Tuesday, June 9, 2009

My first rating and commenting of a PLoS article in my own field (Scary!)

SJK 6/9/09: Here is a link to related friendfeed discussion.

I just finished reading and commenting on a PLoS One article that is near my own field of research. The article is titled, "Dissection of Kinesin's Processivity." The authors are: Sarah Adio, Johann Jaud, Bettina Ebbing, Matthias Rief, and G√ľnther Woehlke. You can see my rating and overall comments here. (Since I'm not sure if that link will work, I'll also repost my comments below.)

Throughout the process of reading and commenting on this article, I learned a lot more about my fears and barriers to PLoS commenting. I discussed some of these in my prior post about my first PLoS rating. In contrast to my first rating, this article is smack in the middle of my field of interest (the kinesin molecular motor). I deliberately chose the most relevant PLoS article I could find. I'd estimate that my fear of placing comments was at least 10 times higher than for an article outside my field. I definitely felt like my comments were piping directly into the author's email inbox, ready to enrage them at any misunderstanding or criticism I posted. I still feel this way and am a bit worried. My worries are probably justified to some extent, since I am very new to this field. Thus, I could easily be seen as an ungrateful newcomer who hasn't paid his dues. And of course the people who wrote the article could end up anonymously reviewing my own papers and grants.

Given those worries, I came close to deciding not to post my rating. However after much reading and thinking about their results, I felt compelled to make a serious comment about error analysis supporting one of their conclusions (not their major conclusion). I was confident that my criticism was fair, and convinced myself that posting the comment was the right thing to do--perhaps I can save another reader a lot of time, or even help the authors out if they read it. I posted my criticism directly in the article, along with several typo corrections. After doing that (late last night), I realized that if / when the authors DO see my comments, they'll see a string of petty typo corrections and then this criticism, but nothing positive at all. That's a problem!!! Because of this, I decided to sleep on it, and compose an overall rating with positive comments today. I was busy most of the day, but finally tonight was able to finish my rating. In all honesty, though, without having travelled that slippery slope of commenting, I don't think I would have posted this rating tonight. I would have balked at the risk of angering the authors, sticking my neck out, and possibly being wrong. I probably would have convinced myself that these risks outweighed any meager potential gain that the world of science would get from my remarks.

I'm a bit worn out now. Hopefully in the comments here or more likely, on FriendFeed, we can talk about these things. I hope in the next couple days to expand on my review of the paper in my research blog, and to include it as my first Research Blogging attempt.

Reposting of my rating and overall comments on the article

This is what I submitted to PLoS as my rating:

Insight: 4 stars, Reliability 3 stars, Style, 4 stars.

The authors recently characterized NcKin3, which is the first known,
naturally dimeric but non-processive and plus-end motor. In this
report, they are leveraging this discovery to study chimeric constructs
between NcKin (a dimeric, processive Kinesin-1 motor in the same
organism) and NcKin3. They make two different chimeric constructs: one
with the head of NcKin and the neck of NcKin3, and the other with head
of NcKin3 and neck of NcKin. Importantly, the head included the core
motor domain AND the neck linker region.

I congratulate the
authors on a lot of very nice work that must have been very difficult!
The results they report come from an impressive array of difficult
assays spanning single-fluorophore position tracking, single-molecule
bead motility assays with optical tweezers, gliding assays, and a
variety of ensemble biochemical assays.

Study of the two
chimeric constructs, in comparison with the NcKin and NcKin3 wildtypes
allowed the authors to gain insight into which parts of the kinesin
motor are important for conferring processivity onto dimeric
constructs. (And also, which parts are important in NcKin3 for
inactivating one of the heads.) As far as I know, these are the very
first two chimeras created between these two kinesins and thus open the
door for many more investigations into how processivity is regulated in
the motor domain, neck-linker, and neck regions. The results here
indicate that many more chimeric structures and site-directed
mutagenesis studies will be necessary and valuable. Of course, that is
a lot of work, but the results here open the door for those further

For me, the most fascinating result was point (iii) on
page 4. The authors show that the Head3/Neck1 construct seems to get
stuck in a "kinetic dead end." As they say, the kinesin-1 neck appears
to confer some elements of processivity, but not all. Combined with the
missing elements (which kinesin-3 head lacks), the motor is actually a
bit more handicapped, as shown by a gradual decrease in gliding
velocity as the concentration of motors is increased.

I also had a couple questions about the paper that I noted previously (see prior article comments):

* Statistical significance of processivity measurements.

* Lack of discussion and comparison with previous Ncd/Kinesin-1 chimera results

Our lab (http://openwetware.org/wiki/Koch_Lab) has recently obtained
major funding to study kinesin. I do not think we have competing
interests with these authors or the work they've presented here, but I
thought it worth mentioning.

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