The effect of triethylenetetraamine (Trien) on the ion flotation of Cu(2+) and Ni(2+)

Ion flotation is a separation process involving the adsorption of a surfactant and counterions at an air/aqueous solution interface. It shows promise for removing toxic heavy metal ions from dilute aqueous solutions. Here we report the effect of a neutral chelating ligand, triethylenetetraamine (Trien), on the ion flotation of cations with dodecylsulfate, DS(-), introduced as sodium dodecylsulfate, SDS. Ion flotation in the aqueous SD-Cu(II)-Ca(II)-Trien system gave strongly preferential removal of Cu(II) over Ca(II), which is a reversal of the order of selectivity seen in the SDS-Cu(II)-Ca(II) system containing no Trien. The removal rates of Cu(2+) and Ni(2+) with DS(-) were much faster in the presence of Trien than for simple aquo ions, and the final metal concentration was significantly lower. Surface tension measurements showed that Trien enhanced the surface activity and adsorption density for SDS-Cu(II) and SDS-Ni(II) solutions. The overall change in the Gibbs free energy for adsorption resulting from complexation was -3.60 kJ/mol for Cu(II) and -3.50 kJ/mol for Ni(II). This included the effects of hydrophobic interactions between the metal-Trien complexes at the air/solution interface, along with changes in the amount of dehydration associated with cosorption of the metal-Trien complex with DS(-) at the air/solution interface.     

New prodrugs derived from 6-aminodopamine and 4-aminophenol as candidates for melanocyte-directed enzyme prodrug therapy (MDEPT)

Two novel tyrosinase mediated drug delivery pathways have been investigated for the selective delivery of cytotoxic units to melanocytes from urea and thiourea prodrugs. The synthesis of these prodrugs is reported, as well as oximetry data that illustrate that the targets are substrates for tyrosinase. The stability of each of the prodrugs in (i) phosphate buffer and (ii) bovine serum is discussed, and the urea prodrugs are identified as lead candidates for further studies. Finally, HPLC studies and preliminary cytotoxicity studies in a melanotic and an amelanotic cell line, that illustrate the feasibility of the approach, are presented.     

Quantitative analysis of solid mixtures by diffuse reflectance measurements

The factors affecting the reflectance of an absorbing substance mixed with material not absorbing at the wavelength of measurement were investigated and it was found that the effect of particle size could be eliminated by prolonged grinding. It is shown that the percentage by weight of the absorbing substance is directly proportional to the quantity (A/R)^1.383 (R = percentage reflectance ; A = 100 — R) and that this quantity is additive for 2 absorbing substances. A method is developed for the accurate determination of low concentrations of one and two absorbing substances mixed with non-absorbing material. The method is applicable to poorly crystallized substances which give no characteristic X-ray powder diffraction patterns as well as to crystalline solids. The reflectance of some substances is shown to be dependent on the previous history of the particular sample. The method is not applicable if there is physical interaction between the components of the mixture.     

The direct synthesis of the cyclic sulphamidate of (S)-prolinol: SimultaneousN-protection and activation towards nucleophilic displacement of oxygen.

The preparation of the cyclic sulphamidate of (S)-prolinol has been achieved by reaction with sulphuryl chloride at low temperature. This material has been shown to be susceptible to acid catalysed nucleophilic attack to furnish 2-(NN-dialkylamino)methyl- and 2-(methoxymethy]pyrrolidines after hydrolysis of the intermediate sulphamic acid derivatives.     

Conductance behavior of 1:1 electrolytes in 3-methyl-2-oxazolidone at 25°C

The conductance behavior of twenty-five 1∶1 electrolytes has been investigated in 3-methyl-2-oxazolidone (3Me20x) at 25°C. Conductance data were analyzed by the Lee-Wheaton equation, and all salts studied were found to be only slightly associated. Ionic limiting equivalent conductances were obtained using tris(iso-pentyl)butylammonium tetraphenylborate as a reference electrolyte. The relative values of the ionic limiting molar conductance are generally similar to those for other dipolar aprotic solvents. However, the order $$\lambda _0 (i - Pent_3 BuN^ + ) > \lambda _0 (Pent_4 N^ + )and\lambda _0 (Br^ - ) > \lambda _0 (ClO_4^ - )$$ is opposite to that found previously in the similar solvent 3-tert-bytyl-2-oxazolidone.     

