CAJ | 학술논문

研究了3种由α-环糊精(α-CD)、不同线性结构及中间连接基团组成的轮烷的穿梭行为，其中，线性结构为烷基链( ALK)或聚乙二醇链( PEG)，中间连接基团为联吡啶或联苯。采用分子动力学模拟方法对室温下这些轮烷在水或二甲基亚砜( DMSO)溶液中α-CD的穿梭过程进行了研究；利用自适应偏置力( ABF)和多副本ABF( MW-ABF)方法计算了穿梭过程的自由能变化。结果表明，由PEG链组成的轮烷在2种溶剂中穿梭所需克服的能垒均比由ALK链组成的轮烷低，并且前者在DMSO中穿梭所需克服的能垒比在水中的能垒要低。由联苯基团组成的轮烷比由联吡啶基团组成的轮烷的能垒要低很多。通过对自由能曲线进行分解表明，破坏联吡啶基团的溶剂化层是穿梭过程能垒形成的主要原因，因此采用疏水的联苯基团可大大降低该能垒高度；另一方面，由于PEG链比ALK链具有更强的亲水性，也导致穿梭过程能垒降低。此外，通过对2种计算方法进行比较发现， MW-ABF能够明显改善对构象空间的采样效率，加快收敛速度。
연구료3충유α-배호정(α-CD)、불동선성결구급중간련접기단조성적륜완적천사행위，기중，선성결구위완기련( ALK)혹취을이순련( PEG)，중간련접기단위련필정혹련분。채용분자동역학모의방법대실온하저사륜완재수혹이갑기아풍( DMSO)용액중α-CD적천사과정진행료연구；이용자괄응편치력( ABF)화다부본ABF( MW-ABF)방법계산료천사과정적자유능변화。결과표명，유PEG련조성적륜완재2충용제중천사소수극복적능루균비유ALK련조성적륜완저，병차전자재DMSO중천사소수극복적능루비재수중적능루요저。유련분기단조성적륜완비유련필정기단조성적륜완적능루요저흔다。통과대자유능곡선진행분해표명，파배련필정기단적용제화층시천사과정능루형성적주요원인，인차채용소수적련분기단가대대강저해능루고도；령일방면，유우PEG련비ALK련구유경강적친수성，야도치천사과정능루강저。차외，통과대2충계산방법진행비교발현， MW-ABF능구명현개선대구상공간적채양효솔，가쾌수렴속도。
In order to investigate the hydrophobic effect of chain-like structures on shuttling in further, three similar rotaxanes are studied in this work. The rotaxanes are formed by anα-CD, two dodecamethylene chains ( ALK) or two poly ( ethylene glycol ) ( PEG ) for stations, one bipyridinium moiety ( PY ) or one biphenyl moiety( PH) for linkers and large end groups at both sides. The shuttling of the rotaxanes was studied by means of molecular dynamics simulations( MD) combined with free-energy calculations in water and DMSO at room temperature. Two methods, the adaptive biasing force ( ABF ) method and the multiple walker ABF ( MW-ABF) method, a modified version of ABF, are adopted for calculating the free-energy change characte-rizing the shuttling process. The potentials of mean force( PMFs) for the three rotaxanes are determined. The free-energy barriers of the PMFs for the PEG-rotaxane are lower than those for the the ALK-rotaxane both in water and DMSO. Furthermore, the barriers for the PEG-rotaxanes in DMSO are lower than that in water, which is in accordance with the ALK-rotaxanes. The barriers for the PH-rotaxanes are significantly lower than those for the PY-rotaxanes. Partitioning the PMFs into free-energy components suggests that change of the the charged group by an hydrophobic biphenyl moiety or decrease of the hydrophobicity of the chain-like structure in two stations from ALK to PEG reduces the free-energy barrier with respect to the stable states in the stations. In addition, comparison of the two free-energy calculation methods shows that the MW-ABF method can significantly improve the uniformity of sampling and hence increase the computational efficiency.