RESUMEN
Polyethylene glycol (PEG) surface modified biocompatible InP/ZnS quantum dots (QDs) act as a potential alternative for conventional carcinogenic cadmium-based quantum dots for in vivo and in vitro studies. Comprehensively, we studied the interaction between a model protein bovine serum albumin (BSA) and PEGylated toxic free InP/ZnS QDs using various spectroscopic tools such as absorption, fluorescence quenching, time resolved and synchronous fluorescence spectroscopic measurements. These studies principally show that tryptophan (Trp) residues of BSA have preferable binding affinity towards PEG-InP/ZnS QDs surface and a blue shift in Trp fluorescence emission is a signature of conformational changes in its hydrophobic microenvironment. Photoluminescence (PL) intensity of Trp is quenched by ground state complex formation (static quenching) at room temperature. However, InP/ZnS@BSA conjugates become unstable with increasing temperature and PL intensity of Trp is quenched via dynamic quenching by PEG-InP/ZnS QDs. Experimentally determined thermodynamic parameters for these conjugates have shown spontaneity, entropy driven and exothermic nature of bio-conjugation. The calculated binding affinity (n â 1, Hill coefficient) suggest that the affinity of InP/ZnS QDs for a BSA protein is not dependent on whether or not other BSA proteins are already bound to the QD surface. Energy transfer efficiency (E), Trp residue to InP/ZnS QDs distances and energy transfer rate (kT ) were all obtained from FÖrster resonance energy.
Asunto(s)
Puntos Cuánticos/química , Albúmina Sérica Bovina/química , Transferencia Resonante de Energía de Fluorescencia , Luminiscencia , Ensayo de Materiales , Polietilenglicoles/química , Conformación Proteica , Puntos Cuánticos/metabolismo , Albúmina Sérica Bovina/metabolismo , Espectrometría de Fluorescencia/métodos , Espectrofotometría Ultravioleta , Sulfuros/química , Temperatura , Termodinámica , Triptófano/química , Compuestos de Zinc/químicaRESUMEN
We present here a systematic investigation on the interaction between a water-soluble alloyed semiconductor quantum dot and bovine serum albumin using various spectroscopic techniques i.e. fluorescence quenching, resonance light scattering and synchronous fluorescence spectroscopy. The analysis of fluorescence spectrum and fluorescence intensity indicates that the intrinsic fluorescence of bovine serum albumin (BSA) gets quenched by both static and dynamic quenching mechanism. The Stern-Volmer quenching constants, energy transfer efficiency parameters, binding parameters and corresponding thermodynamic parameters (ΔH0 , ΔS0 and ΔG0 ) have been evaluated by using van 't Hoff equation at different temperatures. A positive entropy change with a positive enthalpy change was observed suggesting that the binding process was an entropy-driven, endothermic process associated with the hydrophobic effect. The intermolecular distance (r) between donor (BSA) and acceptor (CdSeS/ZnS quantum dots) was estimated according to Förster's theory of non-radiative energy transfer. The synchronous fluorescence spectra revealed a blue shift in the emission maxima of tryptophan which is indicative of increasing hydrophobicity. Negative ΔG0 values implied that the binding process was spontaneous. It was found that hydrophobic forces played a role in the quenching process. Copyright © 2016 John Wiley & Sons, Ltd.
Asunto(s)
Compuestos de Cadmio/química , Puntos Cuánticos , Compuestos de Selenio/química , Albúmina Sérica Bovina/química , Sulfuros/química , Compuestos de Zinc/química , Animales , Bovinos , Solubilidad , Espectrometría de Fluorescencia , Termodinámica , Agua/químicaRESUMEN
Circular dichroism, topological studies, molecular docking, absorbance, and fluorescence spectral titrations were employed to study the interaction of 4-morpholinopyrimido [4',5':4,5] selenolo (2,3-b) quinoline (MPSQ) with DNA. The association constants of MPSQ-DNA interactions were of the order of 10(4) M(-1). Melting temperature, topological, and docking studies confirmed that the mode of interaction was by intercalation with preference to d(GpC)-d(CpG) site of DNA. Cytotoxicity studies showed the MPSQ-induced dose-dependent inhibitory effect on the proliferation of different cancer cells. Colon adenocarcinoma (COLO 205) cells are more sensitive among the cell lines tested, with an IC50 value of 15 µM. Flow cytometry revealed that MPSQ affects the cell cycle progression by arresting at G2M phase. Further, Annexin V staining, mitochondrial membrane potential assay, and caspase-3 activity assay confirmed that MPSQ leads to mitochondria-mediated apoptotic cell death in COLO 205 cells.
