• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Protein studies using spectroscopy

Extracts from this document...

Introduction

Protein studies using spectroscopy Aisha Asam Biomedical sciences (HND) 27.11.03. Dr Caroline Dalton. Introduction The aim of the practical was to investigate two protein methods. Two spectroscopy methods were used. One of them was the Biuret method and the UV method. The Biuret method is based on the formation of coloured complexes, where the UV method depends on absorption of light in UV part of spectrum by certain amino acids in the protein's structure. In this experiment my aim was to find sample Y concentration. Biuret reaction- The Biuret reaction occurs upon treatment of peptides or proteins with an alkaline solution of cu2+ ions. As the copper ions are complexed by the amide nitrogen atoms of the peptide backbone, a violet colour is seen. Spectrophotometric determination of the amount of colour is used as an index of the quantity of peptide present. Various spectroscopic methods are employed in evaluating protein structure and function in ultraviolet light spectroscopy. Peptide and tyrosine bonds in proteins absorb UV light. The efficiency of light energy absorption for each chromophore is related to its molar extinction coefficient. ...read more.

Middle

At the same time five of the 0.5ml samples of Y were put into the test tubes. After getting each test tube prepared, Biuret reagent 4.5ml was added and mixed properly. Then for 15 minutes the solutes were left, to reach their maximum colour. To analyse the samples the spectrometer was used and it was set to a wavelength of 542.7nm. A sample which contained 0ml albumin, 4.5ml of Biuret, 5ml distilled water was added to a cuvette, and spectrometer was set on 0.After setting on 0 the cuvette was taken out. The samples contained the standard solutions (water and Biuret) were analysed and the absorbance was recorded. After absorbance of Biuret was measured, the Y samples were looked at, under the same wavelength. A calibration graph was determined. Five samples of Y were diluted this was done to determine the protein by UV absorbance (1 in 10 dilutions). The spectrometer was set to 278.7nm wavelength and then spectrometer was zeroed using distilled water (1cm). In a silica cuvette (silica cuvettes need to be rinsed before and after). ...read more.

Conclusion

With the UV method I was able to know the structure of the protein (eg if it contained amino acids). Because the absorbance is always proportional to the concentration. (The more aromatic amino acids present in the protein the more rise in protein). Tyrosine and Alanine didn't affect the Biuret method, where as in the UV method it was clear that absorbance was different, this was because the tyrosine which is a phenol group absorbs more UV light which causes decolourisation of the electrons in the tyrosine's benzene ring so the absorbance was high. Where the alanine didn't absorb the UV light so the absorbance was small this is shown in my table of tyrosine results. By looking at my standard deviation, for the biuret method. I would suggest it is very small (0.729) this means my results were reliable/verifiable and I didn't get any anomalous results. The standard deviation for UV method was (0.986). Something went wrong in my practical because the absorbance was low, this happened bacause I didn't mix the solution well or didn't zero the spectrometer. Below is how I identified there was something wrong with my results: * CV was higher than 5% for biuret method (12.4%) and for the UV method (14. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our GCSE Aqueous Chemistry section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related GCSE Aqueous Chemistry essays

  1. Marked by a teacher

    The Effect of pH on the Strength of Keratin (hair protein).

    4 star(s)

    The temperature must be maintained at 20-25�c. The pH probe must be calibrated at this temperature to ensure correct readings. Thermostatically controlled temperature rooms are used to maintain temperature. A thermometer will then be used to check that the area of experimentation is at the correct temperature.

  2. Determination of Partition Coefficient

    0.03270 1.0 0.276 0.03752 1.1 0.262 0.03325 Table 3 Graph 1 From the graph, Kd = slope of graph = 0.13 With the standard value, percentage difference = = 13.3%.

  1. Electronic spectroscopy - Homoleptic chromium(III) complexes and the spectrochemical series.

    The yellow precipitate was redissolved by warming the filtrate, then cooled in an ice bath and filtered. The dark yellow product was washed with methylated spirit, air dried and dessicator dried. The complex [Cr(acac)3] (acac = acetylacetonate) was prepared as follows.

  2. SCIENTIFIC PRACTICAL TECHNIQUES

    The experimental errors in this experiment can be that the multimeters weren't accurate. Another error can be the wires, depending on the wires it gives different resistance. It can be also that the wires are not straight. To improve the accuracy of the experiment is that , using more sensitive and accurate multimeters.

  1. Investigation into the efficiency of various indigestion tablets.

    CaCO3 = 522 / 654 x 100 = 79.8% MgCO3 = 68 / 654 x 100 = 10.4% NaHCO3 = 64 / 654 x 100 = 9.8% nHCl reacting with CaCO3 = 0.00278 / 100 x 79.8 = 0.0022184mol Therefore, nCaCO3 = 0.0022184 / 2 = 0.0011092mol CaCO3 in powder.

  2. copper practical

    The iron sulphide reacts with air and it is then converted into slag. The word equation to describe this is as follows: 2FeS+ 3O2+2SiO2 2FeSiO3+2SO2 (which is the slag) 5) The copper sulphide reacts to produce a copper metal.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work