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1.
ACS Pharmacol Transl Sci ; 7(6): 1746-1757, 2024 Jun 14.
Artigo em Inglês | MEDLINE | ID: mdl-38898944

RESUMO

T cells play a crucial role in antitumor immune responses and the clearance of infected cells. They identify their targets through the binding of T-cell receptors (TCRs) to peptide-major histocompatibility complex (pMHC) molecules present in cancer cells, infected cells, and antigen-presenting cells. This interaction is often weak, requiring multimeric pMHC molecules to enhance the avidity for identifying antigen-specific T cells. Current exchangeable pMHC-I tetramerization methods may overlook TCRs recognizing less stable yet immunogenic peptides. In vivo applications targeting antigen-specific T cells demand the genetic synthesis of a pMHC fusion for each unique peptide antigen, which poses a significant challenge. To address these challenges, we developed a sortase and click chemistry-mediated approach for generating stable pMHC molecules. Leveraging sortase technology, we introduced an azide click-handle near the N-terminus of ß2m, proximal to the MHC-peptide-binding groove. Simultaneously, the peptide was engineered with a multi glycine linker and a C-terminal alkyne click-handle. Azide-alkyne click reactions efficiently immobilized the peptide onto the MHC molecule, providing a versatile and efficient method for pMHC generation. The resulting peptide-clicked-MHC specifically binds to its cognate TCR and remains stable for over 3 months at 4 °C in the absence of any additional free peptide. The stability of the pMHC and its affinity to cognate TCRs are influenced by the linker's nature and length. Multi glycine linkers outperform poly(ethylene glycol) (PEG) linkers in this regard. This technology expands the toolkit for identifying and targeting antigen-specific T cells, enhancing our understanding of cancer-specific immune responses, and has the potential to streamline the development of personalized immunotherapies.

2.
Int J Biol Macromol ; 255: 128313, 2024 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-37995783

RESUMO

Tyrosinase-mediated protein conjugation has recently drawn attention as a site-specific protein modification tool under mild conditions. However, the tyrosinases reported to date act only on extremely exposed tyrosine residues, which limits where the target tyrosine can be located. Herein, we report a tyrosinase from Streptomyces avermitilis (SaTYR), that exhibits a much higher activity against tyrosine residues on the protein surface than other tyrosinases. We determined the crystal structure of SaTYR and revealed that the enzyme has a relatively flat and shallow substrate-binding pocket to accommodate a protein substrate. We demonstrated SaTYR-mediated fluorescence dye tagging and PEGylation of a surface tyrosine residue that was unreacted by other tyrosinases with an approximately 95.2 % conjugation yield in 1 h. We also present a structural rationale that considers the steric hindrance from adjacent residues and surrounding structures along with the extent of solvent exposure of residues, as necessary when determining the optimal positions for introducing target tyrosine residues in SaTYR-mediated protein modification. The study demonstrated that the novel tyrosinase, SaTYR, extends the scope of tyrosinase-mediated protein modification, and we propose that site-specific tyrosine conjugation using SaTYR is a promising strategy for protein bioconjugation in various applications.


Assuntos
Monofenol Mono-Oxigenase , Streptomyces , Monofenol Mono-Oxigenase/metabolismo , Proteínas/metabolismo , Tirosina/química
3.
ACS Nano ; 17(20): 20473-20491, 2023 10 24.
Artigo em Inglês | MEDLINE | ID: mdl-37793020

RESUMO

When the skin is exposed to ultraviolet radiation (UV), it leads to the degradation of the extracellular matrix (ECM) and results in inflammation. Subsequently, melanocytes are triggered to induce tyrosinase-mediated melanin synthesis, protecting the skin. Here, we introduce a proactive approach to protect the skin from photodamage via the topical delivery of Streptomyces avermitilis-derived tyrosinase (SaTy) using single-walled carbon nanotube (SWNT). Utilizing a reverse electrodialysis (RED) battery, we facilitated the delivery of SaTy-SWNT complexes up to depths of approximately 300 µm, as analyzed by using confocal Raman microscopy. When applied to ex vivo porcine skin and in vivo albino mouse skin, SaTy-SWNT synthesized melanin, resulting in 4-fold greater UV/vis absorption at 475 nm than in mice without SaTy-SWNT. The synthesized melanin efficiently absorbed UV light and alleviated skin inflammation. In addition, the densification of dermal collagen, achieved through SaTy-mediated cross-linking, reduced photoinduced wrinkles by 66.3% in the affected area. Our findings suggest that SWNT-mediated topical protein delivery holds promise in tissue engineering applications.


