From ral@batata.fh.huji.ac.il Tue May 10 07:53:12 1994 Received: from batata.fh.huji.ac.il for ral@batata.fh.huji.ac.il by www.ccl.net (8.6.4/930601.1506) id HAA20264; Tue, 10 May 1994 07:28:20 -0400 Received: by batata.fh.huji.ac.il (920330.SGI/911001.SGI/930210.fh.huji.ac.il) for chemistry@ccl.net id AA13765; Tue, 10 May 94 14:27:31 +0300 Date: Tue, 10 May 94 14:27:31 +0300 From: ral@batata.fh.huji.ac.il (Rogatski Alexander) Message-Id: <9405101127.AA13765@batata.fh.huji.ac.il> To: chemistry@ccl.net Subject: WATER-METHANOL CLUSTER FORMATION ENERGY DEAR NETTERS, Could anybody help me in finding the formation energy of the clusters like N(water)-M(methanol)where N,M>=1; the most recent data or referencies. I need also data on theese clusters protonated and neutral clusters N*(methanol). THANKS. Alecsander Rogatski, ral@batata.fh.huji.ac.il From CUNDARIT@MSUVX1.MEMST.EDU Tue May 10 08:53:15 1994 Received: from msuvx1.memst.edu for CUNDARIT@MSUVX1.MEMST.EDU by www.ccl.net (8.6.4/930601.1506) id HAA21537; Tue, 10 May 1994 07:53:12 -0400 Received: from MSUVX1.MEMST.EDU by MSUVX1.MEMST.EDU (PMDF V4.2-14 #5958) id <01HC5YEF815S8X3P2A@MSUVX1.MEMST.EDU>; Tue, 10 May 1994 06:52:58 CST Date: Tue, 10 May 1994 06:52:57 -0600 (CST) From: CUNDARIT@MSUVX1.MEMST.EDU Subject: Metal-containing drug summary To: chemistry@ccl.net Message-id: <01HC5YEF9DEA8X3P2A@MSUVX1.MEMST.EDU> X-VMS-To: IN%"chemistry@ccl.net" MIME-version: 1.0 Content-type: TEXT/PLAIN; CHARSET=US-ASCII Content-transfer-encoding: 7BIT Fellow Net-tenders, Below is a collection of responses to date on metal in drugs. After asking this question I had a few students go up and search J. Med. Chem., which along with net answers and talking to the organo/medicinal folks here at Memphis yielded the following (with apologies to Dave Letterman) 'Top 10' list. The review by Sadler (ref given below) is a veritable gold mine (no pun intended) of 'inorganic drug' discoveries. Thanks for the many replies! Tom Cundari ######################################################## 1) Technetium for radioimaging. We found a nice article in Coord. Chem. Rev. by Clarke on Tc and its medical uses (1987, 78, 253). 2) Fe-complexes. As one letters points out Ken Raymond and his group have done excellent work here. I'm embarassed I forgot this one since I was sitting in the audience when he gave a seminar on this topic at the last ACS meeting! There is a good paper from his group (JACS 1993, 115, 6758) describing work with Transferrin. 3) MRI contrast agents. As one person pointed out, Gd(III) complexes are not the only ones being studied. I had seen Mn(II) work, but there is Fe(III) work as well. 4) Metalloids including arsenic, antimony and boron. The As complexes seem to be historically significant for the treatment of syphilis and are still used for some ailments. 5) Gold. In colloid form or as a complex, Auranofin (which seems to be a carbohydrate complex of Au). One of my students found a paper where Au was tested as an anti-caner agent. 6) Pt anti-cancer drugs. Well known application. 7) Bismuth. I saw a poster on Bi complexes in San Diego and I believe the application was anti-ulcer medicines. Strangely enough, before seeing Doug's e-mail about Pepto Bismol I ran across this one while checking out a bottle an undergrad had (it's finals week here!). 8) Polyoxometallates have been investigated for anti-HIV potential. Craig Hill (Emory) has done the work I am familiar with. There is a recent paper in J Med Chem (1992, 35, 1216). 