Fluorescence enhancement effect of the morin-Al3+ -sodium dodecyl benzene sulphonate-protein system and the determination of proteins

Fluorescent Properties of Morin in Aqueous Solution: A Conversion from Aggregation Causing Quenching (ACQ) to Aggregation Induced Emission Enhancement (AIEE) by Polyethyleneimine Assembly

Unlike normal conversion from aggregation caused quenching (ACQ) to aggregation induced emission enhancement (AIEE) by introducing aromatic rotors tuning aggregation modes, in this study, it is achieved through a supramolecular assembly with polymer. Thus, it provides an easy approach for the inhibition of unwanted H-aggregation between luminogens. As a kind of flavonoid, morin has shown great potential in therapeutics. However, its poor solubility and weak emission in aqueous solution greatly limit its bioapplications. When morin is dissolved in aqueous solution, the presence of 30 × 10^-6 m polyethyleneimine (PEI) induces significant emission enhancement and bathochromic shift. Consequently, the quantum yield (QY) of 24.5% is either achieved by assembling with PEI, versus 0.76% of its ACQ state composed of H-aggregation in aqueous solution. Particularly, the in-depth mechanism studies reveal that it is the assembly with PEI that disassociates the H-aggregation in aqueous solution and further restricts the stretching and/or rotation of morin, which eventually reduce the nonradiative decays and enhance the emission. Therefore, the present study reports a unique phenomenon of AIEE effects on morin. Particularly the in-depth investigation on intrinsic mechanisms will highlight and greatly expand the development of more luminogens from traditional Chinese herbals.

Determination of ultra trace amounts of protein by 4-chlorosulfo-(2'-hyaroxylphenylazo)-rhodanine-Ti(IV) complex [ClSARP-Ti(IV)] as the fluorescence spectral probe in AOT microemulsion

Experiments indicated that protein can enhance the fluorescence of the 4-chlorosulfo-(2'-hydroxylophenylazo)-rhodanine-Ti(IV) complex [ClSARP-Ti(IV)] in the presence of bis(2-ethylhexyl)sulfosuccinate sodium salt (AOT) microemulsion. Based on this, a sensitive and reproducible fluorometric method for the determination of micro amount protein was developed. The calibration curves of four proteins were given. Under the optimum experimental conditions, the enhanced fluorescence intensity of the system was in proportional to the concentration of protein in the range of 0.1-11 microg mL(-1) for bovine serum albumin (BSA), 1.0-10 microg mL(-1) for human serum albumin (HSA), 1.0-50 microg mL(-1) for ovalbumin (Ova) and 2.5-18 microg mL(-1) for gamma-globulins (gamma-G). Their detection limits were 0.070, 0.071, 0.33 and 0.22 microg mL(-1), respectively. The ClSARP-Ti(IV) complex as a spectral probe can be used to the determination of protein in milk powder and oatmeal yielding with satisfactory results. Therefore, the proposed method is one of the most sensitive methods available. In addition, the interaction mechanism of this system is studied by multi-techniques.