This Article Full Text Full Text (PDF) All Versions of this Article: biophysj.105.064667v1 89/4/2558    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Podestà, A. Articles by Dunlap, D. Search for Related Content PubMed PubMed Citation Articles by Podestà, A. Articles by Dunlap, D.

Positively Charged Surfaces Increase the Flexibility of DNA

Alessandro Podestà ^*, Marco Indrieri ^*, Doriano Brogioli , Gerald S. Manning , Paolo Milani ^*, Rosalinda Guerra , Laura Finzi  and David Dunlap 

^* Department of Physics, INFM and CIMAINA, and Department of Biology and CIMAINA, University of Milan, Milan, Italy; Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, New Jersey; and ALEMBIC, San Raffaele Scientific Institute, Milan, Italy

Correspondence: Address reprint requests to David Dunlap, ALEMBIC, DIBIT 3A3, San Raffaele Scientific Institute, Via Olgettina 58, 20132 Milan, Italy. Tel.: 39-022-643-4636; Fax: 39-022-643-4813; E-mail: dunlap.david{at}hsr.it.

Many proteins "bind" DNA through positively charged amino acids on their surfaces. However, to overcome significant energetic and topological obstacles, proteins that bend or package DNA might also modulate the stiffness that is generated by repulsions between phosphates within DNA. Much previous work describes how ions change the flexibility of DNA in solution, but when considering macromolecules such as chromatin in which the DNA contacts the nucleosome core each turn of the double helix, it may be more appropriate to assess the flexibility of DNA on charged surfaces. Mica coated with positively charged molecules is a convenient substrate upon which the flexibility of DNA may be directly measured with a scanning force microscope. In the experiments described below, the flexibility of DNA increased as much as fivefold depending on the concentration and type of polyamine used to coat mica. Using theory that relates charge neutralization to flexibility, we predict that phosphate repulsions were attenuated by 50% in the most flexible DNA observed. This simple method is an important tool for investigating the physiochemical causes and molecular biological effects of DNA flexibility, which affects DNA biochemistry ranging from chromatin stability to viral encapsulation.

This article has been cited by other articles:

				F. Montel, E. Fontaine, P. St-Jean, M. Castelnovo, and C. Faivre-Moskalenko Atomic Force Microscopy Imaging of SWI/SNF Action: Mapping the Nucleosome Remodeling and Sliding Biophys. J., July 15, 2007; 93(2): 566 - 578. [Abstract] [Full Text] [PDF]

				G. S. Manning The Persistence Length of DNA Is Reached from the Persistence Length of Its Null Isomer through an Internal Electrostatic Stretching Force Biophys. J., November 15, 2006; 91(10): 3607 - 3616. [Abstract] [Full Text] [PDF]

				R. J. McDonald, J. D. Kahn, and L. J. Maher III DNA bending by bHLH charge variants Nucleic Acids Res., October 18, 2006; 34(17): 4846 - 4856. [Abstract] [Full Text] [PDF]

				G. S. Manning The Contribution of Transient Counterion Imbalances to DNA Bending Fluctuations Biophys. J., May 1, 2006; 90(9): 3208 - 3215. [Abstract] [Full Text] [PDF]