From lai@csb0.IPC.PKU.EDU.CN Thu Nov 20 01:34:14 1997 Received: from csb0.IPC.PKU.EDU.CN for lai@csb0.IPC.PKU.EDU.CN by www.ccl.net (8.8.3/950822.1) id BAA13897; Thu, 20 Nov 1997 01:15:45 -0500 (EST) Received: by csb0.IPC.PKU.EDU.CN (920330.SGI/940406.SGI.AUTO) for CHEMISTRY@www.ccl.net id AA05934; Thu, 20 Nov 97 14:15:46 -0800 Date: Thu, 20 Nov 1997 14:15:44 -0800 (PST) From: "Prof. Luhua LAI" To: CHEMISTRY@www.ccl.net Subject: Summary for Examples for Main Chain Flexible Docking Message-Id: Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Dear CCLers: Several days ago, I posted the following question: We are studying main chain flexibility in protein-protein or protein-ligand docking. We would like to find some examples where protein main chain conformation changes significantly when binds with other molecule. Could someone give me a few examples? Thanks for all who responded to the question. The following is a summary for all the answers. ----------------------------------------------------------------------------------- German Sastre URL: http://www.ri.ac.uk/DFRL/G.Sastre ---------------------------------------------------------------------------------- it could be of interest bearing in mind what happens in some organic bases called 'proton sponges': some of them have this 'basic group': R# R* \ / R-N N-R | | well, sorry about the picture but, C----C believe it or not, the 'square' is | | a naftalene molecule | | ------ Now the important thing: in the basic form (as depicted) the repulsion between the lone pairs makes the dihedral R#-N-N-R* to have a certain value (the dihedral changes through nearly free rotation around the N-C bonds). In the acid form (after getting a H+) that repulsion becomes attraction (now there is only one lone pair and the proton), and the dihedral changes accordingly. May be you can find a similar effect in your protein-ligand interactions. In your case protein makes the role of sponge and ligand plays the role of the proton. good luck! German \|/ (o o) ------------------------------------------oOO-(_)-OOo----------------------- German Sastre URL: http://www.ri.ac.uk/DFRL/G.Sastre Instituto de Tecnologia Quimica e-mail: gsastre@itq.upv.es Universidad Politecnica de Valencia Phone: +34 (9)6-387-7803 Camino de Vera s/n; 46071 Valencia (Spain) Fax: +34 (9)6-387-7809 ---------------------------------------------------------------------------- oo0 0oo --------------------------------------------------------------------------------------------------------- >From Lutz.Ehrlich@EMBL-Heidelberg.de Wed Nov 12 16:11:19 1997 ------------------------------------------------------------------------------------------- The best example for a main-chain rearrangement upon binding IMHO is the case of Fab50.1, a HIV-1 neutralizing antibody (cf.R.L. Stanfield and I. A. Wilson, Trends in Biotechnology, July 1994 (vol 12), 275-9)). Here a main-chain RMSD of 5.3 Angstrom, corresponding to a scissor-like movement of V_l with respect to V_h is observed. In the case of protein-small molecule binding, I somehow have the thrombin-hirudin case in my mind (you might have to check this, though...). Looking forward to hearing from you. Best regards, Lutz Ehrlich --------------------- Lutz Ehrlich Structural Biology EMBL Meyerhofstr. 1 D-69012 Heidelberg Germany email: lutz.ehrlich@embl-heidelberg.de web : http://www.embl-heidelberg.de/~ehrlich phone: +49-6221-387-140 fax : +49-6221-387-517 -------------------------------------------------------------------------------------------------- >From STEWARTK@RAND.PPRD.Abbott.Com Wed Nov 12 21:09:43 1997 ---------------------------------------------------------------------------------------------- Dr. Lai: The "flap" region of HIV protease undergoes significant rigidification upon binding of a substrate or ligand. In this 99-mer protein, I refer to region 45-55, also called the "flap" region. There is a