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SARS-CoV-2 infections underlie the current coronavirus disease (COVID-19) pandemic and are causative for a high death toll particularly among elderly subjects and those with comorbidities. Selenium (Se) is an essential trace element of high importance for human health and particularly for a well-balanced immune response. The mortality risk from a severe disease like sepsis or polytrauma is inversely related to Se status. We hypothesized that this relation also applies to COVID-19. Serum samples (n = 166) from COVID-19 patients (n = 33) were collected consecutively and analyzed for total Se by X-ray fluorescence and selenoprotein P (SELENOP) by a validated ELISA. Both biomarkers showed the expected strong correlation (r = 0.7758, p < 0.001), pointing to an insufficient Se availability for optimal selenoprotein expression. In comparison with reference data from a European cross-sectional analysis (EPIC, n = 1915), the patients showed a pronounced deficit in total serum Se (mean ± SD, 50.8 ± 15.7 vs. 84.4 ± 23.4 µg/L) and SELENOP (3.0 ± 1.4 vs. 4.3 ± 1.0 mg/L) concentrations. A Se status below the 2.5th percentile of the reference population, i.e., [Se] < 45.7 µg/L and [SELENOP] < 2.56 mg/L, was present in 43.4% and 39.2% of COVID samples, respectively. The Se status was significantly higher in samples from surviving COVID patients as compared with non-survivors (Se; 53.3 ± 16.2 vs. 40.8 ± 8.1 µg/L, SELENOP; 3.3 ± 1.3 vs. 2.1 ± 0.9 mg/L), recovering with time in survivors while remaining low or even declining in non-survivors. We conclude that Se status analysis in COVID patients provides diagnostic information. However, causality remains unknown due to the observational nature of this study. Nevertheless, the findings strengthen the notion of a relevant role of Se for COVID convalescence and support the discussion on adjuvant Se supplementation in severely diseased and Se-deficient patients.

The Trypanosoma brucei cysteine protease cathepsin B (TbCatB), which is involved in host protein degradation, is a promising target to develop new treatments against sleeping sickness, a fatal disease caused by this protozoan parasite. The structure of the mature, active form of TbCatB has so far not provided sufficient information for the design of a safe and specific drug against T. brucei. By combining two recent innovations, in vivo crystallization and serial femtosecond crystallography, we obtained the room-temperature 2.1 angstrom resolution structure of the fully glycosylated precursor complex of TbCatB. The structure reveals the mechanism of native TbCatB inhibition and demonstrates that new biomolecular information can be obtained by the \"diffraction-before-destruction\" approach of x-ray free-electron lasers from hundreds of thousands of individual microcrystals.

RESULTS. Participants with CAD ( n = 723) had 12% higher mean relative levels of nHDL ox compared with those with invasively excluded CAD ( n = 502, P < 0.001). Patients presenting with symptoms of an ACS had the highest nHDL ox values when compared with the elective cohort (median 1.35, IQR 0.97 to 1.85, P < 0.001). In multivariate analysis adjusted for age, sex, body mass index, and hypertension, nHDL ox was a strong independent predictor of ACS ( P < 0.001) but not of CAD ( P > 0.05).CONCLUSION. HDL antioxidant function is reduced in patients with CAD. nHDL ox is strongly associated with ACS. TRIAL REGISTRATION. German Clinical Trials Register DRKS00014037. FUNDING. Brandenburg Medical School Theodor Fontane, the BIOX Stiftung, and NIH grants R01AG059501 and R03AG059462. BACKGROUND. High-density lipoprotein (HDL) function rather than its concentration plays an important role in the pathogenesis of coronary artery disease (CAD). The aim of the present study was to determine whether reduced antioxidant function of HDL is associated with the presence of a stable CAD or acute coronary syndrome (ACS).METHODS. HDL function was measured in 2 cohorts: 1225 patients admitted electively for coronary angiography and 196 patients with ACS. A validated cell-free biochemical assay was used to determine reduced HDL antioxidant function, as assessed by increased HDL-lipid peroxide content (HDL ox ), which was normalized by HDL-C levels and the mean value of a pooled serum control from healthy participants (nHDL ox ; unitless). Results are expressed as median with interquartile range (IQR).

A 'protein quake' is directly monitored on the picosecond timescale using the method of time-resolved wide-angle X-ray scattering at an X-ray free-electron laser. We describe a method to measure ultrafast protein structural changes using time-resolved wide-angle X-ray scattering at an X-ray free-electron laser. We demonstrated this approach using multiphoton excitation of the Blastochloris viridis photosynthetic reaction center, observing an ultrafast global conformational change that arises within picoseconds and precedes the propagation of heat through the protein. This provides direct structural evidence for a 'protein quake': the hypothesis that proteins rapidly dissipate energy through quake-like structural motions.

