DFT Study of Geometrical and Vibrational Features of Sulfur Containing Amino Acids in Hydrated Media： L-Cysteine and L-Methionine

Geometry optimization at the B3LYP/6-31＋＋G＊ level of theory has been undertaken on clusters containing L-Met （L-methionine） or L-Cys （L-cysteine） surrounded by eight water molecules. The comparison of the structural parameters of L-Met and L-Cys with X-ray experimental values is in good agreement within 4.8%. This result shows that the privileged positions of water molecules and the possible hydrogen bonding network formed around the backbone of both AAs （amino acids） are adequate. Subsequent calculations of the harmonic vibrational modes followed by a post-processing treatment enable us to assign the vibrational modes of L-Met and L-Cys surrounded explicitly by eight water molecules. The frequencies of the assigned modes are in good agreement with available IR （infra red） and Raman values within 5%.

甲硫氨酸腺苷转移酶1A在雌雄大鼠肝脏中性别差异表达研究

目的 观察SD大鼠体内性激素水平的变化对大鼠肝脏组织表达甲硫氨酸腺苷转移酶1A（MAT1A）的影响.方法 选取适龄性成熟的SD大鼠,给予对应处理后构建具有性激素浓度梯度差异的SD大鼠模型（雌、雄各3组,每组6只）,应用酶联免疫吸附试验（ELISA）法分别测量各组大鼠体内性激素浓度,再应用实时定量反转录聚合酶链反应（RT-qPCR）、Western blot法观察测定不同分组的大鼠的肝脏组织中MAT1A的表达.结果 ELISA法测性激素结果：空白对照雌鼠（FM0）组浓度为（43.125±11.066）ng/L,去卵巢雌鼠（FM＋）组0 ng/L,去卵巢后补充雄激素的雌鼠（FM＋T）组（31.738 ±7.142） ng/L（P ＜0.01）;空白对照雄大鼠（M0）组浓度为（28.945±9.379） mmol/L,去势雄鼠（M＋）组0 mmol/L,去势后补充雌激素的雄大鼠（M＋E）组（26.158 ±7.846） mmol/L（P＜0.01）.RT-qPCR结果：雌鼠MAT1A mRNA表达水平FM0组＞FM＋组＞FM ＋T组,平均值为0.4714 ＞0.1334 ＞0.0660（P＜0.01）;雄鼠MAT1A mRNA表达水平M0组＜M＋组＜M＋E组,平均值为0.0298 ＜0.0687 ＜0.205 5（P ＜0.01）.Western blot结果：雌雄大鼠肝脏MAT1A蛋白表达趋势与RT-qPCR一致.结论 大鼠肝脏表达MAT1A存在明显性别差异,高水平的雌激素有利于MAT1A的表达,雄激素则抑制MAT1A的表达,而性激素则通过调控MAT1A的性别差异表达进而在肝癌性别差异分布中起重要调控作用.