molecular knot
now leigh and his team have made a knot with eight crossings, making it the most complex molecular knot ever tied .
sauvage' s knot was the simplest knot possible - a' trefoil knot' that looked kind of like a three - leaf clover. but it took scientists another 25 years to achieve another molecular knot .
the eight - crossings molecular knot is the most complex regular woven molecule yet made by scientists .
the first molecular knot – one of the most mathematically simple kinds called a trefoil knot – was tied in 1989. from then until 2011, chemists only knew how to coax molecules into that one type of knot .
braiding a molecular knot | january 16, 2017 issue - vol. 95 issue 3 | chemical & engineering news
the first molecular knot was created by chemist jean - pierre sauvage, one of three scientists who won last year' s nobel prize in chemistry for work in creating parts for future molecular machines .
in 2011, leigh was part of the first team to create a synthetic pentafoil knot. whereas the strands of a trefoil knot cross over one another three times, those in a pentafoil knot have five crossings .
scientists have successfully manipulated strands of molecules to create the tightest physical knot ever, with eight crossings twisting molecules into a celtic knot - structure .
for the first time, scientists have synthesized a three - stranded molecular braid that twisted into a knot with eight crossings, as in this rendering .
“the eight - crossings molecular knot is the most complex regular woven molecule yet made by scientists, ” professor leigh said in a statement. “we ‘tied’ the molecular knot using a technique called ‘self - assembly’, in which molecular strands are woven around metal ions, forming crossing points in the right places just like in knitting – and the ends of the strands were then fused together by a chemical catalyst to close the loop and form the complete knot .
a molecular knot with twelve amide groups - one - step synthesis, crystal structure, chirality extracts were presented during a talk at the universität... - pubmed - ncbi
the first molecular knot was tied back in 1989 by chemist jean - pierre sauvage, who went on to win last year' s nobel prize in chemistry for related work .
scientists have twisted molecules into the tightest knot ever: the two - way this new knot has eight crossings, far more than previous molecular knots. the
rope
is very short — just 192 atoms long, or 500 times smaller than a red blood cell .
molecular knots are common in nature. polymer chains can often form them, and even circular dna and about 1 percent of known proteins show knotted structures. there are more than 6 billion known molecular knots possible and so far only three nontrivial knot topologies have been made by scientists .
this new knot has eight crossings, he says, and what' s more, it' s the tightest knot ever, which he says is defined by just
the length of your rope, and then how complex the knot is, how many crossings you have .
using iron atoms to guide their molecular building blocks, chemists have now constructed the first braided knot (science 2017, doi: 10. 1126 / science. aal1619). this new knot, crafted by david a. leigh and coworkers at the university of manchester, is considerably more complex than previous examples of molecular knots, which were based on just two twisted strands .
we' tied' the molecular knot using a technique called' self - assembly', in which molecular strands are woven around metal ions, forming crossing points in the right places just like in knitting - and the ends of the strands were then fused together by a chemical catalyst to close the loop and form the complete knot ,
explained leigh in a press release .
for the first time, scientists have synthesized a three - stranded molecular braid that twisted into a knot with eight crossings, as in this rendering. stuart jantzen / biocinematics. com / science hide caption
molecular orbital conformational analysis of prototypical organic systems. 1. ethylene glycol and 1, 2 - dimethoxyethane
to form these crossings, the team wrapped the molecular strands around metal ions to manipulate their formation .
his knot had loops that made it look a bit like a three - leaf clover. this
trefoil knot
is the simplest kind of knot possible, leigh says ,
and then for the next 25 years, chemists weren' t able to make any more - complicated knots than that .
this latest knot is the tightest and most intricate yet. it looks a lot like a celtic knot, with three strands, and eight crossings holding it together. here it is in all its glory :
it looks a lot like a celtic knot and is designed to effectively tie itself in a test tube. molecular strands wrap around metal ions that act like knitting needles and set up strand crossings in just the right spots .
over the past few years, leigh and his colleagues, along with several other teams, have managed to produce a few more molecular knots - but they' ve been limited to two molecular strands, and little more than three crossings .
