Yugkugyughk

BMS1041 – Laboratory Practical: Studies with Amino Acids

Dr Alfred Thumser & Dr Raphaelle Winsky-Sommerer

Thin Layer Chromatography of Amino Acids

http://www.papercamp.com/essay/155374/Biochemistry

Amino Acid | Distance (mm) travelled by amino acid | Solvent front (mm) | Rf value |

Glycine | | | |

Threonine | | | |

Tryptophan | | | |

Unknown | | | |

1. Why does touching the silica gel with your hands potentially contaminate your plate? [5]

2. Why must you use a pencil to write on the TLC plate (starting line, solvent line, identification of the spots)? Why can’t you use a pen? [5]

3. Include a picture of your TLC plate below [10]

4. Why can a Rf value never be greater than 1? [5]

5. Which amino acid had the highest Rf value? Explain these findings, based on your knowledge of the chemical properties of this amino acid? [10]

6. Which amino acid lowest Rf value? Explain these findings, based on your knowledge of the chemical properties of this amino acid? [10]

7. Identify your “unknown” sample. Justify your answer [10]

Data Analysis: UV/Vis Absorbance Scans of Amino Acids

See Appendix of the Practical 1 Protocol for UV/Visible absorbance scans of four amino acids, i.e. glycine, phenylalanine, tyrosine and tryptophan.

Questions (relating to UV/Visible absorbance scans):

8. The amino acid absorbances were scanned between 200-350 nm, using a quartz cuvette. Why? [5]

9. Why were you not given the opportunity to measure the UV-visible absorbance scans? [5]

10. Which amino acid has the highest absorbance (at 280 nm) per unit concentration? [5]

11. Relate the amino acid absorbances to the structures and chemical properties of the amino acids. Discuss. [10]

12. Plot the absorbance values for tryptophan at 280 nm (Y-axis) against concentration (X-axis)...