Asunto(s)
Apoptosis/efectos de los fármacos , Puntos de Control del Ciclo Celular/efectos de los fármacos , Quinolinas/farmacología , Adenocarcinoma/metabolismo , Antineoplásicos/química , Antineoplásicos/farmacología , Caspasa 3/metabolismo , Línea Celular Tumoral , Neoplasias del Colon/metabolismo , ADN/metabolismo , Puntos de Control de la Fase G2 del Ciclo Celular/efectos de los fármacos , Humanos , Concentración 50 Inhibidora , Potencial de la Membrana Mitocondrial/efectos de los fármacos , Modelos Moleculares , Conformación Molecular , Quinolinas/químicaRESUMEN
PURPOSE: To examine the impact of ultraviolet (UV) laser radiation on the embryos of Calotes versicolor in terms of its effects on the protein profile of the adrenal-kidney-gonadal complex (AKG), sex determination and differentiation, embryonic development and hatching synchrony. MATERIALS AND METHODS: The eggs of C. versicolor, during thermo-sensitive period (TSP), were exposed to third harmonic laser pulses at 355 nm from a Q-switched Nd:YAG laser for 180 sec. Subsequent to the exposure they were incubated at the male-producing temperature (MPT) of 25.5 ± 0.5°C. The AKG of hatchlings was subjected to protein analysis by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and to histology. RESULTS: The UV laser radiation altered the expression of the protein banding pattern in the AKG complex of hatchlings and it also affected the gonadal sex differentiation. SDS-PAGE of AKG of one-day-old hatchlings revealed a total of nine protein bands in the control group whereas UV laser irradiated hatchlings expressed a total of seven protein bands only one of which had the same Rf as a control band. The UV laser treated hatchlings have an ovotestes kind of gonad exhibiting a tendency towards femaleness instead of the typical testes. CONCLUSIONS: It is inferred that 355 nm UV laser radiation during TSP induces changes in the expression of proteins as well as their secretions. UV laser radiation had an impact on the gonadal differentiation pathway but no morphological anomalies were noticed.
Asunto(s)
Glándulas Suprarrenales/efectos de la radiación , Desarrollo Embrionario/efectos de la radiación , Gónadas/efectos de la radiación , Riñón/efectos de la radiación , Rayos Láser/efectos adversos , Proteínas de Reptiles/metabolismo , Rayos Ultravioleta/efectos adversos , Glándulas Suprarrenales/embriología , Glándulas Suprarrenales/metabolismo , Animales , Femenino , Gónadas/embriología , Gónadas/metabolismo , Riñón/embriología , Riñón/metabolismo , Lagartos , Masculino , Factores de TiempoRESUMEN
Fluorescence resonance energy transfer (FRET), time-resolved fluorescence and anisotropy decays were determined in large unilamellar vesicles (LUVs) of egg phosphatidylcholine with the FRET pair N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)-1,2-dipalmitoyl-sn-glycero-3-phospho-ethanolamine as donor and lissamine rhodamine B 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine as acceptor, using 2-ps pulses from a Ti:sapphire laser on LUVs with incorporated plant growth regulators: triacontanol (TRIA) and jasmonic acid (JA). FRET efficiency, energy transfer rate, rotation correlation time, microviscosity, and diffusion coefficient of lateral diffusion of lipids were calculated from these results. It was observed that TRIA and JA differentially modulated all parameters studied. The effect of JA in such modulations was always partially reversed by TRIA. Also, the generalized polarization of laurdan fluorescence indicated that JA enhances the degree of hydration in lipid bilayers to a larger extent than does TRIA. Solid-state (31)P magic-angle spinning nuclear magnetic resonance spectra of LUVs showed two chemical shifts, at 0.009 and -11.988 ppm, at low temperatures (20 degrees C), while at increasing temperatures (20-60 degrees C) only one (at -11.988 ppm) was prominent and the other (0.009 ppm) gradually became obscure. However, LUVs with TRIA exhibited only one of the shifts at 0.353 ppm even at lower temperatures and JA did not affect the chemical shifts.