MT Molecules Research Articles

Structural effects, corrosion inhibition mechanisms and timeliness of three tetrazole derivatives on copper in a 3.5wt.% NaCl solution

The structural effects, corrosion inhibition mechanisms and timeliness of 5-methyltetrazole (MT), 5-aminotetrazole (AT) and 5-mercapto-1-methyltetrazole (MMT) on copper in a 3.5 wt.% NaCl solution were studied by electrochemical experiments, surface characterizations and theoretical calculations. At the initial soaking stage, MT exhibited higher corrosion inhibition efficiency (99.65 %), which might stem from the electron donating effect and hydrophobic interaction of -CH3. While MMT exhibited lower corrosion inhibition efficiency (92.64 %), which might stem from the electron withdrawing effect and hydrophilicity of -SH. As the soaking time prolonged, the corrosion inhibition efficiencies of AT and MMT increased (99.49 % and 99.51 %). This might be because the N and S atoms of -NH2 and -SH could also provide lone pair electrons to coordinate with copper, especially S atom. As the soaking time was further prolonged, the formation of corrosion products weakened the interaction between N and S with copper, reducing the corrosion inhibition performance of AT and MMT. MT, AT and MMT molecules on Cu (111) surface can mainly undergo perpendicular adsorption, simultaneously accompanied by parallel adsorption.

Surface lithiophilicity modification with triazole to realize dendrite-free lithium metal anode

A large nucleation overpotential on most metal substrates can cause uneven nucleation of Li, causing inhomogeneous Li deposition, leading to tip effects and gradually evolve into dendrites and dead Li. Surface lithiophilicity modification is conducive to promoting Li nucleation, thus avoid the generation of dendrites and form uniform Li deposition. Herein, 3-mercapto-1,2,4-triazole (MT) is used to modify the surface of Cu foil to form lithiophilic modification layer decorated Cu electrode (MT/Cu). Due to the lone pair of electrons on N and S in the MT molecules, Li+ can be easily absorbed, thus realizing uniform and dendrite-free deposition, and improving cycling stability. After plating/stripping cycles for asymmetric cell, an average Coulombic efficiency up to 99.76 % can be achieved. When the Li-loaded composite anode (Li/MT/Cu) is matched with LiFePO4 cathode, the full cell possesses a capacity retention rate of 98.3 % after 200 cycles at 1 C, and the Coulombic efficiency throughout the process maintains over 99 %. This method of surface lithiophilicity modification is simple and effective, which can provide new ideas for the composition and modification of Li metal anodes.

Adsorption and heterogeneous Fenton degradation of 17α-methyltestosterone on nano Fe3O4/MWCNTs in aqueous solution

A novel catalyst, inverse-spinel ferroferric oxide nanoparticles decorated multiwalled carbon nanotubes (Fe3O4/MWCNTs) was successfully prepared, and applied for the adsorption and degradation of trace artificial androgen 17α-methyltestosterone (MT) in the presence of H2O2. The regular growth of ferroferric oxide crystal on multiwalled carbon nanotubes was achieved by in situ oxidation of Fe2+ in hot alkaline solution. The catalyst was characterized by BET, XRD, TEM, XPS and Raman spectroscopy. The effects of initial pH, catalyst loading, oxidant concentration and iron leaching on the degradation of MT were investigated. The Fe3O4/MWCNTs showed higher ability of adsorption and degradation efficiency of MT than bare Fe3O4 in the batch degradation experiment. The degradation efficiencies increased with the initial pH decreasing in the wide pH range of 8.0–3.5. Further, the catalyst showed stable catalytic activity, fairly good mechanic stability and convenient recycling. Negligible iron leaching showed the reused Fe3O4/MWCNTs withstood the oxidation. The enhanced degradation efficiency of Fe3O4/MWCNTs may relate to the enrichment of trace MT molecules by MWCNTs in the vicinities of active sites.