molecular knots, held taut by zinc ions, can capture bromide by cleavage of carbon - bromine bonds and thereby promote catalysis .
over the past decade, chemists have used metal ion templating to prepare a wide variety of knotted molecular strands. marcos et al. now show that one such pentafoil knot can be applied to catalysis. when held taut by zinc ions, the knot can capture a chloride or bromide ion from a halocarbon, thereby unleashing the reactivity of the residual cation for applications such as lewis acid catalysis. removing the zinc ions lowers the knot' s affinity for the halides, offering a reversible modulation mechanism for the catalysis .
a molecular knot with twelve amide groups - one - step synthesis, crystal structure, chirality extracts were presented during a talk at the universität düsseldorf on january 11, 2000. we thank dr. christian seel and dr. rudolf hartmann for suggestions and measurements .
molecular knots occur in dna, proteins, and other macromolecules. however, the benefits that can potentially arise from tying molecules in knots are, for the most part, unclear. here, we report on a synthetic molecular pentafoil knot that allosterically initiates or regulates catalyzed chemical reactions by controlling the in situ generation of a carbocation formed through the knot - promoted cleavage of a carbon - halogen bond. the knot architecture is crucial to this function because it restricts the conformations that the molecular chain can adopt and prevents the formation of catalytically inactive species upon metal ion binding. unknotted analogs are not catalytically active. our results suggest that knotting molecules may be a useful strategy for reducing the degrees of freedom of flexible chains, enabling them to adopt what are otherwise thermodynamically inaccessible functional conformations .
knots are being discovered with increasing frequency in both biological and synthetic macromolecules and have been fundamental topological targets for chemical synthesis for the past two decades. here, we report on the synthesis of the most complex non - dna molecular knot prepared to date: the self - assembly of five bis - aldehyde and five bis - amine building blocks about five metal cations and one chloride anion to form a 160 - atom - loop molecular pentafoil knot (five crossing points). the structure and topology of the knot is established by nmr spectroscopy, mass spectrometry and x - ray crystallography, revealing a symmetrical closed - loop double helicate with the chloride anion held at the centre of the pentafoil knot by ten ch···cl – hydrogen bonds. the one - pot self - assembly reaction features an exceptional number of different design elements—some well precedented and others less well known within the context of directing the formation of (supra) molecular species. we anticipate that the strategies and tactics used here can be applied to the rational synthesis of other higher - order interlocked molecular architectures .
a crystal structure of the leigh group’s braided knot with ions. gray = c, blue = n, red = o, purple = fe, green = cl, turquoise shows one repeat unit of the knot. counter ions and hydrogen atoms have been omitted for clarity .
the' rope' that they used was just 192 atoms long - or 500 times smaller than a red blood cell - and yet, they were able to put an unheard - of eight crossings in it, knitting the structure together into the tightest molecular knot ever created .
the tightest knot ever is also one of the tiniest. made of strings of molecules braided together, the knot is only 20 nanometres long, and its properties are as yet unknown. but researchers hope that these tied - up molecules could lead to lighter body armour or more flexible surgical sutures .
now, in the journal science, a team of chemists says it has made a huge advance — manipulating molecules to create the tightest knot ever .
the researchers created the knot using a technique called “self - assembly, ” wherein molecular strands are woven around metal ions, forming crossing points in the right places — in this case, eight places. the ends of the strands were then fused together by a chemical catalyst to close the loop .
three molecular strands get braided together in this knot, he adds ,
and being able to braid, like you braid a girl' s hair in elementary school, allows you to make much, much more complicated knots and ultimately opens the door for weaving as well, which will be very exciting .
knots may ultimately prove just as versatile and useful at the nanoscale as at the macroscale. however, the lack of synthetic routes to all but the simplest molecular knots currently prevents systematic investigation of the influence of knotting at the molecular level. we found that it is possible to assemble four building blocks into three braided ligand strands. octahedral iron (ii) ions control the relative positions of the three strands at each crossing point in a circular triple helicate, while structural constraints on the ligands determine the braiding connections. this approach enables two - step assembly of a molecular 8 19 knot featuring eight nonalternating crossings in a 192 - atom closed loop ~ 20 nanometers in length. the resolved metal - free 8 19 knot enantiomers have pronounced features in their circular dichroism spectra resulting solely from topological chirality .
