From hebant@ext.jussieu.fr Thu Oct 24 04:31:42 1996 Received: from shiva.jussieu.fr for hebant@ext.jussieu.fr by www.ccl.net (8.8.0/950822.1) id EAA21994; Thu, 24 Oct 1996 04:02:58 -0400 (EDT) Received: from idf.ext.jussieu.fr (idf.ext.jussieu.fr [134.157.81.129]) by shiva.jussieu.fr (8.7.6/jtpda-5.2) with ESMTP id KAA26347 ; Thu, 24 Oct 1996 10:02:56 +0200 (METDST) Received: from [134.157.11.16] by idf.ext.jussieu.fr (8.6.10/jtpda-4.0) with SMTP; Thu, 24 Oct 1996 10:02:51 +0200 Date: Thu, 24 Oct 1996 10:02:51 +0200 X-Sender: hebant@idf.ext.jussieu.fr Message-Id: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" To: Ramiro Arratia Perez From: hebant@ext.jussieu.fr (Pascal HEBANT) Subject: Re: CCL:II Workshop of Computational Chemistry.. Cc: chemistry@www.ccl.net Dear Sir, I read your annoucement for the II Workshop of Computational Chemistry and molecular spectroscopy. We are interested in participating but can you send me more details about the program Regards Pascal ***************************************************************************** Pascal HEBANT Laboratoire d'Electrochimie et de Chimie Analytique Ecole Nationale Superieure de Chimie de Paris 11 rue Pierre et Marie Curie 75005 Paris FRANCE tel:+33 - 01 44 27 66 94 fax: +33 - 01 44 27 67 50 http://alcyone.enscp.jussieu.fr/Pages/LECA/Electrochimie.html ***************************************************************************** From ap16390@ggr.co.uk Thu Oct 24 05:31:43 1996 Received: from gate.ggr.co.uk for ap16390@ggr.co.uk by www.ccl.net (8.8.0/950822.1) id FAA22278; Thu, 24 Oct 1996 05:19:28 -0400 (EDT) From: Received: from mailhub.ggr.co.uk (uk0x07.ggr.co.uk [147.184.146.69]) by gate.ggr.co.uk; Thu, 24 Oct 1996 10:17:34 +0100 (BST) Received: from itsg02.italy.glaxo (itsg02.italy.glaxo [161.147.83.59]) by mailhub.ggr.co.uk; Thu, 24 Oct 1996 10:21:06 +0100 (BST) Received: by itsg02.italy.glaxo (8.7.5/imd160294) id KAA21015; Thu, 24 Oct 1996 10:17:44 GMT Date: Thu, 24 Oct 1996 10:17:44 GMT Message-Id: <199610241017.KAA21015@itsg02.italy.glaxo> To: chemistry@www.ccl.net Subject: SUMMARY - roto-matrix - Dear Netters, Here is the summary and the original message concerning roto translations. An easy solution to the problem is to use/look the quaternion-fit program as suggested by David Heisterberg, while for theory I found all the other contributions very interesting. Thank you very much for your help -Alfonso ############### Initial Posting ############### Dear Netters, I would like to ask for an expertise about linear transformations performed via rotational matrixes. Given the 3D coordinates of three points P1(xyz) P2(xyz) and P3(xyz) in their initial (T0) and final (T1) position. Which is the best way for calculating the rotational matrix and translation capable of such transformation ? (distances between the three points are constants so we can consider it "rigid" between each others) Any help and or information is very welcome and I will summarize your contributions. Yours sincerely -Alfonso Pozzan ############# ANSWERS ############# ##################### From: Jan Reimers ##################### Without the translation its a simple 3x3 system of equations. Let p1, p2,p3 be the original 3 coordinate vectors and p1', p2' p3' be the transformed vectors. Then [p1x' p2x' p3x'] [r11 r12 r13][p1x p2x p3x] [p1y' p2y' p3y'] = [r21 r22 r23][p1y p2y p3y] [p1z' p2z' p3z'] [r31 r32 r33][p1z p2z p3z] Or in matrix notation p' = Rp and so R = p' * inverse(p) Note that R must be unitary if it is a rotation matrix. In general R can contain dialations as well, this is determined completely by your p and p' vectors. Now to add the translation you will need 1 more vector, and expand to the problem to a 4x4 system [p1x' . . p4x'] [ Tx] [p1x . . p4x] [ . . . . ] = [ R