Rare earth elements activate endocytosis in plant cells.

It has long been observed that rare earth elements (REEs) regulate multiple facets of plant growth and development. However, the underlying mechanisms remain largely unclear. Here, using electron microscopic autoradiography, we show the life cycle of a light REE (lanthanum) and a heavy REE (terbium) in horseradish leaf cells. Our data indicate that REEs were first anchored on the plasma membrane in the form of nanoscale particles, and then entered the cells by endocytosis. Consistently, REEs activated endocytosis in plant cells, which may be the cellular basis of REE actions in plants. Moreover, we discovered that a portion of REEs was successively released into the cytoplasm, self-assembled to form nanoscale clusters, and finally deposited in horseradish leaf cells. Taken together, our data reveal the life cycle of REEs and their cellular behaviors in plant cells, which shed light on the cellular mechanisms of REE actions in living organisms.

Structural basis for the decrease in the outward potassium channel current induced by lanthanum.

The current of the outward K+ channel in the cell of horseradish treated with La3+ and the direct interaction between La3+ and the K+ channel protein were investigated using the whole-cell patch-clamp technique, molecular dynamics simulation, and quantum chemistry calculation methods. It was found for the first time that La3+ decreases the current of the K+ channel in the horseradish mesophyll cell. The decrease results from the formation of a coordination bond and hydrogen bond between La3+ and the K+ channel protein in the plasma membrane. The direct interaction destroys the native structure of the K+ channel protein, disturbing the function of the K+ channel protein in the cells. The results can provide the theoretical foundation for understanding the interaction between metal ions (especially high-valence metal ions) and the channel protein in organisms, including animal and plant cells.

Direct electrochemistry and bioelectrocatalysis of hemoglobin immobilized on carbon black.

It is reported for the first time that hemoglobin (Hb) was immobilized on the surface of carbon black powders modified at the surface of a glassy carbon electrode. The cyclic voltammetric results showed that the immobilized Hb could undergo a direct quasi-reversible electrochemical reaction. Its formal potential, E(0), is -0.330 V in phosphate buffer solution (pH 6.9) at a scan rate of 100 mV/s and is almost independent of the scan rate in the range of 40-200 mV/s. The dependence of E(0), on the pH of the buffer solution indicated that the conversion of Hb-Fe(III)/Hb-Fe(II) is a one-electron-transfer reaction process coupled with one-proton-transfer. The experimental results also demonstrated that the immobilized Hb retained its bioelectrocatalytic activity for the reduction of H(2)O(2). Furthermore, the immobilized Hb can be stored at 4 degrees C for several weeks without any loss of the enzyme activity. Thus, the immobilized Hb may be used as a biocathodic catalyst in biofuel cells.

[Study on spectroscopic properties of rare earth complexes with poly (N-vinylacetamide)].

Terbium-lanthanum (or gadolinium)-poly(N-vinylacetamide) complexes were synthesized and characterized by UV-Vis absorption spectroscopy, FTIR, XPS and fluorescence spectroscopy. The results of UV-Vis, FTIR and XPS suggested that terbium and lanthanum (or gadolinium) ions were bonded to amide group of PNVA polymer. Fluorescence experiment indicated that the characteristic emission intensity of terbium ion was greatly increased and possibly sensitized by lanthanum ion (or gadolinium). Moreover, the wavelengths of terbium characteristic emissions were changed slightly. Also the characteristic emission intensity of terbium ion doped with lanthanum ion was better than that with gadolinium ion.

[Study on interaction between hypocrellin A and hemoglobin or myoglobin using synchronous fluorescence spectra].

The effects of hypocrellin A (HA) on the conformational changes of hemoglobin and myoglobin were studied using synchronous fluorescence spectroscopy. The results indicated that HA can change the conformation of these two proteins, leading to the change in the micro-environment of tryptophane and tyrosine residues from hydrophobic environment to hydrophilic environment to different extent.

[Spectral study on the interaction mechanism between thionine and calf thymus DNA].

The interaction mechanism of thionine (TH) and calf thymus DNA (CT-DNA) was studied with UV-Vis absorption spectoscopy, fluorescence spectroscopy, circular dichroism (CD), and X-ray photoelectron spectroscopy (XPS). It was demonstrated that in the pH 7.2 phosphate buffer solution, the interaction of TH and CT-DNA is in the intercalative mode. The absorbance of the absorption peak of TH decreases and the peak position shifts to the red direction. The binding constant (K) of TH with CT-DNA is 1.45x 10(4) mol x L(-1). The fluorescence intensities of TH decrease drastically with increasing the concentration of CT-DNA. The Stem-Volmer quenching constant (Ksv) was calculated to be 1.01 x 10(4) mol x L(-1). The intercalative sites are mainly located at the G-C sequences of the CT-DNA molecule through the S atom in the TH molecule according to the experimental data obtained from the fluorescence spectra and XPS analysis. The secondary structure conformation of CT-DNA is changed due to its interaction with TH.

[Spectra studies on the interaction of Mn2+ and poly N-isopropylacrylamide].

