RESUMEN
Atom Probe Tomography (APT) is currently a well-established technique to analyse the composition of solid materials including metals, semiconductors and ceramics with up to near-atomic resolution. Using an aqueous glucose solution, we now extended the technique to frozen solutions. While the mass signals of the common glucose fragments CxHy and CxOyHz overlap with (H2O)nH from water, we achieved stoichiometrically correct values via signal deconvolution. Density functional theory (DFT) calculations were performed to investigate the stability of the detected pyranose fragments. This paper demonstrates APT's capabilities to achieve sub-nanometre resolution in tracing whole glucose molecules in a frozen solution by using cryogenic workflows. We use a solution of defined concentration to investigate the chemical resolution capabilities as a step toward the measurement of biological molecules. Due to the evaporation of nearly intact glucose molecules, their position within the measured 3D volume of the solution can be determined with sub-nanometre resolution. Our analyses take analytical techniques to a new level, since chemical characterization methods for cryogenically-frozen solutions or biological materials are limited.
RESUMEN
Measuring biological samples by atom probe tomography (APT) in their natural environment, i.e. aqueous solution, would take this analytical method, which is currently well established for metals, semi-conductive materials and non-metals, to a new level. It would give information about the 3D chemical structure of biological systems, which could enable unprecedented insights into biological systems and processes, such as virus protein interactions. For this future aim, we present as a first essential step the APT analysis of pure water (Milli-Q) which is the main component of biological systems. After Cryo-preparation, nanometric water tips are field evaporated with assistance by short laser pulses. The obtained data sets of several tens of millions of atoms reveal a complex evaporation behavior. Understanding the field evaporation process of water is fundamental for the measurement of more complex biological systems. For the identification of the individual signals in the mass spectrum, DFT calculations were performed to prove the stability of the detected molecules.
RESUMEN
The efficiency of software for a personal computer in the interactive generation of three-dimensional (3D) images from computer tomography was studied in six pig livers after hepatic resection and catheterization of the hepatic and portal veins. After perfusion the livers were submitted to computed tomography angiography, volumetric measurement by water displacement, and production of an acrylic model of the veins by the injection and corrosion method, by which the lengths of the hepatic and portal veins were measured. From the angiogram, the software generated a 3D image that allowed measurement of the vein lengths. The identified branches of the hepatic and portal veins were correlated with the hepatic sectors and segments, respectively. The virtual measures from the 3D images were compared with the real measures. There were no significant differences between the topography and the vessel length. The mean difference between the volumes calculated from software and those measured by water displacement corresponded to 1.2%, and between the vessel lengths, 0.2%. In conclusion, the software for personal computer (named LIVER3D) is efficient, allowing interactive inspection of 3D images. All virtual measurements of liver vessel length and partial/total liver volume were similar to the actual ones.