Left Handed DNA
- Tom Schneider
version = 4.09 of leftyear2004.txt 2009 Sep 29
|Our Story So Far: The story line, if you have not had time to follow the previous 552 or so entries (!) is my slow realization that earth is being invaded by left handed DNA people ...|
Reprinted by permission from
427, 592 - 594 (2004)
copyright 2004 Macmillan Publishers Ltd.
and Peter Carmeliet.
Tue, 24 Feb 2004 10:26:20
You may use the image, as long as you point out that the use of a left-handed DNA is intentional and not accidental.
I am rather familiar with DNA structure, having worked on calculating circular dichroism spectra for DNA in A, B, and Z-conformation (Richterich P, Pohl FM, "Calculation of the CD of oligo (dG-dC): influence of basic optical parameters." Biopolymers. 1987 Feb;26(2):231-50).
I did this work in the laboratory of Prof. Fritz Pohl, who in the 1960s set out to search from left-handed DNA, and discovered the B -> Z transitions of GC-oligomers when going from low salt to high salt (J Mol Biol. 1972 Jun 28;67(3):375-96; Proc Natl Acad Sci USA. 1986 Jul;83(14):4983-7).
There are many who credit to Prof. Pohl the fact that the first crystal structure of DNA to be solved was left handed (see, for example, T J Thamann, R C Lord, A H Wang, and A Rich, "The high salt form of poly(dG-dC).poly(dG-dC) is left-handed Z-DNA: Raman spectra of crystals and solutions.", Nucleic Acids Res. 1981 October 24; 9 (20): 54435457). If I recall correctly, these crystallizations were actually carried out in low-salt and high-salt solutions; however, since the effective salt concentration in the crystals is very high, both solutions gave rise to left handed helices in the crystals.
I chose a left-handed DNA for our logo in reverence to Prof. Pohl, an outstanding and very original scientist who I worked with during my undergraduate and graduate studies (and who unfortunately died at a young age). I am always interested in how many people notice that the helix in the picture is left-handed - very few people seem to notice it, so congratulations to Dennis Maeder for noticing.
Peter Richterich, Ph.D.
58 Beech Street
Dedham, MA 02026
(781) 686-1131 phone
(781) 407-0807 fax
(c) 1999 Robert A. Freitas Jr.
All Rights Reserved
Hello, Tom. Thanks to you and Dennis Maeder for noticing that the DNA pictured on the front cover of my book, Nanomedicine, Vol. I (1999) http://www.nanomedicine.com/NMI.htm, is intentionally left-handed rather than right-handed. Your implication that my book recommends employing left-handed DNA to build medical nanodevices, while amusing, is not quite right, since antibodies can recognize both B-DNA and Z-DNA. In fact, all of the nanorobotic devices I've proposed (e.g., respirocytes http://www.foresight.org/Nanomedicine/Respirocytes.html, microbivores http://www.rfreitas.com/Nano/Microbivores.htm, etc.) use mostly diamondoid materials in their construction, not DNA.
My technical books make the case that in future years, it will be possible to construct medical nanorobots -- micron-sized mechanical robots built from molecularly-precise nanoscale components. A most important function of these nanorobots will be conducting in vivo cellular repair operations, including operations on individual macromolecules if necessary and even base-by-base repair or manufacture of DNA.
The cover art for Volume I depicts tiny workers manually handling molecular components -- to emphasize that nanorobots will be capable of performing trajectory-constrained positional assembly, not just random-trajectory self-assembly as is customary in biology. The cover art also depicts the construction of Z-DNA rather than B-DNA -- to emphasize that nanorobots will not be restricted to manipulating conventional organic materials but can also build many useful "unnatural" molecular arrangements so long as those new arrangements are chemically stable. You'll also notice that my nanocaduceus logo image http://www.nanomedicine.com/Graphics/NanoMedRS.gif, featured prominently on the cover spine and inside my books and on my websites (and showing right-handed DNA!), depicts two similarly unnatural 7-fingered human hands -- to emphasize that the advent of nanorobotic medicine may allow us easily to modify our natural forms. Apparently these artistic subtleties have been lost on some readers.
Robert A. Freitas Jr. http://www.rfreitas.com
Author, Nanomedicine http://www.nanomedicine.com
Research Fellow, Institute for Molecular Manufacturing http://www.imm.org
Just returned from the American Society for Microbiology annual meeting in New Orlea ns, where I encountered the exhibitor display pictured in the attached image. Gen-Probe makes various molecular genetic assays, primarily for the detection of infectious diseases.First reported on 2004 June 3, as of 2004 June 3 (Thanks to Henry Shaw, hfshaw at hotmail.com, for pointing this one out!)
When I called attention to the fact that their DNA "scupture" (which rotates in real life) has the wrong handedness, the nice salepeople staffing the booth seemed less than concerned. They said that the error had been pointed out to them a couple of years ago, but no one else seemed to notice!
For your first visit to the Left Handed Hall of Fame page I suggest that you follow the story over all of the years. After that you can look at each year individually from the table below. Note: just because a year has gone by does not mean we haven't found more examples for that year!
|Year||Number of Left Handed DNAs|
|1990||16 (5 from the Tessman letter)|
|2005||44 (minimizing images)|
|2006||17 (minimizing images)|
|2007||26 (no images, sorry)|
|2008||16 (no images, sorry)|
|2009||23 (no images, sorry)|
|2010||26 (no images, sorry)|
|2011||11 (only 2 images, sorry)|
|2012||11 (only rare images, sorry)|
|2013||12 (only rare images, sorry)|
|2014||12 (only rare images, sorry)|
|2015||3 (images under Fair Use copyright policy)|
|2016||2 (images under Fair Use copyright policy)|
|2017||4 (images under Fair Use copyright policy)|