Structure-Function Relationships Affecting the Sensing Mechanism of Monolayer-Protected Cluster Doped Xerogel Amperometric Glucose Biosensors

A systematic study of the structure–function relationships critical to understanding the sensing mechanism of 1st generation amperometric glucose biosensors with an embedded nanoparticle (NP) network is presented. Xerogel-based films featuring embedded glucose oxidase enzyme and doped with alkanethiolate-protected gold NPs, known as monolayer protected clusters (MPCs), exhibit significantly enhanced performance compared to analogous systems without NPs including higher sensitivity, faster response time, and extended linear/dynamic ranges. The proposed mechanism involves diffusion of the glucose to glucose oxidase within the xerogel, enzymatic reaction production of H2O2 with subsequent diffusion to the embedded network of MPCs where it is oxidized, an event immediately reported via fast electron transfer (ET) through the MPC system to the working electrode. Various aspects of the film construct and strategy are systematically probed using amperometry, voltammetry, and solid-state electronic conductivity measurements, including the effects of MPC peripheral chain length, MPC functionalization via place-exchange reaction, MPC core size, and the MPC density or concentration within the xerogel composite films. The collective results of these experiments support the proposed mechanism and identify interparticle spacing and the electronic communication through the MPC network is the most significant factor in the sensing scheme with the diffusional aspects of the mechanism that may be affected by film/MPC hydrophobicity and functionality (i.e., glucose and H2O2 diffusion) shown to be less substantial contributors to the overall enhanced performance. Understanding the structure–function relationships of effective sensing schemes allows for the employment of the strategy for future biosensor design toward clinically relevant targets

Hansenula polymorpha: An attractive model organism for molecular studies of peroxisome biogenesis and function

In wild-type Hansenula polymorpha the proliferation of peroxisomes is induced by various unconventional carbon- and nitrogen sources. Highest induction levels, up to 80% of the cytoplasmic volume, are observed in cells grown in methanol-limited chemostat cultures. Based on our accumulated experience, we are now able to precisely adjust both the level of peroxisome induction as well as their protein composition by specific adaptations in growth conditions. During the last few years a series of peroxisome-deficient (per) mutants of H. polymorpha have been isolated and characterized. Phenotypically these mutants are characterized by the fact that they are not able to grow on methanol. Three mutant phenotypes were defined on the basis of morphological criteria, namely: (a) mutants completely lacking peroxisomes (Per-; 13 complementation groups); (b) mutants containing few small peroxisomes which are partly impaired in the peroxisomal import of matrix proteins (Pim-; five complementation groups); and (c) mutants with aberrations in the peroxisomal substructure (Pss-; two complementation groups). In addition, several conditional Per-, Pim- and Pss- mutants have been obtained. In all cases the mutant phenotype was shown to be caused by a recessive mutation in one gene. However, we observed that different mutations in one gene may cause different morphological mutant phenotypes. A detailed genetic analysis revealed that several PER genes, essential for peroxisome biogenesis, are tightly linked and organized in a hierarchical fashion. The use of both constitual and conditional per mutants in current and future studies of the molecular mechanisms controlling peroxisome biogenesis and function is discussed.

Biological and microbial fuel cells

Biological fuel cells have attracted increasing interest in recent years because of their applications in environmental treatment, energy recovery, and small-scale power sources. Biological fuel cells are capable of producing electricity in the same way as a chemical fuel cell: there is a constant supply of fuel into the anode and a constant supply of oxidant into the cathode; however, typically the fuel is a hydrocarbon compound present in the wastewater, for example. Microbial fuel cells (MFCs) are also a promising technology for efficient wastewater treatment and generating energy as direct electricity for onsite remote application. MFCs are obtained when catalyst layer used into classical fuel cells (polymer electrolyte fuel cell) is replaced with electrogenic bacteria. A particular case of biological fuel cell is represented by enzyme-based fuel cells, when the catalyst layer is obtained by immobilization of enzyme on the electrode surface. These cells are of particular interest in biomedical research and health care and in environmental monitoring and are used as the power source for portable electronic devices. The technology developed for fabrication of enzyme electrodes is described. Different enzyme immobilization methods using layered structures with self-assembled monolayers and entrapment of enzymes in polymer matrixes are reviewed. The performances of enzymatic biofuel cells are summarized and approaches on further development to overcome current challenges are discussed. This innovative technology will have a major impact and benefit to medical science and clinical research, health care management, and energy production from renewable sources. Applications and advantages of using MFCs for wastewater treatment are described, including organic matter removal efficiency and electricity generation. Factors affecting the performance of MFC are summarized and further development needs are accentuated

Diabetic Cardiovascular Disease Induced by Oxidative Stress.

