Highly efficient energy transfer from a water soluble quantum dot to organic J-aggregates in an inorganic–organic nanohybrid associate.

With an aim to understand the interaction between the inorganic and organic components in inorganic–organic hybrid nanostructured materials, we have designed and developed an inorganic–organic nanohybrid associate comprising inorganic fluorescent Au nanoclusters (NCs) and organic J-aggregates of a cyanine-based dye (S2165). The present system is quite interesting as in contrast to previously constructed nanohybrid systems where fluorescent quantum dots are integrated with an organic dye, the present system is developed using fluorescent gold nanoparticles and organic J-aggregates. The hybrid system has been characterized by spectroscopic and microscopic techniques. Steady-state absorption and emission and time-resolved fluorescence measurements have been performed to understand the optical properties of this hybrid system. In particular, the interparticle electronic interaction has been investigated by monitoring nonradiative energy transfer from fluorescent Au NCs (donor) to organic J-aggregates (acceptor). The fluorescence resonance energy transfer (FRET) event for the current system has been verified by various methods. ζ-Potential measurements and thermodynamic calculations have suggested that the interaction between Au NCs and J-aggregates in the hybrid associate is electrostatically driven. The analysis of data based on Förster theory has revealed that the energy transfer efficiency from inorganic to organic particles is very high. The observation of the high energy transfer efficiency in the present inorganic–organic hybrid associate is quite interesting as these results suggest that a metal-based system can also be very useful in designing a highly efficient light-harvesting system for various optoelectronic applications. Interestingly, both Au NCs and the Au–J-aggregate hybrid system are found to be cell-permeable and suitable for bioimaging studies. Additionally, because of the nontoxic nature of these systems, they can also be used in many biological applications.

Dynamin superfamily proteins comprising classical dynamins and related proteins are membrane remodelling agents involved in several biological processes such as endocytosis, maintenance of organelle morphology and viral resistance. These large GTPases couple GTP hydrolysis with membrane alterations such as fission, fusion or tubulation by undergoing repeated cycles of self-assembly/disassembly. The functions of these proteins are regulated by various post-translational modifications that affect their GTPase activity, multimerization or membrane association. Recently, several reports have demonstrated variety of such modifications providing a better understanding of the mechanisms by which dynamin proteins influence cellular responses to physiological and environmental cues. In this review, we discuss major post-translational modifications along with their roles in the mechanism of dynamin functions and implications in various cellular processes.

Although in recent times nanoparticles (NPs) are being used in various biological applications, their mechanism of binding interactions still remains hazy. Usually, the binding mechanism is perceived to be mediated through either the protein corona (PC) or protein complex (PCx). Herein, we report that the nanoparticle (NP)−protein interaction can also proceed via a different pathway without forming the commonly observed PC or PCx. In the present study, the NP−protein interaction between less-toxic zinc−silver−indium-sulfide (ZAIS) quantum dots (QDs) and bovine serum albumin (BSA) was investigated by employing spectroscopic and microscopic techniques. Although the analyses of data obtained from fluorescence and thermodynamic studies do indicate the binding between QDs and BSA, they do not provide clear experimental evidence in favor of PC or PCx. Quite interestingly, highresolution transmission electron microscopy (HRTEM) studies have shown the formation of a new type of species where BSA protein molecules are adsorbed onto some portion of a QD surface rather than the entire surface. To the best of our knowledge, we believe that this is the first direct experimental evidence in favor of a model-free pathway for NP−protein interaction events. Thus, the outcome of the present study, through experimental evidence, clearly suggests that NP−protein interaction can proceed by following a pathway that is different from classical PC and PCx.