Potent Antimalarial Activity of Acriflavine <i>In Vitro</i> and <i>In Vivo</i>

Malaria continues to be a major health problem globally. There is an urgent need to find new antimalarials. Acriflavine (ACF) is known as an antibacterial agent and more recently as an anticancer agent. Here, we report that ACF inhibits the growth of asexual stages of both chloroquine (CQ) sensitive and resistant strains of human malarial parasite, <i>Plasmodium falciparum in vitro</i> at nanomolar concentration. ACF clears the malaria infection <i>in vivo</i> from the bloodstreams of mice infected with <i>Plasmodium berghei</i>. Interestingly, ACF is accumulated only in the parasitized red blood cells (RBCs) and parasite specific transporters may have role in this specific drug accumulation. We further show that ACF impairs DNA replication foci formation in the parasites and affects the enzymatic activities of apicoplast specific Gyrase protein. We thus establish ACF as a potential antimalarial amidst the widespread incidences of drug resistant <i>Plasmodium</i> strains

() Far-UV circular dichroism spectra of wild-type and different mutant variants of the helicase

<p><b>Copyright information:</b></p><p>Taken from "The domain structure of DnaB helicase: the N-terminal domain can be dispensable for helicase activity whereas the extreme C-terminal region is essential for its function"</p><p></p><p>Nucleic Acids Research 2007;35(9):2861-2874.</p><p>Published online 11 Apr 2007</p><p>PMCID:PMC1888833.</p><p>© 2007 The Author(s)</p> CD spectra were measured for each protein in a 2 mm path length quartz cell and data were collected at 1.0 nm wavelength resolution. The arrowheads indicate the CD spectra of the respective protein. () Intrinsic fluorescence spectra of wild-type and different deletion mutants. The fluorescence emission spectra of wild-type and different mutant forms of HpDnaB (as indicated) were recorded from 300 to 400 nm at 25°C. The excitation wavelength was 278 nm and data were collected at 0.5 nm wavelengths resolution. The arrowheads indicate the CD spectra of the respective protein

Electron microscopic observation and analysis of HpDnaBWt, DelN2, DelN3 and DelC1

<p><b>Copyright information:</b></p><p>Taken from "The domain structure of DnaB helicase: the N-terminal domain can be dispensable for helicase activity whereas the extreme C-terminal region is essential for its function"</p><p></p><p>Nucleic Acids Research 2007;35(9):2861-2874.</p><p>Published online 11 Apr 2007</p><p>PMCID:PMC1888833.</p><p>© 2007 The Author(s)</p> Above four proteins were processed for electron microscopy as described in the materials and methods and individual sample was scanned under a Morgagni 268 transmission electron microscope at 80 kV voltage. More than hundred images were captured in each case and the raw images were processed using IMAGIC software. The left panel in each pair shows the unprocessed image and the right panel shows the processed image. HpDnaBWt was found in both C6 and C3 conformations whereas DelN2 was found only in C3 conformations. Bars in the panels are equivalent to 10 nm

ATPase activity of the wild-type and different deletion mutant proteins

<p><b>Copyright information:</b></p><p>Taken from "The domain structure of DnaB helicase: the N-terminal domain can be dispensable for helicase activity whereas the extreme C-terminal region is essential for its function"</p><p></p><p>Nucleic Acids Research 2007;35(9):2861-2874.</p><p>Published online 11 Apr 2007</p><p>PMCID:PMC1888833.</p><p>© 2007 The Author(s)</p> ATPase assay using various HpDnaB forms. Enzyme-linked ATPase assays were performed using protocol as described in the materials and methods either in the absence or presence of DNA. The rates of the reactions against different substrate (ATP) concentrations were plotted for HpDnaBWt, HpDnaBDelN1, HpDnaBDelN2 and HpDnaBDelN3 as shown in panels A, C, E and G, respectively. Lineweaver-Burk plots of the same enzymes were also plotted either in the absence or presence of DNA in each case (panels B, D, F and H, respectively). Maximum velocity of the reaction (Vmax) and turn-over number (Kcat) were calculated in each case (as shown in )