crystal structure of an unliganded form, where the flap is held in place by a crystal contact. But it is obvious that the flap has multiple conformations in solution. In the liganded form, there are probably 30 crystal structures in the PDB which show the flap in nearly identical "locked-down" conformation. Kent Stewart Department of Structural Biology Abbott Laboratories Chicago, IL United States of America -------------------------------------------------------------------------------------------------- >From doyle@chop.swmed.edu Wed Nov 12 23:05:33 1997 ------------------------------------------------------------------------------------------------- The nuclear hormone receptor ligand binding domain is a good example. See Wurtz et al., Nature Structural Biology vol. 3, 1996, pp 87-94 and Renaud et al., Nature vol. 378, 1994, pp. 681-689. Good luck, Donald Doyle ---------------------------------------------------------------------- Donald F. Doyle, Ph.D. doyle@chop.swmed.edu Howard Hughes Medical Institute Phone: (214) 648-6787 UT Southwestern Medical Center Fax: (214) 648-5095 5323 Harry Hines Blvd. Y4.320 Dallas, TX 75235-9050 ---------------------------------------------------------------------- ------------------------------------------------------------------------------------------------- >From wurtz@porto.u-strasbg.fr Thu Nov 13 01:24:53 1997 ------------------------------------------------------------------------------------------------ The ligand binding domain of Nuclear Receptors (NRs) is an interesting case to study. The crystal structure of unliganded and liganded ligand binding domains are available (These is the so called steroid/thyroid hormone superfamily). Ligand binding induces a important transconformation the active complex is then able to modulate the transcription of target genes. Relevant references are the following : - Bourguet, W.; Ruff, M.; Chambon, P.; Gronemeyer, H.; Moras, D. Crystal structure of the ligand-binding domain of the human nuclear receptor RXR-alpha. Nature 1995, 375, 377-382. - Renaud, J. P.; Rochel, N.; Ruff, M.; Vivat, V.; Chambon, P.; Gronemeyer, H.; Moras, D. Crystal structure of the RAR-gamma ligand-binding domain bound to all-trans retinoic acid. Nature 1995, 378, 681-689. - Wagner, R. L.; Apriletti, J. W.; McGrath, M. E.; West, B. L.; Baxter, J. D.; Fletterick, R. J. A structural role for hormone in the thyroid hormone receptor. Nature 1995, 378, 690-697. - Wurtz, J. M.; Bourguet, W.; Renaud, J. P.; Vivat, V.; Chambon, P.; Moras, D.; Gronemeyer, H. A canonical structure for the ligand-binding domain of nuclear receptors [published erratum appears in Nat Struct Biol 1996 Feb; 3(2):206]. Nat. Struct. Biol. 1996, 3, 87-94. Friendly, -- WURTZ Jean-Marie ________________________________________________________________________ IGBMC E-mail : wurtz@igbmc.u-strasbg.fr Laboratoire de Biologie Structurale Phone : (33) 3 88 65 35 29 Parc d'Innovation Fax : (33) 3 88 65 32 01 1, rue Laurent Fries, BP 163 67404 ILLKIRCH, CU STRASBOURG France ________________________________________________________________________ -------------------------------------------------------------------------------------------------- >From info@microsimulations.com Thu Nov 13 09:32:53 1997 ------------------------------------------------------------------------------------------------- Luhua, HIV protease is a good example. The binding site are made of a pair of catalytic triad of Gly, Asp, and Thr. and two beta sheet loops. When it is free of ligand binding, the two loops are open. They are moved about 4 Angstroms Upon binding to a inhibitor, to cover up the binding cavity. You can find the crystal structures of both in free and bounded form. I do not quite remember the file names. let me know if you have difficulty finding it at pdb site. Another one would be antibody binding to antigen. I know much less in this case. Just a