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. 2001 Jul 3;98(14):7694-9.
doi: 10.1073/pnas.141221298.

Communication between noncontacting macromolecules

J Völker  1 , H H Klump, K J Breslauer
Affiliations

Communication between noncontacting macromolecules

J Völker et al. Proc Natl Acad Sci U S A. .

Abstract

We present a quantitative experimental demonstration of solvent-mediated communication between noncontacting biopolymers. We show that changes in the activity of a solvent component brought about by a conformational change in one biopolymer can result in changes in the physical properties of a second noncontacting biopolymer present in solution. Specifically, we show that the release of protons on denaturation of a donor polymer (in this case, a four-stranded DNA tetraplex, iDNA) modulates the melting temperature of a noncontacting, acceptor polymer [in this case poly(A)]. In addition to such proton-mediated cross talk, we also demonstrate counterion-mediated cross talk between noncontacting biopolymers. Specifically, we show that counterion association/release on denaturation of native salmon sperm DNA (the donor polymer) can modulate the melting temperature of poly(dA) x poly(dT) (the acceptor polymer). Taken together, these two examples demonstrate how poly(A) and poly(dA) x poly(dT) can serve as molecular probes that report the pH and free salt concentrations in solution, respectively. Further, we demonstrate how such through-solvent dialogue between biopolymers that do not directly interact can be used to evaluate (in a model-free manner) association/dissociation reactions of solvent components (e.g., protons, sodium cations) with one of the two biopolymers. We propose that such through-solution dialogue is a general property of all biopolymers. As a result, such solvent-mediated cross talk should be considered when assessing reactions of multicomponent systems such as those that exist in essentially all biological processes.

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Figures

Figure 1
Figure 1
Calorimetric melting profiles for d(TC5) donor and poly(A) acceptor in 10 mM Na+ buffer at three different pH values. The large positive transition in each of the three melting curves corresponds to the melting of d(TC5). The small negative peak corresponds to the melting of the poly(A) acid helix in the reference cell; the small positive peak at the higher temperature corresponds to the melting of the poly(A) acid helix in the sample cell. Black curve, pH 6.0, formula image = 0.428 mMstrand, CTpoly(A) = 0.1169 mMbase; blue curve, pH 5.75, formula image = 0.4146 mMstrand, CTpoly(A) = 0.0639 mMbase; red curve, pH 5.5, formula image = 0.4247 mMstrand, CTpoly(A) = 0.068 mMbase.
Figure 2
Figure 2
The measured Tm shifts in two different buffer conditions for poly(A) in the sample cell relative to poly(A) in the reference cell as a function of d(TC5) concentration. The solution conditions are 10 mM Na+ buffer at pH 5.75.
Figure 3
Figure 3
The measured Tm shifts for a trace amount of poly(dA)⋅poly(dT) resulting from the presence of native (circle) and denatured (square) salmon sperm DNA. The dashed lines represent the straight lines of best fit through the experimental data points. The solution conditions are 12 mM Na+/10 M cacodylate/1 mM Na2EDTA, pH 6.8.
See this image and copyright information in PMC

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