Supervised molecular dynamics for exploring the druggability of the SARS-CoV-2 spike protein.

The recent outbreak of the respiratory syndrome-related coronavirus (SARS-CoV-2) is stimulating an unprecedented scientific campaign to alleviate the burden of the coronavirus disease (COVID-19). One line of research has focused on targeting SARS-CoV-2 proteins fundamental for its replication by repurposing drugs approved for other diseases. The first interaction between the virus and the host cell is mediated by the spike protein on the virus surface and the human angiotensin-converting enzyme (ACE2). Small molecules able to bind the receptor-binding domain (RBD) of the spike protein and disrupt the binding to ACE2 would offer an important tool for slowing, or even preventing, the infection. Here, we screened 2421 approved small molecules in silico and validated the docking outcomes through extensive molecular dynamics simulations. Out of six drugs characterized as putative RBD binders, the cephalosporin antibiotic cefsulodin was further assessed for its effect on the binding between the RBD and ACE2, suggesting that it is important to consider the dynamic formation of the heterodimer between RBD and ACE2 when judging any potential candidate.

Identification of Inhibitors of Integrin Cytoplasmic Domain Interactions With Syk.

Leukocyte inflammatory responses require integrin cell-adhesion molecule signaling through spleen tyrosine kinase (Syk), a non-receptor kinase that binds directly to integrin ß-chain cytoplasmic domains. Here, we developed a high-throughput screen to identify small molecule inhibitors of the Syk-integrin cytoplasmic domain interactions. Screening small molecule compound libraries identified the ß-lactam antibiotics cefsulodin and ceftazidime, which inhibited integrin ß-subunit cytoplasmic domain binding to the tandem SH2 domains of Syk (IC50 range, 1.02-4.9 µM). Modeling suggested antagonist binding to Syk outside the pITAM binding site. Ceftazidime inhibited integrin signaling via Syk, including inhibition of adhesion-dependent upregulation of interleukin-1ß and monocyte chemoattractant protein-1, but did not inhibit ITAM-dependent phosphorylation of Syk mediated by FcγRI signaling. Our results demonstrate a novel means to target Syk independent of its kinase and pITAM binding sites such that integrin signaling via this kinase is abrogated but ITAM-dependent signaling remains intact. As integrin signaling through Syk is essential for leukocyte activation, this may represent a novel approach to target inflammation.

Asymmetric synthesis of allylic sulfonic acids: enantio- and regioselective iridium-catalyzed allylations of Na2SO3.

An enantioselective allylation reaction of allylic carbonates with sodium sulfite (Na2 SO3 ) catalyzed by Ir complex was accomplished, providing allylic sulfonic acids in good to excellent yields with a high level of enantio- and regioselectivities. (R)-2-Phenyl-2-sulfoacetic acid, a key intermediate for the synthesis of Cefsulodin and Sulbenicillin, was synthesized as well.

Evaluation of Coli-ID and MUG Plus media for recovering Escherichia coli and other coliform bacteria from groundwater samples.

Several chromogenic media for detecting coliform bacteria in water are commercially available including Coli ID medium (ID) (bioMérieux) and MUG Plus cefsulodin agar (MP) (Laboratorios Microkit, S.L.). Since little is known about the performance of these media, we have evaluated their usefulness for recovering Escherichia coli and other coliform organisms in groundwaters used for direct human consumption. Variance analysis of obtained data showed that no statistically significant differences in counts of E. coli and other coliforms on ID and MP media compared with reference methods. However, the evaluation of sensitivity and recovery efficiency of both media showed that the two chromogenic media were more sensitive and significantly more efficient (P = < 0.05) than reference medium for detecting coliforms in groundwater. However, the identification of 400 typical and atypical colonies isolated from ID and MP media demonstrated a higher specificity when using ID for coliforms and E. coli. In summary, the two chromogenic media evaluated could be used as alternative methods to reference media for detecting and recovering coliform bacteria in groundwater samples. MP agar was more sensitive and efficient than ID agar whereas the latter was more specific and selective.

Radiation induced effects on cephalosporins: an ESR study.

PURPOSE: This paper reports experimental data on the ESR identification of four irradiated cephalosporins (cefpodoxime, cefsulodin, cefixime and ceftizoxime). MATERIALS AND METHODS: Equations to describe the ESR curves versus the dose and storage time were developed using mathematical procedures. RESULTS: Limits of detection (LOD) and limits of quantification (LOQ), estimated on the basis of the S/N ratios are 1.0+/-0.5 kGy and 2.5+/-0.5 kGy respectively. The yield of free radicals are in the range 4.6 10(19) - 2.2 10(20) radicals mol(-1) (G values from 0.1 to 0.4). Besides a very unstable situation (cefsulodin), the time limit of detection of free radicals after storage ranges from about 1 year to over 2 years. These time intervals are comparable with the shelf-life of the antibiotics and to the time limits found for 10 other cephalosporins described previously. Apart from qualitative detection, ESR spectrometry can be used for dose estimation. Exponential loss of ESR signal (first-order reaction) correlates well with the data. CONCLUSION: Given the sensitivity of ESR spectrometry, this experimental technique is promising for identification of irradiated cephalosporins.

Simultaneous determination of the binary mixtures of cefsulodin and clavulanic acid by using first-derivative spectrophotometry.

Two-component mixtures of cefsulodin and clavulanic acid were analysed by a first-derivative spectrophotometric method using a zero-crossing technique of measurement. The relative ease offered by this derivative technique for the quantification of these drugs, with closely overlapping spectral bands, was clearly demonstrated. As the absorption band of clavulanic acid closely overlaps with that of cefsulodin, both direct and derivative spectrophotometric methods have been investigated and evaluated by an exhaustive statistical analysis of the experimental data. The first-derivative spectrophotometric method was found to be more rapid, accurate and reproducible. The procedure does not require any separation step. The calibration graphs were linear in the range 2.0-56.0 micrograms ml-1 for cefsulodin and 2.0-28.0 micrograms ml-1 for clavulanic acid. The lower detection limits of cefsulodin and clavulinic acid (P 0.05 level) were calculated to be 0.16 and 0.24 microgram ml-1, respectively. Mixtures of cefsulodin and clavulanic acid in ratios of 1:4-7:2 were satisfactorily resolved. Both components were also determined in physiological solutions used to prepare intravenous infusions of these antibiotics.