Feng-Lei Jiang

A reaction-based chromogenic and fluorescent chemodosimeter for fluoride anions

An innovative trihexylsilylacetylene-containing BODIPY dye was designed and proved to be a highly selective, sensitive, and fast chromogenic and fluorescent chemodosimeter for fluorides.

Chiral effect at protein/graphene interface: a bioinspired perspective to understand amyloid formation.

Protein misfolding to form amyloid aggregates is the main cause of neurodegenerative diseases. While it has been widely acknowledged that amyloid formation in vivo is highly associated with molecular surfaces, particularly biological membranes, how their intrinsic features, for example, chirality, influence this process still remains unclear. Here we use cysteine enantiomer modified graphene oxide (GO) as a model to show that surface chirality strongly influences this process. We report that R-cysteine modification suppresses the adsorption, nucleation, and fiber elongation processes of Aβ(1-40) and thus largely inhibits amyloid fibril formation on the surface, while S-modification promotes these processes. And surface chirality also greatly influences the conformational transition of Aβ(1-40) from α-helix to β-sheet. More interestingly, we find that this effect is highly related to the distance between chiral moieties and GO surface, and inserting a spacer group of about 1-2 nm between them prevents the adsorption of Aβ(1-40) oligomers, which eliminates the chiral effect. Detailed study stresses the crucial roles of GO surface. It brings novel insights for better understanding the amyloidosis process on surface from a biomimetic perspective.

Mitochondria as target of Quantum dots toxicity

Quantum dots (QDs) hold great promise in many biological applications, with the persistence of safety concerns about the environment and human health. The present work investigated the potential toxicity of CdTe QDs on the function of mitochondria isolated from rat livers by examining mitochondrial respiration, swelling, and lipid peroxidation. We observed that QDs can significantly affect the mitochondrial membrane properties, bioenergetics and induce mitochondrial permeability transition (MPT). These results will help us learn more about QDs toxicity at subcellular (mitochondrial) level.

Toxicity of nano zinc oxide to mitochondria

Zinc oxide nanoparticles (ZnO NPs) are increasingly applied in a diverse array of industrial and commercial products. Therefore, it is urgently required to characterize their toxic behavior. ZnO NPs have been reported to induce toxic effects at the levels of the individual organism, tissue, cell and DNA. However, little is known about the potential impacts of ZnO NPs at a subcellular level. In the present work, we investigated the toxicity of ZnO NPs to the isolated rat liver mitochondria. We found that treatment of mitochondria with ZnO NPs resulted in collapse of mitochondrial membrane potential (Δψ), swelling, depression of respiration, inner membrane permeabilization to H+ and K+, alterations of ultrastructure, release of cytochrome c, generation of reactive oxygen species (ROS), and Zn2+ liberation from ZnO NPs. These results suggested that ZnO NPs can increase the inner membrane permeability and impair the respiratory chain, thus leading to energy dissipation, oxidative stress and even apoptosis. This putative mechanism helps us learn more about the toxicology of this nanomaterial.

Interactions between carbon nanodots with human serum albumin and γ-globulins: The effects on the transportation function.

Carbon nanodots (C-dots) have attracted great attention as a new class of luminescent nanomaterials due to their superior physical and chemical properties. In order to better understand the basic behavior of C-dots in biological systems, a series of photophysical measurements were applied to study the interactions of C-dots with human serum albumin (HSA) and γ-globulins. The fluorescence of proteins was quenched by the dynamic mechanism rather than the formation of a protein/C-dots complex. The apparent dissociation constants of the C-dots bound to HSA and γ-globulins were of the same order of magnitude. Furthermore, it is proven that C-dots showed little influence on the conformation of HSA and γ-globulins. In addition, Fourier transform infrared and fluorescence spectroscopic studies demonstrated that the interaction between C-dots and two kinds of serum proteins was driven by hydrophobic and van der waals forces. Since the bioavailability of drugs can be modulated by their interactions with proteins, the variations of binding constants of three drugs with HSA and γ-globulins in the presence of different concentrations of C-dots (0-84 μmol L(-1)) have also been analyzed in this work, to reflect the effect of C-dots on the transportation function of HSA and γ-globulins.

The adsorption of an anticancer hydrazone by protein: an unusual static quenching mechanism

A novel hydrazone, 4-chloro-N′-(pyridin-2-ylmethylene)benzohydrazide (CPBH) has been synthesized through a one-pot synthesis method and used as a chemical probe to find the structural cause of the unusual static quenching mechanism in the interaction with serum albumin. The adsorption of CPBH by bovine/human serum albumin (BSA/HSA) has been investigated systematically by comprehensive spectroscopy, modeling, electrochemistry and microcalorimetry under physiological conditions. CPBH forms a complex with BSA/HSA with the binding site in Sudlows site I of BSA/HSA. The adverse temperature dependence in the unusual static quenching is found to be a reasonable consequence of the large activation energy requirement in the binding process, which is required to overcome the structural block and it is a direct result of the unique microstructure of the binding pocket.

Binding of fullerol to human serum albumin: spectroscopic and electrochemical approach.

