tag:blogger.com,1999:blog-37148773.post941953694881499660..comments2024-03-27T14:50:47.345-04:00Comments on <center>Sandwalk</center>: Nicholas Wade on the Origin of LifeLarry Moranhttp://www.blogger.com/profile/05756598746605455848noreply@blogger.comBlogger8125tag:blogger.com,1999:blog-37148773.post-22487596560616428122021-06-06T15:50:49.667-04:002021-06-06T15:50:49.667-04:00An interesting article. I tend to agree with Wade&...An interesting article. I tend to agree with Wade's description of J. Am. Chem. Soc., 2008, 130 (4), pp 1158–1159 as freezing and thawing in an article meant for mass consumption. This type of simplification helps the non-scientific reader understand the basic concepts by avoiding too much detail. The poster also raises several interesting issues.Joe Fiditchhttps://www.blogger.com/profile/08858846273796106121noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-654131305044892262021-06-06T15:48:16.254-04:002021-06-06T15:48:16.254-04:00An interesting exchange of information ... I tend ...An interesting exchange of information ... I tend to agree with Wade's simplification of the J. Am. Chem. Soc., 2008, 130 (4), pp 1158–1159 article - as his articles are for the general public. The poster also raises many interesting issues.Joe Fiditchhttps://www.blogger.com/profile/08858846273796106121noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-58883691338956722502009-06-16T16:46:16.360-04:002009-06-16T16:46:16.360-04:00I've heard Prof. Blackmond lecture. The enanti...I've heard Prof. Blackmond lecture. The enantiomeric selection depends on, among other things, a selection effect. Early microcrystals form at random and seed the production of similarly handed crystals, leading to a separation between the soluble and crystal forms. The phenomenon has been repeated in other contexts by, e.g., David Deamer. It's pretty damn good science. <br /><br />Even better is the fun of telling a creationist who raises this old "evidence against evolution" that he's behind on the chemical literature. Hee. Hee.Franknoreply@blogger.comtag:blogger.com,1999:blog-37148773.post-9159217880525598972009-06-16T15:52:38.756-04:002009-06-16T15:52:38.756-04:00I am not sure Wade made the mistake you accuse h...I am not sure Wade made the mistake you accuse him of making... <br /><br />Wade: <br /><i>Left-handed nucleotides are a poison because they prevent right-handed nucleotides linking up in a chain to form nucleic acids like RNA or DNA. Dr. Joyce refers to the problem as “original syn,” referring to the chemist’s <b>terms syn and anti for the structures in the handed forms.</b></i><br /><br />You:<br /><i>In fact, nucleotides like deoxyguanylate can switch between the two conformations even while they are part of DNA. The anti conformation is found in normal B-DNA but the double helix can adopt a Z-DNA conformation under some circumstances and in that conformation the deoxyguanylate residues are in the syn conformation.</i><br /><br />Sure, Wade's sentence is unclear and confusing but it is possible that he meant what you describe: that right-handed nucleotides (D-ribose-based) in anti conformation make up right-handed DNA while in syn conformation the DNA becomes left-handed (Z-DNA)!DKnoreply@blogger.comtag:blogger.com,1999:blog-37148773.post-63834738842302286302009-06-16T15:20:41.551-04:002009-06-16T15:20:41.551-04:00Emergence of a Single Solid Chiral State from a Ne...<a href="http://pubs.acs.org/doi/abs/10.1021/ja7106349" rel="nofollow">Emergence of a Single Solid Chiral State from a Nearly Racemic Amino Acid Derivative</a><br />Wim L. Noorduin,† Toshiko Izumi,‡ Alessia Millemaggi,§ Michel Leeman, Hugo Meekes,† Willem J. P. Van Enckevort,† Richard M. Kellogg,* Bernard Kaptein,*§ Elias Vlieg,*† and Donna G. Blackmond*‡;;;<br />J. Am. Chem. Soc., 2008, 130 (4), pp 1158–1159<br />DOI: 10.1021/ja7106349<br /><br /><i>The evolution of a single chiral solid state is reported for an amino acid derivative starting from a nearly racemic mixture of solid left- and right-handed crystals. Attrition-enhanced dissolution and recrystallization processes based on solubility considerations of the Gibbs−Thomson rule, coupled with solution-phase racemization, drive this near-equilibrium system inexorably to single chirality in the solid phase.</i><br /><br />I suppose "dissolution and recrystallization processes based on solubility considerations" could be interpreted as freezing and thawing(?)Bayesian Bouffant, FCDnoreply@blogger.comtag:blogger.com,1999:blog-37148773.post-79183212197475683652009-06-16T15:03:21.492-04:002009-06-16T15:03:21.492-04:00Postdiluvian posted a link to Donna Blackmond'...Postdiluvian posted a link to Donna Blackmond's publications.<br /><br />I read some of them before I posted. I couldn't find anything that shows how to convert a racemic mixture of amino acids to 100% L-forms by freezing and thawing. <br /><br />Did I miss something?Larry Moranhttps://www.blogger.com/profile/05756598746605455848noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-83643472331947431762009-06-16T14:39:26.637-04:002009-06-16T14:39:26.637-04:00donna blackmond's publications: http://www3.im...donna blackmond's publications: http://www3.imperial.ac.uk/people/d.blackmond/publicationsAndrewhttps://www.blogger.com/profile/10131817444483544280noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-86243049368412139512009-06-16T13:50:49.217-04:002009-06-16T13:50:49.217-04:00Who knows, maybe Wade should have spent less time ...Who knows, maybe Wade should have spent less time on his nifty metaphor and more time on accuracy.gilltnoreply@blogger.com