Butyl Ligands Research Articles

Di‐n‐butyltin aminoarylcarboxylates: structure, properties and in vitro antitumor activity

AbstractThe properties and structures of the tetranuclear dibutyltin complexes [Sn4(µ3‐O)2(C4H9‐n)8­{OOCC6H3(NH2)2‐3,4}4] (1), [Sn4(µ3‐O)2(C4H9‐n)8{OOCC6H3(NH2)2‐3,5}4] (2), [Sn4(µ3‐O)2(C4H9‐n)8­{OOC‐2‐C6H4NNC6H4N(CH3)2‐4}4] (3) are described. Complex 3 adopts a structure with a tetranuclear Sn4(µ3‐O)2 core. All tin atoms are five‐coordinate and form bonds with three oxygen atoms and two butyl ligands. Two carboxylates are bridging and two are terminal ligands. IR and NMR spectra indicate that the same structure is adopted by complexes 1 and 2. The molecular and electronic structures of complex 1 of C i symmetry have been studied using the semi‐empirical PM3 formalism. The calculated structure and bond distances agree with X‐ray data. All complexes are effective antitumor agents. Copyright © 2002 John Wiley & Sons, Ltd.

Microcalorimetric studies of interactions between proteins and hydrophobic ligands in hydrophobic interaction chromatography: effects of ligand chain length, density and the amount of bound protein

Using isothermal titration calorimetry (ITC), this investigation directly measured the adsorption enthalpies of proteins on various hydrophobic adsorbents. Various amounts of butyl and octyl groups were attached onto CM-Sepharose to form C 4 and C 8, two types of hydrophobic adsorbents. The adsorption enthalpies of both trypsinogen and α-chymotrypsinogen A were measured at 4.0 M NaCl and pH 10.0, in which most ionic interaction was suppressed. The adsorption isotherms of both proteins on various adsorbents were also measured, thus allowing us to calculate the Gibbs free energy and entropy of adsorption. Experimental results indicated that the adsorption of both proteins on butyl-containing adsorbents was exothermic, while their adsorption on octyl ones was endothermic. In addition, binding of both proteins with the butyl ligand is basically an adsorption process, while binding with the octyl ligand is adsorption and partition processes. Moreover, on both butyl or octyl, the adsorption enthalpy became increasingly positive as the ligand density increased, while the adsorption entropy became more positive as the alkyl chain length or density of the adsorbent increased. In addition, ITC was used to measure protein–protein interaction. The adsorption enthalpy of both proteins increased as the amount of bound protein increased, and the enthalpy increase of trypsinogen appeared to be higher than that of α-chymotrypsinogen A. This observation implies that protein–protein repulsion was stronger among trypsinogen molecules in the experiments.

Metal-free anionic polymerization of methyl methacrylate

Results on the metal-free anionic polymerization of methyl methacrylate (MMA) are presented. MMA was polymerized in tetrahydrofuran, using tetrabutylammonium diethyl 2-ethylmalonate and tetrabutylammonium 2-nitropropanate as initiators. Immediate polymerization was observed only in cases where the initators did not contain traces of their precursor molecules, the presence of which causes an appreciable inhibition period. This is attributed to the transfer reaction between active species and the precursor molecules. Only after their consumption can the major polymerization start. Using very pure initiators, no inhibition period was observed. Curves from dilatometric measurements showed the existence of an induction period. As usual, this is attributed to an initiation reaction which is slower than the propagation reaction. It is more clearly marked for tetrabutylammonium diethyl 2-ethylmalonate than for tetrabutylammonium 2-nitropropanate as initiator. All polymerizations of MMA usually go to complete consumption of the monomer. However, termination reactions have to be taken into account as well. The well-known intramolecular cyclization reaction was not observed in the MMA system. Here, a Hofmann elimination reaction terminates the growing of chains, which is due to the butyl ligands of the ammonium cation, where a β-hydrogen atom can be transferred to the growing chain under the formation of tri-n-butylamine and 1-butene. To eliminate this termination step, tetramethylammonium diethyl 2-ethylmalonate was synthesized and used as the initiator for the polymerization of MMA. Now transalkylation under the formation of a methyl group terminated the saturated chain end and trimethyl amine could be detected as a second termination reaction. Neither of the termination reactions seems to be very fast. The molecular weight distributions of the synthesized polymers are relatively broad.

Surface Organometallic Chemistry of Germanium: Infrared, CP-MAS 13C Solid State NMR, and Analytical Evidence for the Formation of Highly Thermally Stable −O−Ge(n-C4H9)3 Grafted Fragments by Reaction of Ge(n-C4H9)4 with the Surface of Partially Dehydroxylated Alumina and Silica−Alumina

Interaction of Ge(n-C4H9)4 complex with partially dehydroxylated α- and η-alumina and silica−alumina surfaces has been investigated by 13C CP-MAS NMR, infrared spectroscopy, and analytical methods. At 25 °C, Ge(n-C4H9)4 interacts, via hydrogen bonds, by its butyl ligands, with hydroxyl groups of the surface. At 250 °C, Ge(n-C4H9)4 reacts with the hydroxyl groups to form >X-O-Ge(n-C4H9)3 (X = Si, Al) and 1 mol of butane/mol of grafted germanium. When the complex is grafted on silica−alumina the germanium atom is tetracoordinated, while on alumina it could adopt a tetra- or a pentacoordination. The grafted −O−Ge(n-C4H9)3 fragments exhibit, on both silica−alumina and alumina, extraordinary high thermal stability (until 400 °C in vacuo). This phenomenon had already been observed with ⋮SiOGe(n-C4H9)3 grafted on silica.