Ty] [ . . . . ] [ . . . . ] [ Tz] [ . . . . ] [ 1 1 1 1 ] [0 0 0 1 ] [ 1 1 1 1 ] Now solve the 4x4 system to get R and T. Hope this helps +--------------------------------------+-------------------------------------+ | Jan N. Reimers, Research Scientist | Sorry, Don't have time to write the | | Moli Energy (1990) Ltd. B.C. Canada | usual clever stuff in this spot. | | janr@molienergy.bc.ca | | +--------------------------------------+-------------------------------------+ ######################### From: Dr Mark J Biggs ######################### Hi Alfonso, for transformation matricies around axes or a vector, you can refer to most "robotics" texts, also texts for "computer graphics". A good book is "Mathematical Elements for Computer Graphics" by Rogers and Adams (McGraw Hill, 1976) but most have this sort of thing in. A' another book is Introduction to computing with geometry by Bowyer and Woodwark (Information Geometers, 1993). Hope this helps Mark ############################# From: Dr Malcolm E Parker ############################# Hi If T0 and T1 are the original and final 3*3 co-ordinate matrices and R is your transformation (in this case rotation) matrix then it is the following least squares calculation is required:- if T0 * R = T1 then R = (T0t * T0)**-1 * T0t * T1 where T0t is the transpose of T0. The inverse of the covariance matrix can be calculated via NAG routine or probably numerical recipes. Good luck. -- Dr Malcolm Parker | email: m.e.parker@surrey.ac.uk Department of Chemistry, | www: http://www.chem.surrey.ac.uk/~chs1mp University of Surrey, | Guildford, Surrey. GU2 5XH. UK. | Tel: (01483) 300800x2580 Fax: (01483) 259514 |(International calls replace 01483 by +44 1483) ####################### From: Konrad Hinsen ####################### First of all, there is no unique answer. There are infinitely many combinations of rotation and translation that will do the job. The rotations differ in the point around which you rotate, but not in axis and amount. A convenient choice is to define the translation by the difference between the centers of mass (if you have no masses, take the centre of volume). Then the rotation will be around an axis passing through this centre of mass. All three displacement vectors must be perpendicular to this axis, and that is sufficient information to find its direction (Take the cross product of two non-equal displacement vectors. If all three are equal, then your three points are on a line which is parallel to the axis). After that, finding the angle of rotation is a simple trigonometric problem, which however I will not attempt to solve this late in the day... -- ------------------------------------------------------------------------------- Konrad Hinsen | E-Mail: hinsen@ibs.ibs.fr Laboratoire de Dynamique Moleculaire | Tel.: +33-76.88.99.28 Institut de Biologie Structurale | Fax: +33-76.88.54.94 41, av. des Martyrs | Deutsch/Esperanto/English/ 38027 Grenoble Cedex 1, France | Nederlands/Francais ------------------------------------------------------------------------------- ########################## From: David Heisterberg ########################## Look on the ccl archives for fitest (Fortran) or quaternion-fit (C). Of course for three points this method probably isn't optimal, but it's very robust and will give you essentially the exact rotation matrix. If you do want the best way, that's pretty easy. Just translate T1 so that the centroid is the same as for T0, rotate T1 so that the P1s are coincident, then rotate about P1 to match up P2 and P3. For the initial rotation to match P1, find the cross product of P1 in the initial and final configuration and use that as the axis of rotation. Dave Heisterberg >>>>>>>>>>>>Alfonso Pozzan Ph.D, GlaxoWellcome e-mail: