Document Detail

Interactions of dendrimers with selected amino acids and proteins studied by continuous wave EPR and Fourier transform EPR.
MedLine Citation:
PMID:  15518519     Owner:  NLM     Status:  MEDLINE    
Interactions of polyamidoamine dendrimers, termed Gn, where n indicates the generation (=number of amidoamine layers), at different protonation levels with selected amino acids and proteins have been investigated by means of continuous wave electron paramagnetic resonance (cw-EPR) and pulsed-EPR (electron spin-echo = ESE) analyses. A low-generation dendrimer (G2) and a high-generation one (G6) were labeled with nitroxides for the EPR measurements. Gly, Glu, Arg, and Leu were selected as representative of neutral(zwitterionic)-polar, acidic, basic, and low-polar amino acids, respectively. The water-soluble proteins alpha-chymotrypsin and albumin were selected on the basis of a basic and an acidic isoelectric point, respectively. The cw-EPR spectra were analyzed by computing the line shapes to extract information about the dendrimer-biomolecule interactions. In general, dendrimers at a high protonation level interact stronger with amino acids than those at a low level of protonation. However, even for highly protonated dendrimers, a synergistic effect between hydrophilic and hydrophobic interactions promoted the formation of stable Gn-amino acid adducts, as demonstrated by the enhanced interactions with Leu. As expected from acid-base interactions, stable adducts were formed between Arg and highly protonated dendrimers and between Glu and low level protonated dendrimers. The relatively strong dendrimer interactions with the protein chymotrypsin and the poor interactions of dendrimers with albumin demonstrated that the protonated amino groups of the dendrimers are predominantly involved in the interactions with these proteins and indicated a significant role in the interactions with the dendrimers of the hydrophobic external residues of chymotrypsin. Computer-aided analysis of the ESE experiments was consistent with the cw-EPR results and supported the conclusion of a partial complexation of the nitroxides of the dendrimer with Leu and alpha-chymotrypsin.
M Francesca Ottaviani; Steffen Jockusch; Nicholas J Turro; Donald A Tomalia; Antonio Barbon
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Publication Detail:
Type:  In Vitro; Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  Langmuir : the ACS journal of surfaces and colloids     Volume:  20     ISSN:  0743-7463     ISO Abbreviation:  Langmuir     Publication Date:  2004 Nov 
Date Detail:
Created Date:  2004-11-02     Completed Date:  2006-04-10     Revised Date:  2009-01-08    
Medline Journal Info:
Nlm Unique ID:  9882736     Medline TA:  Langmuir     Country:  United States    
Other Details:
Languages:  eng     Pagination:  10238-45     Citation Subset:  IM    
Institute of Chemical Sciences, University of Urbino, Piazza Rinascimento 6, 61029 Urbino, Italy.
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MeSH Terms
Albumins / chemistry
Amino Acids / chemistry*
Chymotrypsin / chemistry
Electron Spin Resonance Spectroscopy / methods
Fourier Analysis
Leucine / chemistry
Models, Molecular
Polyamines / chemistry*
Proteins / chemistry*
Static Electricity
Reg. No./Substance:
0/Albumins; 0/Amino Acids; 0/PAMAM Starburst; 0/Polyamines; 0/Proteins; 61-90-5/Leucine; EC 3.4.21.-/alpha-chymotrypsin; EC

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