标题： 胞嘧啶甲基化在通过DNA链的电荷传输中的作用 显示英文标题

标题： The Role of Cytosine Methylation on Charge Transport through a DNA Strand

摘要： 胞嘧啶甲基化已被发现在各种生物过程中起关键作用，包括多种人类疾病。 这种小的修饰检测仍然具有挑战性。 在这项工作中，我们通过直接的电导测量计算探索了检测甲基化DNA链的可能性。 使用密度泛函理论和Landauer-Buttiker方法，我们研究了八对碱基的甲基化DNA链及其天然对应物的电子性质和电荷传输。 我们首先分析了胞嘧啶甲基化对两条DNA链的紧束缚参数的影响，然后在有无退相干的情况下对电子的传输和通过链的电导进行了建模。 我们发现，天然DNA和甲基化DNA之间紧束缚参数的主要差异在于（甲基化）胞嘧啶碱基的局域能。 两个最近邻的鸟嘌呤碱基和（甲基化）胞嘧啶碱基之间的链内和链间跃迁积分也随着甲基团的添加而变化。 我们的计算表明，在相位相干极限下，当能量接近最高占据分子轨道水平时，甲基化链的传输接近于天然链，并且在带隙中比天然链大5倍。 在具有相同退相干率的情况下，传输趋势仍然成立。 实验中甲基化链的较低电导被认为是由于引入甲基团导致的更稳定结构。 我们还通过选择从弱耦合到强耦合极限的耦合强度，研究了交换相关泛函的作用以及接触耦合的影响。 显示英文摘要

摘要： Cytosine methylation has been found to play a crucial role in various biological processes, including a number of human diseases. The detection of this small modification remains challenging. In this work, we computationally explore the possibility of detecting methylated DNA strands through direct electrical conductance measurements. Using density functional theory and the Landauer-Buttiker method, we study the electronic properties and charge transport through an eight base-pair methylated DNA strand and its native counterpart. We first analyze the effect of cytosine methylation on the tight-binding parameters of two DNA strands and then model the transmission of the electrons and conductance through the strands both with and without decoherence. We find that the main difference of the tight-binding parameters between the native DNA and the methylated DNA lies in the on-site energies of (methylated) cytosine bases. The intra- and inter- strand hopping integrals between two nearest neighboring guanine base and (methylated) cytosine base also change with the addition of the methyl groups. Our calculations show that in the phase-coherent limit, the transmission of the methylated strand is close to the native strand when the energy is nearby the highest occupied molecular orbital level and larger than the native strand by 5 times in the bandgap. The trend in transmission also holds in the presence of the decoherence with the same rate. The lower conductance for the methylated strand in the experiment is suggested to be caused by the more stable structure due to the introduction of the methyl groups. We also study the role of the exchangecorrelation functional and the effect of contact coupling by choosing coupling strengths ranging from weak to strong coupling limit.