Assuntos
Monofenol Mono-Oxigenase , Nanotubos de Carbono , Suínos , Animais , Camundongos , Monofenol Mono-Oxigenase/metabolismo , Raios Ultravioleta , Melaninas , Inflamação
4.
Curr Opin Biotechnol ; 80: 102914, 2023 04.
Artigo em Inglês | MEDLINE | ID: mdl-36857963

RESUMO

Polyphenols are bioactive molecules that are used in therapeutics. Polyphenol hydroxylation and glycosylation have been shown to increase their bioavailability, solubility, bioactivity, and stability for use in various applications. Ortho-hydroxylation of polyphenols using tyrosinase allows high selectivity and yield without requiring a cofactor, while meta- and para-hydroxylation of polyphenols are mediated by site-specific hydroxylases and cytochrome P450s, although these processes are somewhat rare. O-glycosylation of polyphenols proceeds further after hydroxylation. The O-glycosylation reaction typically requires nucleotide diphosphate (NDP) sugar. However, amylosucrase (AS) has emerged as a promising enzyme for polyphenol glycosylation in large-scale production without requiring NDP-sugar. Overall, this review describes recent findings on the enzymatic mechanisms, enzyme engineering, and applications of enzymatic reactions.


Assuntos
Sistema Enzimático do Citocromo P-450 , Polifenóis , Glicosilação , Hidroxilação , Carboidratos , Açúcares
5.
Des Monomers Polym ; 25(1): 245-253, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36017475

RESUMO

Carbon-based nanomaterials, such as carbon nanotubes, fullerenes, nanodiamonds, and graphene, have been investigated for various biomedical applications, including biological imaging, photothermal therapy, drug/gene delivery, cancer therapy, biosensors, and electrochemical sensors. Graphene oxide (GO) has unique physicochemical properties and can be used to restore conductivity through oxidation. In this study, we developed poly(N-isopropylacrylamide) (PNIPAM)-based nanogel systems containing GO for controlled in vitro drug delivery. The photothermal effects of the PNIPAM/GO- and PNIPAMAAM/GO-based nanogel systems were enhanced. The release of DOX from the PNIPAM/GO-based nanogel was achieved using the photothermal effect of near-infrared irradiation. Using a Cell Counting Kit-8 assay, the cytotoxicity of all conditions demonstrated that the PNIPAM composite-based nanogels were biocompatible with no significance.

6.
RSC Adv ; 12(27): 17434-17442, 2022 Jun 07.
Artigo em Inglês | MEDLINE | ID: mdl-35765459

RESUMO

Melanin nanoparticles (MNPs) used for biomedical applications are often synthesized via the chemical auto-oxidation of catecholic monomers such as dopamine and 3,4-dihydroxyphenylalanine (DOPA) under alkaline conditions. However, the synthetic method for the chemical synthesis of MNP (cMNP) is relatively straightforward and more robust to control their homogenous particle size and morphology than the corresponding enzymatic synthetic methods. In this study, we demonstrated that the simple enzymatic synthesis of MNPs (eMNPs) with homogenous and soluble (<20 nm diameter) properties is possible using dopamine and Burkholderia cepacia tyrosinase (BcTy) under acidic conditions (i.e., pH 3.0). BcTy was highly reactive under pH 5.0, where the natural and chemical oxidation of catechol is complex, and thus melanin was synthesized via the hydroxylation of phenolic substrates. The detailed chemical analysis and characterization of the physical properties of the eMNPs confirmed the higher preservation of the catechol and primary amine moieties in the monomer substrate such as dopamine under acidic conditions. The eMNPs showed enhanced antioxidant activity and conferred stickiness to the formed hydrogel compared to the chemical auto-oxidation method owing to the large number of hydroxyl groups remaining such as catechol and quinone moieties. Because of these advantages and characteristics, the synthesis of MNPs using BcTy under acidic conditions can open a new path for their biomedical applications.