Surface Organometallic Chemistry of Tin: Formation of the Grafted Organometallic Complex (.scharw.Si-O)2Sn(n-C4H9)2 by Reaction of H2Sn(n-C4H9)2 with the Surface of a Partially Dehydroxylated Silica

Reaction of H 2 Sn(n-C 4 H 9 ) 2 with the surface of Aerosil silica dehydroxylated at 200 or 500 o C was followed by surface microanalysis, quantitative analysis of the evolved gases, 13 C CP-MAS NMR, and infrared spectroscopy. At room temperature after a short period of interaction, the starting complex is simply physisorbed on the silica surface. Two types of weak interactions occur between surface silanols and both the CH groups of the butyl ligands and the tin hydride(s). For longer periods of interaction and /or higher temperature, a well-defined surface species (>Si-O) 2 SnBu 2 (2) is formed on both types of silica

Chemical and chromatographic characterization of a new bioprocess™ medium for hydrophobic interaction chromatogrpahy: Butyl Sepharose ® 4 FastFlow

The authors have studied the influence of ligand density, temperature, eluent pH and Triton X-100 on the separation performance of Butyl Sepharose 4 Fast Flow. The proteins used during the study were α-chymotrypsinogen, cytochrome C, ribonuclease A and lysozyme. Small adjustments to the chromatographic conditions can affect the retention times of the proteins. The effects from changes in temperature prove that the separation process is entropy-driven. The functional stability of Buty Sepharose 4 Fast Flow was studied by testing the separation of a protein in mixture during repeated cleaning-in-place (CIP) treatments with 1·0 m sodium hydroxide solution and 0·1 m hydrochloric acid. The separation behaviour of the protein mixture was unaltered after the medium had been treated for a total contact time of 4 weeks with 1·0 m sodium hydroxide solution. However, a slight decrease in retention times was observed in acidic conditions. The study shows that butyl ligands are released due to hydrolysis of the agarose support in acidic conditions. This explains the effect on retention time observed after CIP at pH 1. For this study, a method for determining the ligand content was developed. The amount of butyl groups coupled via ether linkage to the agarose matrix was determined by gas chromatography after cleavage of ether bonds by boron tribromide. The authors have also investigated the clearance of ethanol, 2-propanol and Triton X-100 from an HR 10/10 column packed with Butyl Sepharose 4 Fast Flow. For a column treated with Triton X-100, a regeneration procedure with 2-propanol was necessary in order to retain the original retention behaviour of the medium.

Reactions of chelating alkali metal amides with the Grignard reagent nBuMgCl: crystal structures and solution 1H NMR spectroscopic studies of the expected mono(amido)-product [PhCH 2(Me 2NCH 2CH 2)NMg nBu] 2 and the unexpected bis(amido)-product {[Ph(2-Pyr)N] 2M9 · (THF) 2}

Chelating alkali metal amides derived from metallation of the secondary amines PhCH 2(Me 2NCH 2CH 2)NH and Ph(2-Pyr)NH, react with the Grignard reagent nBuMgCl in 1:1 molar ratios to afford mono(amido) [PhCH2(Me 2NCH 2CH 2)NMg nBu] 2 1 and bis(amido) {[Ph(2-Pyr)N] 2Mg·(THF) 2} 2 (where THF = tetrahydrofuran) respectively. X-Ray crystallography shows 1 to be dimeric having an (amido N-Mg) 2 ring, the central one of a fused tricyclic core, with the other two arising from internal complexation by the tertiary amine nitrogen atoms. Butyl ligands complete the pseudo-tetrahedral coordination of the magnesium atoms. Variable temperature 1H NMR spectroscopic studies indicate that this structure retains its compact, highly rigid nature in arene solution, rendering it resistant to external complexation by THF. In contrast, the crystal structure of 2 is monomeric, with a pseudo-octahedral magnesium centre coordinated by two bidentate Ph(2-Pyr)N − anions and two THF molecules. Bis(amido) 2 appears to result from the THF-induced disproportionation of alkyl(amido) [Ph(2-Pyr)NMg nBu] 2, a dimer akin to 1, but decidedly more flexible sterically and therefore susceptible to attack by external donor molecules.

Hydrophobic Properties of Porcine Fibronectin and Its Functional Domains<xref ref-type="fn" rid="fn1"><sup>1</sup></xref>

The relations between surface hydrophobicities and binding properties of the functional domains of porcine plasma fibronectin were investigated. Porcine plasma fibronectin as well as human plasma fibronectin was adsorbed on a hydrophobic column with butyl or phenyl ligands in the presence of 0.5 M ammonium sulfate, and recovered in a single peak by decreasing the concentration of ammonium sulfate to 0 M, indicating that both fibronectins have very high surface hydrophobicities. On digestion with thermolysin, porcine plasma fibronectin yielded five fragments (140-150, 43, 25, 17, and 14 kDa) similar to those reported for human fibronectin, although porcine fibronectin was more resistant to the digestion than human fibronectin. The three heparin-binding fragments were found to have a wide range of surface hydrophobicities, the 140-150 kDa fragment having the lowest, the 25 kDa fragment a higher, and the 14 kDa fragment the highest among all the fragments. The 43 kDa collagen-binding and 17 kDa fragments had surface hydrophobicities as high as that of fibronectin. It is noteworthy that the 43 kDa collagen-binding fragment contributes to the high surface hydrophobicity of intact fibronectin in spite of the high content of carbohydrates.