螺旋手性SWBNNT尺寸对Lys分子手性转变反应限域的影响

Confined Effect of Size of Helically Chiral SWBNNT on Chiral Transition Reaction of Lys Molecules

用量子力学与分子力学组合的ONIOM方法,研究两种构象的赖氨酸(Lys)分子限域在螺旋手性单壁氮化硼纳米管(SWBNNT)内的手性转变机理.结果表明:限域在小管径螺旋手性SWBNNT的Lys分子骨架形变明显;当两种构象的Lys分子限域在SWBNNT(6,4)时,旋光异构反应的表观能垒分别为175.90,230.44kJ/mol,旋光异构反应决速步骤的内禀能垒分别为211.40,230.44kJ/mol,来源于质子从手性C向氨基N迁移的过渡态,比裸反应的决速步骤能垒(252.60kJ/mol)低.即螺旋手性SWBNNT的管径越小,限域催化作用越明显,限域在SWCNT(6,4)内具有氨基与羧基间单氢键的Lys分子先旋光异构.

We studied the chiral transition mechanism of two conformations of lysine(Lys)molecules confined in the helically chiral SWBNNT by using the ONIOM methods of combination of quantum mechanics and molecular mechanics.The results show that the Lys molecular skeleton deformation of helically chiral SWBNNT in small tube diameter is obvious.When two conformations of Lys molecules confined in the SWBNNT(6,4),the apparent energy barriers of the optical isomerism reaction are 175.90,230.44 kJ/mol,respectively,the intrinsic energy barriers of the rate-determining step of the optical isomerism reaction are 211.40,230.44 kJ/mol,which come from the transition states that the proton transfer from the chiral C to amino N and are lower than the energy barrier of the rate-determining step of bare reaction(252.60 kJ/mol).The smaller tube diameter of the helically chiral SWNT,the better confined catalytic action,and Lys molecules that confined in SWBNNT(6,4)with the single hydrogen bonds between amino group and carboxyl are optical isomerism in the first place.