A dilute atomic gas cooled down to very cold temperatures can enter the so-called quantum degenerate regime, where quantum properties of the gas come to the fore. This regime has been achieved for both bosonic and fermionic atoms, but molecules, with their many internal states, present a special challenge. De Marco et al. cooled a bulk gas of fermionic potassium-rubidium molecules to quantum degeneracy (see the Perspective by Zelevinsky). The authors first cooled atomic potassium and rubidium gases separately, then bound them together into potassium-rubidium molecules, and finally brought the molecules down to their ground state. The density profile of the molecular gas revealed the system's quantum nature, which in turn kept the gas stable by suppressing chemical reactions.
Life probably began with a molecule, or set of molecules, that could make copies of themselves. Now we have taken a big step towards creating such molecules ourselves. Over the last four decades, biologists have made lots of progress towards creating self-replicating molecules in the lab. However, their efforts have been thwarted by an apparent paradox. Now Philipp Holliger and his colleagues at the MRC Laboratory of Molecular Biology in Cambridge, UK say they have found the answer.
If you've been patiently waiting for Media Molecule's Dreams, you'll be happy to learn that early access begins April 16th. You'll be able to buy the PS4 crafting tool and LittleBigPlanet follow-up in the PlayStation Store for $30 in the US, and $40 in Canada. Dreams isn't fully built-out yet, but this rough release will let users test some of the core functions -- like designing games, creating music and sculpting characters. Media Molecule first introduced Dreams in 2015 as a way for PS4 users to create, explore and remix each other's dreams. A handful of beta users have gotten to play around in it, but this is the first public release.
Targeted sensors for ions, molecules, proteins, or DNA can be made by immobilizing specific biomolecules onto a surface. However, it can be difficult to control the surface patterning or reversibly deposit the target molecules, which would allow for reusable surfaces. Ananth et al. selectively immobilized proteins onto silica-covered flat or porous surfaces, with control over orientation and surface density, by incorporating polyhistidine tags into the target proteins. The anchoring is reversible, as demonstrated by real-time switching. For devices that contain both gold and silica surfaces, the authors show that they can passivate the gold by using thiol chemistry while selectively coating the silica with the desired target molecules.
The key to controlling reactions of molecules induced with the current of a scanning tunneling microscope (STM) tip is the ultrashort intermediate excited ionic state. The initial condition of the excited state is set by the energy and position of the injected current; thereafter, its dynamics determines the reaction outcome. We show that a STM can directly and controllably influence the excited-state dynamics. For the STM-induced desorption of toluene molecules from the Si(111)-7x7 surface, as the tip approaches the molecule, the probability of manipulation drops by two orders of magnitude. A two-channel quenching of the excited state is proposed, consisting of an invariant surface channel and a tip height–dependent channel.