Amino Acids Compete with Ammonia in Sulfuric Acid-Based Atmospheric Aerosol Prenucleation: The Case of Glycine and Serine
Amino Acids Compete with Ammonia in Sulfuric Acid-Based Atmospheric Aerosol Prenucleation: The Case of Glycine and Serine
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DOI：
10.1021/acs.jpca.2c03539
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发表时间：
2022-07-27
影响因子：
2.9
通讯作者：
Shields, George C.
中科院分区：
文献类型：
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作者：
Bready, Conor J.;Vanovac, Sara;Shields, George C.
我们对硫酸、甘氨酸、丝氨酸、氨和水系统进行了计算研究，以了解该系统是否可以形成成核前星团，这是大气中更大气溶胶的前驱物质。我们对这个体系中所有可能的团簇进行了全面的构型搜索，从四个不同的单体和0到5个水开始。用DLPNOCCSD(T)/完全基组(CBS)方法在omega b97xd/6-31++G**几何构型上计算了精确的Gibbs生成自由能.对于干燥的硫酸二聚体，最弱的碱-丝氨酸形成最稳定的络合物，这是由于硫酸氢离子和质子化的丝氨酸阳离子之间形成的强双离子络合物的结果。对于不含硫酸的干式二聚体，甘氨酸-丝氨酸络合物比甘氨酸-氨或丝氨酸-氨络合物更稳定，这源于其详细的结构而与碱强度无关。对于较大的络合物，硫酸去质子化，质子转移到甘氨酸、丝氨酸或氨。这两种氨基酸和氨几乎是可以互换的，没有计算结果就没有简单的方法来预测哪个分子会质子化。假设有合理的起始浓度和一个由硫酸、甘氨酸、丝氨酸、氨和五种水组成的封闭体系，我们预测在两种温度下所有可能的复合体在对流层的浓度。最负的&UDelta；G&DEG；值是这些团簇的详细分子相互作用的函数。这些细节比氨、甘氨酸和丝氨酸的碱基强度更重要。
We present a computational investigation of the sulfuric acid, glycine, serine, ammonia, and water system to understand if this system can form prenucleation clusters, which are precursors to larger aerosols in the atmosphere. We have performed a comprehensive configurational search of all possible clusters in this system, starting with the four different monomers and zero to five waters. Accurate Gibbs free energies of formation have been calculated with the DLPNOCCSD(T)/complete basis set (CBS) method on omega b97xd/6-31++G** geometries. For the dry dimers of sulfuric acid, the weakest base, serine, is found to form the most stable complex, which is a consequence of the strong di-ionic complex formed between the bisulfate ion and the protonated serine cation. For the dry dimers without sulfuric acid, the glycine-serine complex is more stable than the glycine-ammonia or serine-ammonia complexes, stemming from the detailed structure and not related to base strength. For the larger complexes, sulfuric acid deprotonates and the proton is shifted to glycine, serine, or ammonia. The two amino acids and ammonia are almost interchangeable and there is no easy way to predict which molecule will be protonated without the calculated results. Assuming reasonable starting concentrations and a closed system of sulfuric acid, glycine, serine, ammonia, and five waters, we predict the concentrations of all possible complexes at two temperatures spanning the troposphere. The most negative & UDelta;G & DEG; values are a function of the detailed molecular interactions of these clusters. These details are more important than the base strength of ammonia, glycine, and serine.