A novel rice genomic sequence encoding coding segments homologous to other metallothionein-like genes was isolated from Oryza sativa genomic library. This sequence, hereby designated as rgMT (rice genomic metallothionein-like gene), consists of two exons and one intron. From the coding sequence, it is predicted that rgMT encodes one protein of 74 amino acids. Differential expression of rgMT in rice plants was observed as mature transcripts were more abundant in roots than in leaves and sheaths. Under different stress conditions, such as excess heavy metals and heat shock, expression of rgMT was significantly elevated. This was especially noticeable with 250 microM CuCl2 for 16 h, 40 degrees C heat for 2 h and 0.06% DMSO for 1 h. Under sucrose starvation, rgMT transcripts also increased with time up to 72 h. During recovery from sucrose starvation, the transcripts declined slightly within 12 h of recovery. rgMT transcripts were also seen to have increased expression in senescent leaves. These results support the notion that rgMT is a stress-inducible gene in rice heretofore unreported.

A series of frozen and vibratome coronal sections of the rat brain were examined by immunocytochemistry for the presence of a cysteine-rich metal binding protein, metallothionein (MT). Astrocytes throughout the brain and brainstem stained positively for MT; neurons and oligodendroglia were unstained. Ependymal cells and tanycyte processes in the hypothalamus were also immunoreactive, along with a narrow zone of immunopositivity along the margins of the area postrema. Gomori-positive astrocytes in the hypothalamus, identifiable by toluidine blue staining, metal-containing cytoplasmic granules, represented a subset of MT-positive astrocytes that may be involved in reactions to blood-borne metal compounds that penetrate into circumventricular organs of the brain.

A type 2 metallothionein-like gene from rice, OsMT-2 (Oryza sativa metallothionein-like gene-2), was isolated in its cDNA form and sequenced. By northern analyses OsMT-2 expression was shown to be induced under stress by sucrose starvation, heat shock and, to a lesser extent, abscisic acid, but not excess metals, including copper. Its response to sucrose starvation was transient and different from OsMT-1, a type 1 metallothionein-like gene of rice inducible by copper. These results suggest that while OsMT-2 is also involved in cellular response to stress, its function may be complementary to that of OsMT-1.

Recombinant wild-type and mutant Chinese hamster metallothioneins, purified from the yeast Saccharomyces cerevisiae, were analyzed for their chemical and spectroscopic properties. The mutant proteins contain cysteine to tyrosine replacements at positions 13 and 50. Wild-type and mutant metallothioneins, in their cadmium-bound forms, all showed characteristic ultraviolet absorption spectra with shoulders at 245-250 nm due to cadmium-thiolate charge transfer. Upon acidification, these absorption shoulders were abolished. In all cases, two distinct titrations were seen, presumably corresponding to two independent cadmium binding domains in each of the proteins. Analysis of domain structures was performed both with the sulfhydryl reagent 5,5'-dithiobis(2-nitrobenzoic acid) and with the protease subtilisin. These studies indicated that both mutations affected domain structure by disrupting the normally tight protein clusters. Circular dichroism spectra obtained for wild-type and mutant metallothioneins showed unique structural rearrangements in mutants containing a cysteine-50 to tyrosine alteration. These data, along with previously obtained 113Cd NMR data, were incorporated into a model which can account for the in vivo and in vitro properties of these mutant proteins.

The quantum-dot light-emitting diodes (QLEDs) that emit near-infrared (NIR) light may be important optoelectronic synaptic devices for the realization of artificial neural networks with complete optoelectronic integration. To improve the performance of NIR QLEDs, we take advantage of their low-energy light emission to explore the use of poly(3-hexylthiophene) (P3HT) as the hole transport layer (HTL). P3HT has one of the highest hole mobilities among organic semiconductors and essentially does not absorb NIR light. The usage of P3HT as the HTL indeed significantly mitigates the imbalance of carrier injection in NIR QLEDs. With the additional incorporation of an interlayer of poly [9,9-bis(3ʹ-(N,N-dimethylamino)propyl)-2,7-flourene]alt-2,7-(9,9-dioctylfluorene)], P3HT obviously improves the performance of NIR QLEDs. As electroluminescent synaptic devices, these NIR QLEDs exhibit important synaptic functionalities such as short-and long-term plasticity, and may be employed for image recognition.

