From chemistry-request@server.ccl.net Sun Dec 1 16:25:28 2002 Received: from smtp018.mail.yahoo.com ([216.136.174.115]) by server.ccl.net (8.11.6/8.11.0) with SMTP id gB1LPRO02129 for ; Sun, 1 Dec 2002 16:25:27 -0500 Received: from mix-marseille-104-1-102.abo.wanadoo.fr (HELO baloo) (lougras@193.250.251.102 with login) by smtp.mail.vip.sc5.yahoo.com with SMTP; 1 Dec 2002 21:25:19 -0000 Message-ID: <005001c29980$460cc1e0$66fbfac1@baloo> From: "olivier maresca" To: Subject: summary: ONIOM and multiplicity Date: Sun, 1 Dec 2002 22:24:34 +0100 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_004B_01C29988.6D584AA0" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2600.0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2600.0000 This is a multi-part message in MIME format. ------=_NextPart_000_004B_01C29988.6D584AA0 Content-Type: text/plain; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable Hi,=20 my question was: > we are performing ONIOM (b3LYP:UFF) calculations on > graphite compounds. > The low and the high level have not the same multiplicity and > consequently the computation stops. > The problem arises from the UFF. Does anybody know how to : > wether specify two different multiplicities for the two levels or > suppress the multiplicity test in the molecular mechanics computation. >=20 > Best Regards >=20 > Olivier the multiplicity of each layers in the case of an ONIOM computation can = be specified in the line related to the charge and multiplicity in the input. For example 0 1 0 3 the high level is a neutral singlet and the low level a neutral = triplet. I would like to thank for their help: Nicolas Ferr=E9, Douglas J. Fox, James Kubicki and Ataualpa Albert Carmo = Braga. Olivier Maresca Domaine de la Bastide Bat A 1 traverse Cazeneuve 13012 Marseille 06 22 97 44 71 ------=_NextPart_000_004B_01C29988.6D584AA0 Content-Type: text/html; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable
Hi,
my question was:
> we are performing ONIOM (b3LYP:UFF) calculations on
> = graphite=20 compounds.
> The low and the high level have not the same = multiplicity=20 and
> consequently the computation stops.
> The problem = arises from=20 the UFF. Does anybody know how to :
> wether specify two different = multiplicities for the two levels or
> suppress the multiplicity = test in=20 the molecular mechanics computation.
>
> Best = Regards
>=20
> Olivier
the multiplicity of each layers in the = case of an=20 ONIOM computation can be specified in the line related
to the charge and multiplicity in = the input.=20 For example
 
0  1  0  = 3
the high level is a  neutral = singlet and the=20 low level a neutral triplet.
 
I would like to thank for their help:
Nicolas Ferr=E9, Douglas J. Fox, James Kubicki and Ataualpa = Albert=20 Carmo Braga.

Olivier = Maresca
Domaine de la=20 Bastide Bat A
1 traverse Cazeneuve
13012 Marseille
06 22 97 44=20 71
------=_NextPart_000_004B_01C29988.6D584AA0-- __________________________________________________ Do You Yahoo!? Sign up for SBC Yahoo! Dial - First Month Free http://sbc.yahoo.com From chemistry-request@server.ccl.net Sun Dec 1 14:42:50 2002 Received: from GWIA.HSC.WVU.EDU ([157.182.105.18]) by server.ccl.net (8.11.6/8.11.0) with ESMTP id gB1JgoO00506 for ; Sun, 1 Dec 2002 14:42:50 -0500 Received: from HSC-DOM5-MTA by GWIA.HSC.WVU.EDU with Novell_GroupWise; Sun, 01 Dec 2002 14:42:50 -0500 Message-Id: X-Mailer: Novell GroupWise Internet Agent 6.0.2 Date: Sun, 01 Dec 2002 14:42:37 -0500 From: "Peter Gannett" To: , , Subject: Re: CCL:Quantum Chemistry in Drug Design Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Disposition: inline Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by server.ccl.net id gB1JgoO00507 I would say the problem is more complicated than just the amount of time required for a QC calc/compound. For example, you can optimized a compound geometry all you want but it is not necessarily the geometry adopted when the molecule is in the active site of an enzyme so there is not much use. Second, there are simple (minded) methods that clearly ignore a large number of interactions and still come out with useful information. CoMFA is an example of this. A rather simple set of compounds (training set of say 20 compounds) provides you with a reasonable ability to predict how to modify/improve on a drug's activity. It has proven to be a fairly powerful method though computationally, it is very inexpensive. So, it think the bottom line here that QC will not play an important role until it can be demonstrated that there are compelling reasons to implement it. Pete Gannett >>> "Parthiban" 11/29/02 08:41PM >>> Dear Friends: While several QSAR related techniques and methodologies are appearing in drug design Journals, very few talk about the more accurate quantum chemical methods in drug design arena. * What are the bottlenecks for the quantum chemical methods to get into the area of drug design. * For small molecules QC methods plays greater role, but for handling drug- like molecules and handling several thousands of compounds, QC methods do not see the limelight (correct me if i am wrong). Is the CPU-intensiveness alone is the reason. Or is there any some conceptual gap in this. [ I hear someone saying CPU-intensive is the reason and one has to wait for months to get results ] * Based on your experience/insight, can you think of some timeframe, say 5 years, 10 years down the line, Quantum chemical methods would play a major role in the area of lead identification/optimization, or would you say "prediction of future is difficult!". I look forward to reading your views. Thanks. S. Parthiban Jubilant Biosys Ltd. http://www.jubilantbiosys.com -= This is automatically added to each message by mailing script =- CHEMISTRY@ccl.net -- To Everybody | CHEMISTRY-REQUEST@ccl.net -- To Admins Ftp: ftp.ccl.net | WWW: http://www.ccl.net/chemistry/ | Jan: jkl@ccl.net