Quantum dots conjugated to lectins from Schinus terebinthifolia leaves (SteLL) and Punica granatum sarcotesta (PgTeL) as potential fluorescent nanotools for investigating Cryptococcus neoformans.

This study reports the development of conjugates based on quantum dots (QD)s and lectins from Schinus terebinthifolia leaves (SteLL) and Punica granatum sarcotesta (PgTeL). Cryptococcus neoformans cells were chosen to evaluate the efficiency of the conjugates. Lectins were conjugated to QDs via adsorption, and the optical parameters (emission and absorption) were monitored. Lectin stability in the conjugates towards denaturing agents was investigated via fluorometry. The conjugation was evaluated using fluorescence microplate (FMA) and hemagglutination (HA) assays. The labeling of the C. neoformans cell surface was quantified using flow cytometry and observed via fluorescence microscopy. The QDs-SteLL and QDs-PgTeL conjugates, obtained at pH 7.0 and 8.0, respectively, showed the maintenance of colloidal and optical properties. FMA confirmed the conjugation, and the HA assay indicated that the lectin carbohydrate-binding ability was preserved after conjugation. SteLL and PgTeL showed stability towards high urea concentrations and heating. Conjugates labeled over 90% of C. neoformans cells as observed via flow cytometry and confirmed through fluorescence microscopy. C. neoformans labeling by conjugates was inhibited by glycoproteins, suggesting specific interactions through the lectin carbohydrate-binding site. Thus, an effective protocol for the conjugation of SteLL or PgTeL with QDs was proposed, yielding new nanoprobes useful for glycobiological studies.

Effects of a solid formulation containing lectin-rich fraction of Moringa oleifera seeds on egg hatching and development of Aedes aegypti larvae.

The measures currently used to minimize the spread of arboviruses, comprising dengue, Chikungunya, and Zika virus, involve controlling the size of population of the mosquito Aedes aegypti. However, the search for formulations containing new insecticides is gaining pace due to reports of mosquito populations showing resistance to commonly used compounds. In this study, tablets containing a protein fraction of Moringa oleifera seeds enriched in the WSMoL lectin, known to show larvicidal and ovicidal activities against A. aegypti, were developed. The compatibility between the fraction and the excipients used in obtaining the tablets was evaluated by thermogravimetry (TG), differential scanning calorimetry (DSC), and Fourier transform infrared (FTIR) absorption spectroscopy. The larvicidal and ovicidal activities of the resulting tablets [5%, 10%, and 15% (w/w) of the fraction] were evaluated, as well as their effect on mosquito oviposition. Assays were also performed using a placebo tablet. According to the TG, DSC, and FTIR results, the protein composition of the fraction did not change when mixed with the components of the formulation. Tablets containing 10% and 15% WSMoL-rich fraction caused mortality of 42.5% and 95% of the larvae after 48 h, respectively, with larvae incubated with these tablets showing reduced acetylcholinesterase activity. All tablets inhibited egg hatching after 72 h (36-74%), and tablets containing 15% fraction were found to exert a repellent effect on oviposition. Our results show that the formulation developed in this study interfered with the life cycle of A. aegypti, and thus show potential for use in the control of this mosquito.

Portulaca elatior root contains a trehalose-binding lectin with antibacterial and antifungal activities.

Lectins are carbohydrate-binding proteins broadly distributed in plants and have several biological functions, including antimicrobial action. Portulaca elatior is a Caatinga plant whose chemical composition and biotechnological potential have not been extensively studied. In this work, a lectin was isolated from P. elatior root extract and evaluated for antimicrobial activity. The P. elatior root lectin (PeRoL) showed native molecular mass of 33 kDa, pI 3.8 and is comprised of two subunits of 15 kDa linked by disulfide bonds. No sequence similarities with Viridiplantae proteins were observed. The PeRoL hemagglutinating activity (HA) was not affected by heating and was detected in a pH ranging from 4.0 to 8.0. Trehalose was identified as an endogenous inhibitor of PeRoL present in the roots. Bacteriostatic activity was detected against Enterococcus faecalis, Pseudomonas aeruginosa and Staphylococcus aureus (minimal inhibitory concentration of 8.1, 32.5 and 4.06 µg/mL, respectively). PeRoL induced the death of Candida albicans, Candida parapsilosis, Candida krusei, and Candida tropicalis cells, with a minimal fungicidal concentration of 16 µg/mL. The lectin (100 µg/mL) was not cytotoxic to human peripheral blood mononuclear cells (PBMCs) and did not show hemolytic activity. In conclusion, the roots of P. elatior contain a trehalose-binding, thermostable, and antimicrobial lectin.

Purification and characterization of a protease from the visceral mass of Mytella charruana and its evaluation to obtain antimicrobial peptides.

This work describes purification of a protease from the visceral mass of the mussel Mytella charruana as well as evaluation of its ability to hydrolyze milk casein to generate antimicrobial peptides. The enzyme showed pI of 4.1 and a single polypeptide band of 83.1 kDa after SDS-PAGE. Sequence similarities with tropomyosin and myosin from mollusks were detected. The protease showed a trypsin-like activity with optimal temperature of 40 °C and stability in a wide pH range (3.0-9.0). Km was 4.28 ±â€¯0.34 mM of the synthetic substrate N-benzoyl-dl-arginyl-ρ-nitroanilide, whereas Vmax was 0.056 ±â€¯0.001 nmol min-1. The enzyme hydrolyzed casein, and the hydrolysate inhibited the growth of Escherichia coli, Micrococcus luteus, Bacillus subtilis, and Klebsiella pneumoniae at a minimal inhibitory concentration of 5.0 µg mL-1. In conclusion, the visceral mass of M. charruana contains a trypsin-like protease that can generate peptides from casein that have a bacteriostatic effect.