ap16390@ggr.co.uk, fax: +39-45-9218196 via Fleming 2, 37100 Verona ITALY <<<<<<<<<<<< From Schiffer@MSMWIA.hoechst.hoechst-ag.d400.de Thu Oct 24 06:31:49 1996 Received: from ixgate02.dfnrelay.d400.de for Schiffer@MSMWIA.hoechst.hoechst-ag.d400.de by www.ccl.net (8.8.0/950822.1) id GAA22432; Thu, 24 Oct 1996 06:16:23 -0400 (EDT) X400-Received: by mta d400relay in /PRMD=dfnrelay/ADMD=d400/C=de/; Relayed; Thu, 24 Oct 1996 11:19:50 +0200 X400-Received: by /PRMD=HOECHST-AG/ADMD=D400/C=DE/; Relayed; Thu, 24 Oct 1996 11:16:59 +0200 X400-Received: by /PRMD=HOECHST-AG-MSM2/ADMD=DBP/C=DE/; Relayed; Thu, 24 Oct 1996 11:14:58 +0200 X400-Received: by /PRMD=HOECHST-AG-MSM/ADMD=DBP/C=DE/; Relayed; Thu, 24 Oct 1996 15:14:52 +0200 Date: Thu, 24 Oct 1996 15:14:52 +0200 X400-Originator: Schiffer@MSMWIA.hoechst.hoechst-ag.d400.de X400-Recipients: non-disclosure:; X400-MTS-Identifier: [/PRMD=HOECHST-AG/ADMD=D400/C=DE/;0009700003738719000002] X400-Content-Type: P2-1984 (2) Content-Identifier: CSI NC V3.0 From: "Schiffer, Heinz, Dr., WIA / SC" Message-ID: <004DAC30.MAI*/S=Schiffer/OU=MSMWIA/O=HOECHST/PRMD=hoechst-ag/ADMD=dbp/C=de/@MHS> To: CCL (Receipt Notification Requested) (Non Receipt Notification Requested) Subject: Charges Hi all, >from time to time there is a discussion about the construction and the use of point charges in molecules. I think there is no doubt within the community, that for intermolecular interactions one should use charges ( and point dipoles, point quadrupoles, etc ) which are adjusted to reproduce as good as possible the electrostatic potential of the molecule. For qualitative discussions of chemical bonding the use of various population analysis ( Mulliken; Davidson-Roby-Ahlrichs, natural orbital populations of Weinhold; Bader; etc. By the way : There is a very promising new one of Marco Haeser in JACS, Vol. 118, 1996, pp. 7311-7325, which I think is more rigorous as any previous ones and without any ad hoc postulates.) are most appropriate. The fitting of the electrostatic potential of a molecule is a highly non-trivial subject ( see e.g. Michelle Miller Francl et al., J. Comput. Chem., Vol. 17, 1996, pp. 367-383, and the very recent review by Sarah L. Price, J. Chem. Soc., Faraday Trans., Vol. 92, 1996, pp. 2997-3008 ) and in my view not a really solved problem, especially for large molecules. Now I became aware of a series of papers by George G. Hall and his coworkers about the fitting of electron densities, which I never heart off bevor and which, I think, are quite unknown to the community. Hall et al. fit the calculated electron densities of molecules to atom-centered gaussians as it is done by many DFT-programs ( "density fitting with an auxillary basis" ) and got a very good ( in my view an excellent ) representation of the electrostatic potential of a molecule. Those DFT- programs with charge density fitting are able to calculate the charge density of molecules within density functional theory with more than thousand basis functions on a single workstation in about an hour of cpu-time ( see e.g. Karin Eichkorn et al., Chem. Phys. Lett. 240 (1995) 283-290 ). As a by-product of the calculation one gets an excellent fit of the electrostatic potential of the molecule with gaussians. After some minor modifications of the programs one gets from this point charges, point dipoles, point quadrupoles, etc. or if one likes it the current bun model of Hall and coworkes. My question to the community is now, wether anyone else has similar thoughts or even experiences with this sort of density fitted electrostatic potentials ? Does anyone has an opinion about using such charge models in force field calculations ( energy minimization of molecular crystals or molecular dynamics calculation of fluids ) ? Please send responses to