Studies of interaction of tumor suppressor p53 with apo-MT using surface plasmon resonance

The interaction of tumor suppressor p53 with apo-metallothionein (apo-MT) has been carried out using a flow injection-surface plasmon resonance (FI-SPR) instrument. MT was first tethered onto the carboxymethylated dextran film. Via incorporation of glycine-HCl (pH 2) to remove the sequestrated metal ions inherent in MT molecules, a more extended and open structure of apo-MT was formed. Substantial SPR angle shift corresponding to the interaction of wild-type p53 with apo-MT was observed. The interaction was originated from the binding between the free sulfhydryl groups of apo-MT and Zn(2+) of p53 with the binding constant of 1.4 x 10(8) M(-1). The specific binding of p53 to consensus double-stranded DNA was hindered after metal chelation from p53 by apo-MT. Furthermore, inhibition of the interaction between p53 and apo-MT imposed by p53/DNA complex was observed. The fluorescence measurements also revealed the binding of p53 to apo-MT, being consistent with the SPR results. Thus, SPR could potentially serve as an attractive technique for monitoring p53 conformational change and transcriptional activity regulated by the MT/apo-MT couple.

Voltammetric Studies of Cadmium‐ and Zinc‐Containing Metallothioneins at Nafion‐Coated Mercury Thin Film Electrodes

AbstractVoltammetric studies of rabbit liver metallothioneins (MTs, containing both Zn and Cd ions) and Zn7‐MT were carried out at Nafion‐coated mercury film electrodes (NCMFEs). The accumulation of MT molecules into the NCMFEs enhances the voltammetric signals and the electrostatic interaction between the Nafion membrane and MT facilitates facile electron transfer reactions. Two well‐defined redox waves, with reduction potential (Epc) values at −0.740 and −1.173 V, respectively, were observed. The peak at Epc =−0.740 V is attributable to the reduction of the Cd‐MT complex, whereas that at Epc=−1.173 V was assigned to the reduction of the Zn‐MT complex. Zn7‐MT exhibits only one redox wave with Epc=−1.198 V. The NCMFE was found to be more advantageous than thin mercury film electrode (MFE), because the pristine metal ions in MTs (e.g., Cd2+ and/or Zn2+) are not significantly replaced by Hg2+. The NCMFE is also complementary to Nafion‐coated bismuth film electrode in that it has a greater hydrogen overpotential, which allows the reduction of the Zn‐MT complex to be clearly observed. Moreover, intermetallic compound formation between Cd and Zn appears to be less serious at NCMFEs. Consequently, the amounts of Cd and Zn deposited into the electrode upon the reduction reactions can be quantified more accurately.

Patterned self-assembly of magnetic biomolecules on semiconductor substrates

The paper reports on the methods of preparing and patterning magnetic metallothionein (Mn,Cd-MT-2) molecules on semiconductor surfaces. The molecules are placed into nanopores prepared on silicon (0 0 1) substrates. We observe the self-assembled growth of those MT molecules on the patterned Si surface. Dense arrays of molecular rods are demonstrated on templates with small pores and pitch sizes. Then the structures of the self-assembled protein are studied by atomic force microscopy (AFM) and magnetic force microscopy (MFM). Our measurements indicate that molecular self-assembly has a magnetic dipole moment which interacts with the applied magnetic field.

Self-assembled molecular magnets on patterned silicon substrates: Bridging bio-molecules with nanoelectronics

The paper reports the methods of preparing molecular magnets and patterning of the molecules on a semiconductor surface. A highly magnetically aligned metallothionein containing Mn and Cd (Mn,Cd-MT-2) is first synthesized, and the molecules are then placed into nanopores prepared on silicon (0 0 1) surfaces using electron beam lithography and reactive ion-etching techniques. We have observed the self-assemble growth of the MT molecules on the patterned Si surface such that the MT molecules have grown into rod or ring type three-dimensional nanostructures, depending on the patterned nanostructures on the surface. We also provide scanning electron microscopy, atomic force microscopy, and magnetic force microscope studies of the molecular nanostructures. This engineered molecule shows molecular magnetization and is biocompatible with conventional semiconductors. These features make Mn,Cd-MT-2 a good candidate for biological applications and sensing sources of new nanodevices. Using molecular self-assembly and topographical patterning of the semiconductor substrate, we can close the gap between bio-molecules and nanoelectronics built into the semiconductor chip.