9) various chelates for treating heavy metal poison. There is a mention of EDTA for lead poisoning and I think Fe-chelation therapy also would come into this area. 10) Mercury, as used in things like Mercurichrome. This is my personal favorite since I can still recall my grandmother swabbing me down with this stuff any time I got a cut! ######################################################## Thomas Years ago a collegue and I tried to model Technetium compounds in an effort to design better coordination compounds. We were unsuccessful for a number of reasons but I believe that this would be an excellent area in which to work. Technetium compounds are widely utilized in imaging and better agents would fill the gaps that now exist. Jerry L. Born Professor of Pharmacy The University of New Mexico jborn@triton.unm.edu ######################################################## Tom - I don't have a complete list for you of metal containing drugs, but I do know that gold in a colloidal form is used to treat arthritis. Bev Beverly Bendiksen Calgon Corporation Pittsburgh, PA ######################################################## Dear Thomas, I think EDTA had been used to flush lead from the body in cases of lead-poisoning. . HOOC COOH . \ / . N---CH ---- CH ---N . / 2 2 \ . HOOC COOH . . EDTA . And what about macrocyclic antibiotics, erythromycin etc? Best, Max ######################################################## an area in which metal or metal ligands may be useful as (part of) drugs is immunoconjugation of, say, radioisotopes with targetting agents such as antibodies (see recent issues of the ACS journal Bioconjugate Chemistry). I do not know of anyone who has used CADD for this purpose, but I guess in principle it could be done. Best wishes, Max ======================================== Max Vasquez, PhD Protein Design Labs, Inc. 2375 Garcia Ave. Mountain View CA 94043 Phone (415) 903 3744 FAX (415) 903 3730 e-Mail wk01189 @ worldlink.com ======================================== ######################################################## The most obvious case is ACE inhibitors... Several refs on the subject: Saunders, M.R. et al. JCAMD 1987, 1, 133-142. Mayer, D. et al. JCAMD 1987, 1, 3-16. Wyvratt, M.J. and Patchett, A.A. Med. Res. Rev. 1985, 5, 483-531. DePriest, S.A. et al. JACS 1993, 115, 5372-5384. Waller, C.L. and Marshall. G.R. J. Med. Chem. 1993, 36, 2390-2403. and refs therein... ******************************************************************** *Chris L. Waller, Ph.D. PHONE 919-541-7976* *Research Chemist FAX 919-541-5394* *waller@thor.herl.epa.gov * *Pharmacokinetics Branch (MD-74) * *ETD/HERL/USEPA * *Research Triangle Park, NC 27711 * * * * Disclaimer: My opinions - not theirs... * ******************************************************************** Of course Lithium is a drug itself. Bill Ross ######################################################## Tom, I believe the current drug of choice for the treatment of iron overload is a siderophore (small molecule iron binding agent) related to a natural product called enterobactin. Sorry, the name and structure of the drug escapes me at the moment. But, this class of compounds has been studied extensively by Prof. Ken Raymond at UC, Berkeley. Its mentioned in: Raymond, K.N.; Muller, G.; Matsanke, B. F. In Topics of Curr. Chem.; Boschke, F. L., Ed.; Springer-Verlag: New York, 1984, pp 49-102 and in many of Raymond's more recent publications. Hope that helps! Joe Urban *********************************************************************** * Joseph J. Urban, Ph.D. * phone:410-671-3332 * * U. S. Army Edgewood Research, Development, * fax:410-671-1912 * * and Engineering Center * * * Attn: SCBRD-RT (Bldg E3160) * email: * * Aberdeen Proving Ground, MD 21010-5423 *jjurban@cbda.apgea.army.mil* * * * ************************************************************************ ######################################################## Dear Dr. Cundari: With your message you touched a very sensitive topic because so far there are no reliable general methods of modeling transition metal systems. I am working now on this topic which requires quite a novel approach. unfortunately, nothing comprehensive is published so far except an abstract and a poster to the 15 Austin Symposium on Molecular Structure (UT at Austin, March 1994).I would like to ask you to summarize all the replies to your question making them avalable to the interested persons.Regards, Isaac -- * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Isaac B. Bersuker | E-mail: Dept. of Chemistry | cmao771@charon.chpc.utexas.edu Univeristy of Texas at Austin | Vox: (512) 471-4671 Austin, TX 78712 | Fax: (512) 471-8696 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * ######################################################## Hi, Dr. Cundari! I am an M.D.