Visualization Detection Of Melamine In The Protein Feed

Methane oxidizing bacteria is one of the branches of methyl oxidation bacteria, It is a kind of gram-negative bacteria, directly with methane as carbon and energy sources. Methanobactin is a fluorescent peptide released by the Methane oxidizing bacteria. It consists of two serine, glycine, serine, two cysteine and methionine.Methanobactin can coordinate Cu(Ⅰ) by two hydroxyimidazolates, with one N and one S atom. Methanobactin can also bind to Au(Ⅲ) and reduce it to Au(0). In the presence of hydroquinone as a electron donator, Mb can catalyze Au(Ⅲ) reduce to Au(0)and yield gold nanoparticles continuously. Surface plasmon resonance of gold nanoparticles makes its aqueous solution has a typical absorption peak between500and600nm, and a unique color that can be observed by naked eyes.It can be identified by the color change.And can be used in the detection of certain substances.Too much protein feed i in recent years have been found with melamine addition. So urgently need to establish a simple and effective analysis of protein feed and other food in the fast detection methods of melamine.Visual detection of melamine inprotein feed based on methanobactin-induced gold nanoparticles formation is the study focus of thesis.Visual detection is convenient and quick, the detection limit is much lower than1ppm melamine stipulated by the state standards.Different concentrations of melamine in protein feed have been detected. The interference of several kinds of ingredients in protein feedhave been investigated. The detection limit and the recovery rate have been calculated, either.1、Methanobactin can bind to Au(Ⅲ) and reduce it to Au(0). In the presence of hydroquinone as a electron donator, Mb can catalyze Au(Ⅲ) reduce to Au(0)and yield gold nanoparticles continuously. The optimal conditions for synthesizing AuNPs has been obtained as below:pH=5.1, the molar ratio of Mb to Au(Ⅲ)is0.8:1, the molar ratio of HQ to Au(Ⅲ)is0.4:1. AuNPs will increase as the extension of time until the reaction finished completely. The AuNPs were characterized by UV-visible absorption spectra and TEM2、Studied the visual detection mechanism ofmelamine n the process ofmethanobactin-induced gold nanoparticles synthesis. Methanobactin can also bind to Au(Ⅲ) and reduce it to Au(0)with apurple or wine red color.melamine will inhibit the synthesis of gold nanoparticles,So the solution no color change.Colorimetric method can be very intuitive to detect melamine,By uv-vis absorption spectroscopy the formation of gold nanoparticles can be found with obvious characteristic absorption peakbetween500nm to600nm. No absorption peak in this scope when melamine added and suggested no formation of gold nanoparticles.The optimal condition for detecting melamine is:at room temperature, pH=5.1, the molar ratio of Mb to Au(Ⅲ) is0.7:1, the molar ratio of HQ to Au(Ⅲ) is0.25:1.For different concentrations of melamine testing, testing minimum standard is0.6ppm, far below the national standard of1ppm.3、the principle of colorimetry detection melamine in protein feed was based on melamine can prevent methanobactincatalyzed reduction of Au (Ⅲ) togold nanoparticles, by colorimetry to detect melamine. The optimal condition to detect the melamine in protein feed is follow:At room temperature, pH=5.1, the molar concentration ratio of Mb:Au(Ⅲ)is0.7:1, HQ:Au(Ⅲ)is0.25:1.The result indicates that the concentration of melamine shows a good liner relationship with the absorption of gold nanoparticles:detection limit is between0.05ppm and0.5ppm can achieve quantitative detection by UV-visible spectrophotometer.the macroscopic qualitative detection limit is0.6ppm. the recovery rate is between97%and103%. We found thatVc and Vb12have a little effect by UV-visible absorption spectra.