suggestion. Best regards! -- Willie Cui voice: 201-512-0486 MicroSimulations fax: 201-512-0489 478 Green Mountain Road email: info@microsimulations.com Mahwah, NJ 07430 URL: http://www.microsimulations.com ------------------------------------------------------------------------------------------------ >From molmodel@banyu.co.jp Fri Nov 14 13:02:40 1997 ----------------------------------------------------------------------------------------------- According to X-ray analysis, the structure of CDK2 shows much movement of main chain when cycinA binds to it. See 1HCK and 1FIN in PDB. $B!v!v!v!v!v!v!v!v!v!v!v!v!v!v!v!v!v!v!v!v(J Toshiharu Iwama Molecular Modeling Group Banyu Pharmaceutical Co.,LTD. Okubo 3, Tsukuba 300-26, JAPAN E-mail molmodel@banyu.co.jp Tel +81-298-77-2000 Fax +81-298-77-2029 $B!v!v!v!v!v!v!v!v!v!v!v!v!v!v!v!v!v!v!v!v(J ------------------------------------------------------------------------------------------------ ------------------------------------------ Luhua Lai Institute of Physical Chemistry & Department of Chemistry Peking University Beijing 100871 CHINA Phone: 86-10-62751490 Fax: 86-10-62751725 E-mail: lai@ipc.pku.edu.cn ----------------------------------------- From val@nmr1.ioc.ac.ru Thu Nov 20 02:34:16 1997 Received: from nmr1.ioc.ac.ru for val@nmr1.ioc.ac.ru by www.ccl.net (8.8.3/950822.1) id CAA14000; Thu, 20 Nov 1997 02:12:42 -0500 (EST) Received: from nmr-v.ioc.ac.ru (nmr-v.ioc.ac.ru [193.233.3.213]) by nmr1.ioc.ac.ru (8.6.12/8.6.9) with SMTP id LAA25623 for ; Thu, 20 Nov 1997 11:13:02 +0400 Message-ID: <34747EC5.7CD8@nmr1.ioc.ac.ru> Date: Thu, 20 Nov 1997 10:17:41 -0800 From: "Ananikov V.P." Reply-To: val@nmr1.ioc.ac.ru Organization: IOCh X-Mailer: Mozilla 3.0Gold (Win16; I) MIME-Version: 1.0 To: CHEMISTRY@www.ccl.net Subject: ECP & bond orders Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit Dear CCL’s, I would be glad to receive your comments concerning this problem: When I perform ECP calculations on simple transition metal ions, such as PtCl5(-), PtCl6(2-), PtI6(2-), etc., Bond Order Analysis sometimes gives small bond order values between nonbonded atoms, i.e. Cl-Cl, I-I. The bond order values are typically in the range of 0.08-0.1 Might it have a reasonable explanation? I am using Stevens-Basch-Krauss-Cundari ECP’s as implemented in GAMESS package. Since this is observed only with ECP bases set, the answer to the next rather general question is also of interest: Does the 'Bond Order' conception in the case of core-potential involved mean exactly the same as for all-electron calculations? thank you. I will summarize. sincerely, Valentin. =============================================================== Valentin P. Ananikov NMR Laboratory N.D. Zelinsky Institute of Organic Chemistry Leninsky Prospect 47 Moscow 117913, Russia e-mail: val@nmr1.ioc.ac.ru http://nmr1.ioc.ac.ru/Staff/AnanikovVP/ Fax (7095) 1355328 Phone (7095) 9383536, (7095) 1359094 From h332262@sirius.cab.u-szeged.hu Thu Nov 20 11:34:20 1997 Received: from sirius.cab.u-szeged.hu for h332262@sirius.cab.u-szeged.hu by www.ccl.net (8.8.3/950822.1) id KAA16019; Thu, 20 Nov 1997 10:52:54 -0500 (EST) Received: (qmail 7305 invoked by uid 32262); 20 Nov 1997 15:51:44 -0000 Date: Thu, 20 Nov 1997 16:51:43 +0100 (MET) From: Kiss Gergo X-Sender: h332262@sirius To: chemistry@www.ccl.net Subject: Tinker outputs Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Hi everybody, I use the Tinker package for some calculations on peptides. The problem is, that the output is in Tinker's xyz format. Rasmol, Molmol and Molden can't read this. If I use the included xyzpdb.x program for converting to pdb, Rasmol and Molden reads the file, but none of them can perform backbone calculations. Do you know about a graphical software, which can read Tinker's xyz format, or about a converter, which can turn this file into usable form. Please help me, I will summarize the