the list, so that anyone else can follow the discussion. Ciao, Heinz PS: Here are the references of Hall and coworkers : George G. Hall and David Martin Approximate Electron Densities for Atoms and Molecules Isr. J. Chem. 19 (1980) 255-259 G. G. Hall and C. M. Smith Fitting Eelectron Densities of Molecules Int. J. Quantum Chem. 25 (1984) 881-890 G. G. Hall and K. Tsujinaga The molecular electrostatic potential of some simple molecules Theor. Chim. Acta 69 (1986) 425-436 K. Tsujinaga and G. G. Hall The currant bun model of simple molecules Theor. Chim. Acta 70 (1986) 257-264 ---------------------------------------------------------------------------- ----------------------------------------------- Dr. Heinz Schiffer 65926 Frankfurt am Main Hoechst AG Phone ++49-69-305-2330 Scientific Computing Fax ++49-69-305-81162 Email : schiffer@wia.hoechst-ag.d400.de schiffer@msmwia.hoechst.hoechst-ag.d400.de ---------------------------------------------------------------------------- ----------------------------------------------- From melchers@chemie.fu-berlin.de Thu Oct 24 08:31:44 1996 Received: from ki1.chemie.fu-berlin.de for melchers@chemie.fu-berlin.de by www.ccl.net (8.8.0/950822.1) id IAA22915; Thu, 24 Oct 1996 08:02:38 -0400 (EDT) Received: by ki1.chemie.fu-berlin.de (Smail3.1.28.1) from Bose.Chemie.FU-Berlin.DE (160.45.26.10) with smtp id ; Thu, 24 Oct 96 14:02 MEST Received: by Bose.Chemie.FU-Berlin.DE (Smail3.2) id ; Thu, 24 Oct 1996 14:02:29 +0200 (MEST) Message-Id: From: melchers@chemie.fu-berlin.de (Bernd Melchers) Subject: Charmm24-benchmark PPro versus SGI To: chemistry@www.ccl.net Date: Thu, 24 Oct 1996 14:02:28 +0200 (MEST) X-Mailer: ELM [version 2.4 PL24 ME8d] MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit hello, we performed some charmm24 benchmarks with a Pentium Pro and with some Silicon Graphics machines: 1. modelling (select, coor orien, hbuild) and some energy minimization (i.e. integer and floating point) a) R4600 100 MHz 24.45 MINUTES b) R4400 150 MHz 14.08 MINUTES c) R8000 75 MHz 7.21 MINUTES d) PPro 200 MHz 5.53 MINUTES e) R10000 195MHz 2.51 MINUTES 2. molecular dynamik simulation (i.e. much floating point) f) R4000 100 MHz 4.36 hours b) R4400 150 MHz 2.90 hours d) PPro 200 MHz 1.29 hours machine/compiler description: a) Indy, IRIX-5.3, R4600SC, 100 MHz, 16+16/0 Cache, cc -O2 b) Indigo, IRIX-5.3, R4400, 150 MHz, 16+16/1024 Cache, cc -O2 c) Power Indigo^2, IRIX-6.2, R8000, 75 MHz, 16+16/2048 Cache, cc -O3 -mips4 d) PentiumPro Asus Natoma Board, 200 MHz, 16+16(?)/256 Cache, gcc-2.7.2/ g77-0.5.18 -O2 running linux kernel 2.0.18 e) R10000, IRIX-6.2, 195 MHz, 32+32/1024 Cache, cc -O3 -mips4 f) Indigo R4000, IRIX-5.3, 100 MHz, 16+16/1024 Cache, cc -O2 the results are not too bad for the intel chips, aren't they? Ciao Bernd -- -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-+-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= Bernd Melchers | melchers@FU-Berlin.DE Freie Universitaet Berlin | Institut fuer Kristallographie | Please replace battery pack, Takustr. 6 | attach external power, D 14195 Berlin | or system will be Germany | shutdown in 10 seconds. Earth | Tel.: ++49-30-8383612 | Fax.: ++49-30-8383464 picture and pgp key: http://www.chemie.fu-berlin.de/~melchers "We don't write software, we compose it." -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-+-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= From hinsen@ibs.ibs.fr Thu Oct 24 09:31:46 1996 Received: from ibs.ibs.fr for hinsen@ibs.ibs.fr by www.ccl.net (8.8.0/950822.1) id IAA23252; Thu, 24 Oct 1996 08:40:46 -0400 (EDT) Received: from lmshp2.ibs.fr (lmshp2.ibs.fr [192.134.36.228]) by ibs.ibs.fr (8.6.12/8.6.12) with SMTP id OAA14921; Thu, 24 Oct 1996 14:42:16 +0100 Message-Id: <199610241342.OAA14921@ibs.ibs.fr> Received: