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SCOPUS: le.j

In order to evaluate the influence of the cyano group on the antiviral activity of pyrimidine deoxyribonucleosides, a moderate yield, unified approach to the synthesis of both 5-cyanouridine and 5-cyano-2'-deoxyuridine was developed. Thus, treatment of the appropriate acetylated 5-bromouracil nucleoside with NaCN or KCN in Me2SO at 90-110 degrees C gave, after deblocking, 35-45% yields of the corresponding 5-cyanouracil nucleosides. 5-Cyanouridine was devoid of significant activity against vaccinia virus, herpes simplex-1, and vesicular stomatitis virus, but 5-cyano-2'-deoxyuridine, while lacking activity against herpes simplex, showed significant inhibition of vaccina virus; for instance, 5-cyano-2'-deoxyuridine inhibited vaccinia virus replication at concentrations 10-20 times that required for inhibition by the known antivirals, 5-iodo-2'-deoxyuridine and 1-(beta-D-arabinofuranosyl)adenine. Replacement of the 5-halogeno substituents of pyrimidine deoxyribonucleosides thus decreases, but does not abolish, antiviral activity.

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Summary: The sensitivity and discriminatory power of the 151 and 215 amplification refractory mutation system (ARMS) were evaluated, and their performance for the detection of drug resistance in mixed genotypic populations of the reverse transcription (RT) gene of HIV-1 were compared with T7 sequencing, cycle sequencing, the line probe assay (LiPA) HIV-1 RT test, and the recombinant virus assay (RVA). ARMS and the LiPA HIV-1 RT test were shown to be able to detect minor variants that in particular cases comprised only 1%. T7 sequencing on an ALF semiautomated sequencer could correctly score mixtures only when variants were present at 50%. Cycle sequencing on an ABI PRISM 310 improved the sensitivity for mixtures to about 25%. Using RVA, it was shown that at least 50% of the virus population needed to carry the resistance mutation at codon 184 to afford phenotypic resistance against lamivudine. The two point mutation assays therefore proved to be more sensitive methods than sequencing and RVA to reliably determine a gradual shift in HIV-1 drug resistance mutations in follow-up of patients infected with HIV-1. In 4 of 5 treated patients who were followed by ARMS, a gradual shift in resistant genotypic populations was observed during a period of 6 to 19 months. For 1 patient, a shift from wild to mutant type at position 151 occurred within 2 months, without mixed genotypic intermediate type's being detected.

Kinyoun cold staining sensitivity was unsatisfactory in field clinics. The sensitivity of the WHO/IUATLD recommended 0.3% fuchsin for 5 min was not significantly different from the original 1% ZN for 5 min, but 1% 15 min hot staining might be superior. A reduced fuchsin concentration together with a short staining time may leave too narrow a margin for error. TB programmes using hot ZN with a concentrated stain or longer staining time should not be urged to change.

(E)-3',5'-Diamino-5-(2-bromovinyl)-2',3',5'-trideoxyuridine (5), the diamino analogue of BVDU (1), was synthesized from BVDU. The protonation behavior of 5 has been studied by means of pH-metric measurements and NMR spectroscopy. This study allows the determination of the basicity constants and the stepwise protonation sites. Thus, the main species at physiological pH is the monoprotonated form. The conformational analysis of this nucleoside analogue was also carried out through 1H NMR spectroscopy. In addition, a convenient synthesis of N-3' and N-5' acylated derivatives was developed by regioselective enzymatic acylation. Thus, Candida antarctica lipase B (CAL-B) selectively acylated the 5'-amino group, thus furnishing nucleosides 8. On the other hand, immobilized Pseudomonas cepacia lipase (PSL-C) exhibited the opposite selectivity, conferring acylation at the 3'-amino group, thus affording derivatives 9.

The antiviral activity of several nucleoside analogues is often limited by their rapid degradation by pyrimidine nucleoside phosphorylases. In an attempt to avoid this degradation, several modified nucleosides have been synthesized. A series of 4´-thio-2´-deoxyuridines exhibits an anti-[herpes simplex virus (HSV)] activity significantly higher (20–600 times) than that shown by the corresponding 4´-oxy counterpart. We investigated the mode of action of these compounds and we found that: (i) several 4´-thio-2´-deoxyuridines are phosphorylated to the mono- and di-phosphates by HSV-1 thymidine kinase (TK) more efficiently than their corresponding 4´-oxy counterpart; (ii) both are inhibitors of cellular thymidylate synthase; (iii) 4´-thio-2´-deoxyuridines are resistant to phosphorolysis by human thymidine phosphorylase; (iv) both 4´-oxy- and 4´-thio-2´-deoxyuridines are phosphorylated to deoxyribonucleotide triphosphate in HSV-1-infected cells and are incorporated into viral DNA; (v) 4´-thio-2´-deoxyuridines are better inhibitors than their 4´-oxy counterparts of [3H]thymidine incorporation in HSV-1-infected cells; (vi) 4´-thio-2´-deoxyuridines are not recognized by HSV-1 and human uracil-DNA glycosylases. Our data suggest that 4´-thio-2´-deoxyuridines, resistant to pyrimidine phosphorylase, can be preferentially or selectively phosphorylated by viral TK in HSV-infected cells, where they are further converted into triphosphate by cellular nucleotide kinases. Once incorporated into viral DNA, they are better inhibitors of viral DNA synthesis than their corresponding 4´-oxy counterpart, either because they are not recognized, and thus not removed, by viral uracil-DNA glycosylase, or because they preferentially interfere with viral DNA polymerase.

In the design of the metrological atomic force microscope (mAFM), the commercial scanhead is adapted to reach a high thermal stability. To achieve this, an Invar support for the probe is kinematically connected to the aluminium commercial head. The interface between both parts allow for thermal expansion with minimum introduction of internal stress, while maintaining sufficient stiffness in the design. This paper describes and evaluates the novel design of the thermally stable probe mount. FEM-simulations of the thermal expansion show a minimum impact of the introduced stress on the accuracy of the mAFM.