Studies of metal ion binding by apo-metallothioneins attached onto preformed self-assembled monolayers using a highly sensitive surface plasmon resonance spectrometer

The use of a flow injection surface plasmon resonance (FI-SPR) spectrometer equipped with a bicell detector or a position-sensitive device for determining coordination of heavy metal ions (Cd 2+ and Hg 2+) by surface-confined apo-metallothionein (apo-MT) molecules is described. To facilitate the formation of a compact MT adsorbate layer with a uniform surface orientation, MT molecules were attached onto a preformed alkanethiol self-assembled monolayer. The method resorts to the generation of apo-MT at the surface by treating the MT-covered sensor chip with glycine–HCl and the measurement of the apo-MT conformation changes upon metal ion incorporation. Domain-specific metal ion binding processes by the apo-MT molecules were observed. Competitive replacement of one metal ion by another can be monitored in real time by FI-SPR. The tandem use of an immobilization scheme for forming a sub-monolayer of MT molecules at the sensor surface and the highly sensitive FI-SPR instrument affords a low concentration detection level. The detection level for Cd 2+ (0.1 μM or 15 ppb) compares favorably with similar studies and the methodology complements to other well-established sensitive analytical techniques. The extent of metal incorporation by apo-MT molecules was also determined.

Guided three-dimensional molecular self-assembly on silicon substrates

We demonstrate three-dimensional (3D) self-assemble growth of the metallothionein (Mn,Cd-MT-2) molecules on patterned semiconductor substrates. The MT molecules deposited on the patterned substrates were found to grow into 3D rod or ring-type nanostructures, depending on the shape of patterned nanostructures on the substrates. Dense arrays of 3D molecular nanorods or rings with an area density close to 1010cm−2 were demonstrated with a pore size of 20nm and a pitch size of 100nm. Those engineered molecular nanostructures provide an excellent opportunity for biological applications, sensing sources of nanodevices, biochemical reactions on surfaces, and even single molecule studies.

New organic metal containing mixed donors: (ET)(MT)2(BF 4)(THF)

Single crystals of new organic metal, (ET)(MT) 2 (BF 4 )(THF), were electrochemically grown in an H-type cell. In the X-ray crystal structure, ETand MT donors together form a layer in ac-plane, which is stacking along b-axis alternatively with the layer formed by BF - 4 and THE Within the mixed-donor layer MT molecules (stacking along a-axis) and ET molecules (arranged side-by-side) are almost perpendicular each other with their long in-plane molecular axes being along b-axis. ETand MT molecules within a layer are closely connected by short S...S interactions (3.226 ∼ 3.694 A) and achieve the 2D S...S network. Band electronic structure calculations on this complex show that it is a 2D metal at r.t. Bands are more dispersive along the a-axis which means that electrical conductivity is possibly better along this direction. However the Fermi surface nesting which arises in many low dimensional metals, was not found.

New organic metal containing mixed donors: (ET)(MT) 2 (BF 4 )(THF)

Single crystals of new organic metal, (ET)(MT) 2 (BF 4 )(THF), were electrochemically grown in an H-type cell. In the X-ray crystal structure, ET and MT donors together form a layer in ac-plane, which is stacking along b-axis alternatively with the layer formed by BF 4 − and THF. Within the mixed-donor layer, MT molecules (stacking along a-axis) and ET molecules (arranged side-by-side) are almost perpendicular each other with their long in-plane molecular axes being along b-axis. ET and MT molecules within a layer are closely connected by short S…S interactions (3.226∼3.694 Å) and achieve the 2D S…S network. Band electronic structure calculations on this complex show that it is a 2D metal at r.t. Bands are more dispersive along the a-axis which means that electrical conductivity is possibly better along this direction. However, the Fermi surface nesting which arises in many low dimensional metals, was not found.

