1,755 research outputs found
Graphene quantum dots with covalently bonded gold nanoparticles winning the battle against methicillin-resistant Staphylococcus aureus under blue light
No full textOver the last decades, bacterial resistance has become one of the emerging health threats. Particularly dangerous are bacterial strains resistant to various antibacterial drugs. Herein, we modified graphene quantum dots (GQDs) to produce efficient photo-induced antibacterial agents. GQDs were modified with (a) ethylene-diamine (EDA), (b) with EDA and gold nanoparticles (AuNPs), and (c) 3-amino-1,2,4-triazole (TA) using carbodiimide coupling. Photo-induced antibacterial activity of modified GQDs was tested against 8 bacterial strains. Treatment with modified GQDs and blue light (wavelength of 470 nm) resulted in remarkable antibacterial activity with minimal inhibitory concentrations (MIC) of 7.81 mu g mL(-1) for K. pneumoniae and S. aureus and 3.9 mu g mL(-1) against MRSA and E. faecalis. Planar organization of GQDs functionalized with AuNPs allowed direct access of molecular oxygen to AuNPs leading to more efficient O-1(2) production as well as the O-1(2) production from excited GQDs. Thus, GQDs functionalized with AuNPs showed outstanding efficiency in the battle against several bacterial strains, particularly those that lead to nosocomial infections
Enhancing photoluminescence of graphene quantum dots by thermal annealing of the graphite precursor
No full textDifferent approaches for enhancement of the graphene quantum dots (GQDs) photoluminescence have been developed lately. We report modified electrochemical procedure for GQDs synthesis. Graphitic rods were thermal annealing at 1700 °C in vacuum and used for electrochemical quantum dots synthesis. We found that the modified GQDs (GQDs-1700) consist of two while in the structure of pristine (p-GQDs) three graphene layers are measured. The main structural difference between GQDs is the increased structural disorder, caused by a higher amount of the oxygen containing functional groups in the structure of GQDs-1700. The photoluminescence of GQDs-1700 is 4 times more intense, red shifted and with doubled Quantum Yield compared to p-GQDs. In addition, the changes in electrochemical behavior of GQDs are observed: the higher capacitance was noticed if GQDs posses more reducible functional groups, such as peroxyl, aldehyde and epoxy groups while increase in keto functional groups leads to the lower capacitance
Fully Automated Electrically Controlled Tunable Broadband Interferometric Dielectric Spectroscopy for Aqueous Solutions
No full textsponsorship: Manuscript received May 16, 2021; accepted June 22, 2021. This work was supported in part by KU Leuven Internal Funding (C2 project mu 2BIO) and in part by the Flemish Hercules. The work of Meng Zhang was supported by the Scholarship provided by the Chinese Scholarship Council. (Corresponding author: Xiue Bao.) (KU Leuven Internal Fund, Flemish Hercules, Chinese Scholarship Council)status: Publishe
CRYSTALLIZATION AND PRELIMINARY X-RAY ANALYSIS OF THE BETA-ISOFORM OF GLUTAMATE DECARBOXYLASE FROM ESCHERICHIA COLI.
