Observation of a single protein by ultrafast X-ray diffraction

The idea of using ultrashort X-ray pulses to obtain images of single proteins frozen in time has fascinated and inspired many. It was one of the arguments for building X-ray free-electron lasers. According to theory, the extremely intense pulses provide sufficient signal to dispense with using crystals as an amplifier, and the ultrashort pulse duration permits capturing the diffraction data before the sample inevitably explodes. This was first demonstrated on biological samples a decade ago on the giant mimivirus. Since then, a large collaboration has been pushing the limit of the smallest sample that can be imaged. The ability to capture snapshots on the timescale of atomic vibrations, while keeping the sample at room temperature, may allow probing the entire conformational phase space of macromolecules. Here we show the first observation of an X-ray diffraction pattern from a single protein, that of Escherichia coli GroEL which at 14 nm in diameter is the smallest biological sample ever imaged by X-rays, and demonstrate that the concept of diffraction before destruction extends to single proteins. From the pattern, it is possible to determine the approximate orientation of the protein. Our experiment demonstrates the feasibility of ultrafast imaging of single proteins, opening the way to single-molecule time-resolved studies on the femtosecond timescale.

MEDICAL MALPRACTICE AND LEGAL LIABILITY IN THE RENDERING OF HEALTHCARE SERVICES IN UKRAINE

The development of medicine, raising the standards of living and education of the population, along with the increasing level of democratization of society, contribute to the increase of demands on medical practitioners, and the fact that people have legal knowledge, including knowledge related to obtaining medical services, causes an increase in the number of cases of holding medical practitioners liable for their offences. Therefore, this research paper deals with the explanation of human rights, as well as the description of a person's right to health care in the context of the general rights stipulated by the Constitution. In addition, the degree of coverage of the chosen topic of research by domestic scholars and the necessity of its further consideration was determined. At the same time, an insight into the history is provided, where the first cases of holding doctors liable are stated and their punishment is determined. The next step in the study is to determine the nature of legal liability and adapt general definition to the needs of the medical industry. The paper also describes the components of the concepts of medical staff, and identifies two areas of their liability: legal and moral. Continuing the line of research, the types of legal liability are considered: criminal, civil law and administrative, as well as moral liability in the form of disciplinary liability. The peculiarities of holding criminally liable are outlined, the structure of crimes which are committed under this category, the number of criminal cases against medical practitioners initiated in 2019 are analysed, and the possible types of liability for their commission are indicated. In addition, the nature and extent of liability for civil and administrative crimes are revealed, as well as the nature of disciplinary liability and the possibility of holding medical practitioners liable. The prospects of reforming the medical sector in terms of the establishment of medical self-government bodies have been identified, which, among other things provided by the legislation, are planned to be assigned the function of resolving cases of offences in the medical sphere. Based on the results of the study, sound conclusions were drawn.

THz streak camera performance for single-shot characterization of XUV pulses with complex temporal structures

The THz-field-driven streak camera has proven to be a powerful diagnostic-technique that enables the shot-to-shot characterization of the duration and the arrival time jitter of free electron laser (FEL) pulses. Here we investigate the performance of three computational approaches capable to determine the duration of FEL pulses with complex temporal structures from single-shot measurements of up to three simultaneously recorded spectra. We use numerically simulated FEL pulses in order to validate the accuracy of the pulse length retrieval in average as well as in a single-shot mode. We discuss requirements for the THz field strength in order to achieve reliable results and compare our numerical study with the analysis of experimental data that were obtained at the FEL in Hamburg - FLASH.

Plasma channel formation in NIR laser-irradiated carrier gas from an aerosol nanoparticle injector

Aerosol nanoparticle injectors are fundamentally important for experiments where container-free sample handling is needed to study isolated nanoparticles. The injector consists of a nebuliser, a differential pumping unit, and an aerodynamic lens to create and deliver a focused particle beam to the interaction point inside a vacuum chamber. The tightest focus of the particle beam is close to the injector tip. The density of the focusing carrier gas is high at this point. We show here how this gas interacts with a near infrared laser pulse (800 nm wavelength, 120 fs pulse duration) at intensities approaching 1016 Wcm-2. We observe acceleration of gas ions to kinetic energies of 100s eV and study their energies as a function of the carrier gas density. Our results indicate that field ionisation by the intense near-infrared laser pulse opens up a plasma channel behind the laser pulse. The observations can be understood in terms of a Coulomb explosion of the created underdense plasma channel. The results can be used to estimate gas background in experiments with the injector and they open up opportunities for a new class of studies on electron and ion dynamics in nanoparticles surrounded by a low-density gas.