BackgroundNon-alcoholic fatty liver disease (NAFLD) is a chronic disease that causes excessive hepatic lipid accumulation. Reducing hepatic lipid deposition is a key issue in treatment and inhibition of NAFLD evolution. Silymarin is a potent hepatoprotective agent; however, it has low oral bioavailability due to its poor aqueous solubility and low membrane permeability. Unfortunately, few studies have addressed the development of convenient oral nanocarriers that can efficiently deliver silymarin to the liver and enhance its lipid-lowering effect. We designed silymarin-loaded lipid polymer hybrid nanoparticles containing chitosan (CS-LPNs) to improve silymarin bioavailability and evaluated their lipid-lowering effect in adiponutrin/patatin-like phospholipase-3 I148M transgenic mice, an NAFLD model.ResultsCompared to chitosan-free nanoparticles, CS-LPNs showed 1.92-fold higher uptake by fatty liver cells. Additionally, CS-LPNs significantly reduced TG levels in fatty liver cells in an in vitro lipid deposition assay, suggesting their potential lipid-lowering effects. The oral bioavailability of silymarin from CS-LPNs was 14.38-fold higher than that from suspensions in rats. Moreover, compared with chitosan-free nanoparticles, CS-LPNs effectively reduced blood lipid levels (TG), improved liver function (AST and ALT), and reduced lipid accumulation in the livers of mice in vivo. Reduced macrovesicular steatosis in pathological tissue after CS-LPN treatment indicated their protective effect against liver steatosis in NAFLD.ConclusionsCS-LPNs enhanced oral delivery of silymarin and exhibited a desirable lipid-lowering effect in a mouse model. These findings suggest that CS-LPNs may be a promising oral nanocarrier for NAFLD therapeutics.Electronic supplementary materialThe online version of this article (10.1186/s12951-018-0391-9) contains supplementary material, which is available to authorized users.

A set of mutant coding sequences for Chinese hamster metallothionein (MT) 2 in which codons for individual cysteines were replaced by serine codons was cloned into a yeast expression system. MT gene expression was placed under control of a constitutive promoter on a multicopy Escherichia coli-yeast shuttle vector. MTs were expressed in a metalsensitive host that lacks the endogenous MT gene. The expressed MTs conferred increased metal resistance to the yeast host. A sensitive assay for cadmium resistance was developed in which population doubling times were monitored in rich liquid medium supplemented with a sublethal dose of CdCl2. Measurements on mutants with single cysteine replacements at 12 positions revealed' two mutant classes. One class (Cys --Ser at position 5, 13, 19, or 33) did not affect the detoxification capacity of MT. A second class (Cys --Ser at position 7, 15, 26, 29, 44, 48, 50, or 60) conferred to the host markedly less resistance to cadmium. Bridging cysteines were more critical to cadmium resistance. AM five bridging cysteine mutants studied (at positions 7, 15, 44, 50, and 60) conferred lower cadmium resistance. In contrast, mutation of four out of seven terminal cysteines (at position 5, 13, 19, or 33) was shown to be inconsequential. Mutations tend to be more detrimental in the a domain than in the (I domain in conveying cadmium resistance, suggesting that the contribution of individual cysteine to the detoxification function of MT is site specific.Metallothioneins (MTs) are metal binding proteins present in all eukaryotic species examined to date (for reviews, see refs. 1 and 2). Mammalian MTs share extensive primary sequence homology, including the invariant positions of 20 cysteine residues out of 61 amino acids. Eight lysine residues, as well as serine or threonine residues, as part of the sequence Cys-(Ser,Thr)-Cys, are also highly conserved (3). The significance of the conservation of these amino acids to the structure and function of MT is a subject of considerable interest.The role of cysteine in MT is to bind metal atoms through coordinate covalent bonds. The sulfhydryl group of cysteine is well suited for this role. Free cysteine has a high affinity for a variety'of transition metal atoms (4, 5). All MT cysteine residues participate in metal binding; none occurs as intramolecular or intermolecular disulfides under native conditions.A prominent structural feature of MT is the arrangement of bound metal atoms through thiolate-metal coordination into two distinct clusters, termed the a and if domains (6). The ( domain consists of amino acids 1-30 and contains 9 cysteine residues that bind to three atoms of zinc or cadmium. The a domain consists of amino acids 31-61 and contains 11 cysteine' residues that bind four atoms of zinc or cadmium (7). Two lysine residues at positions 30 and 31 mark the interdomain boundary.The function ofMT probably depends on the metal it binds. Thus, although the probable function of MT in normal metal metabolism is the storage and mobilization...

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