7.
Front Bioeng Biotechnol ; 10: 830712, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35402392

RESUMO

Several regiospecific enantiomers of hydroxy-(S)-equol (HE) were enzymatically synthesized from daidzein and genistein using consecutive reduction (four daidzein-to-equol-converting reductases) and oxidation (4-hydroxyphenylacetate 3-monooxygenase, HpaBC). Despite the natural occurrence of several HEs, most of them had not been studied owing to the lack of their preparation methods. Herein, the one-pot synthesis pathway of 6-hydroxyequol (6HE) was developed using HpaBC (EcHpaB) from Escherichia coli and (S)-equol-producing E. coli, previously developed by our group. Based on docking analysis of the substrate or products, a potential active site and several key residues for substrate binding were predicted to interpret the (S)-equol hydroxylation regioselectivity of EcHpaB. Through investigating mutations on the key residues, the T292A variant was verified to display specific mono-ortho-hydroxylation activity at C6 without further 3'-hydroxylation. In the consecutive oxidoreductive bioconversion using T292A, 0.95 mM 6HE could be synthesized from 1 mM daidzein, while 5HE and 3'HE were also prepared from genistein and 3'-hydroxydaidzein (3'HD or 3'-ODI), respectively. In the following efficacy tests, 3'HE and 6HE showed about 30∼200-fold higher EC50 than (S)-equol in both ERα and ERß, and they did not have significant SERM efficacy except 6HE showing 10% lower ß/α ratio response than that of 17ß-estradiol. In DPPH radical scavenging assay, 3'HE showed the highest antioxidative activity among the examined isoflavone derivatives: more than 40% higher than the well-known 3'HD. In conclusion, we demonstrated that HEs could be produced efficiently and regioselectively through the one-pot bioconversion platform and evaluated estrogenic and antioxidative activities of each HE regio-isomer for the first time.

8.
Adv Sci (Weinh) ; 9(7): e2103503, 2022 03.
Artigo em Inglês | MEDLINE | ID: mdl-34989175

RESUMO

Tyrosinase-mediated melanin synthesis is an essential biological process that can protect skin from UV radiation and radical species. This work reports on in situ biosynthesis of artificial melanin in native skin using photoactivatable tyrosinase (PaTy). The I41Y mutant of Streptomyces avermitilis tyrosinase (SaTy) shows enzymatic activity comparable to that of wild-type SaTy. This Y41 is replaced with photocleavable o-nitrobenzyl tyrosine (ONBY) using the introduction of amber codon and ONBY-tRNA synthetase/tRNA pairs. The ONBY efficiently blocks the active site and tyrosinase activity is rapidly recovered by the photo-cleavage of ONBY. The activated PaTy successfully oxidizes L-tyrosine and tyramine-conjugated hyaluronic acid (HA_T) to synthesize melanin particles and hydrogel, respectively. To produce artificial melanin in living tissues, PaTy is encapsulated into lipid nanoparticles as an artificial melanosome. Using liposomes containing PaTy (PaTy_Lip), PaTy is transdermally delivered into ex vivo porcine skin and in vivo mouse skin tissues, thus achieving the in situ biosynthesis of artificial melanin for skin tissue protection under UV irradiation. The results of this study demonstrate that this biomimetic system can recapitulate the biosynthetic analogs of naturally occurring melanin. It should therefore be considered to be a promising strategy for producing protective biological molecules within living systems for tissue protection.


