Oxidation of bilayer of labelled DPPC by aqueous hydroxyl radical – elucidating a mechanism for atmospheric science

Oxidation of atmospheric aerosol can produce cloud condensation nuclei capable of changing the reflectivity and lifetime of clouds. The oxidation of organic film on atmospheric mineral dust may activate mineral dust into cloud droplets. To assess the atmospheric importance the chemical lifetime of the organic material to a common atmospheric oxidant (OH radical) must be measured and compared to deposition lifetime of the mineral aerosol (4-10 days). The chemical lifetime will be assessed by measuring the rate of oxidation of a bilayer of a lipid DPPC from the solid-liquid interface of a silica mineral window, using neutron reflection. Selective deuteration, the ability to measure film thickness and amount of material at the solid-liquid interface will allow chemical mechanism to be deduced. Preliminary studies show the experiment viable, and these data are needed for publication.

大气气溶胶的氧化反应可生成云凝结核（cloud condensation nuclei），此类凝结核能够改变云的反射率与生命周期。大气矿物沙尘表面有机膜的氧化过程，可将矿物沙尘活化为云滴。为评估该过程的大气环境重要性，需测定有机物质对常见大气氧化剂——羟基自由基（OH radical）的化学寿命，并将其与矿物气溶胶的沉积寿命（4~10天）进行对比。本研究将通过中子反射（neutron reflection）技术，在二氧化硅矿物窗口的固液界面处，测定脂质二棕榈酰磷脂酰胆碱（DPPC）双层膜的氧化速率，以此评估有机物质的化学寿命。通过选择性氘代技术，结合固液界面处膜厚度与物质含量的测定能力，可推导出该氧化过程的化学机制。预实验结果已证实本实验的可行性，相关实验数据可用于学术论文发表。