TU/e Soft Matter CryoTEM Research Unit

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Aqueous Interfaces

The use of cryoTEM for the analysis of self-organizing systems is a growing area. CryoTEM provides insights in the organization, complexation and interaction of molecules at the self-assembled monolayer interface.

Figure 1:Left- Vitrification robot coupled with the glove-box positioned for the transfer of the grid prior to vitrification. Right- Scheme of the reaction on the cryoTEM grid [3].

For the study of events occurring under Langmuir monolayers in cryoTEM, we developed a sample preparation method using a glovebox that can be connected to the vitrobot [1] (Figure 1). This allowed the vitrification of self-organizing monolayers still in contact with a thin film of the aqueous phase.

This method was used to investigate the interaction of DNA with a positively charged self-assembling monolayer at nanometer resolution with 3D in situ imaging[2]. It was demonstrated that DNA only binds partially to the monolayer such that it leads to a disordered mixed phase complex rather than individual DNA strand organization at the monolayer surface.

Figure 2: Projection along the x- and y-direction of the 3-D reconstructed volume in Amira showing the 2.5 nm DNA strands suspended from the monolayer. Parts of the DNA strands are attached to the cationic monolayer surface resulting in a thin dense layer of DNA at the monolayer surface (indicated by the 10 nm white bar), while the other ends are extending down into the bulk solution [2].

3-D Tomographic reconstruction of surfactant-DNA complex

Subsequently, this preparation method was adapted for the study of mineral formation under Langmuir monolayers. Using this method by the combination of cryo-electron tomography and low-dose selected area diffraction (SAED) not only revealed how monolayer interacted with the developing mineral in parallel, it also led to the first visualization of prenucleation clusters[3-4].

Figure 3: A) CryoTEM image of calcium carbonate particles growing under a stearic acid monolayer, after reaction time of 45 min. Scale bars, 200 nm. B) Diffraction pattern of the particles in (A), showing the development of crystallinity during the mineralization. C) Computer-aided visualization of the tomogram recorded from the area shown in (A)[3].

 

References

1. M.R.J. Vos, P.H.H. Bomans, P.M. Frederik, N.A.J.M. Sommerdijk, The development of a glove-box/Vitrobot combination: Air-water interface events visualized by cryo-TEM, Ultramicroscopy 108 (2008) 1478-1483.
2. M.R. Vos, P.H.H. Bomans, F. de Haas, P.M. Frederik, J.A. Jansen, R.J.M. Nolte, N.A.J.M. Sommerdijk,Insights in the organization of DNA-Surfactant Monolayers using cryo-electron tomography, J.Am.Chem.Soc. 129 (2007) 11894-11895.
3. E.M. Pouget, P.H.H. Bomans, J.A.C.M. Goos, P.M. Frederik, G. de With, N.A.J.M. Sommerdijk, The initial stages of template-controlled CaCO₃ formation revealed by Cryo-TEM, Science, 323(5920), (2009) 1455-1458.
4. A. Dey, P.H.H. Bomans, F.A. Muller, J. Will, P.M. Frederik, G de With, N.A.J.M. Sommerdijk, The role of prenucleation clusters in surface-induced calcium phoshpate crystallization, Nature Materials, 9 [12] (2010) 1010-1014.