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Hydrocarbon Tail (hydrocarbon + tail)

Distribution by Scientific Domains
Chemistry42%

Selected Abstracts

Novel Phthalocyaninatobis(alkylcarboxylato)silicon(IV) Compounds: NMR Data and X-ray Structures To Study the Spacing Provided by Long Hydrocarbon Tails That Enhance Their Solubility

CHEMISTRY - A EUROPEAN JOURNAL, Issue 14 2005
Jose L. Sosa-Sánchez Dr.
Abstract The reaction between trans -PcSiCl2 (1) and the potassium salts of six fatty acids (2,a,2,f) led to the trans -PcSi[OOC(CH2)nCH3]2 compounds (3,a,3,f), which were characterised by elemental analysis, IR, UV/Vis and 1H, 13C, and 29Si NMR spectroscopy. From a detailed study of the NMR spectra, the strong anisotropic currents of the Pc macrocycle were found to have an effect on up to the sixth methylenic group. As expected, the length of the hydrocarbon tail does not affect the chemical shift of the 29Si nucleus of any of the compounds, appearing at around ,222.6. The structures of PcSi[OOC(CH2)nCH3]2, where n=7, 10, 12, 13 and 20, were determined by X-ray crystallography. All the compounds were found to be triclinic with a P space group. In all cases the observed crystallographic pseudosymmetry is Ci and the asymmetric unit consists of half a molecule. The silicon atom is at the centre of a distorted octahedron and hence its coordination number is six. The carboxylate fragments are in a trans configuration with respect to the Pc macrocycle. The supramolecular structures are discussed in detail herein. The correlation between the 1H NMR chemical shifts and the position of the corresponding carbon atoms in the hydrocarbon tail reveals that the dicarboxylate substituents exhibit a spacer-like behaviour that enhances the solubility. A detailed study of the tail variable allowed us to evaluate the loss of radial shielding along the Pc2, ligand. [source]

Linear sulphonate detergents as pour point depressants

LUBRICATION SCIENCE, Issue 2 2004
S. Li
Abstract Oil-soluble metallic sulphonate detergents have been extensively used in automobile lubricants to keep engines clean and to extend their useful life. Calcium alkylbenzene sulphonate is widely used in the lubricant industry as a detergent. However, the authors have discovered that, uniquely, linear sulphonate detergents can play another role in lubricants, namely to depress the pour point of mineral oils. The authors have studied the relationship between the molecular structures of sulphonate detergents and pour point depression, and it has been found that, in order for a sulphonate detergent to be a pour point depressant (PPD), it must have a linear hydrocarbon tail. Other factors, such as the metal type, e.g., Ca or Mg, and the degree of overbasing, are not critical for pour point depression activity. A model is proposed to explain why sulphonate detergents with linear hydrocarbon tails can function as pour point depressants. [source]

Kinetics of the M-Intermediate in the Photocycle of Bacteriorhodopsin upon Chemical Modification with Surfactants

PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 2 2010
Li-Kang Chu
The spectroscopic and kinetic studies of the interaction between bacteriorhodopsin in the M-intermediate and several surfactants (cetyl trimethyl ammonium bromide, dodecyl trimethyl ammonium bromide, diethylene glycol mono- n -hexyl ether, ethylene glycol mono- n -hexyl ether, sodium 1-decanesulfonate and sodium 1-heptanesulfonate) have been investigated using steady-state UV,VIS spectrometry and time-resolved absorption techniques. The steady-state spectral results show that bR retains its trimeric state. Time-resolved observations indicate that the rate of deprotonation of the protonated Schiff base increases in the presence of the cationic surfactants, whereas insignificant changes are observed in the neutral or anionic surfactants. The rate of the reprotonation of the Schiff base in the transition M , N is accelerated in anionic and neutral surfactants, but is decelerated in the presence of the cationic surfactants. Surfactants with a longer hydrocarbon tail have a greater effect on the kinetics when compared with surfactants having shorter hydrocarbon tails. The opposite effect is observed when the hydrophilic head of the surfactants contains opposite charges. These distinct kinetics are discussed in terms of the difference in the modified surface hydrophilicity of the bR and the possible protein configurational changes upon surfactant treatments. [source]

A double mutation of Escherichia coli 2C -methyl- d -erythritol-2,4-cyclodiphosphate synthase disrupts six hydrogen bonds with, yet fails to prevent binding of, an isoprenoid diphosphate

ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 7 2005
Tanja Sgraja
The essential enzyme 2C -methyl- d -erythritol-2,4-cyclodiphosphate (MECP) synthase, found in most eubacteria and the apicomplexan parasites, participates in isoprenoid-precursor biosynthesis and is a validated target for the development of broad-spectrum antimicrobial drugs. The structure and mechanism of the enzyme have been elucidated and the recent exciting finding that the enzyme actually binds diphosphate-containing isoprenoids at the interface formed by the three subunits that constitute the active protein suggests the possibility of feedback regulation of MECP synthase. To investigate such a possibility, a form of the enzyme was sought that did not bind these ligands but which would retain the quaternary structure necessary to create the active site. Two amino acids, Arg142 and Glu144, in Escherichia coli MECP synthase were identified as contributing to ligand binding. Glu144 interacts directly with Arg142 and positions the basic residue to form two hydrogen bonds with the terminal phosphate group of the isoprenoid diphosphate ligand. This association occurs at the trimer interface and three of these arginines interact with the ligand phosphate group. A dual mutation was designed (Arg142 to methionine and Glu144 to leucine) to disrupt the electrostatic attractions between the enzyme and the phosphate group to investigate whether an enzyme without isoprenoid diphosphate could be obtained. A low-resolution crystal structure of the mutated MECP synthase Met142/Leu144 revealed that geranyl diphosphate was retained despite the removal of six hydrogen bonds normally formed with the enzyme. This indicates that these two hydrophilic residues on the surface of the enzyme are not major determinants of isoprenoid binding at the trimer interface but rather that hydrophobic interactions between the hydrocarbon tail and the core of the enzyme trimer dominate ligand binding. [source]

Novel Phthalocyaninatobis(alkylcarboxylato)silicon(IV) Compounds: NMR Data and X-ray Structures To Study the Spacing Provided by Long Hydrocarbon Tails That Enhance Their Solubility

CHEMISTRY - A EUROPEAN JOURNAL, Issue 14 2005
Jose L. Sosa-Sánchez Dr.
Abstract The reaction between trans -PcSiCl2 (1) and the potassium salts of six fatty acids (2,a,2,f) led to the trans -PcSi[OOC(CH2)nCH3]2 compounds (3,a,3,f), which were characterised by elemental analysis, IR, UV/Vis and 1H, 13C, and 29Si NMR spectroscopy. From a detailed study of the NMR spectra, the strong anisotropic currents of the Pc macrocycle were found to have an effect on up to the sixth methylenic group. As expected, the length of the hydrocarbon tail does not affect the chemical shift of the 29Si nucleus of any of the compounds, appearing at around ,222.6. The structures of PcSi[OOC(CH2)nCH3]2, where n=7, 10, 12, 13 and 20, were determined by X-ray crystallography. All the compounds were found to be triclinic with a P space group. In all cases the observed crystallographic pseudosymmetry is Ci and the asymmetric unit consists of half a molecule. The silicon atom is at the centre of a distorted octahedron and hence its coordination number is six. The carboxylate fragments are in a trans configuration with respect to the Pc macrocycle. The supramolecular structures are discussed in detail herein. The correlation between the 1H NMR chemical shifts and the position of the corresponding carbon atoms in the hydrocarbon tail reveals that the dicarboxylate substituents exhibit a spacer-like behaviour that enhances the solubility. A detailed study of the tail variable allowed us to evaluate the loss of radial shielding along the Pc2, ligand. [source]

Linear sulphonate detergents as pour point depressants

LUBRICATION SCIENCE, Issue 2 2004
S. Li
Abstract Oil-soluble metallic sulphonate detergents have been extensively used in automobile lubricants to keep engines clean and to extend their useful life. Calcium alkylbenzene sulphonate is widely used in the lubricant industry as a detergent. However, the authors have discovered that, uniquely, linear sulphonate detergents can play another role in lubricants, namely to depress the pour point of mineral oils. The authors have studied the relationship between the molecular structures of sulphonate detergents and pour point depression, and it has been found that, in order for a sulphonate detergent to be a pour point depressant (PPD), it must have a linear hydrocarbon tail. Other factors, such as the metal type, e.g., Ca or Mg, and the degree of overbasing, are not critical for pour point depression activity. A model is proposed to explain why sulphonate detergents with linear hydrocarbon tails can function as pour point depressants. [source]

Kinetics of the M-Intermediate in the Photocycle of Bacteriorhodopsin upon Chemical Modification with Surfactants

PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 2 2010
Li-Kang Chu
The spectroscopic and kinetic studies of the interaction between bacteriorhodopsin in the M-intermediate and several surfactants (cetyl trimethyl ammonium bromide, dodecyl trimethyl ammonium bromide, diethylene glycol mono- n -hexyl ether, ethylene glycol mono- n -hexyl ether, sodium 1-decanesulfonate and sodium 1-heptanesulfonate) have been investigated using steady-state UV,VIS spectrometry and time-resolved absorption techniques. The steady-state spectral results show that bR retains its trimeric state. Time-resolved observations indicate that the rate of deprotonation of the protonated Schiff base increases in the presence of the cationic surfactants, whereas insignificant changes are observed in the neutral or anionic surfactants. The rate of the reprotonation of the Schiff base in the transition M , N is accelerated in anionic and neutral surfactants, but is decelerated in the presence of the cationic surfactants. Surfactants with a longer hydrocarbon tail have a greater effect on the kinetics when compared with surfactants having shorter hydrocarbon tails. The opposite effect is observed when the hydrophilic head of the surfactants contains opposite charges. These distinct kinetics are discussed in terms of the difference in the modified surface hydrophilicity of the bR and the possible protein configurational changes upon surfactant treatments. [source]