C-phycocyanin as a highly attractive model system in protein crystallography: unique crystallization properties and packing-diversity screening

The unique crystallization properties of the antenna protein C-phycocyanin (C-PC) from the thermophilic cyanobacterium Thermosynechococcus elongatus are reported and discussed. C-PC crystallizes in hundreds of significantly different conditions within a broad pH range and in the presence of a wide variety of precipitants and additives. Remarkably, the crystal dimensions vary from a few micrometres, as used in serial crystallography, to several hundred micrometres, with a very diverse crystal morphology. More than 100 unique single-crystal X-ray diffraction data sets were collected from randomly selected crystals and analysed. The addition of small-molecule additives revealed three new crystal packings of C-PC, which are discussed in detail. The high propensity of this protein to crystallize, combined with its natural blue colour and its fluorescence characteristics, make it an excellent candidate as a superior and highly adaptable model system in crystallography. C-PC can be used in technical and methods development approaches for X-ray and neutron diffraction techniques, and as a system for comprehending the fundamental principles of protein crystallography.

COVID-19 outbreak: The impact of stress on seizures in patients with epilepsy

Objective

Stress is a known trigger for seizures in patients with epilepsy (PWE). However, the association between stress and seizures has not been thoroughly investigated. In December 2019, an outbreak of coronavirus disease (COVID‐19) occurred in Wuhan, Hubei province, China, causing tremendous collateral stress. This study was designed to evaluate the influence of the COVID‐19 outbreak on seizures in PWE in the most severely affected area, Wuhan, and its surrounding cities.

Methods

In this single‐center, cross‐sectional study, PWE were surveyed via online questionnaires between February 23 and March 5, 2020. Collected data included demographic information, epilepsy‐related characteristics (seizure type, frequency, antiepileptic drugs [AEDs], and medication management), direct and perceived threat of COVID‐19, and changes in seizures during the outbreak. Psychological comorbidities were evaluated by the Patient Health Questionnaire–9, Generalized Anxiety Disorder–7 items, and Insomnia Severity Index (ISI). Multivariate logistic regression was used to identify precipitants for seizure exacerbation.

Results

We received 362 completed questionnaires after excluding 12 duplicates (response rate = 63.51%). A total of 31 (8.56%) patients had increased seizures during the outbreak. Exposure history to COVID‐19 (P = .001), uncontrolled seizure after AED therapy (P = .020), seizure frequency of two or more times per month before the outbreak (P = .005), change of AED regimen during the outbreak (AED reduction, withdrawal, replacement, skipping altogether; P = .002), and worry about the adverse effect of the outbreak on overall seizure‐related issues (severity = moderate to critical; P = .038) were risk factors for increased seizures.

Significance

A minority of PWE experienced seizure exacerbation during the outbreak of COVID‐19. Stress, uncontrolled seizures, and inappropriate change in AED regimen were associated with increased seizures. Based on these findings, stress might be an independent precipitant for triggering seizures in some PWE.

Association between Common Etiologies and Precipitants of Acute Decompensated Heart Failure

Background:

Acute decompensated heart failure (ADHF) comprises the etiology of heart failure and the precipitant of acute decompensation. Early identification of the precipitant of ADHF is important in management, but an association between the precipitant and etiology of ADHF has not been established.

Objective:

The objective of this study is to determine whether the precipitant of acute decompensation is associated with the etiology of heart failure.

Methods:

This was a prospective observational study conducted over 2 years. Patients with ADHF secondary to common etiologies such as hypertension and rheumatic heart diseases (RHD) were enrolled in the study. The demographics, precipitants, and relevant variables on echocardiography and electrocardiography were documented. The frequencies of the etiology and precipitants of heart failure were derived. The Chi-square test was used to determine an association between categorical variables, and independent t-test was used to compare the means of continuous variables. A value of P < 0.05 was considered statistically significant.

Results:

There were a total of 190 participants. Hypertensive and RHD were 96 (50.5%) and 94 (49.5%), respectively. One hundred and three (54.2%) were females and males were 87 (45.8%). The precipitants were pneumonia 104 (54.7%), arrhythmias 47 (24.7%), urinary tract infection 36 (19.5%), and infective endocarditis 3 (1.6%). The association between these etiologies and precipitants of ADHF yielded a value of P = 0.597.

