Preliminary Theoretical Studies on the Combination of Halogen Ions with Crown Tetraalanylpeptide

The density functional theory based hybrid-method B3LYP was used to investigate the interaction of the halogen ions with crown tetraalanylpeptide which was the coronary structures of homodetic cyclotetraalapeptide and was represented as the model basic. Many properties including combination energy, optimum geometry structures and population analysis were calculated. It was shown that there was scarcely any change in the coronary structure of C4-Ala after combination with X. The electrons moved from halogen ions to C4-Ala during the combining process. Combination of C4-Ala with F was obviously stronger than that of Cl^- and Br. When the energy of C4-Ala-X was at minimum, the distances between halogen ions and the center of C4-Ala were 0.084 nm, 0.210 nm and 0.200 nm, respectively.

A Theoretical Study on the Interactions of Crown Tetraalanylpeptide with Small Metal Cations

The density functional theory based on hybrid-method B3LYP was used to investigate the interaction of the alkaline-earth cations or alkali cations with crown tetraalanylpeptide which was the coronary structures of homothetic cyclotetraalapeptide and was represented as the model basic. Many properties including binding energy, optimum geometry structures and population analysis were calculated. It was shown that there was little change on the coronary structure before and after C4-AIa combination with small I A or ｜I A cations, and the electrons moved from C4-AIa to alkaline-earth cations or alkali cations during this process. Combination with C4-Ala, Be2~ was more predominant than Mg2~ and Ca2~ remarkably, but Li~ was not more predominant than Na＋ and K＋. The distances between alkaline-earth cations and the center of C4-Ala were 0.000 nm, 0.150 nm and 0.225 nm, respectively, when the binding energy at minimum, and that for alkali cations were 0.225 nm, 0.250 nm and 0.300 nm.

A Theoretical Study on the Dual-recognitions of Crown Tetraalanylpeptide with Small Ions

Under the method of density functional theory, the geometry structures, values of energy and population analysis of the combo of crown tetraalanylpeptide （C4-AIa） with ions （Xn） are calculated, based on the foundation of former studies. It was found that the coronary structure changed little whether in C4-Ala or C4-Ala-Xn, and the electrons transferred between C4-Ala and Xn at the mean time. There were coordinate bonds between Xn＋ and the nitrogen from -NH-, hydrogen bonds between Xa and the hydrogen from -NH-, and they became weaker when the radii of ions turned larger. Besides, the values of the single point bonding energy fluctuated gradually as a shape of saddle, but cations and anions located in opposite directions of the center of coronary structure when reach minimum, respectively.

A Theoretical Study on the Interaction of Crown Tetraalanylpeptide with NO3- and SO4/2-

Crown peptide is a kind of special conformation found on the homodetic cyclopeptide, regular array about the main chain containing imido groups, and the monolithic conformation presents coronary analogy to crown ether. There are high symmetrical ionophores belonging to Cn point group. The channels or apertures can form easily for recognizing certain ion or molecular, and also the function of intending dual-recognition and the ability for transporting as ionophores can be possessed. Under the method of density functional theory, the geometry structures, values energy and population analysis of the combo of crown tetraalanylpeptide （C4-Ala） with NO3- and SO4/2- are calculated, based on the foundation of former studies. Compared with the structure of C4-AIa without NO3- and SO4/2- it is found that the coronary shape changes little in the complex of C4-Ala-YOm/n-, and the electrons transfer between C4-AIa and YOm/n- at the mean time. There are hydrogen bond between oxygen of YOm/n- and the hydrogen from imine groups of C4-AIa, and they become weaker when the average charge density lessens.

冠丙四肽与卤离子结合行为的理论研究

用密度泛函理论B3LYP方法,以环丙四肽的冠型构象(冠丙四肽)为模型基础,对氟、氯、溴等卤离子与其结合形式进行了几何构型优化、能量计算、Mulliken布局数分析等理论研究。结果表明冠丙四肽的构型在与卤离子结合前后几乎没有改变,结合过程中电子由卤离子移向冠肽,氟离子与冠型环丙四肽的结合作用明显优于氯离子和溴离子,卤离子的最佳结合位均略微偏离于模型中心轴线,此时氟、氯、溴离子距冠丙四肽中心的距离依次为0.084 nm、0.210 nm和0.200 nm。

冠丙四肽与前周期ⅥA和ⅦA阴离子结合作用的密度泛函法研究

冠肽是环肽的特殊构型,其结构中的酰胺键主链呈规则排列,形成类似于冠醚的冠型构象,具有高度的对称性,易于形成实现与离子/分子结合的孔径或通道,达到预期的识别作用以及作为超分子离子载体的运输能力。用密度泛函理论的B3LYP方法,以环丙四肽的冠状构象(冠丙四肽)为模型基础,在真空体系中,对其与卤族氧族阴离子结合体系进行了几何构型优化、能量、Mulliken布局数、前沿轨道等方面的理论研究。结果表明:冠丙四肽的构型在与离子结合前后几乎没有改变,结合过程中电子由非金属阴离子移向冠肽主体,价键作用表现为阴离子与氨基氢之间的氢键作用,其中氟与冠型环丙四肽的结合作用并不特别明显优于氯和溴,而氧与冠型环丙四肽的结合作用则明显优于硫和硒;同等情况下,与二价离子的结合作用更显为显著。

前周期ⅥA和ⅦA氢化物分子与冠丙四肽结合作用的理论研究

冠肽是环肽的特殊构型,其结构中的酰胺键主链呈规则排列,形成类似于冠醚的冠型构象,具有高度的对称性,易于形成实现与离子/分子结合的孔径或通道,达到预期的识别作用以及作为超分子离子载体的运输能力。借助于密度泛函理论的B3LYP方法,以冠丙四肽为模型基础,对氧、硫、硒、氟、氯、溴等常见非金属元素的氢化物分子与其结合体系进行了几何构型优化、能量、布局数等理论研究。结果表明:冠丙四肽的构型在与这些氢化物分子结合前后几乎没有改变;结合过程中电子由这些氢化物分子不同程度地移向冠肽主体:在最佳结合位时,氢化物分子中心杂原子距冠丙四肽中心的距离依次为0.278 nm、0.380 nm、0.331 nm、0.266 nm、0.376 nm和0.334 nm对比于与相应离子的结合过程,这些氢化物分子与冠丙四肽没有特别的优势结合,据此可初步预测水等分子存在时,并不影响冠丙四肽对离子实施识别。

冠丙四肽与前周期碱土和碱金属离子结合作用的初步理论研究

借助于密度泛函理论的B3LYP方法,以冠丙四肽为模型基础,对锂、钠、钾、铍、镁、钙等金属离子与该冠丙四肽的结合形式进行了几何构型优化、能量计算、Mulliken布局数分析等理论研究。结果表明:冠丙四肽的构型在与金属离子结合前后几乎没有改变,结合过程中电子由冠肽移向金属离子,锂离子与冠型环丙四肽的结合作用并不明显优于钾离子和钠离子,碱金属离子的最佳结合位距冠丙四肽中心的距离依次为0.225 nm、0.250 nm和0.300 nm;铍离子与冠型环丙四肽的结合作用明显优于镁离子和钙离子,碱土金属离子的最佳结合位距冠丙四肽中心的距离依次为0.000 nm、0.150 nm和0.225nm。