Quasireversible Process of Dopamine on Copper-Nickel Hydroxide Composite/Nitrogen Doped Graphene/Nafion Modified GCE and Its Electrochemical Application.

Cu-Ni(OH)2/N-GR/Nafion/GCE has been prepared by electrodeposition and activation with NaOH. The proposed modified GCE was studied by electrochemical methods. It is found that dopamine shows favorable redox cyclic voltammetric response on the proposed modified GCE with peak separation of 25 mV and large current compared with on single-component modified GCE. The kinetic of electrode process has also been investigated with rate constant of 6.618 × 10(-3) cm/s, which can be deduced to be a quasireversible or near-reversible process. The proposed method has been used for DA detection with linear range of 1.0 × 10(-7) mol/L to 4.6 × 10(-5) mol/L, and the detection limit is 3.3 × 10(-8) mol/L. The proposed method has favorable stability and reproducibility and has also been used to determine DA in simulated samples and DA injections with favorable recoveries of 98.4% to 102.6%.

[Non-compaction cardiomyopathy in a 5-generation Chinese family].

OBJECTIVE: Familial left ventricular noncompaction(LVNC) is quite rare. We screened for the presence of LVNC and related clinical characteristics in a 5-generation Chinese family. METHODS: Comprehensive medical history was obtained from 40 members in a 5-generation Chinese family. Systemic clinical investigations including echocardiography (UCG), routine and ambulatory electrocardiogram (ECG), X-rays were performed in 33 family members. Cardiovascular magnetic resonance image (MRI) was carried out in 2 family members. RESULTS: Sudden cardiac death (including 1 occurred while following-up) was reported in 7 family members (17.5%, 7/40). LVNC was diagnosed in 10 out of the 33 family members (30.3%) and heart enlargement was evidenced in 3, heart failure in 2, complete left branch conductive block in 3, serious sick sinus syndrome (SSS) treated with permanent pacemaker implantation in 1 and paroxysmal supraventricular tachycardia treated with radiofrequency ablation procedure in 1 out of these 10 LVNC patients. Primary pedigree analysis revealed that offspring from female patients were at the highest risk to be affected by LVNC (15/18, 83.3%) while LVNC was absent in offspring of male LVNC patients (0/8). Moreover, clinical heart failure symptoms and arrhythmias were more severe in female LVNC patients than in male LVNC patients. CONCLUSION: Primary familial investigation reveals the matrilineal inheritance of familial LVNC in this 5-generation Chinese family, further investigations are warranted to explore the potential mutations in the mitochondrial genome responsible for LVNC in this family.

Hydrogen peroxide biosensor based on the direct electrochemistry of myoglobin immobilized on silver nanoparticles doped carbon nanotubes film.

A novel H(2)O(2) biosensor has been fabricated based on the direct electrochemistry and electrocatalysis of myoglobin (Mb) immobilized on silver nanoparticles doped carbon nanotubes film with hybrid sol-gel techniques. A pair of redox peaks with peak separation of 160 mV and formal potential of -0.295V was observed at this composite film, corresponding to the direct electrochemistry of Mb. The heterogeneous rate constant was estimated to be 0.41s(-1). Under optimum conditions, the amperometric determination of H(2)O(2) was performed with a linear range of 2.0 x 10(-6)-1.2 x 10(-3)molL(-1) and a detection limit of 3.6 x 10(-7)mol/L (S/N=3). The Michealis-Menten constant was also estimated to be 1.62mmolL(-1). The proposed biosensor showed favorable reproducibility, stability, selectivity and accuracy, and has been used to determine H(2)O(2) in real samples with favorable recoveries.

The electrochemical behavior of p-benzenediol on a self-assembled monolayers Pt electrode modified with N-(2-mercapto-1,3,4-thiadiazol-5-yl)-N'-(4-substituted-arylacetyl) urea.

Two novel N-(2-mercapto-1,3,4-thiadiazol-5-yl)-N'-(4-substituted-arylacetyl) urea compounds have been synthesized, characterized by NMR and MS, and used as self-assembly reagents to form self-assembled monolayers (SAMs) on Pt electrodes. The modified electrodes were characterized by electrochemical methods. The electrochemical behavior of p-benzenediol at the SAMs electrodes was investigated. It was found that the electrochemical response to p-benzenediol is controlled by diffusion and can be electrocatalyzed to obtain more symmetrical redox peaks and higher voltammetric current response at the SAMs electrodes, with a peak separation of 80 mV. For p-benzenediol the process at the SAMs electrodes is quasi-reversible with a rate constant of 0.6742 s-1. The SAMs electrodes have been used to determine p-benzenediol by differential pulse voltammetry. The peak current was linear for concentrations of p-benzenediol in the range 1x10(-7)-5x10(-4) mol L-1 and the detection limit was 4.0x10(-8) mol L-1. The SAMs electrodes were used to determine p-benzenediol in real photographic developer and in a synthetic waste water sample; the standard addition recovery was in the range 96.6-100.4%.

The crystal structure of human IRE1 luminal domain reveals a conserved dimerization interface required for activation of the unfolded protein response.