Conclusion:

There is no association between the precipitant and etiology of ADHF. Therefore, the precipitant of ADHF should be actively sought for in every case for optimal management and better outcomes.

Precipitant-ligand exchange technique reveals the ADP binding mode in Mycobacterium tuberculosis dethiobiotin synthetase

Dethiobiotin synthetase from Mycobacterium tuberculosis (MtDTBS) is a promising antituberculosis drug target. Small-molecule inhibitors that target MtDTBS provide a route towards new therapeutics for the treatment of antibiotic-resistant tuberculosis. Adenosine diphosphate (ADP) is an inhibitor of MtDTBS; however, structural studies into its mechanism of inhibition have been unsuccessful owing to competitive binding to the enzyme by crystallographic precipitants such as citrate and sulfate. Here, a crystallographic technique termed precipitant-ligand exchange has been developed to exchange protein-bound precipitants with ligands of interest. Proof of concept for the exchange method was demonstrated using cytidine triphosphate (CTP), which adopted the same binding mechanism as that obtained with traditional crystal-soaking techniques. Precipitant-ligand exchange also yielded the previously intractable structure of MtDTBS in complex with ADP solved to 2.4 Å resolution. This result demonstrates the utility of precipitant-ligand exchange, which may be widely applicable to protein crystallography.

Compatibility of Vancomycin and Oxacillin During Simulated Y-Site Delivery

BACKGROUND

Vancomycin and oxacillin may be used together as empiric coverage in patients with proven or suspected Staphylococcus aureus infections. Though vancomycin hydrochloride 20 mg/mL and oxacillin sodium 160 mg/mL are reported to be compatible via Y-site delivery, Y-site compatibility of commonly used concentrations, vancomycin 10 mg/mL and oxacillin 20 mg/mL, has not yet been reported.

OBJECTIVE

To determine the Y-site compatibility of vancomycin 10 mg/mL and oxacillin 20 mg/mL.

METHODS

One vancomycin hydrochloride 1 g vial was reconstituted with 10 mL sterile water for injection (SWFI) and diluted with 90 mL 5% dextrose in water (D5W) in an evacuated intravenous (IV) bag. One oxacillin sodium 2 g vial was reconstituted with 11.5 mL sterile water for injection and diluted with 88 mL sterile water for injection in an evacuated IV bag. Three mL of each vancomycin and oxacillin were mixed in 4 test tubes to simulate Y-site delivery. Spectrometry, pH evaluation, and visual examination were performed for each test tube immediately following mixing and at 30 minutes, 1 hour, and 2 hours after mixing.

RESULTS

Upon visual examination with multiple backgrounds, a white precipitant was immediately evident in the test tubes with vancomycin and oxacillin combined. Spectrometry results strongly supported evidence of precipitation throughout the duration of the experiment.

CONCLUSIONS

Vancomycin 10 mg/mL and oxacillin 20 mg/mL were determined to be physically incompatible for Y-site delivery in this study, despite prior evidence that the 2 medications in different concentrations were suitable for Y-site co-administration.

Co-Precipitation of YAG Powders for Transparent Materials: Effect of the Synthesis Parameters on Processing and Microstructure

The fabrication of transparent polycrystalline Y₃Al₅O₁₂ (YAG) is still a challenge, requiring the achievement of highly pure and fully dense, homogeneous materials. An important role is played by the powder characteristics: pure, fine and unagglomerated powders are essential for achieving full density and the required microstructural features. Keeping in mind these requirements, the aim of this work was to investigate the role of different synthesis parameters during co-precipitation, which is widely used to prepare YAG powders for transparent devices. The key role of the precipitant solution is here illustrated, by comparing the effect of aqueous ammonia (AA) versus ammonium hydrogen carbonate (AHC). This latter allowed the preparation of softly agglomerated powders, characterized by a very good sinterability. However, when AHC is used, attention should be paid to its concentration. By comparing the effect of two AHC precipitant solutions (at 0.5 M and 1.5 M, respectively), only the former one allowed the preparation of pure YAG powders, free from secondary phases. In this last condition, by using both chlorides and nitrates as YAG precursors, pressureless sintering at 1500–1600 °C/3 h gave rise to pure materials, highly dense and characterized by a fine and homogeneous microstructure.