From chpajt@bath.ac.uk Sat Oct 21 05:12:53 1995 Received: from goggins.bath.ac.uk for chpajt@bath.ac.uk by www.ccl.net (8.6.10/950822.1) id FAA04552; Sat, 21 Oct 1995 05:03:13 -0400 Received: from bath.ac.uk (actually host mary.bath.ac.uk) by goggins.bath.ac.uk with SMTP (PP); Sat, 21 Oct 1995 10:03:15 +0100 Date: Sat, 21 Oct 1995 10:03:08 +0100 (BST) From: A J Turner To: CHEMISTRY@www.ccl.net Subject: Re: CCL:XMol for SGI ... In-Reply-To: Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Hi! Can anyone tell me where to get the source for Xmol for a SGI 4D-25 running 4.0.5? Thanks Alex +--------------------------------------------------+ |Alternate E-mail A.J.Turner@Bath.ac.uk | |www home @ http://www.bath.ac.uk/~chpajt/home.html| +--------------------------------------------------+ From parcom.ernet.in!gadre@parcom.ernet.in Sat Oct 21 08:42:59 1995 Received: from sangam.ncst.ernet.in for parcom.ernet.in!gadre@parcom.ernet.in by www.ccl.net (8.6.10/950822.1) id IAA05922; Sat, 21 Oct 1995 08:32:47 -0400 Received: from parcom.UUCP (uucp@localhost) by sangam.ncst.ernet.in (8.6.12/8.6.6) with UUCP id SAA03816 for CHEMISTRY@www.ccl.net; Sat, 21 Oct 1995 18:03:42 +0530 Received: from parcom.UUCP by iucaa (4.1/SMI-4.1) id AA25841; Sat, 21 Oct 95 17:51:35+050 Received: from parcom by parcom.parcom.ernet.in (4.1/SMI-4.1) id AA26609; Sat Oct 21 17:44:33 1995 (GMT + 0530) Date: Sat Oct 21 17:44:33 1995 (GMT + 0530) From: gadre@parcom.ernet.in Message-Id: <9510211214.AA26609@parcom.parcom.ernet.in> To: CHEMISTRY@www.ccl.net Subject: MICELLES Dear Netters : You may recollect that I had sent you a small mail regarding micellar molecules. We have now completed this exciting study. An extended abstract is enclosed. We will be grateful for your comments and suggestions. Thnaks a lot!......................................Shridhar Gadre *************************************************************************** An Electrostatic Investigation : How Polar is the Tail-group of Ionic Micellar Molecules? Shridhar R. Gadre and Subhash S. Pingale Department of Chemistry, University of Pune, Pune - 411007, India. A comparison of the electronic charge distribution for isolated micellar ionic molecules and the respective hydrocarbons is carried out using ab-initio calculations. The systems studied are n-dodecanoate, n- decylsulfate and the corresponding hydrocarbons, viz. n-dodecane and n-decane. It is observed that the molecular electrostatic potential at the hydrocarbon ends of dodecylcarboxylate and decylsulfate is almost ten times more negative than n-dodecane and n-decane molecules respectively. In other words, for ionic micellar molecules, the charge of the polar head group percolates through the molecule upto the end of the hydrocarbon tail. In view of this, caution is warranted in the use of charge models for simulation of micelles involving charged molecular systems. To examine the effect of this MESP distribution on the possible binding energy of water as one goes down the chain, starting from the polar head group, we have calculated water interaction energies with two typical moities. Table for water interaction energies in kcal/mol with n-dodecanoate and n-dodecane molecules, by using ab initio calculations at STO-3G basis set. -------------------------------------------------------------------- Part of molecule n-dodecanoate n-dodecane where water interacts molecule molecule -------------------------------------------------------------------- Head group part -26.942 ---- -------------------------------------------------------------------- Middle part -1.674 -0.168 (Typically 5 to 6 carbons away from the head group) -------------------------------------------------------------------- Tail group part -0.470 -0.134 -------------------------------------------------------------------- Note that there is substantial difference in the water binding energies (between the