Editing Molecular assembler (section)

==History==
Beginning in 2007, the British [[Engineering and Physical Sciences Research Council]] has funded development of [[ribosome]]-like molecular assemblers.  Clearly, molecular assemblers are possible in this limited sense. A technology roadmap project, led by the [[Battelle Memorial Institute]] and hosted by several [[United States Department of Energy national laboratories|U.S. National Laboratories]] has explored a range of atomically precise fabrication technologies, including both early-generation and longer-term prospects for programmable molecular assembly; the report was released in December, 2007.<ref name="RoadMap">{{Cite web|url=http://www.foresight.org/roadmaps/Nanotech_Roadmap_2007_main.pdf|title=Productive Nanosystems: A Technology Roadmap|website=Foresight Institute|access-date=2008-04-01|archive-date=2016-10-25|archive-url=https://web.archive.org/web/20161025172233/https://www.foresight.org/roadmaps/Nanotech_Roadmap_2007_main.pdf|url-status=dead}}</ref> In 2008, the Engineering and Physical Sciences Research Council provided funding of £1.5 million over six years (£1,942,235.57, $2,693,808.00 in 2021<ref>{{Cite web|title=Value of 2008 British Pounds today - Inflation calculator|url=https://www.inflationtool.com/british-pound/2008-to-present-value?amount=1500000|access-date=September 5, 2021|website=Inflation Tool}}</ref>) for research working towards mechanized [[mechanosynthesis]], in partnership with the Institute for Molecular Manufacturing, amongst others.<ref>{{cite web |url=http://gow.epsrc.ac.uk/ViewGrant.aspx?GrantRef=EP/G007837/1 |title=Grants on the Web |url-status=dead |archive-url=https://web.archive.org/web/20111104152935/http://gow.epsrc.ac.uk/ViewGrant.aspx?GrantRef=EP%2FG007837%2F1 |archive-date=November 4, 2011 }}</ref>

Likewise, the term "molecular assembler" has been used in [[science fiction]] and [[popular culture]] to refer to a wide range of fantastic atom-manipulating nanomachines. Much of the controversy regarding "molecular assemblers" results from the confusion in the use of the name for both technical concepts and popular fantasies. In 1992, Drexler introduced the related but better-understood term "molecular manufacturing", which he defined as the programmed "[[chemical synthesis]] of complex structures by mechanically positioning reactive molecules, not by manipulating individual atoms".<ref name="counterpoint">{{cite web|url=http://pubs.acs.org/cen/coverstory/8148/8148counterpoint.html|title=C&En: Cover Story - Nanotechnology}}</ref>

This article mostly discusses "molecular assemblers" in the popular sense. These include hypothetical machines that manipulate individual atoms and machines with organism-like [[Self-replicating machine|self-replicating]] abilities, mobility, ability to consume food, and so forth. These are quite different from devices that merely (as defined above) "guide chemical reactions by positioning reactive molecules with atomic precision".

Because synthetic molecular assemblers have never been constructed and because of the confusion regarding the meaning of the term, there has been much controversy as to whether "molecular assemblers" are possible or simply science fiction. Confusion and controversy also stem from their classification as [[nanotechnology]], which is an active area of laboratory research which has already been applied to the production of real products; however, there had been, until recently,{{When|date=September 2021}} no research efforts into the actual construction of "molecular assemblers".

