Molecular self-assembling and the fluorescence enhancement in morin–Al3+–cetyltrimethylammonium bromide–protein system

Study on the interaction of 6-(2-morpholin-4-yl-ethyl)-6H-indolo [2,3-b]quinoxaline hydrochloride with human serum albumin by fluorescence spectroscopy

Under physiological conditions, in vitro interaction between the bio-active substance 6-(2-morpholin-4-yl-ethyl)-6H-indolo[2,3-b]quinoxaline hydrochloride (MIQ) and human serum albumin (HSA) was investigated at an excitation wavelength 260 nm and at different temperatures (298 K, 308 K and 313 K) by fluorescence emission spectroscopy. From spectral analysis, MIQ showed a strong ability to quench the intrinsic fluorescence of HSA through a static quenching procedure. The binding constant is estimated asK _A   =  2.55  ×  10^-4 l · mol^-1 at 298 K. Based on the thermodynamic parameters evaluated from the van 't Hoff equation, the enthalpy change (ΔH°) and entropy change (ΔS°) were derived to be negative values. A value of 2.37 nm for the average distance r between MIQ (acceptor) and tryptophan residues of HSA (donor) was derived from the fluorescence resonance energy transfer. UV/vis absorption spectra were used to confirm the quenching mechanism.

Phosphoprotein staining for sodium dodecyl sulfate-polyacrylamide gel electrophoresis using fluorescent reagent morin hydrate

A fluorescence-based stain with 3,5,7,2',4'-pentahydroxyflavone (morin hydrate, MH) was designed to stain phosphoproteins in one-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Al(3+) was applied as a "fixed bridge," providing an efficient energy transfer channel between phosphoprotein and MH, to produce a strong fluorescent complex for the determination of phosphoprotein. As little as 62.5ng of α-casein (7 or 8 phosphates) and β-casein (5 phosphates), 125ng of ovalbumin (2 phosphates), and κ-casein (1 phosphate) could be visualized with a wide linear dynamic range. In comparison with conventional methods, MH stain is a time-saving method that takes just 90min. It also has good compatibility with routine protein stainings such as Coomassie Brilliant Blue R (CBBR) and SYPRO Ruby for total protein analysis.

Analysis of interaction between tamoxifen and ctDNA in vitro by multi-spectroscopic methods

Multi-spectroscopic methods including resonance light scattering (RLS), ultraviolet spectra (UV), fluorescence spectra, (1)H NMR spectroscopy, coupled with thermo-denaturation experiments were firstly used to study the interaction of antitumor drug tamoxifen (TMX) with calf thymus (ctDNA) in acetate buffer solutions (pH 4.55). The interaction of TMX with ctDNA could cause a significant enhancement of RLS intensity, the hyperchromic effect, red shift of absorption spectra and the fluorescence quenching of TMX, indicating that there is an inserting interaction between TMX and ctDNA. This inference was confirmed by (1)H NMR spectroscopy. The chemical shift of the benzene proton changes significantly which indicates that TMX could insert into the base pairs of ctDNA. These studies are valuable for a better understanding the mode of TMX-ctDNA interaction further, which are important and useful for designing of new ctDNA targeted drug. And the antitumor drug TMX inserted directly into ctDNA in vitro, which can provide a lot of useful information to explore the development of new and highly effective anti-cancer drugs.