Folding and misfolding of potassium channel monomers during assembly and tetramerization

The dynamics and folding of potassium channel pore domain monomers are connected to the kinetics of tetramer assembly. In all-atom molecular dynamics simulations of Kv1.2 and KcsA channels, monomers adopt multiple nonnative conformations while the three helices remain folded. Consistent with this picture, NMR studies also find the monomers to be dynamic and structurally heterogeneous. However, a KcsA construct with a disulfide bridge engineered between the two transmembrane helices has an NMR spectrum with well-dispersed peaks, suggesting that the monomer can be locked into a native-like conformation that is similar to that observed in the folded tetramer. During tetramerization, fluoresence resonance energy transfer (FRET) data indicate that monomers rapidly oligomerize upon insertion into liposomes, likely forming a protein-dense region. Folding within this region occurs along separate fast and slow routes, with τfold ∼40 and 1,500 s, respectively. In contrast, constructs bearing the disulfide bond mainly fold via the faster pathway, suggesting that maintaining the transmembrane helices in their native orientation reduces misfolding. Interestingly, folding is concentration independent despite the tetrameric nature of the channel, indicating that the rate-limiting step is unimolecular and occurs after monomer association in the protein-dense region. We propose that the rapid formation of protein-dense regions may help with the assembly of multimeric membrane proteins by bringing together the nascent components prior to assembly. Finally, despite its name, the addition of KcsA’s C-terminal “tetramerization” domain does not hasten the kinetics of tetramerization.

Spatial Environment of Home, Stress Management, and Welfare of Family Living in Two-Level Marginal Regions

This study aims to analyze the home environment, stress management, and families' welfare in marginal areas. The study design was cross-sectional, and samples were selected by random cluster sampling, as many as 126 families consisting of 63 families from the very dense region (VDR> 200 people per Ha) and 63 families from a rather dense region (RDR, 121-160 people per Ha) in Bogor, West Java, Indonesia. The data were collected by interview using a questionnaire in March and April 2014 and analyzed using descriptive and comparison tests. The analysis showed that families in RDR had a lower density but had a higher crowd level than in VDR, so that families in RDR had to try harder to get non-physical privacy. RDR families had a higher source of stress, thus encouraging them to did more coping strategies. The analysis showed that families in RDR had higher objective well-being but lowered subjective welfare than families in VDR. Families in RDR had higher physical welfare and lowered social and psychological welfare than families in VDR. The research findings had implications for the importance of strengthening the family environment and developing research methodologies in the field of family ecology.

Determination of Dislocation Density and Correlation Length of Si, Ti, Au and Zno on Ge by Peak Profile

In this study, X-ray diffraction peaks of Si, Ti, Au and ZnO grown on Ge substrate with thickness of 500 nm by using sputtering method are analyzed to determine correlation length and dislocation density. It is seen that in most dense region of peaks, peak behaviour is in accordance with Gauss function. Right and left tails of peaks are in good accordance with q3 law. For randomized dislocations, obeying q3 law is typical and they can be monitored with w-scans by using open detectors. Whole profile is fitted with a limited dislocation dispersion. Edge dislocation density and correlation length are determined in the degree of 1010cm-2 and 103 nm, respectively. In order to gain these values, semi-experimental equations in Kragner method are used. For making a good fit, fit iteration step is taken as 9x106.

Restoration of chiral symmetry in cold and dense Nambu-Jona-Lasinio model with tensor renormalization group

We analyze the chiral phase transition of the Nambu-Jona-Lasinio model in the cold and dense region on the lattice, developing the Grassmann version of the anisotropic tensor renormalization group algorithm. The model is formulated with the Kogut-Susskind fermion action. We use the chiral condensate as an order parameter to investigate the restoration of the chiral symmetry. The first-order chiral phase transition is clearly observed in the dense region at vanishing temperature with μ/T ∼ O(103) on a large volume of V = 10244. We also present the results for the equation of state.

Population genomics in two cave-obligate invertebrates confirms extremely limited dispersal between caves

Caves offer selective pressures that are distinct from the surface. Organisms that have evolved to exist under these pressures typically exhibit a suite of convergent characteristics, including a loss or reduction of eyes and pigmentation. As a result, cave-obligate taxa, termed troglobionts, are no longer viable on the surface. This circumstance has led to an understanding of highly constrained dispersal capabilities, and the prediction that, in the absence of subterranean connections, extreme genetic divergence between cave populations. An effective test of this model would involve (1) common troglobionts from (2) nearby caves in a cave-dense region, (3) good sample sizes per cave, (4) multiple taxa, and (5) genome-wide characterization. With these criteria in mind, we used RAD-seq to genotype an average of ten individuals of the troglobiotic spider Nesticus barri and the troglobiotic beetle Ptomaphagus hatchi, each from four closely located caves (ranging from 3 to 13 km apart) in the cave-rich southern Cumberland Plateau of Tennessee, USA. Consistent with the hypothesis of highly restricted dispersal, we find that populations from separate caves are indeed highly genetically isolated. Our results support the idea of caves as natural laboratories for the study of parallel evolutionary processes.

8 in 10 Stars in the Milky Way Bulge experience stellar encounters within 1000 AU in a gigayear

ABSTRACT The Galactic bulge is a tumultuous dense region of space, packed with stars separated by far smaller distances than those in the Solar neighbourhood. A quantification of the frequency and proximity of close stellar encounters in this environment dictates the exchange of material, disruption of planetary orbits, and threat of sterilizing energetic events. We present estimated encounter rates for stars in the Milky Way bulge found using a combination of numerical and analytical methods. By integrating the orbits of bulge stars with varying orbital energy and angular momentum to find their positions over time, we were able to estimate how many close stellar encounters the stars should experience as a function of orbit shape. We determined that ∼80 per cent of bulge stars have encounters within 1000 AU and that half of bulge stars will have >35 such encounters, both over a gigayear. Our work has interesting implications for the long-term survivability of planets in the Galactic bulge.

Testing the ‘caves as islands’ model in two cave-obligate invertebrates with a genomic approach

Caves offer selective pressures that are distinct from the surface. Organisms that have evolved to exist under these pressures typically exhibit a suite of convergent characteristics, including a loss or reduction of eyes and pigmentation. As a result, cave-obligate taxa, termed troglobionts, are no longer viable on the surface. This circumstance has led to a “caves as islands” model of troglobiont evolution that predicts extreme genetic divergence between cave populations even across relatively small areas. An effective test of this model would involve (1) common troglobionts from (2) nearby caves in a cave-dense region, (3) good sample sizes per cave, (4) multiple taxa, and (5) genome-wide characterization. With these criteria in mind, we used RAD-seq to genotype an average of ten individuals of the troglobiotic spider Nesticus barri and the troglobiotic beetle Ptomaphagus hatchi, each from four closely located caves (ranging from 3-13 km apart) in the cave-rich southern Cumberland Plateau of Tennessee, USA. Consistent with the caves as islands model, we find that populations from separate caves are indeed highly genetically isolated. In addition, nucleotide diversity was correlated to cave length, suggesting that cave size is a dominant force shaping troglobiont population size and genetic diversity. Our results support the idea of caves as natural laboratories for the study of parallel evolutionary processes.