scholarly journals A Pyrene@Micelle Sensor for Fluorescent Oxygen Sensing

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Yan-xia Yuan ◽  
Hong-shang Peng ◽  
Jian-tao Ping ◽  
Xiao-hui Wang ◽  
Fang-tian You
Keyword(s):  
Oxygen Sensor ◽  
Stokes Shift ◽  
Nonlinear Behavior ◽  
Excimer Emission ◽  
Specialized Knowledge ◽  
Excimer Fluorescence ◽  
Site Model ◽  
Volmer Plot ◽  
Fluorescent Oxygen Sensor

For most fluorescent oxygen sensors developed today, their fabrication process is either time-consuming or needs specialized knowledge. In this work, a robust fluorescent oxygen sensor is facilely constructed by dissolving pyrene molecules into CTAB aqueous solution. The as-prepared pyrene@micelle sensors have submicron-sized diameter, and the concentration of utilized pyrene can be reduced as low as 0.8 mM but still can exhibit dominant excimer emission. The excimer fluorescence is sensitive to dissolved oxygen in both intensity and lifetime, and the respective Stern-Volmer plot follows a nonlinear behavior justified by a two-site model. Because of the merits of large Stokes shift (~140 nm), easy fabrication, and robustness, the pyrene@micelle sensors are very attractive for practical determination of oxygen.

Is it necessary to calculate Young’s modulus in AFM nanoindentation experiments regarding biological samples?

2020 ◽  
Vol 12 ◽  
Author(s):  
S.V. Kontomaris ◽  
A. Malamou ◽  
A. Stylianou
Keyword(s):  
Young’S Modulus ◽  
Biological Samples ◽  
Young's Modulus ◽  
Reference Sample ◽  
Nonlinear Behavior ◽  
Accurate Method ◽  
Accurate Solution ◽  
Hertz Model ◽  
Work Done

Background: The determination of the mechanical properties of biological samples using Atomic Force Microscopy (AFM) at the nanoscale is usually performed using basic models arising from the contact mechanics theory. In particular, the Hertz model is the most frequently used theoretical tool for data processing. However, the Hertz model requires several assumptions such as homogeneous and isotropic samples and indenters with perfectly spherical or conical shapes. As it is widely known, none of these requirements are 100 % fulfilled for the case of indentation experiments at the nanoscale. As a result, significant errors arise in the Young’s modulus calculation. At the same time, an analytical model that could account complexities of soft biomaterials, such as nonlinear behavior, anisotropy, and heterogeneity, may be far-reaching. In addition, this hypothetical model would be ‘too difficult’ to be applied in real clinical activities since it would require very heavy workload and highly specialized personnel. Objective: In this paper a simple solution is provided to the aforementioned dead-end. A new approach is introduced in order to provide a simple and accurate method for the mechanical characterization at the nanoscale. Method: The ratio of the work done by the indenter on the sample of interest to the work done by the indenter on a reference sample is introduced as a new physical quantity that does not require homogeneous, isotropic samples or perfect indenters. Results: The proposed approach, not only provides an accurate solution from a physical perspective but also a simpler solution which does not require activities such as the determination of the cantilever’s spring constant and the dimensions of the AFM tip. Conclusion: The proposed, by this opinion paper, solution aims to provide a significant opportunity to overcome the existing limitations provided by Hertzian mechanics and apply AFM techniques in real clinical activities.

Tensorial Deformation Measures for Flexible Joints

2010 ◽  
Vol 6 (3) ◽  
Author(s):  
Olivier A. Bauchau ◽  
Leihong Li ◽  
Pierangelo Masarati ◽  
Marco Morandini
Keyword(s):  
Finite Deformation ◽  
Nonlinear Behavior ◽  
Critical Issue ◽  
Finite Deformations ◽  
Flexible Joints ◽  
Elastic Bodies ◽  
Infinitesimal Deformations ◽  
Stiffness Characteristics ◽  
Definition Of