by lmshp2.ibs.fr (1.37.109.4/16.2) id AA06005; Thu, 24 Oct 96 14:36:36 +0100 Date: Thu, 24 Oct 96 14:36:36 +0100 From: Konrad Hinsen To: Schiffer@MSMWIA.hoechst.hoechst-ag.d400.de Cc: chemistry@www.ccl.net In-Reply-To: <004DAC30.MAI*/S=Schiffer/OU=MSMWIA/O=HOECHST/PRMD=hoechst-ag/ADMD=dbp/C=de/@MHS> Subject: Re: CCL:G:Charges > postulates.) are most appropriate. The fitting of the electrostatic > potential of a > molecule is a highly non-trivial subject ( see e.g. Michelle Miller Francl > et al., > J. Comput. Chem., Vol. 17, 1996, pp. 367-383, and the very recent review by > Sarah L. Price, J. Chem. Soc., Faraday Trans., Vol. 92, 1996, pp. 2997-3008 > ) > and in my view not a really solved problem, especially for large molecules. I don't agree. The charge fitting problem is not essentially different >from other fitting problems in all branches of science and engineering, and lots of articles and books have been written about it. There are well established and robust techniques to find optimal charges and to judge to what degree they are well determined by the reference data. Much of this is not generally known in the computational chemistry community, but that's another problem. There remains of course the problem that the electrostatic potential in a reasonable region may not be sufficient to determine all charges uniquely. But that is not really fatal: if after adding all reference data you can reasonably get (e.g. from multiple conigurations) some charges still remain illdetermined, then they probably don't matter much in real life. If they do, then probably the fixed point charge model is not good enough. > are quite unknown to the community. Hall et al. fit the calculated electron > densities > of molecules to atom-centered gaussians as it is done by many DFT-programs > ( "density fitting with an auxillary basis" ) and got a very good ( in my > view an > excellent ) representation of the electrostatic potential of a molecule. Essentially that means choosing a more complicated model (gaussian densities rather than point charges), and it is not surprising that you can get better results. The question is whether people are willing to work with such more complicated models in their force fields. It is certainly worthwhile exploring in which situations such models can give better results. -- ------------------------------------------------------------------------------- Konrad Hinsen | E-Mail: hinsen@ibs.ibs.fr Laboratoire de Dynamique Moleculaire | Tel.: +33-76.88.99.28 Institut de Biologie Structurale | Fax: +33-76.88.54.94 41, av. des Martyrs | Deutsch/Esperanto/English/ 38027 Grenoble Cedex 1, France | Nederlands/Francais ------------------------------------------------------------------------------- From chpajt@bath.ac.uk Thu Oct 24 10:31:44 1996 Received: from goggins.bath.ac.uk for chpajt@bath.ac.uk by www.ccl.net (8.8.0/950822.1) id KAA23906; Thu, 24 Oct 1996 10:23:51 -0400 (EDT) Received: from bath.ac.uk (actually host mary.bath.ac.uk) by goggins.bath.ac.uk with SMTP (PP); Thu, 24 Oct 1996 15:10:26 +0100 Date: Thu, 24 Oct 1996 15:10:02 +0100 (BST) From: A J Turner To: "Schiffer, Heinz, Dr., WIA / SC" cc: CCL Subject: Re: CCL:G:Charges In-Reply-To: <004DAC30.MAI*/S=Schiffer/OU=MSMWIA/O=HOECHST/PRMD=hoechst-ag/ADMD=dbp/C=de/@MHS> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Hi! I am working on the charge fitting area right now. My experiance may be of interest. The approxiation of placing charges on nuclear centres can greatly outweigh to variation in method of attaining the charges in the first place. I am using QM/MM technology to _directly_ fit a MM force field to a QM/MM force field. This shows that several 'off centre' points _must_ be included if one is to get anything like a reasonable