A New workflow applied to flash-frozen biological samples allows to surpass electron-dose limitations intrinsic to high-resolution Electron Microscopy Tomography

Recently low-temperature treatments applied to flash-frozen biologics resulted in bypassing the majority of electron-dose limitations for electron microscopy tomography. Although samples may not be considered free from artefacts at this stage, structures do not show typical distortions implicit to air-drying, and are able to sustain the rigors implicit to a tomography scan with >120 images at high-electron dose, necessary to maximize the signal-to-noise (since detectors measured with Poissonian statistics). Very recent experiments demonstrated that metal ions chemically adsorbed to the surface of proteins are not necessary, nor they create major rearrangements above a few Å length scales. Here results on very deformable samples are discussed, which this conditioning protects from destruction as before documented. Temperature Conditioning putatively allows to image directly before solvent evaporation. Here for the first time images pertaining both a notoriously soft materials (like enveloped virus) and a rigid biopolymer (microtubules of pure tubulin) are disclosed revealing unexpected structures, much larger than inter-atomic distances. In order to retain only protecting effect on flash-frozen biological samples, probably the origin of artifacts needs to be investigated, possibly studying distance and geometry of metal ions bonds to proteins. This may be done in-situ using aberration corrected microscopes.