Electrospray sample injection for single-particle imaging with x-ray lasers

The possibility of imaging single proteins constitutes an exciting challenge for x-ray lasers. Despite encouraging results on large particles, imaging small particles has proven to be difficult for two reasons: not quite high enough pulse intensity from currently available x-ray lasers and, as we demonstrate here, contamination of the aerosolized molecules by nonvolatile contaminants in the solution. The amount of contamination on the sample depends on the initial droplet size during aerosolization. Here, we show that, with our electrospray injector, we can decrease the size of aerosol droplets and demonstrate virtually contaminant-free sample delivery of organelles, small virions, and proteins. The results presented here, together with the increased performance of next-generation x-ray lasers, constitute an important stepping stone toward the ultimate goal of protein structure determination from imaging at room temperature and high temporal resolution.

Rayleigh-scattering microscopy for tracking and sizing nanoparticles in focused aerosol beams

Ultra-bright femtosecond X-ray pulses generated by X-ray free-electron lasers (XFELs) can be used to image high-resolution structures without the need for crystallization. For this approach, aerosol injection has been a successful method to deliver 70-2000 nm particles into the XFEL beam efficiently and at low noise. Improving the technique of aerosol sample delivery and extending it to single proteins necessitates quantitative aerosol diagnostics. Here a lab-based technique is introduced for Rayleigh-scattering microscopy allowing us to track and size aerosolized particles down to 40 nm in diameter as they exit the injector. This technique was used to characterize the 'Uppsala injector', which is a pioneering and frequently used aerosol sample injector for XFEL single-particle imaging. The particle-beam focus, particle velocities, particle density and injection yield were measured at different operating conditions. It is also shown how high particle densities and good injection yields can be reached for large particles (100-500 nm). It is found that with decreasing particle size, particle densities and injection yields deteriorate, indicating the need for different injection strategies to extend XFEL imaging to smaller targets, such as single proteins. This work demonstrates the power of Rayleigh-scattering microscopy for studying focused aerosol beams quantitatively. It lays the foundation for lab-based injector development and online injection diagnostics for XFEL research. In the future, the technique may also find application in other fields that employ focused aerosol beams, such as mass spectrometry, particle deposition, fuel injection and three-dimensional printing techniques.

Our Experience in Diagnosis and Treatment of Children with Biliary Atresia

Biliary atresia is a congenital disease that occurs with lesions of the bile ducts leading to the development of cholestasis and manifests in the neonatal period. Without timely surgical treatment, patients with this pathology die during the first year of liver failure, esophagus bleeding or infections.The objective of the research was to analyze the results of examinations and treatment of 21 children with biliary atresia who were treated at the surgical department of conformational abnormalities in children in Lviv City Children’s Clinical Hospital since 2008 to 2015.Methods of the research included follow-up, laboratory ones, duodenal intubation, ultrasound, scintigraphy, MRI, diagnostic laparoscopy, liver paracentesis, determination of hepatitis B and C markers, DNA of CMV virus.Results of the research. Among the examined children biliary atresia was diagnosed in 18 patients at the age under 2 months. All children were operated timely. 6 patients needed liver transplantation. Diagnosis was made in 3 children under the age of 3 months. The Kasai onoperat was conducted in 2 children. All 3 children needed liver transplantation. Children with satisfactory quality of life after liver transplantation are on permanent immunosuppressive therapy. They have signs of biliary cirrhosis and undergo periodically inpatient treatment of an ascending cholangitis.Maintenance of normal nutritional (food) status, biliary tract patency and prevention of cholangitis and infections are the primary task in the course of postoperative treatment (The Kasai procedure).Conclusions. Early diagnosis of biliary atresia and timely conducted surgical treatment (under 2 months of age) makes it possible to improve the prognosis, neurological status, quality of life and to prevent the necessity of liver transplantation at an early age.