fit of the mm forces to the qm ones. My present example being ch3o- , where the forcing of the negative charg onto the 'centre' of the oxygen causes maiisve 'artificial' +ve charge build up on the carbon and hence large negaive charges on the protons. The use of a QM/MM force field where the same vdw paramters apply shows that these negative protons are very very far from correct. Does anyon else have similar experiances? Best wishes Alex ------------------------------------------------------------------- |Alexander J Turner |A.J.Turner@bath.ac.uk | |Post Graduate |http://www.bath.ac.uk/~chpajt/home.html| |School of Chemistry |+144 1225 8262826 ext 5137 | |University of Bath | | |Bath, Avon, U.K. |Field: QM/MM modeling | ------------------------------------------------------------------- From kotelyan@che.udel.edu Thu Oct 24 15:31:47 1996 Received: from che.udel.edu for kotelyan@che.udel.edu by www.ccl.net (8.8.0/950822.1) id OAA26145; Thu, 24 Oct 1996 14:33:08 -0400 (EDT) Received: by che.udel.edu (AIX 3.2/UCB 5.64/4.03) id AA34232; Thu, 24 Oct 1996 14:32:10 -0400 Date: Thu, 24 Oct 1996 14:31:37 +22305133 (EDT) From: Michael Kotelyanskii Subject: Re: CCL:Charmm24-benchmark PPro versus SGI To: Bernd Melchers Cc: chemistry@www.ccl.net In-Reply-To: Message-Id: Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII That's interesting , but why is R10000 missing from the MD ? Michael Kotelyanskii PhD Department of Chemical Engineering University of Delaware kotelyan@che.udel.edu Newark DE 19716 On Thu, 24 Oct 1996, Bernd Melchers wrote: > hello, > we performed some charmm24 benchmarks with a Pentium Pro and with some > Silicon Graphics machines: > > 1. modelling (select, coor orien, hbuild) and some energy minimization > (i.e. integer and floating point) > a) R4600 100 MHz 24.45 MINUTES > b) R4400 150 MHz 14.08 MINUTES > c) R8000 75 MHz 7.21 MINUTES > d) PPro 200 MHz 5.53 MINUTES > e) R10000 195MHz 2.51 MINUTES > > > 2. molecular dynamik simulation (i.e. much floating point) > f) R4000 100 MHz 4.36 hours > b) R4400 150 MHz 2.90 hours > d) PPro 200 MHz 1.29 hours > > > machine/compiler description: > > a) Indy, IRIX-5.3, R4600SC, 100 MHz, 16+16/0 Cache, cc -O2 > b) Indigo, IRIX-5.3, R4400, 150 MHz, 16+16/1024 Cache, cc -O2 > c) Power Indigo^2, IRIX-6.2, R8000, 75 MHz, 16+16/2048 Cache, cc -O3 -mips4 > d) PentiumPro Asus Natoma Board, 200 MHz, 16+16(?)/256 Cache, gcc-2.7.2/ > g77-0.5.18 -O2 running linux kernel 2.0.18 > e) R10000, IRIX-6.2, 195 MHz, 32+32/1024 Cache, cc -O3 -mips4 > f) Indigo R4000, IRIX-5.3, 100 MHz, 16+16/1024 Cache, cc -O2 > > the results are not too bad for the intel chips, aren't they? > > Ciao > Bernd > -- > -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-+-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= > Bernd Melchers | melchers@FU-Berlin.DE > Freie Universitaet Berlin | > Institut fuer Kristallographie | Please replace battery pack, > Takustr. 6 | attach external power, > D 14195 Berlin | or system will be > Germany | shutdown in 10 seconds. > Earth | > Tel.: ++49-30-8383612 | Fax.: ++49-30-8383464 > picture and pgp key: http://www.chemie.fu-berlin.de/~melchers > "We don't write software, we compose it." > -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-+-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= > > -------This is added Automatically by the Software-------- > -- Original Sender Envelope Address: melchers@chemie.fu-berlin.de > -- Original Sender From: Address: melchers@chemie.fu-berlin.de > CHEMISTRY@www.ccl.net: Everybody | CHEMISTRY-REQUEST@www.ccl.net: Coordinator > MAILSERV@www.ccl.net: HELP CHEMISTRY or HELP SEARCH | Gopher: www.ccl.net 73 > Anon. ftp: www.ccl.net | CHEMISTRY-SEARCH@www.ccl.net -- archive search > Web: http://www.ccl.net/chemistry.html >