Total synthesis of (±) zoapatanol: a stereospecific synthesis of a key intermediate

The development of a stereospecific synthesis of a key intermediate in the synthesis of (±)-zoapatanol from the Weiland-Miescher ketone is described.     

Stereochemical control of reductions. 9. Haptophilicity studies with 1,1-disubstituted 2-methyleneacenaphthenes

A series of 1-methyl-2-methyleneacenaphthenes has been synthesized, bearing an additional variable substituent (R) at the 1-position. These compounds have been hydrogenated in ethanol over a 5% Pd/C catalyst under standardized conditions in order to assess the haptophilicity of R, its ability to enforce addition of hydrogen from its own face of the molecule by coordination to the catalyst surface. The order of decreasing haptophilicity, assessed as the product epimer ratio, for the groups studied was R = CH(2)NH(2), CH(2)NMe(2), CH(2)OH, CHNOH, CH(2)OMe, CHO, CONH(2), CH(2)NHCOMe, COOK, COMe, CN, CONHOH, COOH, COOMe, COONa, COOLi. Because knowledge of group haptophilicities offers potential for stereochemical control in such reductions, comparisons are provided with haptophilic orders found in other molecular systems. It is shown that absolute haptophilicities can be manipulated by varying the dielectric constant of the solvent employed.     

Effect of surface attachment on synthesis of bacterial cellulose

Gluconacetobacter spp. synthesize a pure form of hydrophilic cellulose that has several industrial specialty applications. Literature reports have concentrated on intensive investigation of static and agitated culture in liquid media containing high nutrient concentrations optimized for maximal cellulose production rates. The behavior of these bacteria on semisolid and solid surfaces has not been specifically addressed. The species Gluconacetobacter hansenii was examined for cellulose synthesis and colony morphology on a range of solid supports, including cotton linters, and on media thickened with agar, methyl cellulose, or gellan. The concentration and chemical structure of the thickening agent were found to be directly related to the formation of contiguous cellulose pellicules. Viability of the bacteria following freezer storage was improved when the bacteria were frozen in their cellulose pellicules. This article was authored by a contractor of the US government under contract no. DEAC05-00OR22725. Accordingly, the US government retains a nonexclusive, royalty-free license to publish or reproduce the published form of this contribution, or allow others to do so, for US government purposes.     

Quantitative Raman Analysis of Carotenoid Protein Complexes in Aqueous Solution

Carotenoids are naturally abundant, fat-soluble pigmented compounds with dietary, antioxidant and vision protection advantages. The dietary carotenoids, Beta Carotene, Lutein, and Zeaxanthin, complexed with in bovine serum albumin (BSA) in aqueous solution, were explored using Raman spectroscopy to differentiate and quantify their spectral signatures. UV visible absorption spectroscopy was employed to confirm the linearity of responses over the concentration range employed (0.05–1 mg/mL) and, of the 4 Raman source wavelengths (785 nm, 660 nm, 532 nm, 473 nm), 532 nm was chosen to provide the optimal response. After preprocessing to remove water and BSA contributions, and correct for self-absorption, a partial least squares model with R² of 0.9995, resulted in an accuracy of the Root Mean Squared Error of Prediction for Beta Carotene of 0.0032 mg/mL and Limit of Detection 0.0106 mg/mL. Principal Components Analysis clearly differentiated solutions of the three carotenoids, based primarily on small shifts of the main peak at ~1520 cm⁻¹. Least squares fitting analysis of the spectra of admixtures of the carotenoid:protein complexes showed reasonable correlation between norminal% and fitted%, yielding 100% contribution when fitted with individual carotenoid complexes and variable contributions with multiple ratios of admixtures. The results indicate the technique can potentially be used to quantify the carotenoid content of human serum and to identify their differential contributions for application in clinical analysis.