Showing 4 results for Surface Plasmon Resonance
Azadeh Azizi, Bijan Ranjbar, Khosro Khajeh, Tayebeh Ghodselahi, Soraya Hoornam,
Volume 3, Issue 2 (11-2012)
Abstract
The stability of enzymes with no reduction in their catalytic activity still remains a critical issue in industrial applications. Naturally occurring osmolytes are commonly used as protein stabilizer. Apart from increasing the stability and catalytic activity, these osmolytes do not change the structure of enzyme. There are a few general schemes about the stabilization mechanism of these osmolytes but the details of their mechanism have not been found so far. In this study, we investigated the simultaneous effects of sorbitol and trehalose on the activity and structural stability of Pseudomonas cepacia lipase (PCL) using UV–visible, fluorescence and circular dichroism (CD) spectroscopy. In order to trace the refractive index and dielectric constant alterations upon the addition of osmolytes, microenvironment of the enzyme (PCL) was studied by means of SPR technique.The results revealed that osmolytes increased catalytic activity and intrinsic fluorescence intensity of PCL. In the presence of both osmolytes the activity of enzyme is greater than when each of the osmolytes is used individally. Far-UV CD spectra indicated that the secondary structural content of protein has been some what increased upon interacting with these osmolytes.The results of SPR technique indicated none of the above osmolytes could change the dielectric constant of medium considerably. This study revealed the synergy of two osmolytes toward increasing the activity and stability of enzyme.
S.s. Mirjalili, T. Tohidi Moghadam, R. Hassan Sajedi ,
Volume 10, Issue 4 (12-2019)
Abstract
Recent researches on the application of nanoparticles have been focused on nanostructures of gold with rod morphology, due to having outstanding optical properties for diagnostics and therapeutics of the diseases. The rod morphology of the nanostructures enables strong and sensitive absorption of surface plasmon in the infrared region. In the present research, based on the sensitivity of surface plasmon resonance of gold nanorods to trace changes in the local environment, as well as the importance of rapid detection of trace amounts of albumin in urine, functionalization, and stability of these nanostructures with anti-albumin antibody has been investigated in different concentrations, volumes, time and pH changes. The results of spectroscopic studies of different samples in the visible spectrum near-infrared waves showed that gold nanorods have desirable stability, and their rod morphology characteristic is maintained. The study of the temporal stability of samples showed that the complex samples were stable up to 48 hours for sensing applications. Primary monitoring of the function of the nanobiosensor in the presence of albumin with two normal and abnormal levels of concentration revealed remarkable changes in interparticle distance, size, and morphology of the nanostructures. According to this research, the rod nanostructures can be used to design simple nanobiosensors.
Zahra Abolghasemi, Zeinoddini Zeinoddini, Seyedmorteza Robatjazi,
Volume 14, Issue 3 (2-2024)
Abstract
Gold nanoparticles (GNPs) with unique optical properties, such as easy operation and visualized assay, have a great ability to detect different types of analytes. Today, the use of gold nanoparticles has wide applications in the field of medicine and biotechnology, including the detection of microorganisms that cause contamination in water, air and food and it is considered a suitable alternative for chemical and physical methods. New technologies in the design of biosensors based on GNPs provide the ability to identify biological compounds accurately and quickly. One of these technologies is a detection sensor based on surface plasmon resonance (SPR), which based on its optical properties, is capable of very sensitive and specific measurement of biomolecule interactions without time delay. This technology can quantify in a short time the properties of biomolecular mediators (such as oligonucleotides, proteins and bacteria) on the surface, including reaction speed, tendency and concentration of surface mediators. In this review, while investigating the surface plasmon properties of gold nanoparticles, the simple diagnostic applications of gold nanoparticles based on the localized surface plasmon (LSPR) method and detection in biomedicine.
Volume 20, Issue 136 (5-2023)
Abstract
Enterotoxigenic Escherichia coli is the most common bacterial agent causing diarrhea by binding to the intestinal mucosa and producing heat-labile enterotoxins. The aim of this study was to elucidate the interaction of two forms of dextran exopolysaccharides (molecular weights of (11-9 kDa) and (76-60 kDa)) produced by the probiotic bacterium Leuconostoc mesenteroides with the heat-labile enterotoxin ((B-pentamer) (LTB)) by using surface plasmon resonance (SPR). According to the results of interaction kinetics at 298 K, both low and high molecular weight dextran types exhibited high affinity (KA) (1.07×106 M-1 and 0.95×106 M-1, respectively) for LTB toxin in vitro. From a thermodynamic point of view, the values calculated of the Gibbs energy were negative (ΔG <0), and also enthalpy and entropy achieved both positive values (ΔH> 0 and ΔS> 0) via the van’t Hof equation, indicating that the interaction was spontaneous, endothermic, and disordered, respectively. With these findings, hydrophobic interactions appear to be important in the interaction between dextran and LTB toxins with hydrogenic bindings. Therefore, dextran molecules are capable of binding to LTB toxin and relatively displaying antitoxin effects. To sum up, these results could provide further insights for initiating extensive research with other lactic acid-derived exopolysaccharides in bacterial interactions and also with foodborne pathogen toxins.