-Ph.D. doing my Radiology Residency. My Ph.D. is in Pharmacology and Biophysics with emphasis in computational chemistry. I will attemp to shed some light on your question, and will get back to you with a review article on the topic. 1) Chelating agents for the removal of toxic metals are already in clinical use. For example, Penicillamine has a variety of uses in Emergency Room medicine for toxic ingestion of metals. Which ones? I don't remember at this time. Patients that receive multiple transfusions, like those suffering from Sickle Cell anemia, receive chelating therapy for Iron because of severe Iron overload. The review article should have the name of the compound. Similarly, Wilson's Disease is a devastating genetic disorder where Cu metabolism is impaired due to the absence of a carrier protein Ceruloplasmin (pardon my spelling here). I also believe they receive chelating therapy. 2) Other therapeutic agents in use today include gold salts for the treatment of Rheumatoid arthritis. In the early days of "modern" pharmacologic treatment many inorganic compounds were used for treatment. Unfortunately, many were very toxic and felt out of favor quickly. Silver nitrate is still used in some nurseries to treat/prevent ophthalmic gonorrhea in the newborn, but most places use modern penicillin derivatives. Obviously, many of the intravenous hyperalimentation formulae used in hospitals today include metals as trace element supplements. 3) The most extensive clinical application of metals or organometallic complexes has ocurred primarily in radiology. (At least to my knowledge!). Early radiologists new that the heavier metals were radiopaque to X-rays and used multiple compounds to generate contrast in their images. Today, almost all of these are no longer in use, and only the iodinated organic compounds remain in use in radiography. MRI has resurrected organometallics for radiologits. You are aware of gadolinium complexes, but many other compounds are in preparation. For example, Mn(II), and Fe(III) chelates for liver and tumor imaging. Almost every week somebody describes a new compound in the radiology literature (check out Magnetic Resonance Imaging, Magnetic Resonance In Medicine, Journal of Investigative Radiology, etc). 4) Porphyrin derivatives are used to identify tumors, particularly, radiologically undetectable lung cancer. They are also used to sensitize tumors prior to radiation therapy. Unfortunately, I don't know if any of these are metalloporphyrins. 5) No, I don't know of any design effort using computational methods that has been used or has been successful to design new drugs that contain metals. Extensive applications exists in using computational chemistry to understand metalloproteins. Who can forget the heme group in MYOGLOBIN and HEMOGLOBIN! But, specific applications in medicinal chemistry... Regarding 5) I am involved in the rational design of new paramagnetic metal chelates that can be used as intravenous MRI contrast agents. Currently, my time is limited and I have only begun to do density functional computations in some metaloporphyrins, but I have accepted a fellowship in the NIH (Laboratory of Diagnostic Radiology Research) where I hope to pursue this research full time. They are interested in developing contrast media and have tested some variations of FexOy particles embedded in Transferrin, an iron carrier molecule in the body. I have experience in the computational chemistry of mostly organic compounds and I will complete my radiology