How rigid are viruses.

Viruses have traditionally been studied as pathogens, but in recent years they have been adapted for applications ranging from drug delivery and gene therapy to nanotechnology, photonics, and electronics. Although the structures of many viruses are known, most of their biophysical properties remain largely unexplored. Using Brillouin light scattering, we analyzed the mechanical rigidity, intervirion coupling, and vibrational eigenmodes of Wiseana iridovirus (WIV). We identified phonon modes propagating through the viral assemblies as well as the localized vibrational eigenmode of individual viruses. The measurements indicate a Young's modulus of approximately 7 GPa for single virus particles and their assemblies, surprisingly high for "soft" materials. Mechanical modeling confirms that the DNA core dominates the WIV rigidity. The results also indicate a peculiar mechanical coupling during self-assembly of WIV particles.

Pregnancy outcome following first-trimester exposure to fluoxetine (Prozac)

OBJECTIVE: To compare pregnancy outcome following first-trimester fluoxetine (Prozac) exposure with pregnancy outcome in two matched control groups. Fluoxetine is a new antidepressant used by many young women. Currently, no published data exist on its safety in pregnancy. DESIGN: We prospectively collected and followed up 128 pregnant women exposed to a mean daily dose of 25.8 mg (+/- 13 mg) of fluoxetine during the first trimester and compared pregnancy outcome with two matched groups of women exposed during the first trimester of pregnancy to either nonteratogens or tricyclic antidepressants. RESULTS: Rates of major malformations were comparable within the three groups and did not exceed those expected in the general population. Women treated with fluoxetine had a tendency for increased risk for miscarriage when compared with women exposed to nonteratogens (relative risk, 1.9; 95% confidence interval, 0.92 to 3.92). The rate of miscarriages in the fluoxetine group was comparable with the tricyclic group (13.5% and 12.2% vs 6.8% in the nonteratogens). CONCLUSIONS: Our study suggests that the use of fluoxetine during embryogenesis is not associated with an increased risk of major malformations. Women exposed to both fluoxetine and tricyclic antidepressants tended to report higher rates of miscarriage; further studies will be needed to confirm this observation and to separate the effects of the psychiatric condition from the associated drugs. Long-term studies will be warranted to rule out potential developmental teratology of fluoxetine, which affects a central nervous system neurotransmitter.