Background: The mechanism explaining low cholesterol concentrations in chronic inflammatory rheumatic disease (CIRD) is incompletely understood. We hypothesized that chronic inflammation impairs the functionality of high-density lipoprotein (HDL), for example, by oxidative processes. Objectives: Assessment of oxidized HDL (HDLox), a marker of dysfunctional HDL, in newly diagnosed patients with CIRD before and after initiation of immunosuppressive therapy and comparison of HDLox values of patients with CIRD to non-CIRD controls. Design: Prospective observational trial. Methods: The study was conducted on 44 newly diagnosed CIRD patients, who were initiated on immunosuppressive therapy (baseline). A total of 136 patients without CIRD served as control. Lipid profiles including HDLox levels and C-reactive protein (CRP) were measured in both groups at baseline. In CIRD patients, measurements were repeated 12 weeks after baseline. Validated outcome tools for disease activity and function were assessed at baseline and 12 weeks. Results: A total of 33 (75%) patients with rheumatoid arthritis, 7(16%) with axial spondyloarthritis, and 4 (9%) with systemic lupus erythematosus were included. Groups were comparable for age and BMI. CIRD patients had higher HDLox concentrations (1.57 versus 0.78, p = 0.02) and tended to have lower low-density lipoprotein cholesterol, HDL cholesterol, and cholesterol concentrations compared to controls. HDLox (1.57 versus 1.4, p = 0.26) and CRP levels (2.1 versus 0.7 mg/dl, p < 0.01) decreased in CIRD patients from baseline to follow-up. Conclusion: CIRD is associated with an impairment of the anti-inflammatory properties of HDL as reflected by an increase in HDLox concentrations. This effect may contribute to the increased cardiovascular risk in chronic inflammatory diseases.

X-ray free-electron lasers have enabled new approaches to the structural determination of protein crystals that are too small or radiation-sensitive for conventional analysis 1 . For sufficiently short pulses, diffraction is collected before significant changes occur to the sample, and it has been predicted that pulses as short as 10 fs may be required to acquire atomic-resolution structural information 1 , 2 , 3 , 4 . Here, we describe a mechanism unique to ultrafast, ultra-intense X-ray experiments that allows structural information to be collected from crystalline samples using high radiation doses without the requirement for the pulse to terminate before the onset of sample damage. Instead, the diffracted X-rays are gated by a rapid loss of crystalline periodicity, producing apparent pulse lengths significantly shorter than the duration of the incident pulse. The shortest apparent pulse lengths occur at the highest resolution, and our measurements indicate that current X-ray free-electron laser technology 5 should enable structural determination from submicrometre protein crystals with atomic resolution. Researchers describe a mechanism capable of compressing fast and intense X-ray pulses through the rapid loss of crystalline periodicity. It is hoped that this concept, combined with X-ray free-electron laser technology, will allow scientists to obtain structural information at atomic resolutions.

Serial femtosecond crystallography is an X-ray free-electron-laser-based method with considerable potential to have an impact on challenging problems in structural biology. Here we present X-ray diffraction data recorded from microcrystals of the Blastochloris viridis photosynthetic reaction centre to 2.8 Å resolution and determine its serial femtosecond crystallography structure to 3.5 Å resolution. Although every microcrystal is exposed to a dose of 33 MGy, no signs of X-ray-induced radiation damage are visible in this integral membrane protein structure. Serial femtosecond crystallography is an X-ray free-electron-laser-based method that uses X-ray bursts to determine protein structures. Here the authors present the structure of a photosynthetic reaction centre, an integral membrane protein, achieved with no sign of X-ray-induced radiation damage.

Lipidic sponge phase crystallization yields membrane protein microcrystals that can be injected into an X-ray free electron laser beam, yielding diffraction patterns that can be processed to recover the crystal structure. X-ray free electron laser (X-FEL)-based serial femtosecond crystallography is an emerging method with potential to rapidly advance the challenging field of membrane protein structural biology. Here we recorded interpretable diffraction data from micrometer-sized lipidic sponge phase crystals of the Blastochloris viridis photosynthetic reaction center delivered into an X-FEL beam using a sponge phase micro-jet.

Membrane proteins are key players in biological systems, mediating signalling events and the specific transport of e.g. ions and metabolites. Consequently, membrane proteins are targeted by a large number of currently approved drugs. Understanding their functions and molecular mechanisms is greatly dependent on structural information, not least on complexes with functionally or medically important ligands. Structure determination, however, is hampered by the difficulty of obtaining well diffracting, macroscopic crystals. Here, the feasibility of X-ray free-electron-laser-based serial femtosecond crystallography (SFX) for the structure determination of membrane protein–ligand complexes using microcrystals of various native-source and recombinant P-type ATPase complexes is demonstrated. The data reveal the binding sites of a variety of ligands, including lipids and inhibitors such as the hallmark P-type ATPase inhibitor orthovanadate. By analyzing the resolution dependence of ligand densities and overall model qualities, SFX data quality metrics as well as suitable refinement procedures are discussed. Even at relatively low resolution and multiplicity, the identification of ligands can be demonstrated. This makes SFX a useful tool for ligand screening and thus for unravelling the molecular mechanisms of biologically active proteins.