Luxene’s comment on: Selective Tuning of Elastin-like Polypeptide Properties via Methionine Oxidation

By Luxene Belfleur

Luxene blog image 18-05

Figure 1. Kekule structure of and synthesis of ELP 2 and 3. Cartoon representation of ELPs solution, the LCST behavior and measurement of ELPs

In this article, the authors reported the LCST modulation of Elastin-like polymers (ELP) by the modification towards oxidation reactions of the methionine thioester group of the ELP 1 to form sulfoxide and sulfone ELPs derivatives 2 and 3 respectively (Figure 1). They isolated ELP 1 from plasmid DNA of E.coli bacteria and purified it by SDS-Page. In acidic media, using 30% hydrogen peroxide and 1% of acetic acid or formic acid in water, they obtained ELP derivatives 2 and 3 respectively and the molecular weight and structural elucidation of ELP 1 and its derivatives 2 and 3 had been examined and confirmed by mass spectrometry and NMR respectively.
They performed turbidity experiments to determine the cloud points of those three ELPs. As expected, both ELP derivatives 2 and 3 had a higher LCST behavior (55 °C and 43 °C for 2 and 3 respectively) compared to ELP 1 which is 25 °C (Figure 1). This is due to the increasing of water solubility of the modified ELPs (2 and 3), which required more energy to break the interaction between water and them (ELP 2 and 3) in order to evacuate the hydration shell around these ELPs and favored the collapse of the letters. Moreover, it was expected that ELP 3 would have a higher cloud point than the ELP 2 counterpart, however, this was not the case because the large dipole moment of ELP 3 favored intramolecular and intermolecular interactions between them and the protein respectively which promoted a decrease of the water solubility. They evaluated the influence of the I¯ and NO3¯ anions on the phase transition of the three ELPs and found that those anions had no significant effect on the LCST point of the ELP 1 while I¯ increased the LCST of ELP 2 and NO3¯ decreased the solubility of ELP 3 in agreement with the Hofmeister series effect.
They reported an interesting and straightforward work by turning the LCST behavior of ELPs towards synthetic modification. This work has inspired and motivated my team for designing and synthesizing sulfoxides and sulfones containing guanosine derivatives in order to both, stabilize the thioester containing guanosine derivatives compounds that we synthesize, and modulate the LCST properties of the SGQs that will be made from oxidizing 8ArG derivatives product.


7 thoughts on “Luxene’s comment on: Selective Tuning of Elastin-like Polypeptide Properties via Methionine Oxidation

  1. Rating (synopsis): 2/5
    Rating (image): 3/5

    There are a few inaccuracies in the way the experiment is described. For example, ELP 1 isn’t isolated from plasmid DNA of E.coli bacteria. Also, some of the phrasing could use revision to make it more comprehensible such as “modulation (…) by the modification towards oxidation reactions”, and occasionally some words are misused (letters instead of latter). In general, although it is possible to understand the synopsis, it would greatly benefit from some feedback in writing before posting. Maybe someone else from the lab can quickly proofread before submitting? At least I can volunteer to do so.
    The increase in LCST temperature with increasing hydrophilicity of the derivatives is said to be due to the energy required to break the interaction between water and the ELPs, which sounds misleading to me. It seems to suggest the existence of attractive interactions between water and the peptide. I’m not sure this is what Luxene meant to convey, however I think it would be better described saying that the increased hydrophilicity has the effect of decreasing the energetic penalty of solubilizing the peptide. Because the penalty increases with raising temperature, the more hydrophilic peptides have a higher threshold before separating from solution. Furthermore, I didn’t understand the explanation given as to why ELP 3 doesn’t present a higher LCST temperature: what does “the large dipole moment of ELP 3 favored intramolecular and intermolecular interactions between them and the protein respectively” mean?
    I did like the relationship drawn between the research presented and the research done in our group.
    The figure looks attractive. The steps of heating to produce phase separation and determining LCST seem to be set as two different processes (illustrated by different arrows in sequential steps), something which I think could be misleading.

  2. Rating (synopsis): 3/5
    Rating (image): 4/5

    The narrative of Luxene’s comment is very dense and has some misspellings. For example, in the last paragraph, instead of writing “tuning the LCST behavior”, he wrote “turning the LCST behavior.” I agree with Diana that we should proofread before posting, not only Luxene’s but all of our comments, as this will improve the quality of the writing in the blog and ours.

    The image constructed by Luxene explains the article, but I have some recommendations. For example, instead of the word “heated” you could substitute it with T>LCST. Also, I don’t think it’s necessary to include a description of the figure, but I guess we can discuss that later.

  3. Rating (synopsis): 3/5
    Rating (figure): 4/5

    The summary was not very clear to me about the central idea. However, I was able to familiarize myself with the techniques they use in their procedures, such as the SDSPage technique. These are biochemical techniques that I have seen in my class.

    The image is very direct. And easy to understand. I agree with Luis that is not necessary to include a description of the figure because in the synopsis should be describe.

  4. Rating Synopsis: 3/5
    Rating Figure: 5/5

    As Valeria commented, I didn’t get the clearly the main goal of the paper and also got me confused as I read it because of the various ELP’s that they were working with. Still It discussed the LCST which is something that we work with in the lab and it is quite important for the formation of the Hacky Sacks. It really helped me to understand better and associate it with what we do in the lab and how it affect.
    The figure was very well presented and organized.

  5. Rating (Synopsis): 3/5
    Rating (Figure): 4/5

    The synopsis in general is very heavy going and makes it hard to understand the important idea of the paper. On the other hand, reading the paper and in the presentation I did understand the use of solvents with different Hofmeister salts to detect different transition temperatures and ,also, understood much better the LCST behavior, important for our Supramolecular Hacky Sacks system. I agree with Diana and Luis that we should all collaborate to do proof reading to anyone that needs help organizing ideas and in grammatical issues.

    The picture is very well designed and delivers the full step by step idea of the synopsis.

  6. Rating (Synopsis): 3/5
    Rating (Figure): 3.5/5

    I was not here for this presentation and I did not have the interpretation of the information given by Luxene at the group meeting. Because of this it was an interesting experiment to see if I could correlate the information i understood from the article through reading it and this synopsis. I can say that Luxene’s synopsis does a great job of compiling the experimental results from the article, but apart from I understood about the same from both sources which was not much. Apart from the errors already reported by my colleagues, the synopsis is useful, but not enlightening. The figure is also very simple and to the point, but I wished Luxene had tried to one-up the authors and be a little bit more creative.

  7. Synopsis: 2.5/5
    Figure: 3/5

    The article itself is very interesting leaving the reader somewhat wanting more. That I blame on what have become our second nature of not only looking at the “How was this done?” but at the “What is the application of this?”. They briefly state it in the paper. But as our lab’s discussion goes leaded by Luxene for this paper, it is lacking exactly that. The construction of the system, as in the paper, Luxene goes over it in somewhat detailed way. Yet in Luxene’s narrative, the transitions between points that he wants to convey seems choppy and to some of them disjointed. Still, the referring to the image may be helpful on some points of his narrative. The image itself, although not a TOC Figure, is a scheme that summarizes the paper very well.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

w

Connecting to %s