RESUMEN
A sample preparation method was developed to simulate the process of intracellular metabolites metabonomics analysis of Escherichia coli. The Escherichia coli cell was firstly quenched with cold sodium chloride solution ( 0. 85 %，precooled at -80℃ for 15 min).The quenched bacterial cell was treated by using the technique of vacuum freeze-drying and liquid nitrogen freezing combined with ultrasonic processing to increase cell membrane penetrability. Finally，a cold aqueous solution of methanol (MeOH:H2O, 1:1，V/ V, 4 ℃) was used as extraction solvent to extract metabolites. In the present research，flow cytometry and OD value recovery were performed to evaluate the degree of cell damage caused by quenching at single cell level and at integral level respectively. The tested results indicated that the degree of damage to cells caused by cold sodium chloride solution was less than 5%. The peak quantity and the total ion intensity detected by LC-TOF in low collision energy were used to evaluate extraction effects. Three different cell membrane penetrability modes and 4 kinds of extraction solvents were investigated and compared.The results showed that the technique of liquid nitrogen freezing combined with ultrasonic processing for cell membrane penetrability and a cold aqueous solution of methanol (MeOH/H2O，1:1，V/V, 4℃) for extraction of metabolites had the best extraction effect(peak quantity was greater than or equal to 105，and total ion intensity was in the range of 106-107).Therefore，in this work，the freeze drying，grinding with liquid nitrogen and ultrasonic extraction were combined to extract metabolites. In this way，it effectively promoted cell lysis and improved the efficiency of extraction. The result of synthetic analysis showed that the method proposed here could meet the requirements of the metabonomics analysis of Escherachaa coli.
RESUMEN
A method for measuring 13C isotopic abundance of intracellular metabolites of Saccharopolysporaerythraea by ultra-high performance liquid chromatography (UPLC)-triple quadrupole mass spectrometry was established.First, the chromatographic conditions of UPLC were optimized, and then the MS conditions such as unique tube lens voltage, collision energy, and ion pair were optimized.On the bases of length of the parent and daughter ions carbon chains and whether the daughter ions contain 13C atoms, the one-to-one method, one-to-many method and SIM method were established for measuring 13C isotopic abundance.Then these methods were used to measure naturally labeled intracellular metabolite standards and 13C labeled samples, and according to the gap between the experimental value and the theoretical value, the best method was established for each metabolite of different characteristics.The results showed that one-to-one method was most effective for measuring the metabolites of daughter ions not containing 13C atoms represented by sugar phosphates, one-to-many method was the best for measuring the metabolites of both parent and daughter ions containing 13C short carbon chains represented by carboxylic acids, SIM method could play a role in measuring the metabolites of both parent and daughter ions containing 13C long carbon chains represented by coenzyme A.This method had a good measurement precision and could be applied to the measurement of Saccharopolysporaerythraea intracellular metabolites, which contributed to the consequent study of metabolic mechanism and the efficient expression of erythromycin.