Self-Assembly of a [2]Pseudorotaxane by an Inchworm-Motion Mechanism

The threading of biomolecules through pores or channels in membranes is important to validate the physiological activities of cells. To aid understanding of the controlling factors required for the translocation in space with confined size and distorted conformation, it is desirable to identify expe...

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Bibliographic Details
Published in:Chemistry : a European journal 2016-10, Vol.22 (42), p.15075-15084
Main Authors: Meng, Zheng, Wang, Bo-Yang, Xiang, Jun-Feng, Shi, Qiang, Chen, Chuan-Feng
Format: Article
Language:English
Subjects:
Biomolecules
Chains
Channel pores
Channels
Chemistry
Complexity
Conformation
Crown ethers
Distortion
Dynamical systems
Entropy
Ethers
Formations
Holes
inchworm motion
Mathematical models
Membranes
Molecular dynamics
NMR
Nuclear magnetic resonance
Physiological effects
Physiology
Pores
Porosity
rotaxanes
Self assembly
Spectroscopic analysis
Threaded
threading mechanism
Translocation
triptycene
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Summary:The threading of biomolecules through pores or channels in membranes is important to validate the physiological activities of cells. To aid understanding of the controlling factors required for the translocation in space with confined size and distorted conformation, it is desirable to identify experimental systems with minimized complexity. We demonstrate the mechanism of a linear guest L1 threading into a tris(crown ether) host TC with a combinational distorted cavity to form a triply interlocked [2]pseudorotaxane 3in‐[L1⊂TC]. An inchworm‐motion mechanism is proposed for the process. For the forward‐threading steps that lead to the formation of higher‐order interlocked species, guest L1 must adopt a bent conformation to find the next crown ether cavity. Two simplified models are applied to investigate the self‐assembly dynamic of 3in‐[L1⊂TC]. Kinetic NMR spectroscopic and molecular dynamics (MD) studies show that formation of the singly penetrated species is fast, whereas formation of the doubly and triply threaded species is several orders of magnitude slower. During threading the freedom of both the guest L1 and host TC gradually decrease due to their interactions. This results in a significant entropy effect for the threading dynamic, which is also observed for the threading of a biomolecular chain through a channel. Inch by inch: A linear guest threaded into a tris(crown ether) host with a distorted cavity to form a triply interlocked [2]pseudorotaxane follows an inchworm‐motion mechanism, in which the guest must adopt a bent conformation to find the next crown ether site for forward threading (see figure).
ISSN:0947-6539
1521-3765
DOI:10.1002/chem.201602785