residency in 1 more year (hopefully be Board Certified in the same time! : - ) ). My experience in Inorganic Chemistry is limited to a couple of Graduate chemistry courses, so I am slowly learning the ropes to perform computations with bioinorganic/organometallic compounds. I have followed some of your work, particularly the computations using Harold Basch and Morris Krauss effective core potentials, and believe that you can make a significant contribution to medicinal chemistry if you extend your computational expertise to the rational design of contrast media. Sorry for the bandwidth! I wish you well and will get back to you with the reference! good luck gustavo mercier, jr mercie@cumc.cornell.edu (notice the absence of the last "r" from my last name!) ######################################################## There are not many drugs containing metals. The major problem is the degradation of the compound may result in free metal, which can be toxic. The Pt compounds you mention are a particular case due to the particular problems arising in canc er cancer, toxicity is only one of the issues. There are also some Au containing aniinflammatory agents (non steroidal), see auranofin for instance. These compounds are used as slow acting antiinflammatories. I berlieve that after sometime in the market, some of them were removed, because of severe secondary effects in some people. The uses are mainly in Rheumatism. I do not think there are many more. For instance Fe containing things are for the most part avoided, as they can become liver toxic, as many other dications. I believe hat I would ake a serious look, if I were you to the area of bi biosensors. I believe, some work has been done there theoretically. There are not many repored successes of drug design, and even fewer with metal containg compounds. You may be aware of all the work on metalloenzymes. Regards, Hugo O. Villar, Senior Scientist Terrapin Technologies ######################################################## Hi! Here is the reference I promised: Inorganic Chemistry and Drug Design by Peter J. Sadler In: Advances in Inorganic Chemistry, Vol. 36, pp: 1-48, 1991. I believe the whole issue may have been dedicated to pharmaceuticals and inorganic chemistry. Finally, how could I forget?! The most extensive CURRENT MEDICAL application of organometallics are in antineoplastics (as you already know), and Nuclear Medicine, a cousin of Diagnostic Radiology. All (except for PET) radiopharmaceuticals used today for imaging in Nuclear Medicine use heavy metals chelates. In fact, the liver imaging agents developed for MRI where modeled after similar agents in hepatobiliary imaging in Nuclear Medicine. They simply exchanged the radioactive metal with the paramagnetic metal ion. As far as I know, the most likely candidates to have applied some rational drug design to metal containing pharmaceuticals are the antineoplastic agents (I believe recently discussed in Chemical and Engineering News), and the Nuclear Medicine people. The latter group eagerly looks at the medicinal chemistry literature for compounds that bind to receptors so they can tag them with their radioactive metals. This practice is not always successful, as any chemist familiar with principles of chemical reactivity may expect! Good Luck, gus mercier, jr. mercie@cumc.cornell.edu ######################################################## Tom, I am finishing up my thesis here at Duke. I am engaged in computational studies on boronated nucleotides. I know that boron is technically a metalloid. If you are interested (ie, fits what you are looking for, I can send some references and a general overview). I look forward to your summary on the net! -mark ********************************************** * * * Mark A. Zottola * * markz@chem.duke.edu * * Department of Chemistry * * Duke University * * * * 'The fault, dear Brutus, lies not with * * ourselves, rather within our CPU's...' * * (with due apologies to W.S.) * ######################################################## Tom - I don't have all the lit. here, but there are a number of others. For example, there are the Gold anti-arthrritic (sp?) drugs, and don't forget peptobismol -- which contains bismuth!