The intensity change decreases when the DNA is removed and the viral capsid is filled up with water. This change clearly depends on the water content inside the nanocontainer. Therefore, PD0332991 the presence of DNA or water inside the cavity clearly enhances the contrast of the container image, although it does not provide good images of the actual geometry of the sample. Figure 3 Normalized transmitted power versus SNOM tip position over the capsid. The calculation has been performed for the dsDNA virus (green triangles) and for empty nanocontainers with different water occupancy: 100% (blue triangles),
50% (green diamonds), 10% (red squares) and 0% (black circles). The relative position of the tip with respect to the virus capsid (represented
with blue squares), for three different values of the scan direction, is shown. Inset shows the asymmetry degree in the optical signal (see text) for the empty capsid and for a container with a 50% water content. There is another interesting point that must be addressed. In this specific case, we can take advantage of the signal’s broadening to study the evaporation dynamics related to LDN-193189 meniscus Ilomastat solubility dmso geometry induced by the asymmetry porous position. This is clearly reflected by the following important feature: the power transmitted as a function of the tip position is not symmetric. This property is due to the intrinsic virus geometry, with a single porous on one side of Vitamin B12 the viral capsid implying a nonsymmetric water disposition inside the container. Interestingly, information about virus geometry as well as water evaporation dynamics may be obtained by the position of the maximum of the transmitted signal. For example, note how a porous located at the left implies a maximum on the signal displaced to the right. This asymmetry in the power is quantified in the inset in Figure 3, where the ratio between left and right transmitted signals, at equidistant points from the geometric center in the scan direction, are plotted versus distance to center. We consider an empty capsid and a container with 50% water content. Note that for the last case,
a slight asymmetry shows up with a maximum value of almost 1%. Conclusions We have presented a theoretical study in which we combine the lattice gas model to simulate water meniscus formation and a FDTD algorithm for light propagation through the media involved. We simulate a tapered dielectric waveguide that scans, at constant height, a sample containing a viral capsid. Our results show different contrasts related to different water contents and different meniscus orientations. We propose this method as a way to study water content and evaporation process in nanocavities being either biological, like viral capsides, or nonbiological, like photonic crystals. Acknowledgements This work has been funded through projects FIS2009-13403-C02-01 (MINECO), S2009-MAT-1467 (CAM), and CSD2010-00024 (MINECO). References 1.