There are essentially four stages for gene cloning.1.Preparation of the Gene Cloning bacterial genes is generally achived from total chromosomal DNA preparations (“shotgun”cloning)by cleaving the DNA with a restriction endonuclease that generates fragment...[继续阅读]

    It would be difficult to overemphasize the importance of proteins in living systems.For instance,certain types of proteins form important parts of structural components in all cells and in spaces between cells. Furthermore,enzymes,antibodies (抗体)[ which a...[继续阅读]

    Wastes occur in all three states,i. e. solids,liquids and gases,They are derived from three primary sources:urban,agriculture,and industry. By weight and volume solid wastes,i. e. urban refuse,crops and food processing wastes,and manures,are the most sign...[继续阅读]

    Vinegar,the aqueous solution of acetic acid,is produced in fermentation by oxidation of a dilute ethanol solution. The metabolic process involves conversion by alcohol dehydrogenase of ethanol to acetaldehyde and conversion by acetaldehyde dehydrogenase o...[继续阅读]

    (1) Bench-top(工作台)or Portable Autoclaves(手提式灭菌锅)Bench-top or portable autoclaves are useful for sterilizing small items,i.e. bottles,a small number of 500 ml conical flasks(锥形瓶,三角瓶),automatic pipette tips(自动移液管吸头),etc.Such autoclaves work on the same prin...[继续阅读]

    Flavour compounds include other alcohols,esters,carbonyl compounds,organic acids,sulphur compounds,amines and phenols.Quantitatively,and in terms of their flavour-producing effects,the most important compounds present in beverages and spirits are the high...[继续阅读]

    A cup of sugar left undisturbed for twenty years will change very little. But when you put some of the sugar in your mouth,it undergoes chemical change very rapidly. Enzymes secreted by some of your cells account for the difference in the rate of change,E...[继续阅读]

    1. Introduction The Pierce BCA≠Protein Assay Reagent (一种分析试剂的名称) is a highly sensitive reagent for the spectrophotometric (分光光度计的)determination of protein concentration. This unique reagent system combines the well known reaction of protein with Cu2-in an...[继续阅读]

    The ion-exchange chromatography is a more predictable extraction and concentration method than absorption chromatography,provided the required product is capable of reacting with an appropriate ion-exchange resin,Many types of anionic and cationic resins ...[继续阅读]

    Nucleotides are vital to the operation and the reproduction of cells. Each nucleotide contains three different kinds of components: a five-carbon sugar (ribose or deoxyribose),a nitrogen-containig base (either a single-ringed pyrimidine or a doubleringed ...[继续阅读]