The utility of metal affinity SPE was tested on mixtures of dG and dGp, wherein nucleotide extracts contained no detectable nucleosides by CE/UV analysis. An in vitro BPDE-DNA incubation was then digested using the above procedure. Metal affinity solid-phase extraction (SPE) was subsequently used for the selective isolation of phosphorylated components, i.e., adducted nucleotides, from the mixture of enzymes and non-adducted nucleosides. SPE extracts were enriched in nucleotide adducts and analyzed using sample stacking and CE/MS. This method has several advantages over previously described cleanup procedures for dGp-BPDE adducts: fast, simple, uses commercially available materials, no need for excessive dilution (small scale), the suitability for use with automation, and possible applicability to other bulky hydrophobic adducts.

摘要

苯并[a]芘(BP)是一种普遍存在的环境多环芳烃(PAH),经代谢转化为具有反应活性的苯并[a]芘-7,8-二醇-9,10-环氧化物(BPDE)后,已发现其能与DNA共价结合。鉴于体内或体外通常存在的DNA加合物水平较低,在对DNA消化产物进行毛细管电泳/质谱(CE/MS)(或液相色谱/质谱(LC/MS))分析之前,关键的第一步是去除大量未加合的核苷酸、酶或盐,并分离富集的加合物。本报告重点关注新型样品处理方法的开发,旨在促进通过CE/MS对BPDE-DNA加合物进行分析。该方法涉及对消化程序进行简单修改,并结合使用金属亲和ZipTip,以便更有效地净化体外形成的BPDE-DNA加合物,用于后续的CE/MS分析。先前描述的消化程序由微球菌核酸酶、脾脏磷酸二酯酶和核酸酶P1组成,可使正常核苷酸选择性去磷酸化,同时使加合的核苷酸保持完整。通常用于选择性提取磷酸肽的金属亲和ZipTip在此用于提取加合的核苷酸。在dG和dGp的混合物上测试了金属亲和固相萃取(SPE)的效用,通过CE/UV分析,核苷酸提取物中未检测到核苷。然后使用上述程序消化体外BPDE-DNA孵育物。随后使用金属亲和固相萃取(SPE)从酶和未加合核苷的混合物中选择性分离磷酸化成分,即加合的核苷酸。SPE提取物富含核苷酸加合物,并使用样品堆积和CE/MS进行分析。与先前描述的dGp-BPDE加合物净化程序相比,该方法具有几个优点:快速、简单、使用市售材料、无需过度稀释(小规模)、适用于自动化以及可能适用于其他大分子疏水加合物。

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