Fluorescence spectroscopy was employed to investigate the interaction between fluorophore fluoresceinamine(FA) and bovine serum albumin(BSA) under physiological conditions. In the mechanism discussion, it was proved that the fluorescence quenching of BSA by FA is a result of the formation of a BSA-FA complex. Fluorescence quenching constants were determined using the modified Stern-Volmer equation to provide a measure of the binding affinity between FA and BSA. The results of the thermodynamic parameters △G, △H, and △S at different temperatures indicated that several kinds of interactions, except for the electrostatic interactions play cooperative roles in BSA-FA association. Furthermore, the conformation of BSA upon interaction with FA was also studied by synchrotron fluorescence spectroscopy.
It is significant to quantify the intermolecular physisorption extent in biomedical field.By taking the advantage of a significant difference from either sizes or weights,we introduced a combination of Scatchard equation and either ultracentrifugation or size exclusion chromatography to obtain both the binding constant and the number of binding sites by using bovine serum albumin and eosin B as models.Compared to the photoluminescence quenching-based methods like Stern-Volmer and Hill equations,the introduced method is not only more precise but also simpler and more straightforward for the operation.Moreover,the protein conformational changes and the corresponding theoretical binding mode with an atomic resolution were also studied by using three-dimensional fluorescence spectroscopy and molecular docking method,respectively.These comparative results could help scientists select right methods to study any interactions between two molecules with significant differences from either sizes or weights.
Peptide GAV-9 is derived from 3 different disease related proteins. The self-assembly of GAV-9 in a water nanofilm attracted much attention recently. We studied how the temperature factor influenced the peptide selfassembly in a water nanofilm and found interesting phenomena: 1) the higher the temperature, the faster the nanofilaments grow; 2) the GAV-9 peptide formed double monolayers in a water nanofilm at 60℃, which further supports the hypothesis that the water nanofilm could change the hydrophobicity of mica. We believe these results can help not only the microcontact printing of amyloid peptides, but also a better understanding on how temperature controls the properties of water nanofilm.
Strategies for labeling proteins with fluorophores are always important for biotechnology. Here we take a model protein(bovine serum albumin) and a typical fluorophore(rhodamine B) to demonstrate a direct labeling method just by physical adsorption. In combination with size exclusion chromatography and the Scartchard equation, we have developed a facile analysis method for calculating the binding constant and binding sites.The molecular docking method has been used to study the binding site in amino acid level.
We studied the kinetic characterizations of the Trifolium pratense seedlings copper-containing amine oxidase(TPAO) by using various amine-containing substrates.The catalyzing rate for all of amine-containing substrates can be ordered as diamines > polyamines > aromatic monoamines,and it shows an apparent trend in each category of substrates such as the longer the carbon chain,the lower the V_(max) is,so does the V_(max)/K_m values but is opposite for the K_m value of TPAO.The distinct differences between the kinetic parameters for different amine-containing substrates indicated that the rate-determining step of the catalytic reaction strongly depends on the substrate's chemical structure.It is concluded that both pH and ionic strength can affect the catalytic activity of TPAO via influencing the coulomb interaction-mediated enzyme-substrate docking processes,which can be attributed to the potential of charged groups from both substrates and the activity sites of TPAO by the regulation of ionic strength.
Mercury ions have been considered highly toxic to human health. What would be great is to develop the ionic probes without any toxicities themselves. Here, we report a friendly, highly sensitive mercury(II) ionic probe, watersoluble photoluminescence carbon dots which were synthesized by simply hydrothermal treatment of fresh cherry tomatoes without adding any other reagents. The ultra-small(\1 nm) carbon dots show robust excitation-depended photoluminescence under a wide p H range(4–10) or a strong ionic strength of up to 1 M, and the detection limit of mercury(II) has been determined as low as 18 n M. We envision such water-soluble, biocompatible carbon dots that could be applied to biolabeling, bio-imaging, and biosensing fields.
Bio-nanosensors(Bio-NSs)have attracted much attention recently due to their unique properties.Among all of the bio-NSs,the intracellular proton sensor is significant for biomedicine studies and clinic diagnosis.Proton nanosensors(PNSs)with different pH sensitive ranges could satisfy different research requirements.Here we report a facile method to build a PNS with a neutral to basic pH sensitive range,in which the commercial pH indicator,fluoresceinamine(FA),was covalently coupled to the carboxylic-rich amphiphilic polymer(AP)coated gold nanoparticles(AuNPs).
