Highly packed and oriented DNA mesophases identified using in situ microfluidic X-ray microdiffraction.
DNA condensation in vivo usually requires proteins and/or multivalent salts. Here, we explore the in vitro compaction of DNA by cationic dendrimers having an intermediate size and charge. The dynamic assembly of DNA-dendrimer mesophases is discernible due to the laminar flow in a specially designed X-ray compatible microfluidic device. The setup ensures a nonequilibrium ascent of reactant concentration, and the resulting progression of DNA compaction was detected online using microfocused small-angle X-ray diffraction. The evolution of a DNA-dendrimer columnar square mesophase as a function of increasing dendrimer content is described. Additionally, in regions of maximum shear, an unexpected high-level perpendicular ordering of this phase is recorded. Furthermore, these assemblies are found to be in coexistence with a densely packed DNA-only mesophase in regions of excess DNA. The latter is reminiscent of dense packing found in bacteriophage and chromosomes, although surprisingly, it is not stabilized by direct dendrimer contact.
Pfohl
Thomas
T
Max Planck Institute for Dynamics and Self-Organization, Bunsenstrasse 10, Göttingen, Germany. thomas.pfohl@ds.mpg.de
Otten
Alexander
A
Köster
Sarah
S
Dootz
Rolf
R
Struth
Bernd
B
Evans
Heather M
HM
D004247:DNA / Q000737:chemistry*; D050091:Dendrimers / Q000737:chemistry; D044085:Microfluidics; D012542:Scattering, Radiation; D014961:X-Ray Diffraction / Q000379:methods*
D050091:Dendrimers; D004247:DNA