Competition between Photoinduced Electron Transfer and Resonance Energy Transfer in an Example of Substituted Cytochrome c–Quantum Dot Systems

Abstract

Colloidal quantum dots (QDs) are nanoparticles that are able to photoreduce redox proteins by electron transfer (ET). QDs are also able to transfer energy by resonance energy transfer (RET). Here, we address the question of the competition between these two routes of QDs’ excitation quenching, using cadmium telluride QDs and cytochrome c (CytC) or its metal-substituted derivatives. We used both oxidized and reduced versions of native CytC, as well as fluorescent, nonreducible Zn(II)CytC, Sn(II)CytC, and metal-free porphyrin CytC. We found that all of the CytC versions quench QD fluorescence, although the interaction may be described differently in terms of static and dynamic quenching. QDs may be quenchers of fluorescent CytC derivatives, with significant differences in effectiveness depending on QD size. SnCytC and porphyrin CytC increased the rate of Fe(III)CytC photoreduction, and Fe(II)CytC slightly decreased the rate and ZnCytC presence significantly decreased the rate and final level of reduced FeCytC. These might be partially explained by the tendency to form a stable complex between protein and QDs, which promoted RET and collisional quenching. Our findings show that there is a net preference for photoinduced ET over other ways of energy transfer, at least partially, due to a lack of donors, regenerating a hole at QDs and leading to irreversibility of ET events. There may also be a common part of pathways leading to photoinduced ET and RET. The nature of synergistic action observed in some cases allows the hypothesis that RET may be an additional way to power up the ET.

Luminescent gold nanoclusters as a signal reporter for cytochrome c assay with a double signal amplification strategy

“…[ 20 ] When the positively charged Cyt c is mixed with the negatively charged GSH‐AuNCs, GSH‐AuNCs‐Cyt c nanobioconjugates may be formed through electrostatic interactions. This may induce fluorescence quenching due to electron transfer from GSH‐AuNCs to the heme cofactor of Cyt c. [ 21 ] It has been suggested that thiol groups and sulfur donor ligands (such as thiolates) can specifically bind to iron of Cyt c (Fe‐S). [ 22 ] The coordination of GSH sulfur with Cyt c iron facilitates electron transfer between GSH‐AuNCs and Cyt c. On the other hand, the absorption spectrum of Cyt c ranges from 300 to 650 nm with two absorption peaks at 409 and 528 nm due to the heme group of Cyt c protein (Figure S4).…”

Fluorescence Biosensor for One-Step Simultaneous Detection of Mycobacterium tuberculosis Multidrug-Resistant Genes Using nanoCoTPyP and Double Quantum Dots

“…The two fluorescence emission peaks of the double QDs-ssDNA were located at 535 and 648 nm (Figure S1A). The double QDs-ssDNA could adsorb onto nanoCoTPyP via electrostatic interaction, π–π stacking, and hydrogen bonding, , leading to fluorescence quenching due to the fluorescence resonance energy transfer (FRET) and photoinduced electron transfer (PET). ,, As shown in Figure S1B, the UV–vis absorption spectra of nanoCoTPyP overlapped with the fluorescence emission spectrum of the double QDs-ssDNA, which was beneficial for the FRET processes. However, in the presence of target DNAs, target DNAs and ssDNA hybridized specifically to form more stable double-stranded DNA (dsDNA).…”

Simple and Cost-Effective Quantum Dot Chemodosimeter for Visual Detection of Biothiols in Human Blood Serum

“…Various approaches for qualitative as well as quantitative analysis of these bioanalytes have been developed, mainly based on electroanalytical techniques, , high-performance liquid chromatography (HPLC), , capillary electrophoresis separation, immunoassays based on derivatization with fluorescent/phosphorescent reagents, spectrophotometric methods, etc. , Unfortunately, all of these methods require either expensive reagents or equipment or skilled manpower to ensure reproducibility. In this context, much attention is being paid to the development of simple and cheap fluorescent probes, without compromising selectivity and sensitivity. − Nanoparticles have been proven to be an efficient substitute for organic fluorophores, particularly for developing emission “turn on/off” sensors. − Among various nanoparticles, quantum dots (QDs) are of particular interest in developing novel biosensors owing to their unique properties such as broad absorption band, emission in the visible region, photostability, etc. − Moreover, the potential of QDs to transfer electrons or holes to biologically important molecules, interacting covalently or noncovalently with their surface, can be used to tune the QD emission intensity and thus generate charge transfer-based emission “on/off” signaling. − …”