A metal–peptide capsule by multiple ring threading

Abstract

Cavity creation is a key to the origin of biological functions. Small cavities such as enzyme pockets are created simply through liner peptide folding. Nature can create much larger cavities by threading and entangling large peptide rings, as learned from gigantic virus capsids, where not only chemical structures but the topology of threaded rings must be controlled. Although interlocked molecules are a topic of current interest, they have for decades been explored merely as elements of molecular machines, or as a synthetic challenge. No research has specifically targeted them for, and succesfully achieved, cavity creation. Here we report the emergence of a huge capsular framework via multiple threading of metal–peptide rings. Six equivalent C4-propeller-shaped rings, each consisting of four oligopeptides and Ag+, are threaded by each other a total of twelve times (crossing number: 24) to assemble into a well-defined 4 nm-sized sphere, which acts as a huge molecular capsule.

Isogonal weavings on the sphere: knots, links, polycatenanes

“…Weavings, knots, links and related geometrical structures are currently of considerable interest in materials chemistry and biochemistry, as testified in recent reviews (Lim & Jackson, 2015;Flapan, 2015;Bruns & Stoddart, 2016;Pieters et al, 2016;Horner et al, 2016;Fielden et al, 2017) and in other recent reports (Danon et al, 2017;Wu et al, 2017;Kim et al, 2018;Zhang et al, 2018;Leigh et al, 2019;Sawada, Saito et al, 2019;Sawada, Inomata et al, 2019;Inomata et al, 2020). Suggested knots most suitable for self-assembly have recently been identified (Marenda et al, 2018).…”

“…2) in which pairs of 4-rings are parallel and each is catenated to four others, symmetry 432, catenation symbol 6-4-4, crossing number 24 (12 Hopf links). Interestingly, a molecular example of a catenane with the rkc structure has recently been reported (Sawada, Inomata et al, 2019) showing that links with large crossing numbers are realistic targets for synthesis.…”

The Rise and Promise of Molecular Nanotopology

“…Given the recent developments 21,42,43 and breakthroughs [45][46][47][48][49][50] in molecular nanotopology, 44 we believe that a sea change is afoot and that molecular nanotopology is waiting in the wings to be embraced by the wider community of chemists and other scientists. It follows that it is timely to review this rapidly emerging field in order to encourage more young scientists to participate in promoting it by pursuing research into molecular links and knots, some of which will prove to be transformative, in the years to come.…”

“…In this Mini-Review, following our brief discussion of the historical development of molecular nanotopology, we will present a blueprint and a roadmap for its implementation by placing the emphasis on the rational design, practical syntheses, and potential applications of molecular links and knots, as well as interwoven molecular frameworks. Rather than trying to discuss lots of examples from the past, we will focus mainly on a few seminal contributions 39,40,[51][52][53][54][55][56] and some recent accomplishemnts [45][46][47][48][49][50][57][58][59] so as to offer readers as good an overview as possible of ongoing research in the field.…”

Controlling the Shape and Chirality of an Eight-crossing Molecular Knot

“…7 Knotting at the molecular level thus has major effects upon material properties. 8,9 Since Sauvage's first full characterisation of synthetic knotted molecules three decades ago, 10 the beauty of these woven architectures has attracted chemists, 11 leading to recent breakthroughs in the synthesis of complex, highly symmetric, knots, 12,13,14,15,16,17,18 and to investigations of their functions. 19,20 To date, synthetic routes to molecular knots and links have focussed on the preparation of highly symmetric knots with few crossing points, such as the threecrossing trefoil knot.…”