UV-VIS and FTIR spectroscopic analyses of inclusion complexes of nonylphenol and nonylphenol ethoxylate with beta-cyclodextrin.

A study of inclusion complexation of liquid non-ionic surfactants, nonylphenol (NP) and nonylphenol 9 mole ethoxylate (NP9EO), with beta-cyclodextrin (beta-CD), was carried out by mass spectrometry, surface tension, and ultraviolet-visible (UV-VIS) and Fourier transform infrared (FTIR) spectroscopies. The inclusion complexation was effectuated by heating at 80 degrees C and filtration of aqueous NP+beta-CD and NP9EO+beta-CD suspensions. The mass spectrometry and surface tension measurements revealed that NP and NP9EO form inclusion complexes with beta-CD and beta-CD possesses a higher affinity for NP. These results are supported by the data from UV-VIS spectroscopic analyses that have indicated that a three times greater amount of NP is entrapped into beta-CD than NP9EO. This phenomenon has been associated with the smaller size and a higher degree of hydrophobicity of NP that favours its entrapment into beta-CD as compared to that of NP9EO. At the structural level, the data from FTIR spectroscopic study have indicated that alkyl chains of NP and NP9EO can form van der Waals interactions with the cavity of beta-CD. Moreover, NP and NP9EO seem to cause a reorganization of the intramolecular hydrogen bonds and change of the hydration of beta-CD, but did not appear to strongly interact with C-C, C-O-C, and OH groups of beta-CD. Together these results suggest that the formation of inclusion complexes by NP and NP9EO with beta-CD molecules could constitute an effective and advantageous technique to remove liquid non-ionic surfactants from wastewater due to the non-toxic character of beta-CD to humans and the environment.

A comparison between electrokinetic capillary chromatography and absorption spectroscopy for the analysis of peptide-micelle association by weak hydrophobic interactions.

Micellar electrokinetic capillary chromatography (MEKC) was compared to absorption spectroscopy to estimate equilibrium association constans (K(as)) for peptide-micelle systems involving three peptides (leucine-enkephalin, methionine-enkephalin and leucine-phenylalanine (LF)) and two surfactant micelles (sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB)). Buffer pH was chosen to minimize purely electrostatic interactions between peptides and micelles that could not be interrogated by absorption spectroscopy. Viscosity-corrected MEKC mobilities gave reasonably similar estimates of K(as) between the two methods for all three peptide-SDS micelle systems, with K(as) values ranging from 13.7 +/- 0.3 to 49 +/- 1 M(-1). For CTAB, estimates of K(as) for LF-CTAB micelle association were of the same order of magnitude as the SDS micelle by the two methods of estimation. On the other hand, enkephalin-CTAB micelle binding was about 10 times stronger (K(as) = 122 +/- 3 M(-1) to 311 +/- 9 M(-1)) than the enkephalin-SDS micelle binding. In addition, MEKC underestimated the K(as) values relative to spectroscopy by a factor of 2-3 for the enkephalin-CTAB system.

Oxidation-induced misfolding and aggregation of superoxide dismutase and its implications for amyotrophic lateral sclerosis.

The presence of intracellular aggregates that contain Cu/Zn superoxide dismutase (SOD1) in spinal cord motor neurons is a pathological hallmark of amyotrophic lateral sclerosis (ALS). Although SOD1 is abundant in all cells, its half-life in motor neurons far exceeds that in any other cell type. On the basis of the premise that the long half-life of the protein increases the potential for oxidative damage, we investigated the effects of oxidation on misfolding/aggregation of SOD1 and ALS-associated SOD1 mutants. Zinc-deficient wild-type SOD1 and SOD1 mutants were extremely prone to form visible aggregates upon oxidation as compared with wild-type holo-protein. Oxidation of select histidine residues that bind metals in the active site mediates SOD1 aggregation. Our results provide a plausible model to explain the accumulation of SOD1 aggregates in motor neurons affected in ALS.