Sequencing the exposome: developing an integrated approach using nontargeted mass spectrometry and computational chemistry

暴露量包括一生中环境暴露的总和。在化学和化学生物学中，这些暴露表现为内源性和外源性化学物质，由饮食、生活方式、辐射、压力和暴露于环境污染物引起。与基因组不同，暴露体是可变的，因此需要对随时间变化的暴露进行频繁、具有成本效益和可靠的测量，最合适的方法是取样少量血液（如干血斑）。这种测量对于确定大多数慢性疾病的病因至关重要，但取得进一步进展的障碍是巨大的：c.使用现有的分析平台无法检测到滴血中90%的未知污染物；大多数环境毒物的特性及其在引起慢性疾病中的作用都是未知的！我们小组的研究将通过开发创新的质谱（MS）技术来解决这些挑战，即流动调制多维气相色谱-大气压电离（GCxGC-API），辅以最先进的计算工具。所提出的分析平台提供了无与伦比的分离，并且在与可适应高流量的API源相结合时显著提高了检测极限。尽管有这样的承诺，但以前从未有人尝试过！这种方法的发展将能够：用3-50微升血液（1博士，1学士）识别未知污染物，这是对现有方法的显著改进，需要集中采样和过量血容量（100毫升）；创新的电离（1个MSc）和激活（1个PhD， 1个BSc）连接技术，将为识别未知毒物提供急需的新信息。非靶向筛选（NTS）是旨在利用质谱鉴定未知有机化合物的定性实验的技术术语。普遍认为，在评估环境意义之前，必须先阐明化合物的结构，但考虑到样品的复杂性，这种方法是不切实际的。我们认为，一种未知化学物质的环境意义可以从其在质谱仪中的行为（和反应性）推断出来，而无需先验地了解其结构。我实验室的学员将：开发加速污染物发现的自动化软件（1名博士，1名理学士）；研究和利用质谱仪中丰富的化学物质，反映体内代谢，可用于区分有毒和无毒化学物质（1个博士学位，1个学士学位）；最后，进行调查研究（3个理学硕士，1个理学学士），旨在回答这个问题：这些新发现的污染物对环境和健康构成什么风险？预计该研究项目的结果将有助于指导有效环境法规的制定；并指导行业开发更安全、更可持续的化学品。

The exposome encompasses the totality of environmental exposures during a lifetime. In chemistry and chemical biology, these exposures manifest as endogenous and exogenous chemicals that result from diet, lifestyle, radiation, stress, and exposure to environmental pollutants. Unlike the genome, the exposome is variable and thus requires frequent, cost-effective and reliable measurements of exposures that evolve over time, most appropriately by sampling small quantities of blood (e.g. dried-blood spots). Such measurements will be vital in order to identify the causes of most chronic diseases, but the obstacles to further progress are formidable: c. 90% of unknown pollutants in a drop of blood are not detectable using existing analytical platforms; and the identities of most environmental toxicants and their role in causing chronic disease are unknown! My group's research will address these challenges through the development of innovative mass spectrometry (MS) techniques, viz. flow modulated multidimensional gas chromatography-atmospheric pressure ionization (GCxGC-API), complemented by state-of-the-art computational tools. The proposed analytical platform affords unparalleled separation and significantly improves detection limits when coupled with an API source that is resilient to high flows. Despite its promise, this has not been previously attempted! The development of this approach will enable: the identification of unknown pollutants with 3-50 microliters of blood (1 PhD, 1 BSc), a remarkable improvement over existing methodologies that require pooled sampling and excessive blood volumes >300uL; and innovative hyphenation of ionization (1 MSc) and activation (1 PhD, 1 BSc) techniques that will provide new information critically needed to identify unknown toxicants. Nontargeted screening (NTS) is the term-of-art for qualitative experiments aimed at identifying unknown organic compounds using MS. The prevailing thought is that a compound's structure must be elucidated prior to assessing environmental significance, but this approach is impractical considering sample complexity. We suggest that that the environmental significance of an unknown chemical may be inferred from its behavior (and reactivity) in the mass spectrometer without a priori knowledge of its structure. Trainees in my lab will: develop automated software that accelerates pollutant discovery (1 PhD, 1 BSc); investigate and exploit the rich chemistry occurring in the mass spectrometer that mirrors in vivo metabolism and can be used to differentiate toxic from non-toxic chemicals (1 PhD, 1 BSc); and finally, conduct reconnaissance studies (3 MSc, 1 BSc) aimed at answering the question: What risk do these newfound pollutants pose to the environment and health? It is anticipated that the results from this research program will help guide the creation of effective environmental regulation; and guide industry on the development of safer, more sustainable chemicals.