Red fluorescent benzothiadiazole derivative loaded in different nanoformulations: Optical properties and their use in bio-imaging

Fluorophores with optimized nonlinear optical properties have become prominent as contrast labels in laser scanning microscopy (LSM). The purpose of this work is to report on a novel benzothiadiazole derivative, namely 4,7-bis(5-((9,9-dioctyl-9H-fluoren-2-yl)ethynyl)thiophen-2-yl)benzo[c][1,2,5]thiadiazole (EFBT) and its optical performance when it is loaded into organic nanostructures intended as labels for LSM. Four different nanostructured labels were prepared: i) EFBT-loaded silica nanoparticles (SiNPs); ii) folate-bioconjugated SiNPs (SiNPs-FA); iii) EFBT-loaded PEGylated nanoparticles (NPs-PEG); and iv) EFBT-loaded folate-terminated PEGylated nanoparticles (NPs-PEG-FA). All these nanostructures are reported through a comparative study of their linear and nonlinear optical properties, including their performance as exogenous label agents in the cervical cancer cell line HeLa. This assessment of the performance of a specific fluorophore loaded into different nanostructured matrices (labels), and fairly compared under the same characterization conditions, including the LSM settings, is less common while previous reports had focused in comparing silica and PEGylated nanoparticles but loaded with different fluorophores. The results show that the internal molecular organization into each type of organic nanostructure impacted differently the properties of EFBT, where the silica matrix tend to preserve the optical performance of the fluorophore by preventing intermolecular interactions; in contrast, PEGylated nanoparticles favored molecular interactions and introduced non-radiative decay channels that degrades drastically the optical performance. Nevertheless, the use of functionalized ends entities produced a better cellular label uptake with PEGylated that with silica nanoparticles. In overall, the NPs-PEG-FA label produced the best HeLa imaging.

Bursera fagaroides, effect of an ethanolic extract on ornithine decarboxylase (ODC) activity in vitro and on the growth of Entamoeba histolytica

The effect of an ethanolic extract from the stem bark of Bursera fagaroides on ornithine decarboxylase (ODC) activity in vitro and on the growth of Entamoeba histolytica was evaluated. For this purpose, increasing concentrations of the extract, up to 8.0mg/mL, were added to amoeba cultures or ODC reaction mixtures, which were incubated at 37 degrees C. Metronidazole and G418 were added as controls. After 1.5 and 72 h, the ODC activity in vitro and growth, respectively, were determined. Results revealed a strong inhibition of growth with IC(50) values on the order of 0.05 mg/mL. ODC activity, on the other hand, was inhibited by 12% and 50% at concentrations of 4.0 and 8.0mg/mL, respectively.

Biosynthesis of Glycoproteins in the Human Pathogenic Fungus Sporothrix Schenckii: Synthesis of Dolichol Phosphate Mannose and Mannoproteins by Membrane-Bound and Solubilized Mannosyl Transferases

A membrane fraction obtained from the filamentous form of Sporothrix schenckii was able to transfer mannose from GDP-Mannose into dolichol phosphate mannose and from this inTermediate into mannoproteins in coupled reactions catalyzed by dolichol phosphate mannose synthase and protein mannosyl transferase(s), respectively. Although the transfer reaction depended on exogenous dolichol monophosphate, membranes failed to use exogenous dolichol phosphate mannose for protein mannosylation to a substantial extent. Over 95% of the sugar was transferred to proteins via dolichol phosphate mannose and the reaction was stimulated several fold by Mg2+ and Mn2+. Incubation of membranes with detergents such as Brij 35 and Lubrol PX released soluble fractions that transferred the sugar from GDP-Mannose mostly into mannoproteins, which were separated by affinity chromatography on Concanavilin A-Sepharose 4B into lectin-reacting and non-reacting fractions. All proteins mannosylated in vitro eluted with the lectin-reacting proteins and analytical electrophoresis of this fraction revealed the presence of at least nine putative mannoproteins with molecular masses in the range of 26-112 kDa. The experimental approach described here can be used to identify and isolate specific glycoproteins mannosylated in vitro in studies of O-glycosylation.

Entamoeba histolytica: biochemical and molecular insights into the activities within microsomal fractions

One of the most fascinating aspects of the Entamoeba histolytica trophozoite ultrastructure is the lack of a typical secretory pathway, particularly of rough endoplasmic reticulum and Golgi system, in a cell with such a high secretory activity. Here, we describe the isolation of amoeba cell structures containing ER-typical activities. Following isopycnic centrifugation of plasma membrane-free extracts, microsomes enriched in enzymatic activities such as dolichol-P-mannose synthase (DPMS; EC 2.4.1.83), UDP-GlcNAc:dolichol-P GlcNAc-1-P transferase (NAGPT; EC 2.7.8.15), and UDP-D-GlcNAc:dolichol-PP GlcNAc (NAGT; EC 2.4.1.141) were resolved from phagolysosomal fractions. Sec61alpha-subunit, an ER-marker involved in the translocation of nascent proteins to the ER, was found to co-fractionate with DPMS activity indicating that they are contained in microsomes with a similar density. Further, we optimized conditions for trophozoite homogenization and differential centrifugation that resulted in the separation of a 57,000 g-sedimenting microsomal fraction containing EhSec61alpha-subunit, EhDPMS, and EhPDI (protein disulfide isomerase, a soluble marker of the lumen of the ER). A relevant observation was the lack of ER markers associated to the nuclear fraction. Large macromolecular structures such as Ehproteasome were sedimented at a higher speed. Our knowledge of the molecular machinery involved in the biosynthesis of dolichol-linked oligosaccharide was enriched with the identification of putative genes related to the stepwise assembly of the dolichol-PP-GlcNAc(2)Man(5) core. No evidence of genes supporting further assembly steps was obtained at this time.