it is not uncommon when braiding hair or bread to intertwine three different strands. at the molecular level, however, synthetic knots have thus far been restricted to architectures accessible from two - strand braids. danon et al. used iron ion coordination to guide three organic ligand strands to form a knot geometry with eight separate crossings .
tying a knot can be tricky. just ask any kid struggling with shoelaces. and scientists have it even harder when they try to make knots using tiny molecules .
they knew it was possible - mathematicians have predicted billions of possible molecular knots - but it' s much harder to get chemicals to weave together than it sounds .
knots are extremely useful in everyday life, even at the nanoscale level. now, researchers from the university of manchester have just created the first three - strand molecular braid .
“tying knots is a similar process to weaving so the techniques being developed to tie knots in molecules should also be applicable to the weaving of molecular strands, ” leigh added .
molecular knots like this are probably more analogous with the knots in mathematics, which are closed loops twisted into different shapes, than with the knots in your phone charger’s cord .
but in just the past few years, scientists including leigh have managed to produce a few more complex knots. his team' s latest knot is the most intricate yet .
in order to create it, the researchers actually had to take three molecular braids, and get them to self - assemble in a test tube and tie themselves up into the structure .
once the knot structure is assembled, the chemists remove the iron ions, as well as a chloride ion the structure sequesters at its center, to generate a metal - free knot. this molecule, leigh points out, is chiral. despite having no chiral centers, it can be made in two distinct forms that are nonsuperimposable mirror images of one another that can be separated using chiral chromatography .
“the strands that we’re knotting are so small that you can’t grab the ends and mechanically tie them like you would a shoelace, ” leigh, who was part of the first team that created a synthetic pentafoil knot in 2011, told new scientist. “unlike tying your shoelaces, where you do them one at a time, with self - assembly we can tie many billions of molecular knots at the same time. ”
that might not sound too impressive, but researchers have only ever managed to tie a few, very simple molecular knots to date. and figuring out how to make these braided formations will be the key to unlocking powerful new materials .
knots should be just as important at the molecular level, but we can' t exploit that until we learn how to make them, and that' s really what we' re beginning to do ,
added leigh .
“this is the long - awaited step into totally new molecular knots, ” adds amar flood, an expert in self - assembly at indiana university bloomington. “the design with circular helicates is elegant and expedient, and the execution masterful. ”
trying to knot tiny molecules together is a task that is exactly as difficult as it sounds. however, manipulating molecules into ever tighter knots is a goal that many researchers eagerly pursue, and not just for the daunting challenge it provides .
leigh and his team used a precise mix of ions under controlled conditions to braid the strands of molecules together in a process called self - assembly. the final knot is made up of 192 atoms and includes chlorine, hydrogen and nitrogen, among other elements .
leigh hopes to use what his group learned from making the braided knot to create even more complex braided knots and possibly even woven polymers. “what we’re really interested in doing is finding general ways that could be used to make whatever sort of knot that you want. there are six billion knots that have been tabulated by mathematicians, and chemists have only been able to make three of them up to now. this is the fourth, ” he says. “clearly there’s a huge unexplored area of chemical space out there. ”
leigh’s group made the 192 - atom knot with eight different crossing points by first assembling a circular triple helicate. helicates are helical complexes that contain metal ions. in this case, four iron ions were used to coordinate three bipyridine moieties on four identical ligand strands .
scientists believe that making different types of molecular knots can be used as a method to probe how knotting affects strength and elasticity of materials. this, in turn, can lead to the creation of polymer strands that can be used to build stronger and more flexible materials .
the team, led by professor david leigh, have developed a technique that uses iron ions to carefully direct and braid 192 atoms that intersect at eight distinct points. the breakthrough, published this week in science, represents the most complex knot synthesized in a lab so far .
a team of researchers from the university of manchester has now created a record - breaking knot. it contains eight crossings in a 192 - atom closed loop, and is roughly 10, 000 times thinner than a human hair — the most tightly knotted physical structure ever created .
a team of researchers from the university of manchester has created a record - breaking knot. the structure contains eight crossings in a 192 - atom closed loop, and is roughly 10, 000 times thinner than a human hair — making it the most tightly knotted physical structure ever created .
