在宇宙开始大爆炸的时候,电荷变号与镜象反射共轭（CP）是对称的.但现在我们的宇宙绝大部分是正物质核子和电子等组成的,所以我们的宇宙是不对称的.D和L-丙氨酸通常称为对映体（enantiomer）,实际上它们并不是由正、反粒子组成的真正的对映体,而是空间反演的,即x--x,y--y,z--z的非对映异构体（diastereoisomer）,所以D-和L-丙氨酸是不对称的,两者间有能量的差别.自然界的力只有弱力是宇称不守恒的.在分子物理中,电弱力宇称不守恒是导致D-和L-丙氨酸能差的根源.所有以前的研究都认为L型丙氨酸比D型稳定.但是,最近以Quack[9]和Schwerdtfeger[11]为首的理论物理学家计算了L-丙氨酸在气相和溶液两种状态下,宇称破缺能差与分子构象的关系,提出“D-和L-丙氨酸究竟哪一个稳定”的质疑.由于气相和液相中两面角较难测定,我们用X射线四圆单晶衍射法,测定了270K和250KD和L-丙氨酸的O（1）O（2）C（1）C（2）H（4）的原子坐标,算出了二面角,按照Quack[9]的MC-LR方法,D-和L-丙氨酸宇称破缺能差为1.2 x 10-19Hartree,相当于3.3 x 10-18eV/分子或3.2x10-16kJ·mol-1,从而得出D-丙氨酸能态高于L-丙氨酸的结论.
The formation and growth of calcium phosphate precipitation pattern were investigated in agar gel system. As an important biologic surfactant, the influence of bile salts on the patterns and composition of calcium pho...
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The formation and growth of calcium phosphate precipitation pattern were investigated in agar gel system. As an important biologic surfactant, the influence of bile salts on the patterns and composition of calcium phosphate precipitation was discussed. The results indicated that calcium phosphate precipitation shaped the periodic ring pattern in agar gel system. Addition of bile salts will postpone the creation of the periodic ring pattern of calcium phosphate precipitation. NaTC only postponed the creation but not changed the pattern of it. NaC and NaDC not only postponed the creation but also changed the pattern of it. The results of FT IR spectroscopy demonstrated that NaTC have promoted the transformation of calcium phosphate to hydroxyapatite.
A tri(8 quinolinol)nickel coordination compound, [Ni 2(HQ) 3Q 3] ClO 4, was synthesized and its crystal structure was determined by X ray diffraction. The crystal structure indicated a space group of P2 1/c with a =1....
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A tri(8 quinolinol)nickel coordination compound, [Ni 2(HQ) 3Q 3] ClO 4, was synthesized and its crystal structure was determined by X ray diffraction. The crystal structure indicated a space group of P2 1/c with a =1.613 8(1) nm, b =1.590 0(1) nm, c =1.939 9(1) nm, β =94.663(2)°, V = 4.961 2(6) nm 3 and Z =4. Three strong hydrogen bonds were found in each unique unit between two tri(8 quinolinol) nickel fragments.
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