From chemistry-request@server.ccl.net Fri Jul 30 17:52:32 1999 Received: from mailhost.det.ameritech.net (mpdr0.detroit.mi.ameritech.net [206.141.239.206]) by server.ccl.net (8.8.7/8.8.7) with ESMTP id RAA23420 for ; Fri, 30 Jul 1999 17:52:32 -0400 Received: from kressj.www.ameritech.net ([199.179.190.96]) by mailhost.det.ameritech.net (InterMail v4.01.01.00 201-229-111) with SMTP id <19990730214516.RBIU16694.mailhost.det.ameritech.net@kressj.www.ameritech.net>; Fri, 30 Jul 1999 17:45:16 -0400 Message-ID: <003701bedad4$ce6fade0$60beb3c7@www.ameritech.net> Reply-To: "Jim Kress" From: "Jim Kress" To: "Peter Shenkin" , References: Subject: Re: CCL:Levinthal's paradox Date: Fri, 30 Jul 1999 17:45:13 -0400 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 5.00.2314.1300 X-Mimeole: Produced By Microsoft MimeOLE V5.00.2314.1300 In highly nonlinear systems sudden transitions in states (from one to another) are a well known behavior. Could it be that the 'paradox' is just the result of a simple state change in a protein driven by the highly nonlinear forces that control its configuration? Jim Check out my web site http://www.kressworks.com/ It'll blow your mind (politically), stimulate your senses (artistically) and provide scientific insights that boggle the mind! ----- Original Message ----- From: Peter Shenkin To: Sent: Friday, July 30, 1999 4:35 PM Subject: CCL:Levinthal's paradox > On Fri, 30 Jul 1999, JATI KASTANJA wrote: > > does anyone know something about the Levinthal paradox? > >... > > Until now I am unsuccessful in finding out the journal where Cyrus ... > > Hi, > > If you do find the Journal, you will find that it contains only > a passing reference to what has become known as the Levinthal > paradox. The idea really derives from a comment Cyrus once made at a > meeting. > > The idea is this. Take a 100-residue protein. Let's suppose each > residue can have only, say, 3 conformational states. Then there > are 3^100, or about 10^48, possible states. Now suppose the protein > can explore a new state with every moleculear vibration. Suppose > each vibration takes about a femtosecond. Then exploring all > the states would take about 10^48 fs, or 10^33 s. There are about 10^8 s > in a year, so exploring all the states would take about 10^25 years. > But this is longer than the age of the universe. > > Now, in order for a protein to fold into its global > thermodynamic energy minimum, the folding process has to > be ergodic. That is, it has to explore all its states > within the time-span of the process. But protein folding takes > typically seconds to minutes. So a protein can't be folding > into its thermodynamic energetic minimum, since it can't > possibly find it in so short a time. > > Therefore, protein folding must be a kinetically controlled process. > I.e., proteins fold to the most accessible minimum, rather than the > most stable minimum. In this, protein folding must resemble the > kinetically controlled reactions of organic (and bio-) chemistry. > > The reason it's considered a "paradox" is that most people > don't believe it (at least for globular proteins as small > as 100 residues). Cyrus didn't believe it either, in fact. > But it is fun to think about, and it's great for impressing > people at cocktail parties. (You have to go to the right cocktail > parties, though. :-) ) > > -P. > > -- > ********* Peter S. Shenkin; Schrodinger, Inc.; (201)433-2014 x111 ********* > *********** shenkin@schrodinger.com; http://www.schrodinger.com *********** > > > -= This is automatically added to each message by mailing script =- > CHEMISTRY@ccl.net -- To Everybody | CHEMISTRY-REQUEST@ccl.net -- To Admins > MAILSERV@ccl.net -- HELP CHEMISTRY or HELP SEARCH > CHEMISTRY-SEARCH@ccl.net -- archive search | Gopher: gopher.ccl.net 70 > Ftp: ftp.ccl.net | WWW: http://www.ccl.net/chemistry/ | Jan: jkl@ccl.net > > > >