The unfolded protein response (UPR) is an evolutionarily conserved mechanism by which all eukaryotic cells adapt to the accumulation of unfolded proteins in the endoplasmic reticulum (ER). Inositol-requiring kinase 1 (IRE1) and PKR-related ER kinase (PERK) are two type I transmembrane ER-localized protein kinase receptors that signal the UPR through a process that involves homodimerization and autophosphorylation. To elucidate the molecular basis of the ER transmembrane signaling event, we determined the x-ray crystal structure of the luminal domain of human IRE1alpha. The monomer of the luminal domain comprises a unique fold of a triangular assembly of beta-sheet clusters. Structural analysis identified an extensive dimerization interface stabilized by hydrogen bonds and hydrophobic interactions. Dimerization creates an MHC-like groove at the interface. However, because this groove is too narrow for peptide binding and the purified luminal domain forms high-affinity dimers in vitro, peptide binding to this groove is not required for dimerization. Consistent with our structural observations, mutations that disrupt the dimerization interface produced IRE1alpha molecules that failed to either dimerize or activate the UPR upon ER stress. In addition, mutations in a structurally homologous region within PERK also prevented dimerization. Our structural, biochemical, and functional studies in vivo altogether demonstrate that IRE1 and PERK have conserved a common molecular interface necessary and sufficient for dimerization and UPR signaling.

The unfolded protein response represses differentiation through the RPD3-SIN3 histone deacetylase.

In Saccharomyces cerevisiae, splicing of HAC1 mRNA is initiated in response to the accumulation of unfolded proteins in the endoplasmic reticulum by the transmembrane kinase-endoribonuclease Ire1p. Spliced Hac1p (Hac1ip) is a negative regulator of differentiation responses to nitrogen starvation, pseudohyphal growth, and meiosis. Here we show that the RPD3-SIN3 histone deacetylase complex (HDAC), its catalytic activity, recruitment of the HDAC to the promoters of early meiotic genes (EMGs) by Ume6p, and the Ume6p DNA-binding site URS1 in the promoters of EMGs are required for nitrogen-mediated negative regulation of EMGs and meiosis by Hac1ip. Co-immunoprecipitation experiments demonstrated that Hac1ip can interact with the HDAC in vivo. Systematic analysis of double deletion strains revealed that HAC1 is a peripheral component of the HDAC. In summary, nitrogen-induced synthesis of Hac1ip and association of Hac1ip with the HDAC are physiological events in the regulation of EMGs by nutrients. These data also define for the first time a gene class that is under negative control by the UPR, and provide the framework for a novel mechanism through which bZIP proteins repress transcription.

Structure and intermolecular interactions of the luminal dimerization domain of human IRE1alpha.

Accumulation of unfolded proteins in the lumen of the endoplasmic reticulum activates a signal transduction cascade that culminates in the transcriptional induction of genes encoding adaptive functions. One proximal sensor for this unfolded protein response is the protein kinase/endoribonuclease IRE1alpha. IRE1alpha is a type-I transmembrane glycoprotein for which the N-terminal luminal domain (NLD) senses the accumulation of unfolded proteins. Previously we demonstrated that the NLD forms a stable ligand-independent dimer linked by disulfide bridges. In this report we have identified the cysteine residues responsible for intermolecular disulfide bonding. However, this covalent interaction was not required for dimerization and/or signaling, suggesting that a cryptic dimer interface exists in the NLD that is independent of covalent disulfide interactions. Limited proteolysis of the NLD revealed characteristic fragments, all retaining the same N-terminal sequences as full-length NLD. Biochemical and functional studies using NLD truncation mutants indicated that the dimerization domain of the NLD is confined to the conserved motifs at the N-terminal regions where putative hydrophobic interactions exist. In addition, the peptide binding domain of the endoplasmic reticulum protein chaperone BiP interacted with the N-terminal region within the NLD. Our findings suggest that the NLD has at least two distinct types of interactions mediating dimerization and function in signaling, i.e. covalent interactions involving disulfide bond formation and hydrophobic interactions, with the hydrophobic interaction being the driving force for dimerization.

The unfolded protein response in nutrient sensing and differentiation.

Eukaryotic cells coordinate protein-folding reactions in the endoplasmic reticulum with gene expression in the nucleus and messenger RNA translation in the cytoplasm. As the rate of protein synthesis increases, protein folding can be compromised, so cells have evolved signal-transduction pathways that control transcription and translation -- the 'unfolded protein response'. Recent studies indicate that these pathways also coordinate rates of protein synthesis with nutrient and energy stores, and regulate cell differentiation to survive nutrient-limiting conditions or to produce large amounts of secreted products such as hormones, antibodies or growth factors.

The protein kinase/endoribonuclease IRE1alpha that signals the unfolded protein response has a luminal N-terminal ligand-independent dimerization domain.

In response to accumulation of unfolded proteins in the endoplasmic reticulum (ER), cells activate an intracellular signal transduction pathway called the unfolded protein response (UPR). IRE and PERK are the two type-I ER transmembrane protein kinase receptors that signal the UPR. The N-terminal luminal domains (NLDs) of IRE1 and PERK sense ER stress conditions by a common mechanism and transmit the signal to regulate the cytoplasmic domains of these receptors. To provide an experimental system amenable to detailed biochemical and structural analysis to elucidate the mechanism of ER-transmembrane signaling mechanism mediated by the NLD, we overexpressed the soluble luminal domain of human IRE1alpha in COS-1 cells by transient DNA transfection. Here we report the expression, purification, and characterization of the soluble NLD. The biological function of the NLD was confirmed by its ability to associate with itself and to interact with both the membrane-bound full-length IRE1alpha receptor and the ER chaperone BiP. Functional and spectral studies suggested that the highly conserved N-linked glycosylation site is not required for proper protein folding and self-association. Interestingly, we demonstrated that the NLD forms stable dimers linked by intermolecular disulfide bridges. Our data support that the luminal domain represents a novel ligand-independent dimerization domain.