Assuntos
Melaninas , Nanopartículas , Animais , Lipossomos , Camundongos , Monofenol Mono-Oxigenase
9.
ACS Omega ; 6(43): 28848-28858, 2021 Nov 02.
Artigo em Inglês | MEDLINE | ID: mdl-34746577

RESUMO

Bio-based polyurethane (PU) has recently drawn our attention due to the increasing interest in sustainability and the risks involved with petroleum depletion. Herein, bio-based self-healing PU with a novel polyol, i.e., eugenol glycol dimer (EGD), was synthesized and characterized for the first time. EGD was designed to have pairs of primary, secondary, and aromatic alcohols, which all are able to be involved in urethane bond formation and to show self-healing and antioxidant effects. EGD was incorporated into a mixture of the prepolymer of polyol (tetramethylene ether glycol) and 4,4'-methylene diphenyl diisocyanate to synthesize PU. EGD-PU showed excellent self-healing properties (99.84%), and it maintained its high self-healing property (84.71%) even after three repeated tests. This dramatic self-healing was induced through transcarbamoylation by the pendant hydroxyl groups of EGD-PU. The excellent antioxidant effect of EGD-PU was confirmed by 2,2-diphenyl-1-picrylhydrazyl analysis. Eugenol-based EGD is a promising polyol chain extender that is required in the production of bio-based, self-healing, and recyclable polyurethane; therefore, EGD-PU can be applied to bio-based self-healable films or coating materials as a substitute for petroleum-based PU.

10.
Microorganisms ; 9(9)2021 Sep 02.
Artigo em Inglês | MEDLINE | ID: mdl-34576760

RESUMO

Tyrosinase is generally known as a melanin-forming enzyme, facilitating monooxygenation of phenols, oxidation of catechols into quinones, and finally generating biological melanin. As a homologous form of tyrosinase in plants, plant polyphenol oxidases perform the same oxidation reactions specifically toward plant polyphenols. Recent studies reported synthetic strategies for large scale preparation of hydroxylated plant polyphenols, using bacterial tyrosinases rather than plant polyphenol oxidase or other monooxygenases, by leveraging its robust monophenolase activity and broad substrate specificity. Herein, we report a novel synthesis of functional plant polyphenols, especially quercetin and myricetin from kaempferol, using screened bacterial tyrosinases. The critical bottleneck of the biocatalysis was identified as instability of the catechol and gallol under neutral and basic conditions. To overcome such instability of the products, the tyrosinase reaction proceeded under acidic conditions. Under mild acidic conditions supplemented with reducing agents, a bacterial tyrosinase from Bacillus megaterium (BmTy) displayed efficient consecutive two-step monophenolase activities producing quercetin and myricetin from kaempferol. Furthermore, the broad substrate specificity of BmTy toward diverse polyphenols enabled us to achieve the first biosynthesis of tricetin and 3'-hydroxyeriodictyol from apigenin and naringenin, respectively. These results suggest that microbial tyrosinase is a useful biocatalyst to prepare plant polyphenolic catechols and gallols with high productivity, which were hardly achieved by using other monooxygenases such as cytochrome P450s.

11.
Sci Adv ; 7(26)2021 06.
Artigo em Inglês | MEDLINE | ID: mdl-34162541

RESUMO

Pancreatic ß cell therapy for type 1 diabetes is limited by low cell survival rate owing to physical stress and aggressive host immune response. In this study, we demonstrate a multilayer hydrogel nanofilm caging strategy capable of protecting cells from high shear stress and reducing immune response by interfering cell-cell interaction. Hydrogel nanofilm is fabricated by monophenol-modified glycol chitosan and hyaluronic acid that cross-link each other to form a nanothin hydrogel film on the cell surface via tyrosinase-mediated reactions. Furthermore, hydrogel nanofilm formation was conducted on mouse ß cell spheroids for the islet transplantation application. The cytoprotective effect against physical stress and the immune protective effect were evaluated. Last, caged mouse ß cell spheroids were transplanted into the type 1 diabetes mouse model and successfully regulated its blood glucose level. Overall, our enzymatic cross-linking-based hydrogel nanofilm caging method will provide a new platform for clinical applications of cell-based therapies.