The potential impact of human exposure to carbonaceous nanomaterials in the environment becomes a concerning issue. Here we report on the interaction of fullerol with human serum albumin (HSA) using spectroscopic and electrochemical methods. The water-soluble fullerene derivative (fullerol) was synthesized and characterized by IR, (1)H NMR, TG-DSC, XRD, HR-TEM, etc. The spectroscopic methods show that the fluorescence quenching of HSA by fullerol is the result of the formation of an HSA-fullerol complex. Binding parameters such as ΔG, ΔH and ΔS were calculated, and the quenching constant K(a) at different temperatures was determined using the modified Stern-Volmer equation. The electrochemical experiments further confirmed the conclusions. In addition, the influences of coexisting heavy metal ions have also been studied in the present system. The circular dichroism spectra (CD), 3D fluorescence spectra and FT-IR spectra results suggest that the secondary structure of HSA was changed by fullerol. Based on the site marker competitive experiments, we can predict the possible binding position of fullerol on the HSA was located at the site of sub domain II A. Furthermore, the distance r between donor (HSA) and acceptor (fullerol) was obtained according to the famous fluorescence resonance energy transfer (FRET) mechanism.

Syntheses, Characterization, and Photophysical Properties of Conjugated Organometallic Pt-Acetylide/Zn(II) Porphyrin-Containing Oligomers

Two conjugated organometallic oligomers of the type (-C[triple bond]CPt(L)(2)C[triple bond]C(ZnP)-)(n) and model compounds [PhC[triple bond]CPt(L)(2)C[triple bond]C(ZnP)C[triple bond]CPt(L)(2)C[triple bond]CPh] with L = tri(n-butyl)-phosphine and ZnP = zinc(II)(10,20-bis(Ar)porphyrine) (Ar = mesityl (Mes; P1 and M1) or 3,4,5-trihexadecyloxyphenyl (P2 and M2)) were synthesized and characterized ((1)H and (31)P NMR, HRMS, elemental analysis, IR, GPC, and TGA). GPC indicates that P1 and P2 exhibit respectively approximately 6 and approximately 3 units with a polydispersity of 1.4. M1 was also characterized by X-ray crystallography. The Pt...Pt separation in M1 is 1.61 nm, which makes P1 approximately 9.6 nm long. The spectral measurements show that the absorption and photoluminescence spectra of M1, M2, P1, and P2 are remarkably red-shifted. For example, the low energy Q-band is observed at 677 +/- 1 nm in comparison with their precursors HC[triple bond]C(ZnP)C[triple bond]CH, L1 and L2 (Ar = mesityl (Mes; L1) or 3,4,5-trihexadecyloxyphenyl (L2)), both at 298 and 77 K, for which the Q-band is observed at 622 nm. The photophysical parameters, fluorescence lifetimes (tau(F)), and quantum yields (Phi(F)) show a slight decrease by a factor of approximately 2 (at most 3) following the trend L1 approximately L2 > M1 approximately M2 > P1 approximately P2, a trend explained by a combination of the heavy atom effect and an increase in internal conversion rate due to the increase in oligomer dimension. This small variation of the photophysical data for materials of a few nm in dimension contrasts with the larger change in tau(P), phosphorescence lifetimes of the Pt-containing unit in the (-C(6)H(4)C[triple bond]CPt(L)(2)C[triple bond]C-CC(6)H(4)(ZnP)-)(n) oligomers with n = 3, 6, and 9 reported earlier (Liu, L.; Fortin, D.; Harvey, P. D. Inorg. Chem. 2009, 48, 5891-5900). In this later case, tau(P) decreased by steps of an order of magnitude as n increased from 3 to 6 to 9. This decrease was explained by a T(1) energy transfer from the Pt unit (donor) to MP (acceptor) in combination with an excitonic process (energy delocalization). Because of the full conjugation in P1 and P2, these oligomers behave as distinct molecules, and no energy transfer occurs. These properties make these materials suitable candidates for photocell applications.

Interaction between a cationic porphyrin and bovine serum albumin studied by surface plasmon resonance, fluorescence spectroscopy and cyclic voltammetry

The interaction between a cationic porphyrin and bovine serum albumin (BSA) was studied by using surface plasmon resonance (SPR) spectroscopy, which was combined with fluorescence quenching method and cyclic voltammetric method to confirm the binding kinetic results. In this paper, the SPR method used to study the drug-protein interaction was described in detail. The association rate constant, dissociation rate constant and the equilibrium association constant of porphyrin binding to BSA obtained from this method were 1067 ± 18.23 M(-1) s(-1), 0.01644 ± 0.00012 s(-1), and 6.49 × 10(4) M(-1), respectively. The equilibrium association constants obtained from the fluorescence quenching method and the cyclic voltammetric method were 1.102 × 10(5) M(-1) and 1.21 × 10(5) M(-1), respectively.

Spectroscopic and microscopic studies on the mechanisms of mitochondrial toxicity induced by different concentrations of cadmium.

The deleterious action of Cd2+ on rat liver mitochondria was investigated in this work using spectroscopic and microscopic methods. The concentration dependence of Cd2+ on mitochondrial swelling, membrane potential and membrane fluidity was studied. Our aim was to detect the active sites of Cd2+ in the mitochondrial membrane treatments with cyclosporin A (CsA) and EGTA on the mitochondrial permeability transition (MPT) induced by low and high concentrations of Cd2+. The protective effects of dithiothreitol, human serum albumin and monobromobimane+ on Cd2+-induced MPT were also monitored. All of these investigations indicated that Cd2+ can directly affect MPT at two separate localization sites at different concentrations: the classic Ca2+ triggering site and the thiol (–SH) groups of membrane proteins matched by MPT pore opening (defined as “S” site). At the high concentration of Cd2+, other free –SH groups in the mitochondrial matrix may be involved in this process. These findings were supported by transmission electron microscopy and shed light on the toxic mechanism of Cd2+ on mitochondria.