answers. Bye, Kiss, Gergo h332262@sirius.cab.u-szeged.hu From Jeffrey.Gosper@brunel.ac.uk Thu Nov 20 12:01:47 1997 Received: from eros.brunel.ac.uk for Jeffrey.Gosper@brunel.ac.uk by www.ccl.net (8.8.3/950822.1) id KAA16046; Thu, 20 Nov 1997 10:58:24 -0500 (EST) Received: from castjjg.brunel.ac.uk (actually chem-pc-03.brunel.ac.uk) by eros.brunel.ac.uk with SMTP-BRUNEL (PP); Thu, 20 Nov 1997 15:58:01 +0000 Date: Thu, 20 Nov 1997 15:59:06 PST From: Jeffrey Gosper Subject: Re: CCL:visualizing normal modes? To: Dan Strahs cc: CHEMISTRY@www.ccl.net Message-ID: Priority: Normal MIME-Version: 1.0 Content-Type: TEXT/PLAIN; CHARSET=US-ASCII > I'm trying to visualize some the normal mode eigenvectors for systems I've > been working with. > > Is there some package (preferably free) which will: > > 1) Display atoms and eigenvectors in a 3-D, rotatable reference > frame; > 2) Allow me to import the entire calculated set of normal modes > and visualize them individually without progressive reloads; > > 3) Generate some form of output (i.e. Postscript) > > Thanks for any help that can be offered in this regard. Yes, yes and yes (even output as an Mpeg if you want). Re_View2 is what you need it runs under Windows3.1,95,NT please see http://www.brunel.ac.uk/depts/chem/ch241s/re_view/re_view2.htm /\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\ Dr. Jeff Gosper, Dept. of Chemistry, BRUNEL University Uxbridge Middx UB8 3PH, UK voice: 01895 274000 x2187, facsim: 01895 256844 internet/email/work: Jeffrey.Gosper@brunel.ac.uk internet/WWW: http://www.brunel.ac.uk/~castjjg Re_View's home page (molecular animations or Chem-4D): http://www.brunel.ac.uk/depts/chem/ch241s/re_view/re_view.htm \/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/ From Jeffrey.Gosper@brunel.ac.uk Thu Nov 20 12:05:22 1997 Received: from eros.brunel.ac.uk for Jeffrey.Gosper@brunel.ac.uk by www.ccl.net (8.8.3/950822.1) id LAA16052; Thu, 20 Nov 1997 11:00:36 -0500 (EST) Received: from castjjg.brunel.ac.uk (actually chem-pc-03.brunel.ac.uk) by eros.brunel.ac.uk with SMTP-BRUNEL (PP); Thu, 20 Nov 1997 16:00:14 +0000 Date: Thu, 20 Nov 1997 16:01:19 PST From: Jeffrey Gosper Subject: Re: CCL:Imaginary Freq. To: "Douglas E. Stack" cc: "CHEMISTRY@www.ccl.net" Message-ID: Priority: Normal MIME-Version: 1.0 Content-Type: TEXT/PLAIN; CHARSET=US-ASCII On Wed, 19 Nov 1997 08:52:46 -0600 Douglas E. Stack wrote: > From: Douglas E. Stack > Date: Wed, 19 Nov 1997 08:52:46 -0600 > Subject: CCL:Imaginary Freq. > To: "CHEMISTRY@www.ccl.net" > > I've had a calculation converge to a transition state structure, but the = > value of my one imaginary frequency seems to low ca. 7 cm-1. > Animation of the mode seems to connect the nucleophile to the Micheal = > acceptor, but I was under the impression that the absolute value of the = > imaginary freq. should b between 600 to 200 cm-1. I have a ring system = > composed of two fused six membered rings (the Micheal acceptor) would = > this make for a low value? > > The question really is whether this mode connects the reactants to the products. Have you run an IRC? /\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\ Dr. Jeff Gosper, Dept. of Chemistry, BRUNEL University Uxbridge Middx UB8 3PH, UK voice: 01895 274000 x2187, facsim: 01895 256844 internet/email/work: Jeffrey.Gosper@brunel.ac.uk internet/WWW: http://www.brunel.ac.uk/~castjjg Re_View's home page (molecular animations or Chem-4D): http://www.brunel.ac.uk/depts/chem/ch241s/re_view/re_view.htm \/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/ From aholder@cctr.umkc.edu Thu Nov 20 15:34:24 1997 Received: from ns1.umkc.edu for aholder@cctr.umkc.edu by www.ccl.net (8.8.3/950822.1) id PAA17058; Thu, 20 Nov 1997 15:05:28 -0500 (EST) Received: from 134.193.11.2 (holder.chem.umkc.edu [134.193.11.2]) by ns1.umkc.edu (8.8.7/8.8.7) with SMTP id OAA20884; Thu, 20 Nov 1997 14:05:27 -0600 (CST) X-Mailer: InterCon tcpCONNECT4 