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This Week in PNAS: Jul 22, 2009

This week in PNAS, Harvard systems biologists used fine-needle aspirates to detect and profile cancer cells. The diagnostic magnetic resonance sensor, which combines a miniature NMR probe with targeted magnetic nanoparticles, "measures the transverse relaxation rate of water molecules in biological samples in which target cells of interest are labeled with magnetic nanoparticles," they say in the abstract. Using their sensor, they were able to detect as few as two cancer cells in 1-μL sample volumes.

University of Utah scientists researched the influence of the state of the bound nucleotide (ATP, ADP-Pi, or ADP) on the conformational free-energy landscape of actin. Using all-atom molecular dynamics calculations, they found that in the ADP-bound monomer, the folded and unfolded states of the DNase-I binding loop have similar relative free-energy, whereas in the ADP-bound actin trimer, the folded DB loop is stable and in a free-energy minimum. Their results suggest "a mechanism of allosteric interactions between the nucleotide binding cleft and the DB loop."

Scientists led by lead author Hong Ma at Fudan University used high-throughput RNA sequencing to profile the transcriptome of embryonic and neonatal mouse cortex. They used over 27 million reads to identify mRNAs from the mouse cortex for more than 16,000 genes at either embryonic day 18 (E18) or postnatal day 7 (P7), "a period of significant synaptogenesis for neural circuit formation." They found that neurogenesis-related genes were more highly expressed at E18 than at P7 whereas synaptic proteins such as synaptotagmin, complexin 2, and syntaxin were up-regulated from E18 to P7.

Finally, in work from RainDance Technologies' Michael Samuels, with help from Norbert Perrimon among others, developed a droplet-based microfluidic technology for high-throughput screening of single mammalian cells. The platform captures single cells in microdroplets from 1 pL to 10 nL volumes that rest in a carrier oil. They validated a "full droplet screening workflow by conducting a droplet-based cytotoxicity screen," they say in the abstract.

The Scan

Pig Organ Transplants Considered

The Wall Street Journal reports that the US Food and Drug Administration may soon allow clinical trials that involve transplanting pig organs into humans.

'Poo-Bank' Proposal

Harvard Medical School researchers suggest people should bank stool samples when they are young to transplant when they later develop age-related diseases.

Spurred to Develop Again

New Scientist reports that researchers may have uncovered why about 60 percent of in vitro fertilization embryos stop developing.

Science Papers Examine Breast Milk Cell Populations, Cerebral Cortex Cellular Diversity, Micronesia Population History

In Science this week: unique cell populations found within breast milk, 100 transcriptionally distinct cell populations uncovered in the cerebral cortex, and more.