Cardiovascular disease (CVD) is the leading cause of morbidity and mortality among patients with diabetes mellitus (DM). DM can lead to multiple cardiovascular complications, including coronary artery disease (CAD), cardiac hypertrophy, and heart failure (HF). HF represents one of the most common causes of death in patients with DM and results from DM-induced CAD and diabetic cardiomyopathy. Oxidative stress is closely associated with the pathogenesis of DM and results from overproduction of reactive oxygen species (ROS). ROS overproduction is associated with hyperglycemia and metabolic disorders, such as impaired antioxidant function in conjunction with impaired antioxidant activity. Long-term exposure to oxidative stress in DM induces chronic inflammation and fibrosis in a range of tissues, leading to formation and progression of disease states in these tissues. Indeed, markers for oxidative stress are overexpressed in patients with DM, suggesting that increased ROS may be primarily responsible for the development of diabetic complications. Therefore, an understanding of the pathophysiological mechanisms mediated by oxidative stress is crucial to the prevention and treatment of diabetes-induced CVD. The current review focuses on the relationship between diabetes-induced CVD and oxidative stress, while highlighting the latest insights into this relationship from findings on diabetic heart and vascular disease

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Department of Chemical EngineeringLignin peroxidase is promising ingredient for skin whitening cosmetics because it is capable of oxidizing melanin with high redox potential. Crude lignin peroxidase from fungal fermentation is usually utilized owing to its difficulties of expression and purification. Lignin peroxidase is hard to express and purify so it was usually applied as crude form for cosmetics. In this study, lignin peroxidase isozyme H8 (LiPH8) from Phanerochaete chrysosperium was expressed in E. coli and purified for further use of melanin decolorization. The pH optimum for the decolorization of melanin was pH 4.0. Melanin decolorization efficiency was reached to 73% by intermittent addition of hydrogen peroxide (H2O2), since excessive concentration of H2O2 converts LiPH8 into compound III which is the inactivated form of lignin peroxidase. Considering that the intermittent supply of H2O2 is not practical for cosmetic applications, glucose oxidase from aspergillus niger (GOx) was utilized for in-situ generation of H2O2. GOx and ??-D-glucose concentration was optimized and melanin decolorization efficiency reached 63.3% within 1h. LiPH8 retained its activity for 8h with 84.0% of melanin decolorization efficiency. With these results, melanin decolorization catalyzed by LiPH8 with H2O2 generated from GOx was proven to be a prospective approach for skin whitening applications.clos

Diabetes, hypertension, and cardiovascular disease: clinical insights and vascular mechanisms

Hypertension and type 2 diabetes are common comorbidities. Hypertension is twice as frequent in patients with diabetes compared with those who do not have diabetes. Moreover, patients with hypertension often exhibit insulin resistance and are at greater risk of diabetes developing than are normotensive individuals. The major cause of morbidity and mortality in diabetes is cardiovascular disease, which is exacerbated by hypertension. Accordingly, diabetes and hypertension are closely interlinked because of similar risk factors, such as endothelial dysfunction, vascular inflammation, arterial remodelling, atherosclerosis, dyslipidemia, and obesity. There is also substantial overlap in the cardiovascular complications of diabetes and hypertension related primarily to microvascular and macrovascular disease. Common mechanisms, such as upregulation of the renin-angiotensin-aldosterone system, oxidative stress, inflammation, and activation of the immune system likely contribute to the close relationship between diabetes and hypertension. In this article we discuss diabetes and hypertension as comorbidities and discuss the pathophysiological features of vascular complications associated with these conditions. We also highlight some vascular mechanisms that predispose to both conditions, focusing on advanced glycation end products, oxidative stress, inflammation, the immune system, and microRNAs. Finally, we provide some insights into current therapies targeting diabetes and cardiovascular complications and introduce some new agents that may have vasoprotective therapeutic potential in diabetes

Minimizing acetate formation in E. coli fermentations

Escherichia coli remains the best established production organisms in industrial biotechnology. However, during aerobic fermentation runs at high growth rates, considerable amounts of acetate are accumulated as by-product. This by-product has negative effects on growth and protein production. Over the last 20 years, substantial research efforts have been spent to reduce acetate accumulation during aerobic growth of E. coli on glucose. From the onset it was clear that this quest should not be a simple nor uncomplicated one. Simple deletion of the acetate pathway, reduced the acetate accumulation, but instead other by-products were formed. This minireview gives a clear outline of these research efforts and the outcome of them, including bioprocess level approaches and genetic approaches. Recently, the latter seems to have some promising results