Bringing biological insights to solar cells

December 3, 2011 ~ Chris Wolverton ~ Leave a comment

Converting the energy from sunlight into a useful electric potential in order to charge a battery or power a lightbulb is almost always carried out by silicon solar panels. There are a lot of good reasons why silicon is used for light collection, but there is no reason this process must rely on this material. In fact, one reason to look at other possible materials is that nature itself has a number of materials that convert light energy into electrochemical gradients.

The capacity to harvest light energy and use it for powering the cell is ancient, having evolved on Earth at least 1 billion years ago. We find the results of this in all of the true plants today, as well as numerous algae and phytoplankton. But it’s also found in many more primitive organisms, and they may have some tricks for collecting light efficiently that could prove useful as a model to follow for solar technology. That’s exactly what a research group has been working on at the Photosynthetic Antenna Research Center at Washington University.

Taking a page out of the way primitive photosynthetic cells harvest light, they have found a way to assemble the pigments needed to harvest light by studying a structure called the chlorosome, found in photosynthetic green bacteria. Unlike the high degree of structural specialization found in land plant chloroplasts, these bacteria lack any such specialization, instead relying on the chlorosome region to harvest light. It is the self-assembling nature of the pigments into the chlorosome that the researchers find to have potential application in the development of alternative solar technology. Seems obvious to look throughout nature to solve difficult problems like these, and to provide the funds in basic research to do so.

Lytro cameras and research imaging

October 20, 2011 ~ Chris Wolverton ~ Leave a comment

All of the tech blogs are abuzz over a new kind of camera by a company called Lytro. Rather than focus on a plane in space to form an image, the Lytro captures an entire light field in front of the camera, allowing you to focus on any plane in the field after capture. To get an idea how it works, go play with their photo gallery and come back.

As someone who uses images as data to understand how plants grow and respond to stimuli, I’m very intrigued by this concept. One of the obvious weaknesses of our current methodology is that we usually limit our growth analysis to a 2-D plane because it’s tough to capture 3-D data. To get an idea of how this problem has been overcome in the past, see the article by Randy Clark and others from June 2011 in Plant Physiology (see Figure 1 in particular). If I understand this technology correctly, it could overcome that limitation in an elegant way and allow us to collect full 3-D data sets with a single, inexpensive camera. I’ll be curious to get ahold of one and try it out when they ship early next year.

Herbicide Tolerance in the Fields

October 18, 2011 ~ Chris Wolverton ~ Leave a comment

I’ve had a chance to drive I-71 through southwestern Ohio a few times this fall, and I can’t help but notice the explosion of weeds in the soybean fields this year. I’m guessing almost all larger growers are using Roundup-Ready soybeans, a genetically-engineered cultivar that allows growers to control weeds with the potent herbicide, Roundup. This herbicide is actually an enzyme inhibitor which, when present, prohibits the plant from making aromatic amino acids, killing them. Roundup-Ready crops have a gene originating from bacteria that encodes the target enzyme. This variant of the enzyme is less inhibited by Roundup, allowing the crop to survive even in the presence of Roundup.

Because of its combination of specificity and relatively short half-life in the soil, Roundup has been considered a once-in-a-lifetime herbicide, not likely to be matched anytime soon. And now, because of misapplication and overuse, we are seeing the artificial selection of plants with tolerance for Roundup, rendering it an ineffective herbicide in certain locations. The implications of losing Roundup are huge, as it has been a key enabler for no-till agriculture practice, which helps improve soil structure and reduce soil erosion.

An Update on the BRCA1 Story

July 29, 2011 ~ Chris Wolverton ~ 1 Comment

First, the setup:

In an opinion issued in March 2010, United States District Judge Robert W. Sweet in Manhattan ruled the patents were invalid. The importance of DNA, he said, was the information content it carried in terms of how proteins should be made. In that aspect, he said, the isolated DNA was not really different from the DNA in the body. The argument that isolating the DNA made it different, he said, was just “a lawyer’s trick.”

Then:

But the appellate decision Friday rejected Judge Sweet’s reasoning, saying that since DNA is a chemical, the chemical structure is what matters and that “informational content is irrelevant to that fact.”

