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A bicyclic undecapeptide of sequence cyclo-(Ala(1)-Pro(2)-Asp(3)-Glu(4)-Lys(5)-Ala(6)-Pro(7)-Asp(8)-Ser(9) -Glu(10))-cyclo-(10gamma --> 5varepsilon)-Gly(11), designed to mimic the calcium coordination site I of Calmodulin, has been synthesized and its conformation and calcium binding properties have been investigated by means of CD and nmr spectroscopy. The nmr analysis of the free peptide, carried out in DMSO and in TFE/H(2)O at different pH values, shows the presence in solution of one stable conformer, exhibiting trans configuration around both Proline residues. The nmr results in both solvents suggest for the molecule a rectangular shape constituted by two antiparallel beta-strands connected by two beta-turns. Interproton distances, evaluated by NOE contacts, have been used to obtain feasible models by means of Restrained Molecular Dynamic (RMD). The average models from RMD calculations, for both solvents, exhibit good analogies with Calmodulin site I. The model system, when compared with the reference system (Asp(20)-Glu(31) segment in CaM), shows similar dimensions and an effective superimposition of the respective sequence segments Ala(1)-Glu(4) and Thr(28)-Glu(31). The remaining segments of the model peptide exhibit a bending that is intermediate between that of the free and Ca(2+)-coordinated site I. CD spectra, recorded in TFE solutions, point to a 1:1 stoichiometry for the Ca(2+)-peptide complex, with an association constant of at least 1 x 10(5) M(-1).

Background and aims. Real-time reverse transcription polymerase chain reaction (RT-PCR) is the gold-standard assay to detect SARS-CoV-2, but it has limitations compared to viral load analysis. Quantitative detection improves surveillance, diagnosis, and prevention. We performed a comparative study of qualitative and quantitative tests for the diagnosis of COVID-19 on respiratory samples from patients screened for SARS-CoV-2 infection, and explored the correlation between viral load compared to the threshold cycle (Ct) value obtained in RT-PCR.Materials and methods. Sixty respiratory samples from patients affected by SARS-CoV-2 were subjected to both the qualitative (Allplex ™ 2019-nCoV Seegene) and the quantitative (Clonit® Quanty COVID-19) assays, and the relationship between viral load and Ct value was assessed by Spearman correlation analysis (ρ). In addition, the viral load of samples collected from a patient with symptomatic cancer was monitored. Results. The results show 100% agreement between the results obtained with quantitative assay and the reference standards, whereas 99.2% agreement was found for the qualitative test. A strong negative Spearman’s correlation between the Ct values of the N genes and RdRP gene was observed from qualitative assay values and viral loads.Conclusions. Quantitative assay has a higher sensitivity than qualitative assay, and viral load testing allows the clinicians to better orient themself in the choice of therapeutic treatment to be adopted. The constantly higher viral load of clinical cases considered, irrespective of the different therapies used, confirms that viral load monitoring could represent a great advantage in clinical practice.

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