“in our everyday world, we know the benefits of weaving fabrics, ” he says. “you get materials that can stretch in different directions, hold their shape, they’re light and strong and flexible – hopefully we can use the same principles and get related effects at the molecular level. ”
“tying knots is a similar process to weaving, so the techniques being developed to tie knots in molecules should also be applicable to the weaving of molecular strands, ” david leigh from the university of manchester, one of the authors of the a study detailing the achievement, said in a statement. “for example, bullet - proof vests and body armor are made of kevlar, a plastic that consists of rigid molecular rods aligned in a parallel structure — however, interweaving polymer strands have the potential to create much tougher, lighter and more flexible materials in the same way that weaving threads does in our everyday world. ”
“the strands that we’re knotting are so small that you can’t grab the ends and mechanically tie them like you would a shoelace, ” says leigh. “unlike tying your shoelaces, where you do them one at a time, with self - assembly we can tie many billions of molecular knots at the same time. ”
bullet - proof vests and body armour are made of kevlar, a plastic that consists of rigid molecular rods aligned in a parallel structure - however, interweaving polymer strands have the potential to create much tougher, lighter and more flexible materials in the same way that weaving threads does in our everyday world ,
said leigh .
the chemists heated the metal - ligand mixture, allowing it to arrive at its thermodynamic minimum, which corresponds to the braided structure. they then used metathesis chemistry to link olefins at the ends of the ligand strands together to produce the knot. the tough part, leigh says, is designing the ligand strand so that it will coordinate the iron ions and so that the strand ends will meet up in just the right way .
historically, knotting and weaving have led to all kinds of breakthrough technologies ,
says david leigh at the university of manchester in the u. k. , who notes that knots led to prehistoric innovations such as fishing nets and clothes .
knots should be just as important at the molecular level, but we can' t exploit that until we learn how to make them, and that' s really what we' re beginning to do .
“some polymers, such as spider silk, can be twice as strong as steel so braiding polymer strands may lead to new generations of light, super - strong and flexible materials for fabrication and construction, ” continued leigh. “for example, bullet - proof vests and body armour are made of kevlar, a plastic that consists of rigid molecular rods aligned in a parallel structure – however, interweaving polymer strands have the potential to create much tougher, lighter and more flexible materials in the same way that weaving threads does in our everyday world. ”
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angew chem int ed engl. 2000 may; 39 (9): 1616 - 1618 .
kekulé - institut für organische chemie und biochemie der universität bonn gerhard - domagk - strasse 1, 53121 bonn (germany) .
science 13 jan 2017: vol. 355, issue 6321, pp. 159 - 162 doi: 10. 1126 / science. aal1619
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school of chemistry, university of manchester, oxford road, manchester, m13 9pl, uk .
science 24 jun 2016: vol. 352, issue 6293, pp. 1555 - 1559 doi: 10. 1126 / science. aaf3673
guide to scientific products, instruments and services: science innovation; meeting abstracts (journal, magazine, 1992) [ worldcat. org ]
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braiding—the interlacing of three or more strands—seems fairly straightforward, but as any parent of a long - haired child will tell you, it takes skilled hands to master the technique. braiding a molecule poses an even greater challenge because no hands are nimble enough to entwine structures on such a small scale .
