Departamento de Física, Universidade Federal do Paraná, Caixa Postal 19044, 81531-990 Curitiba, Paraná, Brazil.
J Chem Phys. 2016 Dec 7;145(21):214313. doi: 10.1063/1.4968602.
We report integral cross sections (ICSs) for both positron and electron scattering by glycine and alanine amino acids. These molecules differ only by a methyl group. We computed the scattering cross sections using the Schwinger multichannel method for both glycine and alanine in different levels of approximation for both projectiles. The alanine ICSs are greater in magnitude than the glycine ICSs for both positron and electron scattering, probably due to the larger size of the molecule. In electron scattering calculations, we found two resonances for each molecule. Glycine presents one at 1.8 eV, and another centered at around 8.5 eV, in the static-exchange plus polarization (SEP) approximation. The ICS for alanine shows one resonance at 2.5 eV and another at around 9.5 eV, also in SEP approximation. The results are in good agreement with most of the data present in the literature. The comparison of the electron scattering ICSs for both molecules indicates that the methylation of glycine destabilizes the resonances, shifting them to higher energies.
我们报告了甘氨酸和丙氨酸氨基酸的正电子和电子散射的积分截面（ICS）。这两种分子仅相差一个甲基。我们使用斯威格多通道方法计算了不同近似水平的两种射弹的甘氨酸和丙氨酸的散射截面。对于正电子和电子散射，丙氨酸的 ICS 比甘氨酸的 ICS 大，可能是由于分子的尺寸较大。在电子散射计算中，我们发现每个分子都有两个共振。在静态交换加极化（SEP）近似中，甘氨酸在 1.8 eV 处有一个共振，在 8.5 eV 左右处还有另一个共振。丙氨酸的 ICS 在 2.5 eV 处有一个共振，在 9.5 eV 左右处还有另一个共振，也在 SEP 近似中。结果与文献中存在的大多数数据非常吻合。两种分子的电子散射 ICS 的比较表明，甘氨酸的甲基化使共振不稳定，将其移至更高的能量。
