ScienceDaily (Oct. 30, 2012) ? New research has found that the transport of proteins into chloroplasts in plants is differentially regulated by the age of the chloroplast; upturning the previously accepted notion that this process is age-independent or only globally up- or down- regulated for all proteins.
The research, led by Dr. Hsou-min Li, a Research Fellow from the Institute of Molecular Biology, Academia Sinica of Taiwan, is published October 30 in the open access journal PLOS Biology.
It's long been known that gene expression changes with age, for example, some genes are expressed in young organisms, others in aged organisms. However, up until now, it has been generally believed that the protein-transport processes that take place inside a cell occur independently of the cell's age.
Dr. Li and colleagues investigated pea leaves of different ages and discovered that proteins imported into chloroplasts -- the organelles in plant cells where photosynthesis occurs -- can be divided into three groups: one group prefers to be imported into very young chloroplasts, the second group has no special preference, and the third group prefer to be imported into older chloroplasts.
"Age-dependent regulation at the protein transport level had not been thoroughly investigated due to technical difficulties," Dr Li explained. "Pea seedlings offer an excellent model for such studies because each plant has leaves of different ages on a single stem and they are cheap to grow. Other scientists have taken advantage of this but at that time, they only had a very limited number of proteins to test. Now with data from genomic and proteomic analyses, we can test a lot more proteins and can show not only that the regulation exists, but also that every protein can be regulated differently."
After finding this novel regulation, Dr Li's group then attempted to find the signal that controls age selectivity. They found that, for each protein, the age-selective signal is located within the signal peptide that controls organelle import. They also identified a signal-peptide motif that is necessary for targeting proteins to older chloroplasts.
"We knew that signal peptides specify the organelle a protein is supposed to be targeted to, acting like address labels," said Dr Li. "When we found that they also contain the information for the age selectivity we observed, we decided to try to identify the "code" that instructs a protein to go to older chloroplasts first. The existence of such a code means that chloroplast signal peptides are not just address labels -- they also contain information about "when" a protein should be delivered."
These findings may have implications for selectively targeting proteins into organelles of aging tissues, said Dr Li. "We believe similar kinds of regulation mechanisms may also exist for other organelles in other organisms, like humans. For example, there may be signal peptide motifs that will allow us to specifically target therapeutic proteins into mitochondria in aging cardiac tissues."
Share this story on Facebook, Twitter, and Google:
Other social bookmarking and sharing tools:
Story Source:
The above story is reprinted from materials provided by Public Library of Science.
Note: Materials may be edited for content and length. For further information, please contact the source cited above.
Journal Reference:
- Yi-Shan Teng, Po-Ting Chan, Hsou-min Li. Differential Age-Dependent Import Regulation by Signal Peptides. PLoS Biology, 2012; 10 (10): e1001416 DOI: 10.1371/journal.pbio.1001416
Note: If no author is given, the source is cited instead.
Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.
Source: http://feeds.sciencedaily.com/~r/sciencedaily/top_news/~3/H0_87hNtj-Y/121030210341.htm
Sandy Hurricane flight tracker Marina Krim Justin Bieber cancer lil wayne Mockingbird Lane Lena Dunham
This piece is part of the Africa and the War on Drugs debate ? a series of articles and reviews commissioned to coincide with the launch of the latest book in the African Arguments series: ?Africa and the War on Drugs.
Early Signs and Symptoms
Dear Lifehacker,
Obviously, you're only syncing a small portion of your library to your device, which means you've probably hand-picked which songs you want to sync. Before you start trying to fit more songs, I'd recommend re-evaluating which of those songs you actually need, putting them on a playlist, and then syncing that playlist to your device. Check out our guide to cleaning out your music library for more info. You don't even have to delete the files from your library if you don't want to, but those techniques should help you nail down what you're actually listening to and sync only those albums to your phone. You might also want to check out how to clean up your iPhone and Android phone in case there's something else taking up space on your device.
Let's do a quick refresher on bitrate: as we've explained before, audio files can be lossless (which takes up a lot of space) or lossy (which takes up far less space). Lossless is a great format for archiving your files, but it isn't necessary to listen to them in this format, since it's impossible for most people to tell the difference between a lossless MP3 and a 320kbps MP3. If you were storing them in lossless, feel free to convert them to MP3. You'll save a ton of space and your ears won't notice a thing.
However, you don't want to just convert your existing MP3s to VBR, or you will lose quality. Instead, grab a program like dBpoweramp for Windows or XLD for Mac and re-rip the original CD (or convert from a lossless file, if you have one). Obviously this will take you awhile to re-rip your entire collection, but it's the only way you'll fit more MP3s without losing quality. For what it's worth, I did this and saved 30MB or so per album using V0 instead of 320kbps. After converting about 100 albums, I'd freed up 3GB on my iPhone?and that isn't chump change when it comes to music. If you really want to go crazy, you could even experiment with more efficient file formats like AAC and Ogg Vorbis, which will be higher quality at lower bitrates.
If that sounds like too much trouble and you're willing to "cheat" a little, you can get more of that music with a streaming service like Google Music. Check out our guide on how to use Google Music as a secondary music player and you can have your entire library ready as long as you have an internet connection on your smartphone or Wi-Fi enabled MP3 player. You could alternatively use something like Spotify and Rdio, but they're much harder to set up if you're trying to duplicate your existing library.