α-Domain of human metallothionein IA can bind to metals in transgenic tobacco plants

With a view to exploring its use as a metal-binding factor in transgenic plants we prepared the alpha-domain of metallothionein by reconstitution of rabbit apometallothionein and proteolysis of MT-1 and MT-2 with subtilisin. The isolated alpha-domains were characterised by UV and CD spectroscopy Double-Stranded. DNA encoding the alpha-domain (106 bp) of the human MT-IA was constructed from chemically synthesized oligomers by repair synthesis and enzymatic ligation, cloned into pUC19 and sequenced. A expression construct containing the cloned alpha-domain was introduced into tobacco cells on a disarmed Agrobacterium tumefaciens Ti-plasmid. Transformed tobacco cells were selected and regenerated on medium containing cadmium and kanamycin. The growth of roots and shoots of transformants was unaffected by up to 100 microM cadmium, whereas control plants showed severe inhibition of root and shoot growth, and chlorosis of leaves on medium containing only 10 microM cadmium. Southern hybridization confirmed the presence of the transgene in the transformed plant tissues. The concentration of human alpha-domain peptides in transgenic tobacco leaves was determined by the Cd/hemoglobin saturation assay and polarography using the rabbit alpha-domain as standard. The results indicate that the alpha-domain, one of two domains in MT molecules, is not only stable in vitro, but is also expressed efficiently and functions independently in transgenic plant cells.

An improved method for isolation and identification of Zn-metallothionein from cadmium-induced rat liver.

Zn-metallothioneins (MT-1 and MT-2) were isolated and purified from Wistar rat liver induced by subcutaneous injection with cadmium chloride over a short time. Instead of Sephadex G-50 and DEAE Sephadex A-50, new chromatographic media produced by Pharmacia, Sephacryl S-200, S-100 and DEAE Sepharose Fast Flow were used in the purification of metallothioneins. The time required for purification with the new method was only 1/3 that required with the usual method and had the same purification effect and rate of recovery. The number of mercapto groups measured with modified Ellman's reagent and cysteine as standard is 20 in MT molecules. Zn and Cd concentrations in each fraction were measured by single sweep polarography rather than atomic absorption spectrophotometry. MT-1 and MT-2 contained 6 gram atoms of zinc, but no cadmium. Purified MT-1 and MT-2 were shown by high performance liquid chromatographic analysis to be highly homogeneous and had an amino acid composition similar to that of Cd-MT.

The adsorption of a new derivative of mercaptothiazole on copper studied by XPS and AES

XPS (X-ray photoemission spectroscopy) and AES (Auger electron spectroscopy) have been used to study the adsorption of a new synthetic flotation collector, a derivative of mercaptothiazole (C 6H 6NS 2K), on a polycrystalline copper surface in basic solution at various concentrations in order to characterize the nature of the surface film. The XPS Cu 2p, 5 2p, N 1s edges and CuL 3M 4.5M 4.5 Auger line were detected. On interaction with the ligands copper is partially oxidized to Cu(I) indicating that the MT molecules interact directly with the copper atoms present on the surface. There is no evidence of any complex between copper and MT formed in the solution and precipitate. The analysis of CuL 3M 4.5M 4.5 Auger spectra suggests that a chemical bond is formed between the collector and copper. There is a visible interaction between the ligands and the copper substrate, the effect of which is to prevent the oxidation of the metal even at very low concentration. The 2×10 −4 M ligand concentration would appear to be the most efficient for ensuring the best corrosion inhibition under the experimental conditions adopted. From 7×10 −4 M to 1×10 −2 M the shape of the Auger line remains stable, showing that the CuMT component makes a relevant surface contribution. The chemical bond occurring between copper and the collectors does not change when the solution concentration is varied: in fact, there is no alteration in either the shape or the binding energy of the XPS signals from the S 2p and N 1s edges.

Both DR and MT class II HLA molecules may restrict proliferative T-lymphocyte responses to antigen.

Antigen-primed T-cell blasts may be separated from alloreactive T cells on Percoll gradients. By means of this method, HLA restriction of antigen-specific proliferative T-cell responses may be studied, using allogeneic antigen-presenting cells carrying foreign D/DR antigens. The reported data confirm that the D/DR molecules as such are major restriction elements in the T-cell response to herpes simplex virus (HSV) and purified protein derivative (PPD). However, evidence is presented that other Class II HLA molecules, the MT molecules, may also function as restriction elements for the HSV response.