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.
In this study, we investigated an experimental and Monte-Carlo computational characterization of self-assembled antennae built of CdTe colloidal quantum dots (QDs). These clusters provide efficient excitation of phycocyanine (PC) or...
While
quantum dots (QDs) are useful as fluorescent labels, their
application in biosciences is limited due to the stability and hydrophobicity
of their surface. In this study, we tested two types of proteins for
use as a cover for spherical QDs, composed of cadmium selenide. Pumilio
homology domain (Puf), which is mostly α-helical, and leucine-rich
repeat (LRR) domain, which is rich in β-sheets, were selected
to determine if there is a preference for one of these secondary structure
types for nanoparticle covers. The protein sequences were optimized
to improve their interaction with the surface of QDs. The solubilization
of the apoproteins and their assembly with nanoparticles required
the application of a detergent, which was removed in subsequent steps.
Finally, only the Puf-based cover was successful enough as a QD hydrophilic
cover. We showed that a single polypeptide dimer of Puf, PufPuf, can
form a cover. We characterized the size and fluorescent properties
of the obtained QD:protein assemblies. We showed that the secondary
structure of the Puf proteins was not destroyed upon contact with
the QDs. We demonstrated that these assemblies do not promote the
formation of reactive oxygen species during illumination of the nanoparticles.
The data represent advances in the effort to obtain a stable biocompatible
cover for QDs.
The bionanohybrids are the junctions of at least two objects of different origin: abiotic and biotic. The abiotic part is a nanoparticle (often a fluorescent quantum dot), the biotical one may be a protein (especially fluorescent one or redox-active one), nucleic acid, carbohydrate as well as a simple organic molecule. When such a junction undergoes illumination, the energy transfer between the partners is possible. The nanoparticles, depending on their characteristics, may be donors, acceptors or mediators of the energy transfer. In most cases, the mechanism of the transfer is the Förster resonance energy transfer (FRET) or the electron transfer (ET). Here, we reviewed the newest achievements in the field with special attention paid to those bionanohybrids which allow FRET or ET. Such nanohybrids are important not only for exploration of the mechanism of the partner interaction but mainly for working out nanobiodevices for biosensing and nanotools for modern therapies.
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