The interaction of Mn2+ and poly (N-isopropylacrylamide) (PNIPAAm) was studied by using UV-Vis, FTIR and fluorescence spectroscopic methods. The results indicated that Mn2+ could be bonded to oxygen atoms of carbonyl in PNIPAAm and form the complex of Mn2+ -PNIPAAm. It was found that there existed efficient Förster energy transfer from Mn2+ to PNIPAAm due to the emission spectra of Mn2+ overlapping the excitation spectra of PNIPAAm and that the emission peak of Mn2+ at 561 nm disappeared in Mn2+ -PNIPAAm complex. Therefore the fluorescence intensity at 307 nm was increased by 314%.

[Study on interaction between CT-DNA and cytochrome C using UV-vis spectroscopy and electrochemistry].

The interaction between CT-DNA immobilized on the positively charged nylon membrane and cytochrome C was studied using UV-Vis reflectance absorption spectroscopy and electrochemistry. It was found that cytchrome C can be adsorbed on the negative charged CT-DNA surface with the active positive charge area. Therefore, CT-DNA can promote the direct electrochemical reaction of cytochrome C.

[Effect of aggregation extent of microperoxidase-8 on its interaction with La3+].

Oxygen of two propionic acid groups of the heme group in an MP-8 molecule, leading to an increase in the non-planarity of the porphyrin ring of the heme group. The increasing extent in the non-planarity of the porphyrin ring of the heme group due to the interaction of La3+ and MP-8 molecule would be significantly decreased because NaCl could increase the aggregation extent of MP-8 molecules. Although methanol can reduce the aggregation extent of MP-8 molecules, it has little influence on the increasing extent in the non-planarity of the porphyrin ring of the heme group due to the interaction of La3+ and MP-8 molecule.

[Fluorescence spectroscopic study of interaction between Fe-protoporphyrin in myoglobin and Cu(II) ions].

In this paper, the interaction between Cu(II) ions and Fe-protoporphyrin in horse-heart myoglobin (FePP-Mb) was studied. As a result, some of the Fe(II) ions in FePP-Mb were found to be replaced by Cu(II) ions forming CuPP-Mb, by adding Cu(II) ions into the myoglobin solution. The interaction became stronger when adding more Cu(II) ions into the myoglobin solution. By studying the metal ions' interaction with myoglobin proteins as macromolecules and discussing the interaction mechanism, this work provides a theoretical basis for the further study of hazardous metal ions' interaction with the human body and its mechanism. The fluorescence spectroscopic method used in this study has higher sensitivity than the ordinary UV and CD methods.

MTX/LDHs hybrids synthesized from reverse microemulsions: particle control and bioassay study.

Reverse microemulsions have been used to control the growth of methotrexatum intercalated layered double hydroxides (MTX/LDHs) hybrids, and the influence of reaction temperature, water content (noted as ω) and MTX content (noted as R) on the properties of MTX/LDHs was systematically investigated. The synthesized hybrids were then characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and atomic force microscopy (AFM), etc. XRD and FTIR investigations manifest the successful intercalation of MTX anions into the interlayer of LDHs. The process of particle control has been explored emphatically, and it was found that temperature, water content, and addition of solutes can determine the structural evolution as well as the size of the "water pools" in the reverse microemulsions, while ω plays a critical role in the particle growth. Then in vitro release tests of all hybrids in pH 7.4 phosphate buffered saline (PBS) were explored, and the parabolic diffusion model simulate the release progress best, showing that the release process belongs to multi phase diffusion process via ion exchange. At last, the anticancer efficacy of all MTX/LDHs hybrids was also estimated by MTT assay with the human lung cancer (A549). It is found for the first time that the drug efficacy is closely associated with dispersion coefficient (noted as ϵ).

Arginine-assisted synthesis and catalytic properties of single-crystalline palladium tetrapods.

Noble metallic nanocrystals (NMNCs) with highly branched morphologies are an exciting new class of nanomaterials because of their great potential application in catalysis, sensing, optics, and electronics originating from their unique structures. Herein, we report a facile water-based method to synthesize high-quality palladium (Pd) tetrapods with the assistance of arginine molecule, which is more economical and environmentally friendly than the previous reported carbon monoxide (CO)-assisted synthesis in the organic system. During the synthesis, arginine molecule plays an essential role in controlling the tetrapod-like morphology. The as-synthesized Pd tetrapods have a potential application in the formic acid (HCOOH)-induced reduction of highly toxic hexavalent chromium (Cr(VI)) owing to their improved catalytic performance for the HCOOH decomposition.

Hydrothermal synthesis of Pt-Ag alloy nano-octahedra and their enhanced electrocatalytic activity for the methanol oxidation reaction.

The high-quality Pt48Ag52 alloy nano-octahedra are synthesized via one-pot hydrothermal method. The catalytic growth of Ag(0) atoms on Pt nuclei and selective oxidative etching on the Ag(0) atoms contribute to the formation of alloy nano-octahedra. Pt48Ag52 alloy nano-octahedra show excellent electrocatalytic activity and durability for the methanol oxidation reaction (MOR).