“it looks like magic, but it’s not, ” says alberto credi, an expert in supramolecular chemistry at the university of bologna, of the synthesis. “this work is an impressive demonstration that sophisticated structural programs can be executed by self - assembly through a careful design. ”
this article has been translated into spanish by urltoken and can be found here .
dear colleagues, the principle of the construction around the metal in octahedral complexes had been proposed by myself in 1973 (russ. chem. revs) and then within my book
introduction to theoretical stereochemistry
, russian version, moscow, 1979, updated english translation, gordon @ breach, london, 1991. this has been recognised by j - p. sauvage in the first publications leading to nobel prize. in one of previous papers david leigh referred to my work, but not here where his team reached the big success. probably, he did not expect that i am still acting scientist. viacheslav i. sokolov, institute of organoelement compounds, moscow, russia
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your idea however original, is not something that any skilled chemist wouldn' t be able to come up with. ideas are cheap, it is the execution that should be prized. a little modesty mr. sokolov .
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the ability to weave complex molecules together can open the door to many applications for nano - knotted materials, from textiles to electronics .
this technology has potential applications in the production of many different types of knots and might soon be in a breakthrough material near you .
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“there are over 6 million different sorts of knots known to mathematicians, and chemists had been able to make just one, which was pretty pathetic, ” says david leigh at the university of manchester, uk .
“this is a synthetic masterpiece, formed in a very simple and extraordinarily elegant manner, ” says thorfinnur gunnlaugsson at trinity college dublin, ireland .
the method may enable chemists to synthesise more types of knotted molecules in large batches .
“it is quite likely that these knotted molecules will show properties different from un - knotted ones, but nobody’s done the research yet to show what those might be, ” says sophie jackson at the university of cambridge .
leigh says the practical applications of knotted molecules will probably only be discovered when chemists try to weave them together, a process that is similar to knotting. he imagines these woven materials could be used to make anything from lighter bulletproof vests to more flexible surgical sutures .
that' s surprising, he says, considering that mathematicians have come up with billions of possible knots .
you can' t tie the knots by grabbing the ends and mechanically tying them like you would a shoelace in our everyday world ,
leigh says .
instead, you have to use chemistry .
it' s fantastic ,
says edward fenlon, a chemist at pennsylvania' s franklin & marshall college who has a special interest in knots but was not part of this research team .
it' s really impressive that they' ve been able to go beyond some of the more simple knots with just three crossings .
in this case, the
rope
is very short — just 192 atoms long, or 500 times smaller than a red blood cell, leigh says .
knots are really fascinating objects or geometric shapes. they have always been around; you observe them in art, in nature. as a boy scout you learn how to tie knots ,
says rigoberto advincula, a chemist at cleveland' s case western reserve university, who notes that knots also are found in dna and proteins .
it' s one of the fascinating things to stretch chemistry in terms of your ability to make synthetic objects .
the two - way was an npr blog that ran from 2009 to 2018 .
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the authors thank the diamond light source (uk) for synchrotron beamtime on i19 (xr029), the engineering and physical sciences research council (epsrc) national crystallography service for data collection, and the epsrc national mass spectrometry service centre (swansea, uk) and c. l. mackay (sircams, university of edinburgh) for high - resolution mass spectrometry. j. e. b. and d. s. are swiss national science foundation postdoctoral fellows. this research was funded by the epsrc and the academy of finland (k. r. , projects 212588 and 218325) .
department of chemistry, nanoscience center, university of jyväskylä, p. o. box 35, 40014 jyu, finland
j - f. a. , j. e. b. , r. t. m. and d. s. carried out the synthesis and characterization studies, helped plan the experiments, and participated in the preparation of the manuscript. k. r. solved the crystal structure. d. a. l. helped plan the experiments and prepare the manuscript .
nature is part of springer nature. © 2018 springer nature limited. all rights reserved .
just picture bullet - proof material that' s as light and flexible as cotton .
historically, knotting and weaving have led to all kinds of breakthrough technologies ,
one of the researchers, david leigh, from the university of manchester in the uk, told nell greenfieldboyce at npr .
just think about clothes, fishing nets, even shoe laces - all inventions that came about thanks to our ability to tie knots .
you can' t just grab two molecules like shoelaces and wrap them around each other - you actually need to nudge chemicals to bond with each other in specific ways .