No full textGlutamate decarboxylase (GAD) is a vitamin B6 enzyme which catalyzes the α-decarboxylation of l-glutamate to γ-aminobutyric acid (GABA). Escherichia coli cells coexpress two highly homologous enzyme isoforms, GADα and GADβ. Well diffracting crystals of GADβ were obtained by taking advantage of the possibility of expressing each isoform separately. They belong to space group P31 or P32 with the unit-cell dimensions a = b = 115.6 and c = 206.6 Å and contain one GAD hexamer in the asymmetric unit. High-resolution synchrotron data were collected at 100 K for the native protein and a potential heavy-atom derivative
Crystal structure of a hypoallergenic isoform of the major birch pollen allergen Bet v 1 and its biological function
No full textCrystallization and preliminary X-ray analysis of gamma-aminobutyric acid transaminase
No full textgamma-Aminobutyric acid transaminase from pig liver, an alpha 2 dimeric enzyme of Mr 110,100, has been crystallized by the vapour diffusion method with polyethylene glycol as precipitant. The crystals are monoclinic, space group P2(1), unit cell dimensions a = 82.1 A, b = 230.0 A, c = 70.3 A, beta = 123.9 degrees and diffract to 2.5 A resolution. There are two dimers per asymmetric unit
Novel 1,3,4-thiadiazole conjugates derived from protocatechuic acid: Synthesis, antioxidant activity, and computational and electrochemical studies
No full textA series of 15 novel 1,3,4-thiadiazole amide derivatives containing a protocatechuic acid moiety were synthesized and structurally characterized. In addition, the corresponding imino (4) and amino (5) analogues of a phenyl-substituted 1,3,4-thiadiazole amide derivative 3a were prepared to compare the effects of the structural changes on the radical-scavenging activity. The obtained compounds were examined for their antioxidative potential by 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assays. In addition, selected compounds were studied by density functional theory (DFT) and cyclic voltammetry experiments. The tested compounds showed high potential to scavenging DPPH radical and ABTS radical cation compared with the referent antioxidants ascorbic acid and nordihydroguaiaretic acid (NDGA). On the basis of the calculated thermodynamic parameters, it can be concluded that the sequential proton loss electron transfer (SPLET) mechanism represents the most probable reaction path in a polar solvent for DPPH radical–scavenging activity. On the other hand, the single electron transfer followed by proton transfer (SET-PT) can be a likely mechanistic pathway in the case of an ABTS radical cation
EMG Biofeedback for online predictive control of grasping force in a myoelectric prosthesis
No full textBackground Active hand prostheses controlled using electromyography (EMG) signals have been used for decades to restore the grasping function, lost after an amputation. Although myocontrol is a simple and intuitive interface, it is also imprecise due to the stochastic nature of the EMG recorded using surface electrodes. Furthermore, the sensory feedback from the prosthesis to the user is still missing. In this study, we present a novel concept to close the loop in myoelectric prostheses. In addition to conveying the grasping force (system output), we provided to the user the online information about the system input (EMG biofeedback). Methods As a proof-of-concept, the EMG biofeedback was transmitted in the current study using a visual interface (ideal condition). Ten able-bodied subjects and two amputees controlled a state-of-the-art myoelectric prosthesis in routine grasping and force steering tasks using EMG and force feedback (novel approach) and force feedback only (classic approach). The outcome measures were the variability of the generated forces and absolute deviation from the target levels in the routine grasping task, and the root mean square tracking error and the number of sudden drops in the force steering task. Results During the routine grasping, the novel method when used by able-bodied subjects decreased twofold the force dispersion as well as absolute deviations from the target force levels, and also resulted in a more accurate and stable tracking of the reference force profiles during the force steering. Furthermore, the force variability during routine grasping did not increase for the higher target forces with EMG biofeedback. The trend was similar in the two amputees. Conclusions The study demonstrated that the subjects, including the two experienced users of a myoelectric prosthesis, were able to exploit the online EMG biofeedback to observe and modulate the myoelectric signals, generating thereby more consistent commands. This allowed them to control the force predictively (routine grasping) and with a finer resolution (force steering). The future step will be to implement this promising and simple approach using an electrotactile interface. A prosthesis with a reliable response, following faithfully user intentions, would improve the utility during daily-life use and also facilitate the embodiment of the assistive system
Synthesis and Biological Screening of New 4-Hydroxycoumarin Derivatives and Their Palladium(II) Complexes
No full textTwo newly synthesized 4-hydroxycoumarin bidentate ligands (L1 and L2) and their palladium(II) complexes (C1 and C2) were screened for their biological activities, in vitro and in vivo. Structures of new compounds were established based on elemental analysis, 1H NMR, 13C NMR, and IR spectroscopic techniques. The obtained compounds were tested for their antioxidative and cytotoxic activities and results pointed to selective antiradical activity of palladium(II) complexes towards •OH and -•OOH radicals and anti-ABTS (2,2′-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) cation radical) activity comparable to that of ascorbate. Results indicated the effect of C1 and C2 on the enzymatic activity of the antioxidative defense system. In vitro cytotoxicity assay performed on different carcinoma cell lines (HCT166, A375, and MIA PaCa-2), and one healthy fibroblast cell line (MRC-5) showed a cytotoxic effect of both C1 and C2, expressed as a decrease in carcinoma cells' viability, mostly by induction of apoptosis. In vivo toxicity tests performed on zebrafish embryos indicated different effects of C1 and C2, ranging from adverse developmental effect to no toxicity, depending on tested concentration. According to docking studies, both complexes (C1 and C2) showed better inhibitory activity in comparison to other palladium(II) complexes
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