RESUMO
The combination of trimeric form of the light-harvesting complex II (LHCII3), a porous graphite electrode (GE), and the application of phenyl-p-benzoquinone (PPBQ), the quinone derivative, allow the construction of a new type of biohybrid photoactive system. The Chl fluorescence decay and voltammetric analyzes revealed that PPBQ impacts LHCII3 proportionally to accessible quenching sites and that PPBQ forms redox complexes with Chl in both ground and excited states. As a result, photocurrent generation is directly dependent on PPBQ-induced quenching of Chl fluorescence. Since PPBQ also undergoes photoactivation, the action of GE-LHCII3-PPBQ depends on the mutual coupling of LHCII3 and PPBQ photocycles. The GE-LHCII3-PPBQ generates a photocurrent of up to 4.5 µA and exhibits considerable stability during operation. The three-dimensional arrangement of graphite scraps in GE builds an active electrode surface and stabilizes LHCII3 in its native form in low-density multilayers. The results indicate the future usability of such designed photoactive device.
Assuntos
Grafite , Complexos de Proteínas Captadores de Luz , Benzoquinonas , Clorofila , Fluorescência , Complexo de Proteína do Fotossistema IIRESUMO
Chronic Mg2+ deficiency is the underlying cause of a broad range of health dysfunctions. As 25% of body Mg2+ is located in the skeletal muscle, Mg2+ transport and homeostasis systems (MgTHs) in the muscle are critical for whole-body Mg2+ homeostasis. In the present study, we assessed whether Mg2+ deficiency alters muscle fiber characteristics and major pathways regulating muscle physiology. C57BL/6J mice received either a control, mildly, or severely Mg2+-deficient diet (0.1%; 0.01%; and 0.003% Mg2+ wt/wt, respectively) for 14 days. Mg2+ deficiency slightly decreased body weight gain and muscle Mg2+ concentrations but was not associated with detectable variations in gastrocnemius muscle weight, fiber morphometry, and capillarization. Nonetheless, muscles exhibited decreased expression of several MgTHs (MagT1, CNNM2, CNNM4, and TRPM6). Moreover, TaqMan low-density array (TLDA) analyses further revealed that, before the emergence of major muscle dysfunctions, even a mild Mg2+ deficiency was sufficient to alter the expression of genes critical for muscle physiology, including energy metabolism, muscle regeneration, proteostasis, mitochondrial dynamics, and excitation-contraction coupling.
Assuntos
Proteínas de Transporte de Cátions/metabolismo , Homeostase/genética , Deficiência de Magnésio/genética , Magnésio/metabolismo , Músculo Esquelético/metabolismo , Animais , Modelos Animais de Doenças , Metabolismo Energético/genética , Camundongos , Camundongos Endogâmicos C57BL , Fibras Musculares Esqueléticas/metabolismo , Transdução de Sinais/genéticaRESUMO
Light-dependent electrochemical properties of the light harvesting complexes of Photosystem II (LHCII) and the corresponding interactions with screen-printed graphite electrodes (GEs) are determined. No exogenous soluble redox mediators are used. LHCII isolated from spinach leaves are immobilized on GE by physical adsorption and through interactions with glutaraldehyde. Importantly, the insertion of LHCII into the pores of a GE is achieved by subjecting the electrode to specific potentials. Both trimeric and aggregated forms of LHCII located within the graphite layer retain their native structures. Voltammetric current peaks centred at ca. -230 andâ¯+â¯50â¯mV vs. Ag/AgCl (+94 andâ¯+â¯374â¯mV vs. NHE) limit the investigation of the reduction and oxidation processes of immobilized LHCII. An anodic photocurrent is generated in the LHCII-GE proportional to light intensity and can reach a value of 150â¯nA/cm2. Light-dependent charge separation in LHCII followed by electron transfer to the GE occurs only at potentials of above -200â¯mV vs. Ag/AgCl (+124â¯mV vs. NHE). Our results illustrate the importance of the structural proximity of LHCII and GE for photocurrent generation.
Assuntos
Grafite/química , Complexos de Proteínas Captadores de Luz/química , Complexo de Proteína do Fotossistema II/química , Folhas de Planta/química , Proteínas de Plantas/química , Spinacia oleracea/química , Adsorção , Técnicas Eletroquímicas , Eletrodos , Transporte de Elétrons , Proteínas Imobilizadas/química , Luz , OxirreduçãoRESUMO
Slow accumulation of plasmids from their diluted, pg/mL solutions (pH 4.7) on a well defined glassy carbon (GC) electrode surface allowed for the formation of stable electrode layers consisting of two types of plasmid DNAs - pUC19 and pGEX-4T-2, in two forms - supercoiled circular (sc) and linear (lin). In the presence of methylene blue (MB), a typical redox indicator, the oxidation signals of nucleic acid bases are significantly enhanced. The interactions of the plasmids with MB are tested and used to distinguish between various types of plasmids. Instead of an MB reduction signal at ca. -0.2V vs. SCE, typically used to study MB interactions with DNAs, we have used the corresponding oxidation signal at ca. -0.2V, MB(I), as well as another oxidation signal at 1.05 V, MB(III). On a bare GC electrode, the MB(III) and MB(I) signals are proportional to each other, while in the presence of the plasmid DNAs the relations between MB(III) and MB(I) depend on the type of plasmid. The plots: MB(III)/MB(I) vs. [MB] and MB(I) potential shift vs. [MB] are used to distinguish between the supercoiled and linear forms of the pUC19 and pGEX-4T-2 plasmids.