the fact that the team is now able to take regular molecules and braid them together means we could be on the verge of creating materials with fascinating new properties .
for example, if we could learn to weave together the molecules in bullet - proof vests, we could develop materials that are lighter, more flexible, but even stronger than kevlar .
some polymers, such as spider silk, can be twice as strong as steel so braiding polymer strands may lead to new generations of light, super - strong and flexible materials for fabrication and construction .
it could also lead to applications beyond what we can picture at the moment, seeing as knots also play an important role in the formation of dna and proteins .
knots are really fascinating objects or geometric shapes. they have always been around; you observe them in art, in nature. as a boy scout, you learn how to tie knots ,
chemist rigoberto advincula from case western reserve university, who wasn' t involved in the study, told npr .
it' s one of the fascinating things to stretch chemistry in terms of your ability to make synthetic objects .
the end product contained, among other elements, chlorine, hydrogen and nitrogen atoms, and its structure was confirmed using x - ray crystallography.
in chemistry , a molecular knot , or knotane , is a mechanically-interlocked molecular architecture that is analogous to a macroscopic knot . a molecular knot in a trefoil knot configuration is chiral , having at least two enantiomers . examples of naturally formed knotanes are dna and certain proteins . lactoferrin has an unusual biochemical reactivity compared to its linear analogue . other synthetic molecular knots have a distinct globular shape and nanometer sized dimensions that make them potential building blocks in nanotechnology . the first knot was synthesised by jean-pierre sauvage in 1989 . the term knotane was coined by fritz vögtle et al. in angewandte chemie international edition in 2000 by analogy with rotaxane and catenane . the term , however , has yet to be adopted by iupac . several synthetic knotanes have been reported . a pentafoil knot prepared using dynamic covalent chemistry has been reported . later in 2016 , a fully organic pentafoil knot was also reported , including the very first use of a molecular knot to allosterically regulate catalysis . in january 2017 an 8 ₁₉ knot ( the tightest knot yet synthesized ) was reported by david leigh 's group . 
in chemistry, a molecular knot, or knotane, is a mechanically-interlocked molecular architecture that is analogous to a macroscopic knot. a molecular knot in a trefoil knot configuration is chiral, having at least two enantiomers. examples of naturally formed knotanes are dna and certain proteins. lactoferrin has an unusual biochemical reactivity compared to its linear analogue. other synthetic molecular knots have a distinct globular shape and nanometer sized dimensions that make them potential building blocks in nanotechnology. the first knot was synthesised by jean-pierre sauvage in 1989. the term knotane was coined by fritz vögtle et al. in angewandte chemie international edition in 2000 by analogy with rotaxane and catenane. the term, however, has yet to be adopted by iupac. several synthetic knotanes have been reported. a pentafoil knot prepared using dynamic covalent chemistry has been reported. later in 2016, a fully organic pentafoil knot was also reported, including the very first use of a molecular knot to allosterically regulate catalysis. in january 2017 an 8 ₁₉ knot (the tightest knot yet synthesized) was reported by david leigh's group.
in chemistry, a molecular knot, or knotane, is a mechanically-interlocked molecular architecture that is analogous to a macroscopic knot. a molecular knot in a trefoil knot configuration is chiral, having at least two enantiomers. examples of naturally formed knotanes are dna and certain proteins. lactoferrin has an unusual biochemical reactivity compared to its linear analogue. other synthetic molecular knots have a distinct globular shape and nanometer sized dimensions that make them potential building blocks in nanotechnology. the first knot was synthesised by jean-pierre sauvage in 1989. the term knotane was coined by fritz vögtle et al. in angewandte chemie international edition in 2000 by analogy with rotaxane and catenane. the term, however, has yet to be adopted by iupac. several synthetic knotanes have been reported. a pentafoil knot prepared using dynamic covalent chemistry has been reported. later in 2016, a fully organic pentafoil knot was also reported, including the very first use of a molecular knot to allosterically regulate catalysis. in january 2017 an 8 ₁₉ knot (the tightest knot yet synthesized) was reported by david leigh's group.