title: [Study on protein extraction methods for Streptococcus mutans].
abstract: OBJECTIVE
  To establish an efficient and stable method for protein extraction of Streptococcus mutans.
  
  
  METHODS
  The collected bacteria were treated by freeze-thaw and ultrasonic (method 1), ultrasonic (method 2), boiling (method 3), boiling and ultrasonic (method 4), respectively. The index such as state of bacteria broken, concentration of extracted protein and SDS-PAGE of protein were employed to evaluate the effects of above four methods.
  
  
  RESULTS
  Beside the method 3, the other three methods could break the bacteria effectively, of which ultrasonic was the key factor. The pattern of SDS-PAGE which treated by method 1, method 2 and method 4 was almost same, but method 1 resulted in the best abundance. There was significantly difference among the four protein concentration extracted by four methods (P < 0.05). All methods exhibited good stability and reproducibility.
  
  
  CONCLUSIONS
  Method of freeze-thaw and ultrasonic resulted in an efficient proteins extraction of Streptococcus mutans which demonstrated good stability and reproducibility and easy to handle.
authors.affiliation: State Key Laboratory of Oral Diseases, Sichuan University, Chengdu 610041, China.
authors.forename: Yong-Hong
authors.initials: YH
authors.lastname: He
authors.forename: Xiao-Bei
authors.initials: XB
authors.lastname: Tian
authors.forename: Hu-Chun
authors.initials: HC
authors.lastname: Wan
authors.forename: Yan-Li
authors.initials: YL
authors.lastname: Wen
authors.forename: Fei-Fei
authors.initials: FF
authors.lastname: Zhang
authors.forename: Qin-Rui
authors.initials: QR
authors.lastname: Ma