Forster-type Nonradiative Energy Transfer Research Articles

Characterization of the interactions of human serum albumin (HSA), gatifloxacin, and metronidazole using spectroscopic and electrochemical methods

Human serum albumin (HSA), the most abundant protein in blood plasma, is an important carrier for many drugs. Understanding HSA-drug interactions is critical in being able to interpret the distribution and acting mechanisms of these drugs, which is particularly important in the case of multi-drug therapy. In this study, we investigated the interactions between HSA and two commonly used antibiotics, gatifloxacin (GFLX) and metronidazole (MET), in Tris–HCl buffer solution (pH=7.4). The efficacy of the individual drugs (GFLX or MET) and the efficacy of a combination of GFLX and MET were measured using fluorescence spectroscopy, UV absorption spectroscopy, and electrochemical methods. Our results demonstrated that GFLX and MET have a synergistic effect. Briefly, one drug decreased the binding stability with HSA of the other drug, thus increasing the concentration of free drug at the action sites. The interaction of drugs with HSA is a process of complex-formation static quenching. There is approximately one binding site between HSA and the drug (GFLX or MET). The binding distance, r, between the drug and HSA was determined on the basis of the theory of Forster-type non-radiative energy transfer. It was shown that the interaction between the two drugs increased the r-value. Using thermodynamic parameters, we found that the binding of drug-HSA interactions is mainly controlled by electrostatic force. Analysis of the synchronous fluorescence spectrum suggested that the interactions between the drugs have important effects on protein conformation. In conclusion, combining GFLX and MET enhances treatment efficacy. Our study provides a basis to understand the mechanism of the interaction of MET, GFLX and HSA in the human body.

Generalized Theory of Förster-Type Nonradiative Energy Transfer in Nanostructures with Mixed Dimensionality

Forster-type nonradiative energy transfer (NRET) is widely used, especially utilizing nanostructures in different combinations and configurations. However, the existing well-accepted Forster theory is only for the case of a single particle serving as a donor together with another particle serving as an acceptor. There are also other special cases previously studied; however, there is no complete picture and unified understanding. Therefore, there is a strong need for a complete theory that models Forster-type NRET for the cases of mixed dimensionality including all combinations and configurations. We report a generalized theory for the Forster-type NRET, which includes the derivation of the effective dielectric function due to the donor in different confinement geometries and the derivation of transfer rates distance dependencies due to the acceptor in different confinement geometries, resulting in a complete picture and understanding of the mixed dimensionality.

The role of cupric in maintaining the structure of CopC

The CopC protein from pseudomonas syringae pathovar tomato is expressed as one of four proteins encoded by the operon CopABCD that is responsible for copper resistance. And there are one tryptophan (83), one tyrosine (79), and three phenylalanines (35, 43, 99) in apoCopC. The fluorescence peak of apoCopC is located near 320 nm, and the peak shifts toward 353 nm in the presence of 10 mol·L−1 urea with excitation at 280 nm. Using urea as a chemical agent, the conformational stabilities of apoCopC and Cu N 2+ -CopC were monitored by fluorescence spectrum in 20 mmol·L−1 phosphate buffer and 100 mmol·L−1 sodium chloride at pH 6.0. The free energy of stabilization for apoCopC and Cu N 2+ -CopC is 16.29±0.65 kJ·mol−1 and 26.26±0.35 kJ·mol−1, respectively. The distance between the tryptophan residue and the Cu2+ in Cu N 2+ -CopC has been studied by observing Forster type nonradiative energy transfer. And it is calculated to be 11.6 A.