The translocation of genetic material from the viral capsid to the cell is an essential part of the viral infection process. Whether the energetics of this process is driven by the energy stored within the confined nucleic acid or cellular processes pull the genome into the cell has been the subject of discussion. However, in vitro studies of genome ejection have been limited to a few head-tailed bacteriophages with a double-stranded DNA genome. Here we describe a DNA release system that operates in an archaeal virus. This virus infects an archaeon Haloarcula hispanica that was isolated from a hypersaline environment. The DNA-ejection velocity of His1, determined by single-molecule experiments, is comparable to that of bacterial viruses. We found that the ejection process is modulated by the external osmotic pressure (polyethylene glycol (PEG)) and by increased ion (Mg(2+) and Na(+)) concentration. The observed ejection was unidirectional, randomly paused, and incomplete, which suggests that cellular processes are required to complete the DNA transfer.
A supercontinuum light source was incorporated into a custom-built scanning white-light interferometer. This light source based on a Nd:YAG pumped microstructured optical fiber exhibits 1.21+/-0.10 microm temporal coherence length. The device operation was validated by characterizing the step height on a microelectromechanical system component. The measured step height- 7.027+/-0.020 microm-agreed with results obtained by employing traditional light sources: a halogen lamp and a white light-emitting diode. The new light source features high output intensity of 20-35 mW, which is beneficial when measuring low-reflectivity samples. As the supercontinuum light source may be modulated at frequencies exceeding 10 MHz, it holds potential for stroboscopic dynamic measurements.
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