Document Detail

Interfacial behavior of N-nitrosodiethylamine/bovine serum albumin complexes at the air-water and the chloroform-water interfaces by axisymmetric drop tensiometry.
MedLine Citation:
PMID:  17315914     Owner:  NLM     Status:  MEDLINE    
Interfacial properties of N-nitrosodiethylamine/bovine serum albumin (NDA/BSA) complexes were investigated at the air-water interface. The interfacial behavior at the chloroform-water interface of the interaction product of phospholipid 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), dissolved in the chloroform phase, and NDA/BSA complex, in the aqueous phase, were also analyzed by using a drop tensiometer. The secondary structure changes of BSA with different NDA concentrations were monitored by circular dichroism spectroscopy at different pH and the NDA/BSA interaction was probed by fluorescence spectroscopy. Different NDA/BSA mixtures were prepared from 0, 7.5 x 10(-5), 2.2 x 10(-4), 3.7 x 10(-4), 5 x 10(-4), 1.6 x 10(-3), and 3.1 x 10(-3) M NDA solutions in order to afford 0, 300/1, 900/1, 1 500/1, 2 000/1, 6 000/1, and 12 500/1 NDA/BSA molar ratios, respectively, in the aqueous solutions. Increments of BSA alpha-helix contents were obtained up to the 2 000/1 NDA/BSA molar ratio, but at ratios beyond this value, the alpha-helix content practically disappeared. These BSA structure changes produced an increment of the surface pressure at the air-water interface, as the alpha-helix content increased with the concentration of NDA. On the contrary, when alpha-helix content decreased, the surface pressure also appeared lower than the one obtained with pure BSA solutions. The interaction of DPPC with NDA/BSA molecules at the chloroform-water interface produced also a small, but measurable, pressure increment with the addition of NDA molecules. Dynamic light scattering measurements of the molecular sizes of NDA/BSA complex at pH 4.6, 7.1, and 8.4 indicated that the size of extended BSA molecules at pH 4.6 increased in a greater proportion with the increment in NDA concentration than at the other studied pH values. Diffusion coefficients calculated from dynamic surface tension values, using a short-term solution of the general adsorption model of Ward and Tordai, also showed differences with pH and the NDA concentration. Both, the storage and loss dilatational elastic modulus were obtained at the air-water and at the chloroform-water interfaces. The interaction of NDA/BSA with DPPC at the chloroform-water produced a less rigid monolayer than the one obtained with pure DPPC (1 x 10(-5) M), indicating a significant penetration of NDA/BSA molecules at the interface. At short times and pH 4.6, the values of the storage elastic modulus were larger and more sensible to the NDA addition than the ones at pH 7.1 and 8.4, probably due to a gel-like network formation at the air-water interface.
J Juárez; J G Galaz; L Machi; M Burboa; L E Gutiérrez-Millán; F M Goycoolea; M A Valdez
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2007-02-22
Journal Detail:
Title:  The journal of physical chemistry. B     Volume:  111     ISSN:  1520-6106     ISO Abbreviation:  J Phys Chem B     Publication Date:  2007 Mar 
Date Detail:
Created Date:  2007-04-02     Completed Date:  2007-06-07     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101157530     Medline TA:  J Phys Chem B     Country:  United States    
Other Details:
Languages:  eng     Pagination:  2727-35     Citation Subset:  IM    
Departamento de Investigación en Polímeros y Materiales, Departamento de Física, Universidad de Sonora, Rosales y Transversal, 83000 Hermosillo Sonora, México.
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MeSH Terms
Androstanes / chemistry
Chloroform / chemistry
Diethylnitrosamine / chemistry*
Phase Transition*
Protein Structure, Secondary
Serum Albumin, Bovine / chemistry*
Spectrometry, Fluorescence
Surface Properties
Water / chemistry
Reg. No./Substance:
0/3-oxo-androstan-17-yl-(2'',2'',6'',6''-tetramethyl-N-oxyl)piperidyl butan-1',4'-dioate; 0/Androstanes; 0/Serum Albumin, Bovine; 55-18-5/Diethylnitrosamine; 67-66-3/Chloroform; 7732-18-5/Water

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