Unravelling the 3-dimensional structure of wood cell walls (3-D NanoWood)

The 3-D Transmission Electron Microscopy (TEM) electron tomography (ET) studies proposed in this project will provide state of the art knowledge on the micro- and nanostructure of wood cell walls leading to an improved understanding of their native structure, assembly and modification during natural (i.e. native modification to perform different physiological and mechanical functions) and industrial processes (i.e. mechanical/chemical pulping), the latter related to energy savings. Studies will involve high-resolution TEM-ET to reveal the macromolecular arrangement of major wood polymers (cellulose, lignin, hemicelluloses) in wood cell walls. Emphasis is focused on understanding the architecture of S2 secondary wall layers whose structure is poorly understood despite being the dominating layer in all wood species and the most important concerning mechanical, physical and chemical attributes. Initially, work will involve TEM-ET analyses of conventionally prepared (i.e. fixed, resin embedded, ultrathin sections) samples with further developments using cryo-prepared samples (i.e. high pressure frozen (HPM), freeze substituted (FS), cryo-sectioned) and later both cryo-prepared (i.e. HPM, cryo-sections, cryo-transfer to TEM) followed by observations using cryo-TEM. Preliminary 3D TEM-tomograms of HPM fixed, FS and stained wood cell walls have shown great potential in revealing 3D images of wood macromolecular structure not possible using other approaches.