(delicious). Doug Dudis Wright-Patterson AFB, OH ######################################################## Hi there There are several anti-arthritis drugs on the market which are based on gold complexes. Usually the structure consists of Au(II) linked to a phosphine ligand and a sugar ligand (the trade name for one of these drugs is auromycin). The scientific explanation for gold's anti-arthritis activity is not well known, but it has been used for many, many years (some people believe that the ancient Egyptians were the first to try it as a remedy!) I can give you some references if you are interested in this topic. I would also be interested in getting a summary of replies to your initial query. Thanks. Byron DeLaBarre ######################################################## I would be most interested in the replies to your question. I am just finishing a modelling project on Tc(V) complexes used for radiopharmaceuticals. I don't know if any QSAR techniques have been suddessfully applied to this class of compounds. Susan C. Jackels Department of Chemistry Wake Forest University Winston-Salem, NC 27109 Phone: (919)759-5514 FAX: (919)759-4656 Internet: sjackels@ac.wfunet.wfu.edu On sabbatical for 1993-1994 at: Department of Medicinal Chemistry 308 Harvard Street S.E. University of Minnesota Minneapolis, MN 55455 Phone: (612)626-4429 ######################################################## >Dear Dr. Cundari, >We have had considerable success with density functional >methods for transition metal complexes in Biology. >See Noodleman, Case, Adv. Inorg. Chem.38,423-470,1992; >Schmitt et al,JACS 114,6109-6119;also Ziegler, Chem. Rev.91,651-667, 1991; >also Rosa and Baerends, Inorg.Chem.33,584-595,1994. Also, Density >Functional Methods in Chemistry, Labanowski and Andzelm Eds. Springer-Verlag >1991 for various transition metal complexes. >Lou Noodleman >Molecular Biology, MB1 >The Scripps Research Institute >La Jolla, CA92037 >lou@scripps.edu ######################################################## ------------------------------------------------------------------------------ Thomas R. Cundari Asst. Professor of Chemistry Computational Inorganic Chemistry Lab University of Memphis Check out Univ. of Memphis Memphis, TN 38152 Chem Dept. on the World Wide Web phone: 901-678-2629 Organized by Prof. Henry Kurtz fax: 901-678-3447 Suggestions? kurtzh@msuvx1.memst.edu e-mail: cundarit@memstvx1.memst.edu http://www.memst.edu/chemistry/umchem.html ------------------------------------------------------------------------------- From lchirlia@cc.brynmawr.edu Tue May 10 09:53:14 1994 Received: from cc.brynmawr.edu for lchirlia@cc.brynmawr.edu by www.ccl.net (8.6.4/930601.1506) id JAA27725; Tue, 10 May 1994 09:41:15 -0400 Received: by cc.brynmawr.edu (5.57/cc09-01-92) id AA19110; Tue, 10 May 94 09:44:17 -0400 Message-Id: <9405101344.AA19110@cc.brynmawr.edu> Subject: software for protein structure det. and docking To: chemistry@ccl.net Date: Tue, 10 May 94 9:44:17 EDT From: Chirlian Lisa E X-Mailer: ELM [version 2.3 PL11] I am interested in hearing peoples opinions on any commercially available (or public domain) software for protein structure determination and docking. Please e-mail, I will summarize for anyone interested. Thanks, Lisa From tolja@maya.geo.uu.se Tue May 10 12:54:30 1994 Received: from columba.udac.uu.se for tolja@maya.geo.uu.se by www.ccl.net (8.6.4/930601.1506) id MAA06913; Tue, 10 May 1994 12:15:51 -0400 Received: from maya.geo.uu.se.geo (maya.Geo.UU.SE) by columba.udac.uu.se with SMTP id AA24013 (5.67b8/IDA-1.4.4 for chemistry@ccl.net); Tue, 10 May 1994 18:15:50 +0200 Received: by maya.geo.uu.se.geo (4.1/SMI-4.1) id AA04528; Tue, 10 