n-dodecanoate and n-dodecane) even 5 to 6 carbons away from the head group. We find that this is generally in agreement with various statements in the literature. Some of the literature statements are summarized below. Note that our observations are sometime not in full agreement with these statements. An amphiphilic aggregation is dependent strongly upon the electrostatic properties of the water model. In Molecular dynamic simulations of a sodium octanoate micelle in aqueous solution, the hydration of different carbon atoms in the chain is largest for the carboxylic atom, the decrease along the chain, reaching a minimum and then increases again at the end of the chain (Jonsson et al. J.Chem.Phys. 85, 2259(1986)). Beesly et al. (J.Phys.Chem. 92, 791(1988)) concluded from an experimental survey that for cooperative interaction between amphiphilic molecules, hydrogen bonding is essential (Van Os et al. 9, (1993)). The aggregation of amphiphiles to form micelles, vesicles, and bilayers has been established in water, hydrazine (Evans (J.Phys.Chem.87,4538(1983)), Evans (J.Phys.Chem. 89, 1405 (1985)) formamide and glycols. All of these solvents are hydrogen bonding, posses high dielectric constants, and high cohesive energies (Beesley et al. J.Phys.Chem. 87, 5025(1983). Furthermore, micelle formation has also been observed in other liquids such as hydrazine (Ramadan et al. J.Phys.Chem 87, 4538(1983), Ramadan et al. J.Phys.Chem. 89,3405(1985), ethylammoniumnitrate(Evans et al. 87,3537(1983)) formamide,(McDonald et al. J.Pharm.Pharmacole 22, 148(1970), Ray et al. Nature 231, 313(1971) and glycols J.Gen.Chem.USSR 32, 2845(1962). Striking is that all these liquids can form hydrogen bonds (Van Os et al. J.Phys.Chem. 95,6361(1991)). From experimental results, Menger et al. (Acc. Chem. Res. 12, 111(1979)) concluded that the water penetration inside the micelle is significant. Casal (J. Amer. Chem. Soc. 110, 5203(1988)) studied the water penetration into the interior of a micelle using probe molecules. These studies suggest that althoug water can penetrate into a micelle, the central core of the micelle contains no water. Watanabe et al (J. Phys. Chem. 93, 6897 (1989)) have concluded that .."Thus, on an average, there are 8.5 water molecules in contact with the the hydrophobic tail of each monomer forming the micelle". From gadre@unipune.ernet.in Sat Oct 21 08:48:48 1995 Received: from sangam.ncst.ernet.in for gadre@unipune.ernet.in by www.ccl.net (8.6.10/950822.1) id IAA05908; Sat, 21 Oct 1995 08:31:43 -0400 Received: from unipune.UUCP (uucp@localhost) by sangam.ncst.ernet.in (8.6.12/8.6.6) with UUCP id SAA03739 for CHEMISTRY@www.ccl.net; Sat, 21 Oct 1995 18:02:41 +0530 Received: from unipune.UUCP by iucaa (4.1/SMI-4.1) id AA25762; Sat, 21 Oct 95 17:50:10+050 Received: by unipune.unipune.ernet.in (5.0/SMI-SVR4) id AA17970; Sat, 21 Oct 1995 17:37:17 +0500 Date: Sat, 21 Oct 1995 17:37:17 +0500 From: gadre@unipune.ernet.in (Faculty) Message-Id: <9510212237.AA17970@unipune.unipune.ernet.in> To: CHEMISTRY@www.ccl.net Subject: MICELLES...Hydrophilic Tails??? Cc: gadre@unipune.ernet.in Content-Length: 5192 Dear Netters : You may recollect that I had sent you a small mail regarding micellar molecules. We have now completed this exciting study. An extended abstract is enclosed. We will be grateful for your comments and suggestions. Thnaks a lot!......................................Shridhar Gadre *************************************************************************** An Electrostatic Investigation : How Polar is the Tail-group of Ionic Micellar Molecules? Shridhar R. Gadre and Subhash S. Pingale Department of Chemistry, University of Pune, Pune - 411007, India. A comparison of the electronic charge distribution for isolated micellar ionic molecules and the respective hydrocarbons is carried out using ab-initio calculations. The systems studied are n-dodecanoate, n- decylsulfate