First, the purpose of the experiment.
The purpose of this experiment was to determine the total amount of free amino acids in plant tissues by chemical analysis and spectrophotometry. By understanding the content of free amino acids, we can better understand the growth status, nutritional status and relationship between plants and the environment, which provides an important basis for agricultural production, ecological research and plant physiology research.
Second, the principle of experiment.
Free amino acids are amino acids in plant tissues that are not involved in protein synthesis. The determination of free amino acids is usually carried out by acid hydrolysis, that is, proteins in plant tissues are hydrolyzed with acid, and the free amino acids are released, which are then determined by specific analytical methods. In this experiment, spectrophotometry was used to determine the content of free amino acids by adding a specific chromogenic agent to react with the chromogenic agent to form colored substances, and the absorbance was measured by spectrophotometer, so as to calculate the content of free amino acids.
3. Experimental procedures.
1.Sample preparation: Take a certain amount of plant tissue samples and weigh them accurately with an electronic balance. The sample is ground into powder in a mortar, and then an appropriate amount of deionized water is added, stirring well. The milled solution is filtered and the filtrate is collected.
2.Acid hydrolysis: An appropriate amount of concentrated hydrochloric acid is added to the filtrate and the solution is boiled for a period of time to hydrolyze the proteins in plant tissues. After cooling, add an appropriate amount of sodium hydroxide solution to neutralize the hydrochloric acid.
3.Color reaction: Add an appropriate amount of chromogenic agent (such as ninhydrinone) to the above solution and shake the solution well. The chromogenic agent reacts with free amino acids to form colored substances.
4.Spectrophotometer determination: The absorbance of the above solution is determined on a spectrophotometer. Select the appropriate wavelength range and read the absorbance value.
5.Calculation: The amount of free amino acids is calculated from the standard curve and absorbance values. The standard curve was obtained by preparing solutions of amino acid standards at different concentrations and performing chromogenic reactions and absorbance measurements following the steps described above.
Fourth, the experimental results.
Here's an example of a possible experimental result:
Sample Name |absorbance |Free amino acid content (mg g) |
Sample 1 | 0.52 | 12.5 |
Sample 2 | 0.60 | 15.0 |
Sample 3 | 0.48 | 10.0 |
5. Experiment summary.
In this experiment, the total amount of free amino acids in plant tissues was successfully determined by spectrophotometry. The results showed that there were differences in the content of free amino acids in different plant tissues. Through the determination of free amino acids, we can understand the growth status and nutritional status of plants, which provides an important basis for agricultural production, ecological research and plant physiology research. At the same time, this experimental method has the advantages of simple operation and accurate results, and can be widely used in the determination of free amino acids in plant tissues.