Assuntos
Diabetes Mellitus Tipo 1 , Células Secretoras de Insulina , Animais , Glicemia , Hidrogéis/farmacologia , Camundongos , Esferoides Celulares
12.
ACS Appl Bio Mater ; 4(12): 8377-8385, 2021 12 20.
Artigo em Inglês | MEDLINE | ID: mdl-35005927

RESUMO

Stimuli-responsive nanoparticles are favorable for improving the selective delivery and rational vocation that easily avoids the undesirable barriers or side effects, leading to a further improved therapeutic efficiency. Furthermore, multifunctional nanomaterials have been extensively developed as attractive candidates for theranostic reagents for cancer treatment. In this article, we developed reversibly pH-responsive gold nanoparticles (AuNPs) with an enhanced Raman scattering signal as well as an efficient photothermal effect and demonstrated their applications as a theranostic reagent for cancer treatment. Surfaces of these AuNPs were modified with mixed layers of Cy3-modified single-stranded DNA (ssDNA-Cy3) for Raman probing and a negative charge supply and cytochrome C (Cyt C) for pH-responsive charge inversion. This combination of pH-responsive ligands and Raman probes played an important role in inducing the assembly or disassembly of AuNPs corresponding to the neighboring pH, accompanied by an additional highly distinguished Raman signal intensity. An operative reversible response of the AuNPs to pH is endowed with the characteristic behavior of AuNPs with the cancerous cell's acidic microenvironment of low pH. The responsive aggregation of AuNPs in a lower pH medium provides highly amplified signals attributed to well-formed hot spots between the particle surfaces that deliver better Raman scattering signals. The acidic pH-responsive aggregation of the particles also provided efficient photothermal treatments using a long-wavelength laser light with the benefit of deeper penetration for cancer cells. In vitro experiments employing cancer cells and control normal cells well-demonstrated the specificity of the particles to cancer cells in terms of highly enhanced Raman imaging and therapeutic efficiency.


Assuntos
Nanopartículas Metálicas , Neoplasias , Ouro/farmacologia , Concentração de Íons de Hidrogênio , Nanopartículas Metálicas/uso terapêutico , Neoplasias/diagnóstico por imagem , Análise Espectral Raman/métodos , Microambiente Tumoral
13.
Adv Mater ; 32(38): e2002854, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32797695

RESUMO

Post-growth graphene transfer to a variety of host substrates for circuitry fabrication has been among the most popular subjects since its successful development via chemical vapor deposition in the past decade. Fast and reliable evaluation tools for its morphological characteristics are essential for the development of defect-free transfer protocols. The implementation of conventional techniques, such as Raman spectroscopy, atomic force microscopy (AFM), and transmission electron microscopy in production quality control at an industrial scale is difficult because they are limited to local areas, are time consuming, and their operation is complex. However, through a one-shot measurement within a few seconds, phase-shifting interferometry (PSI) successfully scans ≈1 mm2 of transferred graphene with a vertical resolution of ≈0.1 nm. This provides crucial morphological information, such as the surface roughness derived from polymer residues, the thickness of the graphene, and its adhesive strength with respect to the target substrates. Graphene samples transferred via four different methods are evaluated using PSI, Raman spectroscopy, and AFM. Although the thickness of the nanomaterials measured by PSI can be highly sensitive to their refractive indices, PSI is successfully demonstrated to be a powerful tool for investigating the morphological characteristics of the transferred graphene for industrial and research purposes.

14.
Biomaterials ; 242: 119905, 2020 Feb 26.
Artigo em Inglês | MEDLINE | ID: mdl-32145505

RESUMO

Epigallocatechin gallates (EGCGs), isolated from green tea, have intrinsic properties such as anti-oxidant, anti-inflammation, and radical scavenger effects. In this study, we report a tissue adhesive and anti-inflammatory hydrogel formed by high-affinity enzymatic crosslinking of polyphenolic EGCGs. A mixture of EGCG conjugated hyaluronic acids (HA_E) and tyramine conjugated hyaluronic acids (HA_T) was reacted with tyrosinase isolated from Streptomyces avermitillis (SA_Ty) to form that displayed fast enzyme kinetic to form a crosslinked adhesive hydrogel. A 1,2,3-trihydroxyphenyl group in EGCG displayed a high affinity to SA_Ty that allowed HA_E to be quickly oxidized and crosslinked with HA_T to form HA_T and HA_E mixed hydrogel (HA_TE). We then compared the HA_TE hydrogel with commercially available tissue adhesives, such as cyanoacrylate and fibrin glue. We report that the HA_TE exhibited the highest tissue adhesiveness both in wet and dry conditions. Furthermore, HA_TE successfully closed a skin wound and displayed insignificant host tissue responses. This demonstrates that polyphenol-incorporated anti-inflammatory hydrogel may provide a robust tissue adhesive platform for clinical applications.

