A new technology, genetic alphabet expansion using artificial bases (unnatural bases), has created high-affinity DNA ligands (aptamers) that specifically bind to target proteins by ExSELEX (genetic alphabet Expansion for Systematic Evolution of Ligands by EXponential enrichment). We recently found that the unnatural-base DNA aptamers can be stabilized against nucleases, by introducing an extraordinarily stable, unique hairpin DNA (mini-hairpin DNA) and by reinforcing the stem region with G–C pairs. Here, to establish this aptamer generation method, we examined the stabilization of a high-affinity anti-VEGF165 unnatural-base DNA aptamer. The stabilized aptamers displayed significantly increased thermal and nuclease stabilities, and furthermore, exhibited higher affinity to the target. As compared to the well-known anti-VEGF165 RNA aptamer, pegaptanib (Macugen), our aptamers did not require calcium ions for binding to VEGF165. Biological experiments using cultured cells revealed that our stabilized aptamers efficiently inhibited the interaction between VEGF165 and its receptor, with the same or slightly higher efficiency than that of the pegaptanib RNA aptamer. The development of cost-effective and calcium ion-independent high-affinity anti-VEGF165 DNA aptamers encourages further progress in diagnostic and therapeutic applications. In addition, the stabilization process provided additional information about the key elements required for aptamer binding to VEGF165.
Vanadium (V) in the sea squirt (Ciona savignyi) from Onagawa Bay, Miyagi, Japan, was isolated and purified through adsorption on a diamine resin and anion and cation exchanges after the dissolution of sea squirt samples with nitric acid and hydrogen peroxide. The (50)V/(51)V isotope ratio of V thus obtained was mass-spectrometrically determined to be from 2.51×10(-3) to 2.55×10(-3) with the average of 2.53×10(-3) by the thermal ionisation technique. This value agreed with those of vanadyl chloride and vanadyl nitrate both prepared from vanadyl sulphate (Wako Pure Chemical Industries, Ltd., Japan) and of V in coastal seawater (Shimokita Peninsula, Aomori, Japan) within experimental uncertainties (standard deviation of±0.04), which suggested that no appreciable V isotope fractionation occurs accompanying V uptake by the sea squirt from sea water.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.