May 94 18:10:00 +0200 Date: Tue, 10 May 94 18:10:00 +0200 From: tolja@maya.geo.uu.se (Anatoli Belonoshko) Message-Id: <9405101610.AA04528@maya.geo.uu.se.geo> To: chemistry@ccl.net Subject: Xmol -> ps -> color inkjet printer? X-Charset: LATIN1 X-Char-Esc: 29 Dear Netters, I am trying to find out how to print out postscript (color) file (output from Xmol) on my colr inkjet printer (HP DeskJet 550C). Is there any free (preferably) or commercial software for printing postscript files on a non-postscript printers? NOTE: My printer is connected to IBM PC 486/33 - so, the software should be probably for IBM PC? Thank you. Anatoly Belonoshko Uppsala University, Sweden e-mail: tolja@maya.geo.uu.se From Patrick.Bultinck@rug.ac.be Tue May 10 15:53:14 1994 Received: from mserv.rug.ac.be for Patrick.Bultinck@rug.ac.be by www.ccl.net (8.6.4/930601.1506) id PAA18358; Tue, 10 May 1994 15:29:07 -0400 Received: from allserv.rug.ac.be by mserv.rug.ac.be with SMTP id AA25555 (5.67b/IDA-1.5 for ); Tue, 10 May 1994 21:28:32 +0200 Received: by allserv.rug.ac.be (5.0/SMI-SVR4) id AA16249; Tue, 10 May 94 21:25:39 +0200 Date: Tue, 10 May 1994 21:25:36 +0200 (MET DST) From: Patrick Bultinck Subject: energies of conformations To: chemistry@ccl.net Message-Id: Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Content-Length: 2219 Netters, I probably have a bit strange question but anyway.... As probably everybody in the QC-field will aknowledge it is always useful to compare computed results with experiments. I have been reading a number of articles now on theoretical calculations on a number of molecules. The different authors often refer to the same articles with experimental findings. It really strikes me when I find that one author claims that a relative energy X for a certain conformer compared to the energy of the global lowest energy conformation is too big to expect a certain occupation of the confomer, while another one sees it perfectly possible that given the energy difference X there would be a substantial occupation of the higher lying confomer!!! My question is thus simple.... I would like to hear different opinions to how to more or less draw a line between confomers that may show an ***important*** occupation at a temperature T, and which conformers do not show any ***important*** occupation! I have thusfar found a number of quite contradictory statements, and would like to hear other peoples opinions. Reactions may be sent directly to me or the CCl, anyway a summary will be posted some time next week... Thanks a lot, |-----------------------------------------------------------------------| | C-C Patrick Bultinck | | / \ Dept. Physical & Inorganic Chemistry | | C-O O-C Section Quantum Chemistry | | | | University of Ghent | | C-O O-C Krijgslaan 281 (S-3) | | \ / 9000 Gent | | C-C Belgium | | Tel. Int'l code/32/9/264.44.44 | | Macrocycles Fax. Int'l code/32/9/264.49.83 | | Quantum Chemical E-mail : Patrick.Bultinck@rug.ac.be | | Calculations | |-----------------------------------------------------------------------| From GDURST@ELINET1.DOWELANCO.COM Tue May 10 16:53:14 1994 Received: from ELINET1.DOWELANCO.COM for GDURST@ELINET1.DOWELANCO.COM by www.ccl.net (8.6.4/930601.1506) id QAA21220; Tue, 10 May 1994 16:22:20 -0400 Date: Tue, 10 May 1994 15:19:04 -0500 (EST) From: "Gregory L. Durst - DowElanco R&D" To: chemistry@ccl.net CC: GDURST@ELINET1.DOWELANCO.COM Message-Id: <940510151904.2750@ELINET1.DOWELANCO.COM> Subject: QSAR package? Dear Netters, I saw a reference to a QSAR software package and had our library look up the program listed, however nothing was found. The reference reads: STATQSAR Package, CTIS, Lyon, France, 1993. Can anyone help out with an address, phone or email address for this program? Has anyone had any experience with this program? Thanks in advance, Greg +-----------------------------------------------------------------------+ | Gregory L. Durst Computational Chemistry | | phone: 