Mechanistic investigation of electrocatalytic reductive amination at copper electrode.

Reductive amination has been widely used for manufacturing carbon-nitrogen-containing building blocks. Despite its versatility, the need for a chemical reductant or harmful hydrogen gas has limited its further utilization in modern chemical applications. Here, we report electrochemical reductive amination (ERA) to pursue sustainable synthetic routes. Faradaic efficiencies of about 83% are achieved using Cu metal electrodes. In-depth electrokinetic studies reveal the rate-determining step and overall reaction nature of ERA. Through the experiments using deuterated solvent and additional proton sources, we scrutinize the origin of protons during the ERA. Furthermore, CW-EPR analysis captures the radical intermediate species, formed during the catalytic cycle, advancing mechanistic understanding of ERA process.

Formation of a tris(catecholato) iron(III) complex with a nature-inspired cyclic peptoid ligand.

Siderophore-mimicking macrocyclic peptoids were synthesized. Peptoid 3 with intramolecular hydrogen bonds showed an optimally arranged primary coordination sphere leading to a stable catecholate-iron complex. The tris(catecholato) structure of 3-Fe(iii) was determined with UV-vis, fluorescence, and EPR spectroscopies and DFT calculations. The iron binding affinity was comparable to that of deferoxamine, with enhanced stability upon air exposure.

Advanced Electron Paramagnetic Resonance Studies of a Ternary Complex of Copper, Amyloid-ß, and a Chemical Regulator.

Although there has been extensive effort to develop chemical regulators, progress has been static, in part because of these regulators' unclear mechanisms. Here, we report using advanced electron paramagnetic resonance (EPR) spectroscopy to obtain the first molecular-level structural information regarding a ternary complex of CuII-amyloid-ß (Aß) with a chemical regulator that can specifically modulate Cu-induced Aß aggregation. Our advanced EPR spectroscopic results revealed that a chemical regulator (1) for CuII-Aß1-16 disrupted the coordination environment of CuII in Aß, resulting in the detachment of the primary amine at the N-terminal and a carbonyl group between Asp1 and Ala2 from the CuII center and the subsequent formation of a ternary complex, chemical regulator-CuII-Aß1-16. Therefore, our results demonstrate how a chemical regulator interacts with metal-Aß at the molecular level. These findings provide novel insight into working mechanisms and thereby contribute to the establishment of a rational design for chemical regulators of metal-Aß complexes.

IGFBP-3 plays an important role in senescence as an aging marker.

Aging study requires aging markers to measure the degree of aging process. The aging markers such as senescence associated-ß-galactosidase (SA-ß-gal), lipofuscin, telomere, p53 and p16 have been known in aging study until now. Therefore, we investigated the role of genes and proteins related to aging in young, senescent and H2O2-induced old cells to develop a novel aging marker involved in aging mechanism. After cellular aging was compared in young, senescent and H2O2-induced old cells using SA-ß-galactosidase staining assay, the expression level of genes and proteins in senescent and H2O2-induced old cells were compared and analyzed with those of young cells using RT-PCR, western blot and immunofluorescence staining. First of all, the senescent cells and the cells aged by H2O2 showed higher level of SA-ß-galactosidase staining than young cells. In particular, the expression level of IGFBP-3 was decreased in senescent and H2O2-induced old cells compared with young cells. Moreover, the senescent and H2O2-induced old cells showed higher expression levels of p-PI3K, Akt-1, p-mTOR, p-FoxO1 and FoxO1 than young cells. Furthermore, the expression levels of p300, Ac-p53, p53, p-p21 and p16 were significantly increased in senescent and H2O2-induced cells compared to young cells. However, the expression level of SIRT-1 was decreased in senescent and H2O2-induced old cells compared to young cells. In conclusion, IGFBP-3 up-regulates PI3K/Akt/mTOR signaling pathway and down-regulates autophagy during cell aging. These results suggest that IGFBP-3 could play a key role in aging study as an important aging marker.

Inhibitory effect of aminoethyl-chitooligosaccharides on invasion of human fibrosarcoma cells.

Chitooligosaccharides (COS) have been reported to show a variety of biological efficacies such as anti-bacterial activity, anti-tumor activity and immune activity. The purpose of this study is to investigate the inhibitory effect of aminoethyl-chitooligosaccharides (AE-COS) synthesized from COS that were substituted hydroxyl groups with aminoethyl group at C-6 position on cell invasion of human fibrosarcoma cells. First of all, the effect of AE-COS on cell viability was observed using MTT assay. The cytotoxicity of AE-COS was increased in a dose dependent manner. The inhibitory effects of AE-COS on the activity and expression level of MMP-2 and MMP-9 related to invasion of cancer cells were examined using gelatin zymography and western blot. It was found that AE-COS above 20µg/ml showed the inhibitory effect on the activity and expression of MMP-9. Furthermore, AE-COS at 20µg/ml reduced the expression level of p50, a part of NF-κB, compared with phorbol-12- myristate-13- acetate (PMA) group. The available data let us hypothesize that AE-COS could provide chemoprevention as an inhibitor against cell invasion associated with metastasis.