Tweezers, molecular natural

Arai, Y., Yasuda, R., Akashi, K., Harada, Y., Miyata, H., Kinoshita, Jr., K. and Itoh, H. (1999) Tying a molecular knot with optical tweezers. Nature, 399,446 148. 

Naturally, quantum chemical approaches to molecular recognition are usually employed for selected systems since the complexity of these systems requires a system-specific analysis which makes it difficult to extract results of general validity for examples, see Refs. [13-16] for studies of molecular tweezers. Further examples are mentioned in a review article by Schatz considering ab initio calculations on calixarenes and calixarene complexes [17]. Schatz concludes that although the systems are quite big, useful contributions have been made by ab intio calculations. However, a general model is needed in order to make host-guest processes and template-assisted reactions accessible to a comparison of quantitative measurements and calculations, which may finally provide the basis for rational host design and for the prediction of template effects (compare the recent attempt by Hunter [18]). 

Aral Y, Yasuda R, K-i A, Harada Y, Miyata H, Kinosita K, Itoh H (1999) Xying a molecular knot with optical tweezers. Nature 399 446... 

Despite their appeal, the problem with both of the devices described above is that they are activated by small molecules. To approach nanorobotics succesfuUy. one needs many different devices incorporated into a larger matrix, such as the 2D arrays described above. However, both the craciform and the B-Z devices are activated by small molecules, so that the action of these effectors could not be targeted easily to a specific device within the assay. Given the informational nature of DNA, it seems that sequence-dependent devices should be developed to fulfill this purpose. Two such devices have been developed, both based on the same principle of activation by strand addition and strand removal. This approach was pioneered by Yurke et who developed molecular tweezers that were closed by adding a strand of DNA. The strand contained an unpaired segment and could be removed from the tweezers by the addition of its full complement removal of the strand resulted in the tweezers relaxing to their open state. 

Nature beat mankind to the punch with respect to molecular tweezers. For example, echinomycin (Fig. 7) is... 

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