Nonetheless, a 2013 paper by [[David Leigh (scientist)|David Leigh]]'s group, published in the journal ''[[Science (journal)|Science]]'', details a new method of synthesizing a [[peptide]] in a sequence-specific manner by using an artificial molecular machine that is guided by a molecular strand.<ref>{{Cite journal|last1=Lewandowski|first1=Bartosz|last2=De Bo|first2=Guillaume|last3=Ward|first3=John W.|last4=Papmeyer|first4=Marcus|last5=Kuschel|first5=Sonja|last6=Aldegunde|first6=María J.|last7=Gramlich|first7=Philipp M. E.|last8=Heckmann|first8=Dominik|last9=Goldup|first9=Stephen M.|date=2013-01-11|title=Sequence-Specific Peptide Synthesis by an Artificial Small-Molecule Machine|journal=Science|language=en|volume=339|issue=6116|pages=189–193|doi=10.1126/science.1229753|issn=0036-8075|pmid=23307739|bibcode=2013Sci...339..189L|s2cid=206544961|url=https://pure.manchester.ac.uk/ws/files/30033043/POST-PEER-REVIEW-PUBLISHERS.PDF }}</ref> This functions in the same way as a ribosome building proteins by assembling amino acids according to a messenger RNA blueprint. The structure of the machine is based on a [[rotaxane]], which is a molecular ring sliding along a molecular axle. The ring carries a [[thiolate]] group, which removes amino acids in sequence from the axle, transferring them to a peptide assembly site. In 2018, the same group published a more advanced version of this concept in which the molecular ring shuttles along a polymeric track to assemble an [[oligopeptide]] that can fold into an [[Alpha helix|α-helix]] that can perform the [[enantioselective]] [[epoxidation]] of a [[chalcone]] derivative (in a way reminiscent to the ribosome assembling an [[enzyme]]).<ref>{{Cite journal|last1=De Bo|first1=Guillaume|last2=Gall|first2=Malcolm A. Y.|last3=Kuschel|first3=Sonja|last4=Winter|first4=Julien De|last5=Gerbaux|first5=Pascal|last6=Leigh|first6=David A.|date=2018-04-02|title=An artificial molecular machine that builds an asymmetric catalyst|journal=Nature Nanotechnology|volume=13|issue=5|pages=381–385|language=En|doi=10.1038/s41565-018-0105-3|pmid=29610529|bibcode=2018NatNa..13..381D|s2cid=4624041|issn=1748-3395|url=https://www.research.manchester.ac.uk/portal/en/publications/an-artificial-molecular-machine-that-builds-an-asymmetric-catalyst(569800d8-beb2-4d4a-acd5-84d0369ddabb).html}}</ref> In another paper published in ''Science'' in March 2015, chemists at the [[University of Illinois]] report a platform that automates the synthesis of 14 classes of [[small molecule]]s, with thousands of compatible building blocks.<ref>{{cite journal|title=Synthesis of many different types of organic small molecules using one automated process|journal=Science|volume=347|issue=6227|pages=1221–1226|doi=10.1126/science.aaa5414|pmid=25766227|pmc=4687482|year=2015|last1=Li|first1=J.|last2=Ballmer|first2=S. G.|last3=Gillis|first3=E. P.|last4=Fujii|first4=S.|last5=Schmidt|first5=M. J.|last6=Palazzolo|first6=A. M. E.|last7=Lehmann|first7=J. W.|last8=Morehouse|first8=G. F.|last9=Burke|first9=M. D.|bibcode=2015Sci...347.1221L}}</ref>

In 2017, [[David Leigh (scientist)|David Leigh]]'s group reported a molecular robot that could be programmed to construct any one of four different [[stereoisomer]]s of a molecular product by using a nanomechanical robotic arm to move a molecular substrate between different reactive sites of an artificial molecular machine.<ref>{{Cite journal | last1 = Kassem | first1 = S. | last2 = Lee | first2 = A. T. L.. | last3 = Leigh | first3 = D. A. | author-link3 = David Leigh (scientist)| last4 = Marcos | first4 = V. | last5 = Palmer | first5 = L. I. | last6 = Pisano | first6 = S. | doi = 10.1038/nature23677 | pmid = 28933436 | title = Stereodivergent synthesis with a programmable molecular machine | journal = Nature | volume = 549 | issue = 7672 | pages = 374–378 | year = 2017 | bibcode = 2017Natur.549..374K | s2cid = 205259758 | url = https://www.research.manchester.ac.uk/portal/en/publications/stereodivergent-synthesis-with-a-programmable-molecular-machine(dd2b7aed-b6ff-455a-8fb7-e31851cea5e6).html }}</ref> An accompanying News and Views article, titled 'A molecular assembler', outlined the operation of the molecular robot as effectively a prototypical molecular assembler.<ref>{{Cite journal | last1 = Kelly | first1 = T. R. | last2 = Snapper | first2 = M. L. | doi = 10.1038/549336a | pmid = 28933435 | title = A molecular assembler | journal = Nature | volume = 549 | issue = 7672 | pages = 336–337 | year = 2017 | doi-access = free }}</ref>