英语讲课1—3语法和修辞.doc

PAGE 1 PAGE 10 1.3 Grammar Diction 1.3.1正确的语法 人称 We carried out several studies which ( It was carried in several studies that ) First, you adjust the dial at the top of machine to the temperature you wish, then you turn the switch “on-off” to start the machine. It is known to all that there is no air in space. All of these values were obtained by gas chromatography/ mass spectrometry. All further investigations showed ( It was showed that all further investigations ) 时态 Because certain functions of glycoproteins in cell members have attention of biochemists, the structural elucidation of glycoproteins at the molecular level has become a challenging topics. Ovalbumin is an abundantly available, carbohydrate-rich protein contained in the egg white of hens. We used it as a model glycoprotein to investigate mass spectrometric behavior and analytical techniques for this class of compounds. We have conducted structural studies on carbohydrates in hen ovalbumin by fast atom bombardment mass spectrometry (FAB-MS) and chemical derivatization, and have discovered some new glycopeptides ( Wang et al., 1988;1989 ). The heterogeneity of the sugar chains in ovalbumin is well known ( Huang et al., 1970 ) and the molecular weight range of the sugar chains is 1000-3000 Da. There are many methods used to obtain homogeneous states of glycopeptic molecules, for example gel permeation chromatography ( Atlinson et al., 1981 ) gel electrophoresis ( Tai et al., 1975; 1977 ), and HPLC ( Ceccarini et al., 1983; 1984 ). HPLC has been shown to be an effective and convenient method. Our experiments showed that glycopeptides obtained through a series of gel filtration, fractionation and desalting were pure enough for FAB-MS, which can give MW and sequence information for native and permethylated glycopeptides, respectively ( Wang et al., 1988; 1989 ). The present paper describes the procedure for preparing ovalbumin glycopeptides, the specific methods for obtaining pure glycop