This Article Full Text Full Text (PDF) All Versions of this Article: biophysj.105.067793v1 90/10/3672    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 Newby Lambert, M. Articles by Walter, N. G. Search for Related Content PubMed PubMed Citation Articles by Newby Lambert, M. Articles by Walter, N. G.

Mg²⁺-Induced Compaction of Single RNA Molecules Monitored by Tethered Particle Microscopy

Meredith Newby Lambert ^*, Eva Vöcker ^*, Seth Blumberg , Stefanie Redemann ^*, Arivalagan Gajraj , Jens-Christian Meiners  and Nils G. Walter ^*

^* Department of Chemistry, Single Molecule Analysis Group, and Department of Physics and Biophysics Research Division, University of Michigan, Ann Arbor, Michigan 48109-1055

Correspondence: Address reprint requests to Jens-Christian Meiners, Tel.: 734-764-7383; Fax: 734-764-5153; E-mail: meiners{at}umich.edu; or Nils G. Walter, Tel.: 734-615-2060; Fax: 734-647-4865; E-mail: nwalter{at}umich.edu.

We have applied tethered particle microscopy (TPM) as a single molecule analysis tool to studies of the conformational dynamics of poly-uridine(U) messenger (m)RNA and 16S ribosomal (r)RNA molecules. Using stroboscopic total internal reflection illumination and rigorous selection criteria to distinguish from nonspecific tethering, we have tracked the nanometer-scale Brownian motion of RNA-tethered fluorescent microspheres in all three dimensions at pH 7.5, 22°C, in 10 mM or 100 mM NaCl in the absence or presence of 10 mM MgCl₂. The addition of Mg²⁺ to low-ionic strength buffer results in significant compaction and stiffening of poly(U) mRNA, but not of 16S rRNA. Furthermore, the motion of poly(U)-tethered microspheres is more heterogeneous than that of 16S rRNA-tethered microspheres. Analysis of in-plane bead motion suggests that poly(U) RNA, but less so 16S rRNA, can be modeled both in the presence and absence of Mg²⁺ by a statistical Gaussian polymer model. We attribute these differences to the Mg²⁺-induced compaction of the relatively weakly structured and structurally disperse poly(U) mRNA, in contrast to Mg²⁺-induced reinforcement of existing secondary and tertiary structure contacts in the highly structured 16S rRNA. Both effects are nonspecific, however, as they are dampened in the presence of higher concentrations of monovalent cations.

This article has been cited by other articles:

				Z.-J. Tan and S.-J. Chen RNA Helix Stability in Mixed Na+/Mg2+ Solution Biophys. J., May 15, 2007; 92(10): 3615 - 3632. [Abstract] [Full Text] [PDF]