The promise and the challenges of cryo-electron tomography

Structural biologists have traditionally approached cellular complexity in a reductionist manner in which the cellular molecular components are fractionated and purified before being studied individually. This 'divide and conquer' approach has been highly successful. However, awareness has grown in recent years that biological functions can rarely be attributed to individual macromolecules. Most cellular functions arise from their concerted action, and there is thus a need for methods enabling structural studies performed in situ, ideally in unperturbed cellular environments. Cryo-electron tomography (Cryo-ET) combines the power of 3D molecular-level imaging with the best structural preservation that is physically possible to achieve. Thus, it has a unique potential to reveal the supramolecular architecture or 'molecular sociology' of cells and to discover the unexpected. Here, we review state-of-the-art Cryo-ET workflows, provide examples of biological applications, and discuss what is needed to realize the full potential of Cryo-ET

Facilitation by Pinus Flexilis During Succession: a Hierarchy of Mechanisms Benefits Other Plant Species

Studies of facilitation have primarily been limited to single mechanisms, species, or environments. We examined interacting mechanisms governing the facilitative effects of Pinus flexilis on two later successional understory species, Pseudotsuga menziesii and Ribes cereum, in different microhabitats and seasons at the ecotone between the Rocky Mountain forests and Great Plains grasslands in Montana, USA. In field surveys, 69% of Pseudotsuga and 91% of Ribes were located beneath P. flexilis even though P. flexilis subcrowns accounted for a small proportion of available habitat. For three years, we monitored the survival of Pseudotsuga and Ribes seedlings experimentally planted beneath P. flexilis and in the open at a windward and a leeward site. Survival of both species was highest beneath P. flexilis at a site topographically protected from strong unidirectional winds (38% for Pseudotsuga and 63% for Ribes), and lowest at a windward site and in the open where tree crowns did not provide shelter from winds (2% and 6%, respectively). These results suggest that wind amelioration contributed to the facilitative effect of P. flexilis. However, even at the leeward site, where wind speed was low, survival of Pseudotsuga and Ribes was higher beneath P. flexilis, suggesting the importance of shade. To explore the relative importance of different mechanisms, we designed an experiment with six treatments: “shade,” “shade + wind,” “shade + drift,” “wind,” “drift,” and a “control.” After two years, we found shade to be of overwhelming importance for the survival of Pseudotsuga and Ribes. Without shade, no other treatments were significant, but once shade was provided, wind amelioration and snow pack accumulation increased survival of Pseudotsuga, suggesting that these different facilitative mechanisms functioned in a nested hierarchical manner: some mechanisms were important only when others were already functioning. Many studies have demonstrated multiple interacting mechanisms in the way that plants interact, but to our knowledge hierarchical interactive processes have not been previously documented. If the effects of positive or competitive mechanisms are often hierarchical, then studies of isolated mechanisms may not accurately assess their importance in nature. Read More: http://www.esajournals.org/doi/abs/10.1890/0012-9658(2006)87%5B1816%3AFBPFDS%5D2.0.CO%3B

The Beetle Reference Manual: chip version 1.2

This paper details the electrical specifications, operating conditions and port definitions of the readout chip Beetle 1.2. The chip is developed for the LHCb experiment and fulfils the requirements of the silicon vertex detector (VELO, VETO), the silicon tracker and the RICH detector in case of multi-anode photomultiplier readout. It integrates 128 channels with low-noise charge-sensitive preamplifiers and shapers. The pulse shape can be chosen such that it complies with LHCb specifications: a peaking time of 25 ns with a remainder of the peak voltage after 25 ns of less than 30%. A comparator per channel with configurable polarity provides a binary signal. Four adjacent comparator channels are being ORed and brought off chip via LVDS ports. Either the shaper or comparator output is sampled with the LHC-bunch-crossing frequency of 40 MHz into an analog pipeline. This ring buffer has a programmable latency of max. 160 sampling intervals and an integrated derandomising buffer of 16 stages. For analog readout data is multiplexed with up to 40 MHz onto 1 or 4 ports. A binary readout mode operates at up to 80 MHz output rate on two ports. Current drivers bring the serialised data off chip. The chip can accept trigger rates of up to 1.1 MHz to perform a dead-timeless readout within 900 ns per trigger. For te stabi lity and calibration purposes, a charge injector with adjustable pulse height is implemented. The bias settings and various other parameters can be controlled via a standard I2C-interface. Appropriate design measures have been taken to ensure the radiation hardness against total ionising dose effects in excess of 10 Mrad. A robustness against Single Event Upset is achieved by redundant logic

Molecular and cellular dynamics of the 26S proteasome

In eukaryotic cells, the ubiquitin-proteasome system serves to remove proteins that are either dysfunctional or no longer needed. The 26S proteasome is a 2.5 MDa multisubunit complex comprising the 20S core particle, where degradation is executed, and one or two regulatory particles which prepare substrates for degradation. Whereas the 20S core particles of several species had been studied extensively by X-ray crystallography, the 26S holocomplex structure had remained elusive for a long time. Recent advances in single-particle cryo-electron microscopy have changed the situation and provided atomic resolution models of this intriguing molecular machine and its dynamics. Besides, cryo-electron tomography enables structural studies in situ, providing molecular resolution images of macromolecules inside pristinely preserved cellular environments. This has greatly contributed to our understanding of proteasome dynamics in the context of cells

Online gaming addiction: the role of sensation seeking, self-control, neuroticism, aggression, state anxiety and trait anxiety

Research into online gaming has steadily increased over the last decade, although relatively little research has examined the relationship between online gaming addiction and personality factors. This study examined the relationship between a number of personality traits (sensation seeking, self-control, aggression, neuroticism, state anxiety, and trait anxiety) and online gaming addiction. Data were collected over a 1-month period using an opportunity sample of 123 university students at an East Midlands university in the United Kingdom. Gamers completed all the online questionnaires. Results of a multiple linear regression indicated that five traits (neuroticism, sensation seeking, trait anxiety, state anxiety, and aggression) displayed significant associations with online gaming addiction. The study suggests that certain personality traits may be important in the acquisition, development, and maintenance of online gaming addiction, although further research is needed to replicate the findings of the present study

Disentangling within-person changes and individual differences among fundamental need satisfaction, attainment of acquisitive desires, and psychological health

We explored within-person and individual difference associations among basic psychological need satisfaction (autonomy, competence, and relatedness), attainment of acquisitive desires (wealth and popularity) and indicators of well- and ill-being. Participants were 198 undergraduates (51% male) who completed an inventory multiple times over a university semester. Analyses revealed that increased satisfaction of all the needs and desires beyond participants’ normal levels, with the exception of relatedness, were associated with greater psychological welfare. Nonetheless, individual differences in well-being were only predicted by psychological need satisfaction, and not by the attainment of acquisitive desires. Hence, the realization of acquisitive desires may elicit within-person increases in psychological welfare; however, satisfying innate needs may be a better bet for long term psychological health