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DNA unwinding helicase enzymes are a type of motor protein. Motor proteins can translocate along filaments or polymers using energy generated from ATP hydrolysis. Helicases are involved in all the important cellular processes where DNA unwinding is required, such as DNA replication, repair, recombination, and transcription. They are present in all living organisms, but vary in their structure, function, and mechanism of action. For example, in prokaryotes, DnaB helicase binds and translocates...

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Related Experiment Video

Updated: May 30, 2026

Magnetic Tweezers for the Measurement of Twist and Torque

Magnetic Tweezers for the Measurement of Twist and Torque

Published on: May 19, 2014

A molecular leverage for helicity control and helix inversion.

Shigehisa Akine¹, Sayaka Hotate, Tatsuya Nabeshima

¹Graduate School of Pure and Applied Sciences, University of Tsukuba, Ibaraki, Japan. akine@chem.tsukuba.ac.jp

Journal of the American Chemical Society

|August 2, 2011

Summary

A novel molecular complex controls its helical shape. Short guests stabilize one form, while longer guests induce a shape change, demonstrating molecular leverage for helicity control.

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Area of Science:

Supramolecular Chemistry
Coordination Chemistry
Organic Synthesis

Background:

Helical structures are crucial in molecular recognition and materials science.
Controlling and inverting molecular helicity is a significant challenge.
Benzocrown moieties offer potential for guest binding and conformational control.

Purpose of the Study:

To design and synthesize a novel tetranuclear complex for helicity control.
To investigate the influence of guest molecular length on helical handedness.
To explore a new molecular leverage mechanism for helix inversion.

Main Methods:

Synthesis of a tetranuclear zinc-lanthanum complex with benzocrown units.
Spectroscopic characterization of the complex and its isomers.
Binding studies with alkanediammonium guests of varying lengths.
Analysis of conformational changes and helical handedness.

Main Results:

The complex [LZn(3)La(OAc)(3)] was successfully synthesized.
Short alkanediammonium guests (n=4, 6, 8) stabilized the P-helical isomer.
A longer guest (n=12) induced helix inversion, favoring the M-helical isomer.
The gauche/anti conversion of ethylenediamine units mediated the length-to-handedness translation.

Conclusions:

A novel molecular leverage system for controlling helical handedness was developed.
Guest molecular length is a critical factor in dictating helical isomer preference.
The synthesized complex provides a platform for tunable molecular shape and function.