Freestanding Ultrathin Nanomembranes as Sample Supports for Structural Studies

This thesis, entitled: “Freestanding ultrathin nanomembranes as sample supports for structural studies” reports on ultrathin films that have been investigated, developed and applied for fixing biological material (as protein crystals or single molecules) for experiments at synchrotrons, X-ray free electron lasers (XFELs) or in electron microscopes.
When utilized at XFELs these ultrathin membranes with the specimen serve as so-called: “fixed targets” a type of sample delivery system, an alternative to the commonly used liquid jets, initially developed for serial femtosecond crystallography (SFX). The main advantage of the fixed target approach is the possibility of the precise positioning of the sample in relation to the X-ray beam, which in ideal cases can provide 100% hit rate during diffraction data collection.
Low-dose X-ray fluorescence detection of metal markers localized onto the membrane supporting sample can additionally improve the precision and facilitate automation of the data acquisition in SFX, especially on non-regularly and non-uniformly distributed specimens.
Protein crystalline material can be either directly grown on the solid support, as demonstrated by using a model system on silicon nitride membranes on silicon chips or deposited from an aqueous suspension as well as lipidic cubic phase, alternatively another viscous matrix.
Relatively large in situ grown lysozyme crystals sandwiched between two X-ray transparent windows in microfabricated wells served as a sample for studying damage processes at the femtosecond scale in pump/probe measurements with split-and-delay X-ray optical setup.
Further development of two-dimensional materials towards increased performance especially should consider: the requirement of robust mechanical stability, high transparency to the radiation used in the structural study as well as compatibility of their physicochemical properties when preserving the native state of the investigated biomaterial.