15.
ACS Nano ; 14(1): 919-926, 2020 Jan 28.
Artigo em Inglês | MEDLINE | ID: mdl-31841304

RESUMO

The enhanced growth of Cu oxides underneath graphene grown on a Cu substrate has been of great interest to many groups. In this work, the strain and doping status of graphene, based on the gradual growth of Cu oxides from underneath, were systematically studied using time evolution Raman spectroscopy. The compressive strain to graphene, due to the thermal expansion coefficient difference between graphene and the Cu substrate, was almost released by the nonuniform Cu2O growth; however, slight tensile strain was exerted. This induced p-doping in the graphene with a carrier density up to 1.7 × 1013 cm-2 when it was exposed to air for up to 30 days. With longer exposure to ambient conditions (>1 year), we observed that graphene/Cu2O hybrid structures significantly slow down the oxidation compared to that using a bare Cu substrate. The thickness of the CuO layer on the bare Cu substrate was increased to approximately 270 nm. These findings were confirmed through white light interference measurements and scanning electron microscopy.

16.
Rev Sci Instrum ; 90(2): 025103, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30831768

RESUMO

A nuclear environment, including decommissioning activity contains various radioactive nuclides such as pure beta emitters. These radionuclides should be monitored to ensure radiological safety. In particular, beta radionuclides, such as 3H and 14C, can cause internal exposures and should be managed more strictly in terms of health physics. For beta radionuclides, the measurement is carried out in a laboratory through sampling rather than on-site because of the short range. This method is time consuming, laborious, and costly and can also generate secondary waste. In this study, a system for the in situ monitoring of beta radionuclides in water samples is proposed for nuclear facilities and decommissioned environments. A plastic scintillator with low sensitivity to gamma rays and good reactivity with beta radionuclides was used. The detection efficiency was increased by using a detection part, whereby the water sample is made to directly contact the scintillator by utilizing the characteristic of plastic scintillators (i.e., they do not react with water). A coincidence circuit was constructed by using multiple photomultiplier tubes (PMTs) and applied to gross beta activity measurements. The values obtained from a single PMT were used in the spectral analysis to determine the effect of each beta radionuclide. Beta radionuclides in water samples in the field can be monitored by using plastic scintillators and multiple PMTs.

17.
J Radiol Prot ; 39(2): 422-442, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-30703752

RESUMO

In heavy water reactors, radionuclides are generated, then removed and treated by ion exchange resin. The disposal cost of spent resin is expected to increase because of the saturation of the existing storage capacity. In this study, a spent resin treatment process using microwaves is proposed, and a radiological safety assessment and cost evaluation of the spent resin treatment process are performed. A dose assessment was conducted by using the established exposure scenarios and the RESRAD-Build software. A sensitivity analysis was conducted to identify the main contributory radionuclide of the dose according to each exposure pathway because a spent resin consists of various radionuclides. The main exposure pathway was identified, and sensitivity analysis was applied to the working time and radioactivity concentrations of 14C, 60Co and 137Cs to confirm their effect on the dose. Finally, an optimal shielding system for a safe work environment was proposed. The disposal cost of the spent resin is reduced by lowering its radioactivity level via a treatment process using microwaves. The treatment process can reduce the radioactivity level through the desorption of 14C and can also recycle the 14C nuclide. These characteristics have great economic advantages from the viewpoint of the entire nuclear energy cycle. Thus, this study evaluates the radiological safety of the spent resin treatment process for actual application in a heavy water reactor power plant.


