Adenovirus Structure Described

August 29, 2010

Perhaps relatively few people would immediately know what the term adenovirus refers to, but most of us are probably familiar with the effects of a member of this family of viruses, the one that causes the common cold.  Although it is rare that these microbes cause permanent damage or death in people with normally-functioning immune systems, they have certainly been a source of human misery for a long time.

The Medical Daily news site has a report on some new research by scientists at the Scripps Research Institute who, in  a paper [abstract]  published in the August 27 issue of Science, have presented the first detailed description of the structure of an adenovirus, down to atomic scale.  The imaging of the crystalline virus was done using X-ray diffraction, giving a resolution of 3.5 angstroms.   (One angstrom, abbreviated Å, is one nanometer, or 1 × 10-10 meter.)   The virus particles analyzed have a mass of approximately 150 megadaltons, or 150 million times the mass of a single carbon atom, and contain nearly 1 million amino acids.  This is the largest such particle analyzed to date.

The team began to work on determining the molecular structure of the virus in 1998; the subsequent project turned out to take much longer than expected.   One of their major hurdles was getting the virus into a form which could be crystallized.  They developed a variant form of the virus to this end, but eventually also had to use robotic crystallization, which can use samples of solution much smaller than usually possible (samples on the order of 50 nanoliters were used).  The work also used a new synchrotron, the Advanced Photon Source 23 ID-D beamline at the Argonne National Laboratory, to achieve the necessary resolution.

This really is a significant accomplishment.  Of course, elucidating the structure of the virus may some day help in developing treatments for infections caused by the virus, which would delight cold sufferers everywhere.  However, a more important possible benefit relates to the development of genetic therapies.  One of the techniques used in this area is the insertion of the genetic material into a suitably benign virus, which then can infect the target cells.  Researchers in the field have been interested in the adenovirus family because the virus is fairly hardy and can infect a variety of cell types.   A better understanding of the virus’s structure might be of great value in making the therapy more effective, while minimizing side effects.


Will Greener Lighting Save Energy?

August 29, 2010

I feel reasonably sure that we all, by now, have heard some of the urging to reduce our energy consumption, and thereby indirectly help reduce emissions of carbon dioxide.  One of the steps that has been widely recommended, at least here in the US, is to substitute more efficient light sources (such as compact fluorescent lamps) for our traditional incandescent light bulbs.  (Most of the energy used by incandescent bulbs is given off as heat.)  There has also been an expectation (I wrote about it earlier) that further development of light-emitting diodes (LEDs) could give us an even more energy-efficient source of light.    There has been a more or less common but unspoken assumption that people would just switch to the new lighting technologies, thereby saving energy, with nothing else changing.

Now this is a somewhat curious assumption to make from an economic point of view.  If there new lighting devices save energy, that will manifest itself as a lower cost per unit of light obtained.  (Of course, one must account for the total cost of light production, including the purchase of the device, but at least the possibility of net savings exists.)   For most goods that people buy, a drop in the price per unit will tend to produce an increase in the number of units consumed, other things being equal.

This week’s edition of The Economist has an article reporting on a new analysis[abstract] published this week in the Journal of Physics D by a groups of scientists at Sandia National Laboratory [full paper PDF free download for 1 month].  (The PhysOrg.com site also has an article on this.)  The authors examine the history of lighting technology improvements, and find that better, and cheaper, lighting technology has generally produced an increased demand for lighting.  As The Economist puts it,

The light perceived by the human eye is measured in units called lumen-hours. This is about the amount produced by burning a candle for an hour. In 1700 a typical Briton consumed 580 lumen-hours in the course of a year, from candles, wood and oil. Today, burning electric lights, he uses about 46 megalumen-hours—almost 100,000 times as much. Better technology has stimulated demand, resulting in more energy being purchased for conversion into light.

If you have ever tried to manage after dark by candlelight when the power is out, you will probably have gained some appreciation that the artificial light levels we are used to today are rather higher than those expected a few generations ago.

The paper itself is a very good piece of work.  It looks at how lighting consumption has changed as new technologies for producing artificial light have been introduced.   Interestingly, using data from a collection of studies, the authors find that the proportion of world-wide gross domestic product per capita spent on artificial light has remained nearly constant, at about 0..71%.   As the article points out, this is not a perverse result: people don’t do this because they are gluttons, but because the greater availability of useful lighting makes them more productive and brings other benefits, such as being able to read at night.

The authors also develop a model to forecast what the net effect of introducing LED lighting might be.  Using the assumption from current technology forecasts that, by 2030, LEDs will be about three times as efficient as current compact fluorescent lamps, their model predicts that per capita artificial light consumption will increase by about 10× over the same period.  But they also point out some possible ways in which this increase might be mitigated; for example, since LEDs are solid-state electronic devices, it should be possible to control both the amount and color temperature of the delivered light in a much more precise and localized way.

The paper is a good example of trying to think through all the implications of a technology change; it is well worth a read.


%d bloggers like this: