Δε ) / (c l) fileUppgift’5’(10p)’ ’...
Transcript of Δε ) / (c l) fileUppgift’5’(10p)’ ’...
Tentamen i Biomätteknik (TFKE37), 9 januari 2014. Uppgift 1 (10p) For the acronyms FT-‐IR, AUC, AFM, UV and MALDI:
a) spell out the full name of the method described by the acronyms! b) For every method, suggest two properties of biomolecules that can be
favorably analyzed using this method. Uppgift 2 (10p) Below you find four algebraic expressions. Choose any TWO of these expressions and for these two (and only these!), please describe to the best of your ability:
a) what the algebraic expression concerns b) what property of the measurement is addressed in this expression c) how can the properties of this algebraic expression help the
interpretation of the method, data and/or measurements?
Δε = (εL-εR) = (AL-AR) / (c • l)
Uppgift 3 (12p) It has been found that inhibitors of the MdmX-‐P53 interaction lower the viability of cancer cells which could be a novel therapeutic avenue for deriving more efficient cancer drugs. To evaluate this further, a research group set up an assay to screen for compounds inhibiting the p53-‐MdmX-‐interaction. Using the figure below please answer the following questions:
a) What is GFP? What should ’BHQ1’ be? b) Please describe the strategy that this group has taken to screen their
library of compounds. c) Suggest practical concerns when screening a large library of compounds
and motivate why fluorescence is a good choice for a screen like this. d) Why is the fluorescence intensity lowered on increasing the p53-‐probe
concentration? Explain possible designs of the probe part of the p53 peptide that could effectuate this.
e) Sketch an outline of the expected experimentable result curve for an efficient MdmX-‐interacting, p53-‐inhibitory compound and explain/motivate why you believe that the results should look like this.
Tsuganezawa, K., Nakagawa, Y., Kato, M., Taruya, S., Takahashi, F., Endoh, M., et al. (2013). A fluorescent-‐based high-‐throughput screening assay for small molecules that inhibit the interaction of MdmX with p53. Journal of biomolecular screening, 18(2), 191–198.
Uppgift 4 (12p) In this experiment, the p53 binding of a relative of MdmX called MDM2 was assayed. In particular, the role of the MDM2 N-‐terminal residues for efficient p53 binding was assayed.
a) What method was used in the figure below? Name and acronym! b) Explain how the experiment was performed by describing the various
features of the response curves in the figure below. c) What is shown in the inset figures? What do the dots and line represent?
How do you use such a representation of data to derive binding constants?
d) One of the experiments shows a higher affinity than the other. Can you, by simply looking at the experimental curves, suggest a reason for this? Please motivate!
e) What seems to be the role of the N-‐terminal residues in MDM2 with respect to p53 binding? How can this be affected by N-‐terminal phosphorylation?
Zhan, C., Varney, K., Yuan, W., Zhao, L., & Lu, W. (2012). Interrogation of MDM2 phosphorylation in p53 activation using native chemical ligation: the functional role of Ser17 phosphorylation in MDM2 reexamined. Journal of the American Chemical Society, 134 (15), 6855–6864.
Uppgift 5 (10p) In this experiment, a research group evaluated the specific details of the p53 peptide segment binding to MDM2 and found that mutations in p53 position 12 affected binding. A selection of experiments with mutations at position 12 is shown below.
a) Which technique was used? Name and acronym! b) Explain the fundamentals of this technique (describe equipment setup
and how is the experiment is performed, what is measured and how, how are results evaluated; in particular explain difference between top and bottom panels below).
c) Based on the results shown below, did the affinity increase or decrease with the mutations? Motivate your answer by analysing the experimental diagrams.
d) What further difference can you see when comparing the results for p53Ala and p53Asn? What could be the reason for this?
Brown, C. J., Dastidar, S. G., Quah, S. T., Lim, A., Chia, B., & Verma, C. S. (2011). C-‐terminal substitution of MDM2 interacting peptides modulates binding affinity by distinctive mechanisms. PloS one, 6(8), e24122. Uppgift 6 (10p) The following methods depend on the mass of the molecule/protein for their measurement response: SPR, AUC, Fluorescence anisotropy, MALDI and SDS-‐PAGE.
a) For each method, describe how this depends on moleular weight and how the molecular weight dependence is detected experimentally.
b) For each method, give me one mass-‐related, method-‐specific advantage and one mass-‐related, method-‐specific disadvantage in studying biomolecules!
Uppgift 7 (16p) The p53 protein is essential for normal cell growth, and therefore, mechanisms that increase its destruction by proteosomal degradation increase the risk for cancer. In this work, scientists propose a region of interaction for proteins involved in p53 degradation and assay this region by means of mutations and biophysical techniques. The region studied is highlighted (figure at right), and results obtained from two of the mutants are shown below in figure A-‐C.
a) What methods have been used below? Names and acronyms! b) Describe the results obtained in figures A-‐B. How were they recorded?
What differs between the ways of measuring in figure A compared to figure B? What different types of information can be obtained from these two panels of results? How is this information evaluated?
c) Describe results obtained in figure C. Do they agree with results in A+B? d) Compare the efforts required in terms of protein sample preparation for
experiments A-‐B compared to experiment C. Which experiment is more demanding with respect to protein sample preparation? Why?
e) When looking at p53 protein interactions, what additional information could be obtained in the more demanding experiment? Describe!
Bernard, X., Robinson, P., Nominé, Y., Masson, M., Charbonnier, S., Ramirez-‐Ramos, J. R., et al. (2011). Proteasomal degradation of p53 by human papillomavirus E6 oncoprotein relies on the structural integrity of p53 core domain. PloS one, 6(10), e25981.