Assuntos
Óxido de Deutério , Resinas de Troca Iônica , Reatores Nucleares , Exposição Ocupacional/análise , Resíduos Radioativos/análise , Custos e Análise de Custo , Humanos , Resíduos Radioativos/economia , Eliminação de Resíduos/economia
18.
ACS Nano ; 12(12): 12733-12740, 2018 Dec 26.
Artigo em Inglês | MEDLINE | ID: mdl-30516949

RESUMO

The metal/graphene interface has been one of the most important research topics with regard to charge screening, charge transfer, contact resistance, and solar cells. Chemical bond formation of metal and graphene can be deduced from the defect induced D-band and its second-order mode, 2D band, measured by Raman spectroscopy, as a simple and nondestructive method. However, a phonon mode located at ∼1350 cm-1, which is normally known as the defect-induced D-band, is intriguing for graphene deposited with noble metals (Ag, Au, and Cu). We observe anomalous K-point phonons in nonreactive noble metal/graphene heterostructures. The intensity ratio of the midfrequency mode at ∼1350 cm-1 over G-band (∼1590 cm-1) exhibits nonlinear but resonant behavior with the excitation laser wavelength, and more importantly, the phonon frequency-laser energy dispersion is ∼10-17 cm-1 eV-1, which is much less than the conventional range. These phonon modes of graphene at nonzero phonon wave vector (q ≠ 0) around K points are activated by localized surface plasmon resonance and not by the defects due to chemical bond formation of metal/graphene. This hypothesis is supported by density functional theory (DFT) calculations for noble metals and Cr along with the measured contact resistances.

19.
FEMS Microbiol Lett ; 365(19)2018 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-30184116

RESUMO

Soy isoflavones are naturally occurring phytochemicals, which are biotransformed into functional derivatives through oxidative and reductive metabolic pathways of diverse microorganisms. Such representative derivatives, ortho-dihydroxyisoflavones (ODIs) and equols, have attracted great attention for their versatile health benefits since they were found from soybean fermented foods and human intestinal fluids. Recently, scientists in food technology, nutrition and microbiology began to understand their correct biosynthetic pathways and nutraceutical values, and have attempted to produce the valuable bioactive compounds using microbial fermentation and whole-cell/enzyme-based biotransformation. Furthermore, artificial design of microbial catalysts and/or protein engineering of oxidoreductases were also conducted to enhance production efficiency and regioselectivity of products. This minireview summarizes and introduces the past year's studies and recent advances in notable production of ODIs and equols, and provides information on available microbial species and their catalytic performance with perspectives on industrial application.


Assuntos
Glycine max/química , Isoflavonas/metabolismo , Bactérias/metabolismo , Equol/química , Equol/metabolismo , Humanos , Hidroxilação , Isoflavonas/biossíntese , Isoflavonas/química , Oxirredução
20.
Health Phys ; 115(4): 422-431, 2018 10.
Artigo em Inglês | MEDLINE | ID: mdl-30148808

RESUMO

An on-site, rapid, measurement-based, radiation-distribution visualization system with radionuclide recognition was developed for quick decision making during a radiation emergency. After scanning of the area was complete, radionuclide-specific radiation-distribution contours were displayed in two and three dimensions on a map of the measurement area, in a few tens of seconds, by clicking once on an execution file, which was programmed using MathWorks' MATLAB software. The contours were fundamentally verified using Cs and Co standard sources. Radiation distribution in the measurement area was simultaneously displayed in the main office using code division multiple access. It was demonstrated that rapid decision making for public safety is possible through the prompt display of radiation distribution in a nuclear emergency environment. This can also be applied to establish an environmental restoration plan for decontamination and decommissioning of nuclear power plants.


Assuntos
Emergências , Monitoramento de Radiação/métodos , Proteção Radiológica/métodos , Liberação Nociva de Radioativos , Radioisótopos de Césio , Radioisótopos de Cobalto , Tomada de Decisões , Descontaminação , Planejamento em Desastres , Poluição Ambiental , Humanos , Centrais Nucleares , República da Coreia , Gestão da Segurança , Software
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