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Identifying high-affinity antibodies in human serum is challenging due to extremely low number of circulating B cells specific to the desired antigens. Delays caused by a lack of information on the immunogenic proteins of viral origin hamper the development of therapeutic antibodies. We propose an efficient approach allowing for enrichment of high-affinity antibodies against pathogen proteins with simultaneous epitope mapping, even in the absence of structural information about the pathogenic immunogens. To screen therapeutic antibodies from blood of recovered donors, only pathogen transcriptome is required to design an antigen polypeptide library, representing pathogen proteins, exposed on the bacteriophage surface. We developed a two-dimensional screening approach enriching lentiviral immunoglobulin libraries from the convalescent or vaccinated donors against bacteriophage library expressing the overlapping set of polypeptides covering the spike protein of SARS-CoV-2. This platform is suitable for pathogen-specific immunoglobulin enrichment and allows high-throughput selection of therapeutic human antibodies. The authors present a 2D screening approach using antibody libraries against a panel of antigen fragments exposed on the phage surface, which facilitates the mapping of monoclonal antibodies to panels of diverse antigens, even with unknown immunogens. [ABSTRACT FROM AUTHOR]

NMR spectroscopy methods have been used to prove structures of two diastereomers of cyclopropa[a]pyrrolizine spiro-fused with a benzo[4,5]imidazo[1,2-a]indole fragment which were obtained through a three-component 1,3-dipolar cycloaddition reaction and isolated in a ratio of 6:1. Complete signal assignment in 1H and 13C spectra of each compound was made by using some homonuclear (COSY, NOESY) and heteronuclear (HMQC, HMBC) NMR experiments. The spatial structure of the studied diastereomers was proved on the basis of data on interproton through-space interactions obtained from the NOESY spectra at a mixing time of 0.5 s. The comparison of the experimental and calculated values of the vicinal constants and interproton distances indicates that each of the studied diastereomers in solution is characterized by a fast (in the NMR time scale) conformational equilibrium due to the inversion of the nitrogen atom in the cyclopropa[a]pyrrolizine fragment. [ABSTRACT FROM AUTHOR]

NMR spectroscopy methods were used to prove the structures of two similar regioisomers of 2,5,6,7,8-pentaaryl-1H-azepino[3,2,1-ij]quinazoline-1,3(2H)-dione containing various aryl substituents in the azepine ring which were obtained as reaction products and existed in CDCl3 as inseparable mixture of two compounds with almost equal (56:44) relation between them. Complete signal assignment in 1H and 13C spectra of each compound was made by using some homo- and heteronuclear NMR experiments. Long-range distance estimation (up to 5.0 Å) on the base of nuclear Overhauser enhancement approach (NOE) at conditions of extreme-narrow limits (ωoτc < < 1) was used to determine the quantitative level the internuclear distances between protons H6 and H8 situated in the rigid part of molecules and the nearest ortho- and meta-protons in mobile phenyl rings Ph5 and Ph2, respectively. The distance difference between the calculated and experimental values in all cases was not more than 10%. These results allowed us to prove that a dominant regioisomer (3a) has para-methoxy-substituted rings at positions 9 and 12 of seven-membered ring C, and a minor regioisomer (3d) has these rings at positions 10 and 12. The results of an independent approach based on the comparison of the chemical shifts of the 1H and 13C nuclei of the regioisomers under study are in full agreement (or do not contradict) with the obtained conclusions based on the quantitative NOE measurements of interproton distances. The methodological approach on the basis of long-range distance estimation by NOE tested in this work can be used to establish the structure of inseparable mixtures of two or more compounds or to solve similar problems under conditions of complex mixtures of closely related organic compounds. [ABSTRACT FROM AUTHOR]

A series of 3-phosphonylated thiazolo[3,2-a]oxopyrimidines 3a-k was synthesized for the first time by the reactions of chloroethynylphosphonates with 5,6-disubstituted 2-thiouracils. In vitro antiviral activities have shown that the compounds 1i, 1j, 3b and 3e were shown activity against influenza A virus. In vitro antitumor activity was conducted for all compounds against human erythroleukemia (K562) and cervical carcinoma (HeLa) cell lines by MTS assay. Among targeted compounds 3c, 3h and 3j were active against human erythroleukemia (K562) cell line, while 3c and 3j were active against cervical carcinoma (HeLa) cell line. It was discovered that HeLa cells after treatment with compounds 3c and 3j significantly reduced the number of cells with stress fibers and with filopodium-like membrane protrusions. It was concluded that targeted compounds have a cytostatic effect, which could lead to a decrease in the formation of actin filaments and also in the number of filopodium-like membrane protrusions. [ABSTRACT FROM AUTHOR]