317/337-3413 DowElanco R&D | | email: gdurst@dowelanco.com 9330 Zionsville Rd. Bldg 306/D2 | | Indianapolis, IN 46268 USA | +-----------------------------------------------------------------------+ From oles@kjemi.uio.no Tue May 10 16:54:09 1994 Received: from pat.uio.no for oles@kjemi.uio.no by www.ccl.net (8.6.4/930601.1506) id QAA20875; Tue, 10 May 1994 16:15:39 -0400 From: Received: from ulrik.uio.no by pat.uio.no with local-SMTP (PP) id <01925-0@pat.uio.no>; Tue, 10 May 1994 22:15:25 +0200 Received: by kelvin ; Tue, 10 May 1994 22:15:23 +0200 Date: Tue, 10 May 1994 22:15:23 +0200 Message-Id: <9405102015.AA00486@kelvin> To: chemistry@ccl.net Subject: DFT: Failure stories Hello everybody, I'm giving a seminar on chemical applications of DFT. In picking cases to present, I face a dilemma: There are enough success stories to choose from, but for the sake of balance I need to illustrate some weak spots as well. Rumour has it that transition state energy barriers in bond-breaking reactions often are underestimated by DFT, and some of my own results point in the same direction. I would appreciate any information, references, thoughts, etc. on this or other shortcomings of DFT. Please reply by Email; I'll summarize to the net if I'm asked. Thanks in advance, Ole Swang ----------------------------------------------------------------------- Ole Swang assistant lecturer, Dept. of Chemistry, U. of Oslo ole.swang@kjemi.uio.no ------------------ ._.. ._ ..___ ._ __.. --------------------------- From bewilson@emn.com Tue May 10 17:53:15 1994 Received: from emngw1.emn.com for bewilson@emn.com by www.ccl.net (8.6.4/930601.1506) id QAA23232; Tue, 10 May 1994 16:59:51 -0400 Received: by emngw1.emn.com (AIX 3.2/UCB 5.64/4.03) id AA14027; Tue, 10 May 1994 16:58:10 -0400 Date: Tue, 10 May 1994 16:58:10 -0400 From: bewilson@emn.com (Wilson_Bruce) Message-Id: <9405102058.AA14027@emngw1.emn.com> To: chemistry@ccl.net Subject: Re: Energies of conformations Patrick Bultinck asks: > I would like to hear different opinions to how to more or less draw a > line between confomers that may show an ***important*** occupation at a > temperature T, and which conformers do not show any ***important*** > occupation! I have thusfar found a number of quite contradictory > statements, and would like to hear other peoples opinions. Sure, I'll wade in with a very equivocal answer: "It depends!". Seriously. If the Boltzman distribution shows a 1% population of a conformer level, that may be insignificant for some applications, but it may be highly significant for others. But the simple answer is that I'll do a Boltzman analysis, determine a relative population percentage and then decide whether that's significant for the application at hand. And I'll always report the energy difference, so that the reader can decide whether that's significant or not. Bruce Wilson (bewilson@emn.com) From jmendez@redvax1.dgsca.unam.mx Tue May 10 20:53:17 1994 Received: from redvax1.dgsca.unam.mx for jmendez@redvax1.dgsca.unam.mx by www.ccl.net (8.6.4/930601.1506) id UAA04436; Tue, 10 May 1994 20:31:00 -0400 Received: from standard-input by redvax1.dgsca.unam.mx; Tue, 10 May 94 18:25:12 CST Sender: jmendez@redvax1.dgsca.unam.mx Date: Tue, 10 May 1994 18:20:37 -0600 (CST) From: Mendez Acevedo Juan Manuel-IIM Subject: First Panamerican School on Materials To: anuncios quimica Message-Id: Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII The Materials Research Institute of the National University of Mexico (UNAM) is organizing, sponsored by the Oraganization of American States, the First Panamerican School on Materials, which will take place in Mexico City from June the 20th to July the 15th. There will be short courses in five areas: metals, ceramics, polymers, composites and semiconductors. It is aimed to graduate students who are nationals of any of the OAS countries. For more information contact Dr. Juan Manuel Mendez jmendez@redvax1.dgsca.unam.mx