I think my mind just exploded. I guess I better revise my notes on DNA for next semester, since a judge just ruled that its informational content is irrelevant to its chemical nature.

via Gene Patent in Cancer Test Upheld by Appeals Panel – NYTimes.com.

Our Article Got the Cover!

March 20, 2011 ~ Chris Wolverton ~ 1 Comment

The last article I wrote here was about my experiences publishing in science at a liberal arts college. Since getting the article accepted, I’ve completed a couple of rounds of revisions, with a final acceptance in early December. Now I’ve learned that one of our images was selected for the cover of the April 2011 issue! More than anything, I just wanted to note it here for posterity. I’m so grateful I get to work with students I love on interesting research questions.

Publishing in Science with Undergraduates at a Liberal Arts College

October 14, 2010 ~ Chris Wolverton ~ 1 Comment

I just submitted the revisions on a manuscript that was (tentatively) accepted in Physiologia Plantarum in mid-September. I’m hopeful the changes I made will make it acceptable to the reviewers and editor. I’m writing this summary today to remind myself what it takes to see a project through from conception to publication here at OWU. I’m publishing it on my blog in case this narrative might be helpful for other biology faculty members at undergraduate institutions. I don’t expect that my experience is normal, or even comparable, but it might nonetheless be helpful to have another data point. As of today, I am a tenured Associate Professor, in my ninth year at OWU. I have not received extramural funding for my research (to be honest, I haven’t even attempted it yet), but I have benefitted from 2 ASPB SURF awards to students.

Timeline

Now that it’s close to complete, it’s a good time to look back at the project and take stock. I started this project in the spring semester of 2006 with my honors tutorial students, Alex Paya and Natalie Janney. I had been thinking about it for several years before then, but we got to work screening for starchless mutant roots (pgm-1) carrying the DR5-GFP reporter gene during that semester. Alex stayed in my lab that summer, along with Liz Calhoun, and he worked almost exclusively on the starchless mutant project throughout the summer. He also returned to the lab several times over the next three years for independent studies, continuing the work he started as a freshman characterizing the growth and gravitropic response of the mutant. During that time, Jonida Toska joined the lab and worked hard on collecting more auxin flux data using the confocal microscope and our DR5-GFP/pgm-1 plants. Both Alex and Jonida are co-authors, along with me, on the paper.

To be fair, this is not the only project I have been investing in over the last 4 years. I have had a number of other summer and independent study students over this time, and have been driving 2 other projects unrelated to this one. Hopefully I’ll be able to write about those in the same light as I am this one at some point in the not-too-distant future!

Time to write

We first submitted the manuscript to a journal last summer/fall, and it was not accepted. The general sense of the reviewers was that it needed more data, and one experiment in particular, to be accepted at that journal. We tried to complete the suggested experiment, which involved the creation of a new double mutant, but couldn’t identify a successful cross when we screened the putative offspring last winter. So I decided to rewrite the paper and submit it to a different journal. During that process, I used the first set of reviews to identify weaknesses, and I felt the paper was much better by the time I completed the rewrite, a sense that was confirmed upon receiving the favorable editorial decision in mid-September.

Over the last 3 weeks, I made a lot of small-ish changes and improvements in the revision stage, many of which were suggested by the three reviewers. I have to say, the feedback from reviewers was some of the best I’ve ever received on a paper — very balanced, helpful, insightful, and generally positive. They also pointed out some weaknesses that I was able to address in the revision, including the addition of new data I’ve collected over the last 3 weeks.

Accounting

In an attempt to put this publication into the context of the rest of my professional life cheap jerseys from China here at OWU, here is an abridged accounting of the inputs into this project:

1 freshman honors tutorial project
1 summer science research student
4 independent study credits (2 for Alex, 2 for Jonida)
1 sabbatical leave (partial)
3 years of data collection and analysis
4 years to publication

Here is an accounting of my teaching load over this period:

For comparison, our accounting of teaching load in the sciences at OWU is based on ‘contact hours,’ which includes time spent in lectures and labs. We’re asked to maintain an average of 10-12 contact hours. I should note that I taught a new (to me) class and lab in Fall 09, and 2 new classes in Spring 10. I have also been pretty busy with committee work and university service over this time period, but I don’t want to try to account for that!
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