Flexible joints, sometimes called bushing elements or force elements, are found in all multibody dynamics codes. In their simplest form, flexible joints simply consist of sets of three linear and three torsional springs placed between two nodes of a multibody system. For infinitesimal deformations, the selection of the lumped spring constants is an easy task, which can be based on a numerical simulation of the joint or on experimental measurements. If the joint undergoes finite deformations, the identification of its stiffness characteristics is not so simple, especially if the joint itself is a complex system. When finite deformations occur, the definition of deformation measures becomes a critical issue. Indeed, for finite deformation, the observed nonlinear behavior of materials is partly due to material characteristics and partly due to kinematics. This paper focuses on the determination of the proper finite deformation measures for elastic bodies of finite dimension. In contrast, classical strain measures, such as the Green–Lagrange or Almansi strains, among many others, characterize finite deformations of infinitesimal elements of a body. It is argued that proper finite deformation measures must be of a tensorial nature, i.e., must present specific invariance characteristics. This requirement is satisfied if and only if the deformation measures are parallel to the eigenvector of the motion tensor.

Determination of association constants and FRET in hydrazide-based molecular duplex strands

2020 ◽  
Vol 7 (17) ◽  
pp. 2419-2425
Author(s):  
Shi-Chang Gao ◽  
Kang Wan ◽  
Xu Fang ◽  
Yong-Xue Li ◽  
Min Xue ◽  
...  
Keyword(s):  
Association Constants ◽  
Substitution Reactions ◽  
Excimer Emission

The association constants for the hydrazide-based molecular duplex strands can be determined via monitoring the pyrene excimer emission. By mixing pyrene and perylene labelled oligomers, supramolecular substitution reactions induced efficient FRET.

Preparation and Utilization of a Biosensor Based on Galactose Oxidase

1992 ◽  
Vol 57 (11) ◽  
pp. 2287-2294 ◽  
Author(s):  
Eva Vrbová ◽  
Jitka Pecková ◽  
Miroslav Marek
Keyword(s):  
Oxygen Sensor ◽  
Specific Activity ◽  
Galactose Oxidase ◽  
Collagen Membrane ◽  
Michaelis Constant ◽  
Nylon Mesh ◽  
Native Collagen ◽  
The Stability ◽  
Galactose Content

An enzyme electrode for D-galactose determination was prepared by fixation of a carrier with immobilized galactose oxidase (E.C. 1.1.3.9) or coimmobilized galactose oxidase and catalase (E.C. 1.11.1.6) to a Clark-type oxygen sensor. The enzymes were immobilized either on a partially hydrolyzed nylon mesh or on a native collagen membrane using the Ugi reaction with cyclohexyl isocyanide and glutaraldehyde. The biosensors were characterized by the specific activity of the immobilized galactose oxidase, the apparent Michaelis constant KM(app.), and the stability expressed by time and a number of the performed analyses. The substrate specificity of the biosensor and the effect of pH and temperature of the reaction mixture on the response magnitude were also tested. The prepared biosensor was used for the determination of D-galactose content in samples of blood plasma and serum of patients with suspected galactosemia.

Use of Lucifer Yellow VS as a Label in Fluorescent Immunoassays Illustrated by the Determination of Albumin in Serum

1983 ◽  
Vol 20 (4) ◽  
pp. 213-216 ◽  
Author(s):  
M Philip Bailey ◽  
Bernard F Rocks ◽  
Clifford Riley
Keyword(s):  
Human Serum Albumin ◽  
Serum Albumin ◽  
Human Serum ◽  
Binding Assay ◽  
Lucifer Yellow ◽  
Stokes Shift ◽  
Covalent Bonds ◽  
Mild Conditions ◽  
Sulphydryl Groups

The use of a new label for fluoroimmunoassay is described. Lucifer yellow VS is a highly fluorescent vinyl sulphone dye which, under mild conditions, forms covalent bonds with amino and sulphydryl groups but is extremely stable in water. A large Stokes shift (110 nm) and an emission maximum at 540 nm give Lucifer yellow further advantages over the more commonly used labels. The use of the dye as a label has been demonstrated by developing a heterogeneous fluoroimmunoassay for human serum albumin. The fluoroimmunoassay gave comparable results to those obtained using a less specific colorimetric dye-binding assay (r = 0·97, n = 20). The advantages, limitations, and other potential uses of Lucifer yellow are discussed.

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