and the corresponding hydrocarbons, viz. n-dodecane and n-decane. It is observed that the molecular electrostatic potential at the hydrocarbon ends of dodecylcarboxylate and decylsulfate is almost ten times more negative than n-dodecane and n-decane molecules respectively. In other words, for ionic micellar molecules, the charge of the polar head group percolates through the molecule upto the end of the hydrocarbon tail. In view of this, caution is warranted in the use of charge models for simulation of micelles involving charged molecular systems. To examine the effect of this MESP distribution on the possible binding energy of water as one goes down the chain, starting from the polar head group, we have calculated water interaction energies with two typical moities. Table for water interaction energies in kcal/mol with n-dodecanoate and n-dodecane molecules, by using ab initio calculations at STO-3G basis set. -------------------------------------------------------------------- Part of molecule n-dodecanoate n-dodecane where water interacts molecule molecule -------------------------------------------------------------------- Head group part -26.942 ---- -------------------------------------------------------------------- Middle part -1.674 -0.168 (Typically 5 to 6 carbons away from the head group) -------------------------------------------------------------------- Tail group part -0.470 -0.134 -------------------------------------------------------------------- Note that there is substantial difference in the water binding energies (between the n-dodecanoate and n-dodecane) even 5 to 6 carbons away from the head group. We find that this is generally in agreement with various statements in the literature. Some of the literature statements are summarized below. Note that our observations are sometime not in full agreement with these statements. An amphiphilic aggregation is dependent strongly upon the electrostatic properties of the water model. In Molecular dynamic simulations of a sodium octanoate micelle in aqueous solution, the hydration of different carbon atoms in the chain is largest for the carboxylic atom, the decrease along the chain, reaching a minimum and then increases again at the end of the chain (Jonsson et al. J.Chem.Phys. 85, 2259(1986)). Beesly et al. (J.Phys.Chem. 92, 791(1988)) concluded from an experimental survey that for cooperative interaction between amphiphilic molecules, hydrogen bonding is essential (Van Os et al. 9, (1993)). The aggregation of amphiphiles to form micelles, vesicles, and bilayers has been established in water, hydrazine (Evans (J.Phys.Chem.87,4538(1983)), Evans (J.Phys.Chem. 89, 1405 (1985)) formamide and glycols. All of these solvents are hydrogen bonding, posses high dielectric constants, and high cohesive energies (Beesley et al. J.Phys.Chem. 87, 5025(1983). Furthermore, micelle formation has also been observed in other liquids such as hydrazine (Ramadan et al. J.Phys.Chem 87, 4538(1983), Ramadan et al. J.Phys.Chem. 89,3405(1985), ethylammoniumnitrate(Evans et al. 87,3537(1983)) formamide,(McDonald et al. J.Pharm.Pharmacole 22, 148(1970), Ray et al. Nature 231, 313(1971) and glycols J.Gen.Chem.USSR 32, 2845(1962). Striking is that all these liquids can form hydrogen bonds (Van Os et al. J.Phys.Chem. 95,6361(1991)). From experimental results, Menger et al. (Acc. Chem. Res. 12, 111(1979)) concluded that the water penetration inside the micelle is significant. Casal (J. Amer. Chem. Soc. 110, 5203(1988)) studied the water penetration into the interior of a micelle using probe molecules. These studies suggest that althoug water can penetrate into a micelle, the central core of the micelle contains no water. Watanabe et al (J. Phys. Chem. 93, 6897 (1989)) have concluded that .."Thus, on an average, there are 8.5 water molecules in contact with the the hydrophobic tail of each monomer forming the micelle".