4.0.3 (Macintosh) MIME-Version: 1.0 Message-Id: <9711201406.AA44424@134.193.11.2> Date: Thu, 20 Nov 1997 14:06:44 -0600 From: "Andy Holder" To: chemistry@www.ccl.net Subject: MJS Dewar died October 10 Content-Type: Multipart/Mixed;boundary=part_B099F4740018449300000003 --part_B099F4740018449300000003 Content-Type: Text/Plain; charset=US-ASCII Content-Disposition: Inline Dear Netters and Friends, On October 10 of this year MJS Dewar died of congestive heart failure in a hospital in Gainesville, FL. After speaking with his son Steuart, it seems that his death was not difficult. Since most (if not all) of us use his methods and ideas in our work, I thought it beneficial to take a moment and review just a few of Michael Dewar's contributions to computational chemistry. There is a short (and woefully incomplete) list below. Even more than his direct contributions to the literature (over 600 papers), Professor Dewar sparked people to think differently and in unconventional ways. As many of us know, he was involved in many hot controversies in the literature, all of which had the result of advancing science. Michael Dewar would not let you just plod along in the same old rut. His sparkling prose and inimitable speaking style challenged audiences and stimulated discussions for decades. I think it fitting that Michael died in early October, when the Nobel Prize recipients are announced. His contributions are certainly worthy of the prize, and he was a perrenial candidate for it. 1. Perturbation molecular orbital (PMO) theory 2. MINDO3 semiempirical method 3. MNDO semiempirical method 4. AM1 semiempirical method 5. SAM1 semiempirical method 6. AMPAC and MOPAC programs 7. Elucidation of basic reaction mechanisms throughout organic chemistry through the application of theoretical methods 8. Basic contributions in the theory and implementation of semiempirical methodology A little recent history is probably in order. Professor Dewar left the University of Texas about 1990 and accepted a research professorship at the University of Florida. He worked there on development of the SAM1 method until 1992, when he retired. Michael completely left chemistry when he retired, and enjoyed reading (virtually anything), music, old movies, and Chinese cooking to mention just a few of his many interests. Mary Williamson Dewar, his and wife and best friend of over 50 years, passed away in 1994. There was no memorial service for Michael, and his ashes will be spread with those of Mary in the Lake District of northern England, where they honeymooned many years ago. He is survived by his two sons C.E. Steuart Dewar of Morganton, GA and Robert B.K. Dewar of New York City. He challenged those of us who had the great fortune to work with him in ways we never imagined. He was a loyal and caring mentor and was always gracious and kind, even in those painful moments when we insisted on learning the "hard way". Not just those of us who knew him, but SCIENCE will miss him. A great man has left us. Regards, Andy Holder PS. There are preliminary efforts underway to develop an endowment in Professor Dewar's name at the University of Texas at Austin. If you are interested in being added to the mailing list for this, please let me know. -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- UUUU UUU MMM MMKK KKKK CCCC | ANDREW J. HOLDER UU U MM MMK K CC CC | Assoc. Prof. of Comp./Org. Chemistry UU U MMM M MK KK CCC | Dept. of Chemistry UU U M MM MK KK CC CC | University of Missouri-Kansas City UUUUU MMM M MMKK KK CCCC | Kansas City, MO 64110 KK | aholder@cctr.umkc.edu K | (816) 235-2293, FAX (816) 235-5502 -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- --part_B099F4740018449300000003-- From korkin@act.sps.mot.com Thu Nov 20 17:34:24 1997 Received: from spsem02.sps.mot.com for korkin@act.sps.mot.com by www.ccl.net (8.8.3/950822.1) id QAA17650; Thu, 20 Nov 1997 16:50:14 -0500 (EST) Received: from mogate.sps.mot.com by spsem02.sps.mot.com (4.1/SMI-4.1/Email 2.1 10/25/93) id AA17886 for chemistry@www.ccl.net; Thu, 20 Nov 97 14:30:55 MST Received: from emailsps.sps.mot.com by mogate.sps.mot.com (4.1/SMI-4.1/Email-2.0) id AA00848 for chemistry@www.ccl.net; Thu, 20 Nov 97 14:30:33 MST Received: from merchant.sps.mot.com (merchant) by act with ESMTP (1.37.109.16/16.2) id AA161761432; Thu, 20 Nov 1997 14:30:32 -0700 From: Anatoli Korkin Received: (from korkin@localhost) by merchant.sps.mot.com (8.7.1/8.7.1) id OAA18203 for chemistry@www.ccl.net; Thu, 20 Nov 1997 14:30:31 -0700 (MST) Date: Thu, 20 Nov 1997 14:30:31 -0700 (MST) Message-Id: <199711202130.OAA18203@merchant.sps.mot.com> To: chemistry@www.ccl.net Subject: reaction network design X-Mailer: Siren Mail (Motif 2.02 95/05/15) Mime-Version: 1.0 Content-Id: <304_18069_880061431_3@merchant> Content-Type: text/plain; charset="us-ascii" Dear CCLers, Can someone give me reference on last developments (e.g 1995 or later) on reaction network design/generation. Some application results, particularly in gas phase and gas-surface inorganic molecules reactions will be of interest too. Thank you, Anatoli ****************************************************************** Anatoli Korkin Ph.D korkin@act.sps.mot.com Computational Chemist Tel: (602) 655-3171 Fax: (602) 655-2285 Predictive Engineering Lab Semiconductor Products Sector Arizona Technology Motorola Inc., MD M350 Laboratories 2200 West Broadway Road Mesa AZ 85202 ******************************************************************* From Darren.Simpson@unisa.edu.au Thu Nov 20 23:34:25 1997 Received: from Roll.Levels.UniSA.Edu.Au for Darren.Simpson@unisa.edu.au by www.ccl.net (8.8.3/950822.1) id WAA19023; Thu, 20 Nov 1997 22:59:41 -0500 (EST) Received: from EXSTAFF3.Levels.UniSA.Edu.Au ("port 1547"@EXSTAFF3.Levels.UniSA.Edu.Au) by Levels.UniSA.Edu.Au (PMDF V5.0-7 #20435) id <01IQ9WIVZ10A984I94@Levels.UniSA.Edu.Au> for chemistry@www.ccl.net; Fri, 21 Nov 1997 14:27:58 +0930 Received: by EXSTAFF3.Levels.UniSA.Edu.Au with Internet Mail Service (5.0.1458.49) id ; Fri, 21 Nov 1997 14:28:00 +1030 Date: Fri, 21 Nov 1997 14:27:59 +1030 From: Darren Simpson Subject: Electronic configuration of Co To: "'chemistry@www.ccl.net'" Message-id: <5DA42F8A3C18D111979400AA00DD609D0F8B9B@EXSTAFF3.Levels.UniSA.Edu.Au> MIME-version: 1.0 X-Mailer: Internet Mail Service (5.0.1458.49) Content-type: text/plain Content-transfer-encoding: 7BIT X-Priority: 3 Hello computational chemists, I am interested in modeling reactions at the surfaces of NiO and CoO clusters. I am also trying to gather information on the electronic structure of Co in CoO. The d electrons of these oxides are localized on the metal atoms as found in transition-metal complexes. Crystal field theory used to describe the electronic structure of complexes can also be applied to these solids. The structure of these oxides is the rock-salt or face-centred cubic structure and each metal atom in the bulk is surrounded by 6 oxygen atoms in an octahedral environment. For NiO (d8), there is only one configuration ie t2g [dxy(2) dxz(2) dyz(2)] and eg [dz2(1) dx2-y2(1)] thus 2 unpaired electrons per Ni atom. At the 100 surface, t2g/eg energy levels are distorted due to the reduction in coordination from 6 to 5. For CoO, the electronic structure is more complex because Co (d7) can adopt a high-spin (3 unpaired d electrons) or low-spin (1 unpaired d electron) state. However I am unsure of the electronic structure in the bulk and at the surface/boundary of the CoO cluster. Does, Co adopt a low-spin state at the surface and high-spin in the bulk? Any advice, information, references etc on this topic is welcome . A summary of responses will posted to the list. Thanks in advance, Darren Simpson Ian Wark Research Institute University of South Australia The Levels, SA 5095 Australia Email: darren.simpson@unisa.edu.au