Crystallization of ApoA1 and ApoE4 nanolipoprotein particles and initial XFEL-based structural studies.

Nanolipoprotein particles (NLPs), also called "nanodiscs", are discoidal particles with a patch of lipid bilayer corralled by apolipoproteins. NLPs have long been of interest due to both their utility as membrane-model systems into which membrane proteins can be inserted and solubilized and their physiological role in lipid and cholesterol transport via HDL and LDL maturation, which are important for human health. Serial femtosecond crystallography (SFX) at X-ray free electron lasers (XFELs) is a powerful approach for structural biology of membrane proteins, which are traditionally difficult to crystallize as large single crystals capable of producing high-quality diffraction suitable for structure determination. To facilitate understanding of the specific role of two apolipoprotein/lipid complexes, ApoA1 and ApoE4, in lipid binding and HDL/LDL particle maturation dynamics and develop new SFX methods involving NLP membrane protein encapsulation, we have prepared and crystallized homogeneous populations of ApoA1 and ApoE4 NLPs. Crystallization of empty NLPs yields semi-ordered objects that appear crystalline and give highly anisotropic and diffuse X-ray diffraction, similar in characteristics to fiber diffraction. Several unit cell parameters were approximately determined for both NLPs from these measurements. Thus, low-background, sample conservative methods of delivery are critical. Here we implemented a fixed target sample delivery scheme utilizing the Roadrunner fast-scanning system and ultra-thin polymer/graphene support films, providing a low-volume, low-background approach to membrane protein SFX. This study represents initial steps in obtaining structural information for ApoA1 and ApoE4 NLPs and developing this system as a supporting scaffold for future structural studies of membrane proteins crystalized in a native lipid environment.

[Ultrasound diagnosis of the paranasal sinuses: progress in ENT practice?]. / Ultraschalldiagnostik der Nasennebenhöhlen: Ein Fortschritt in der HNO-Praxis?

A-Scan-ultrasound cannot be left out as a routine way of examination of the paranasal sinuses in the practice of an ENT-doctor. This method is not a substitution for X-rays but gives important additional information in case of pathologic contents of the paranasal sinuses. Ultrasound diagnosis plays its main role in diagnosing decreases of the paranasal sinuses in children and pregnant females and in controlling acute sinusitis. B-Scan-ultrasound has no important advantages in diagnosing paranasal sinus diseases compared to A-Scan-ultrasound. But B-Scan-ultrasound is an ideal additional means to examine the soft parts of the head and neck. Tumours can be differentiated as solid or cystic and their relation to different tissue structures can be defined. At the moment, however, a recommendation for the routine use of the B-Scan-ultrasound in the ENT-practice cannot be given.

[Endoscopically controlled ultrasound diagnosis of the paranasal sinuses]. / Endoskopisch kontrollierte Ultraschalldiagnostik der Kieferhöhlen.

261 patients with diseases of the paranasal sinuses were examined by ultrasound (A-Scan). Sinuscopy or surgery was performed on these patients. Samples for histologic examination were taken. The correlation between ultrasound, endoscopy and x-ray was 80-90%. In endoscopic histologic normal maxillary sinuses, however, x-ray examination led to wrong positive results five times as often as ultrasound examination did. X-ray examination was more accurate only in cases where the process was separated from the anterior wall of the maxillary sinus by a layer of air.