Density functional theory based screening of ternary alkali-transition metal borohydrides: A computational material design project

The dissociation of molecules, even the most simple hydrogen molecule, cannot be described accurately within density functional theory because none of the currently available functionals accounts for strong on-site correlation. This problem led to a discussion of properties that the local Kohn-Sham potential has to satisfy in order to correctly describe strongly correlated systems. We derive an analytic expression for the nontrivial form of the Kohn-Sham potential in between the two fragments for the dissociation of a single bond. We show that the numerical calculations for a one-dimensional two-electron model system indeed approach and reach this limit. It is shown that the functional form of the potential is universal, i.e., independent of the details of the two fragments.We acknowledge funding by the Spanish MEC (Grant No. FIS2007-65702-C02-01), “Grupos Consolidados UPV/EHU del Gobierno Vasco” (Grant No. IT-319-07), and the European Community through e-I3 ETSF project (Grant Agreement No. 211956).Peer reviewe

Heterose e distâncias genéticas moleculares para a produção de grãos em soja Heterosis and molecular genetic distances for grain yield in soybeans

Em soja, tem sido relatada a ocorrência de heterose para a produção de grãos, e embora a utilização de cultivares híbridas não seja ainda uma realidade nesta espécie, o conhecimento da heterose é importante para uma pré-seleção de cruzamentos, visto que cruzamentos mais heteróticos estão associados a uma maior divergência entre os genitores. Entretanto, a obtenção de sementes F1 em quantidade suficiente para a avaliação experimental em parcelas é muito difícil e, assim, outros indicadores da ocorrência da heterose poderiam ser muito úteis. Objetivou-se, neste trabalho a avaliação da heterose para a produção de grãos em soja e as suas relações com as distâncias genéticas (DG), obtidas com o marcador molecular AFLP. Seis híbridos F1 oriundos de cruzamentos com diferentes distâncias genéticas (DG) e os respectivos genitores foram avaliados em experimentos com quatro repetições, empregando o delineamento em blocos ao acaso. Foi observada uma grande variação entre os cruzamentos quanto às heteroses, isso é, de 6,29 a 56,50% em relação à média dos genitores ( h mg) e de -0,34 a 51,30% em relação ao genitor superior (h gs). As correlações entre as distâncias genéticas (DG) e as heteroses foram elevadas (r = 0,83 e 0,60, respectivamente, para h mg e h gs), indicando que as distâncias genéticas podem ser utilizadas como indicativas de cruzamentos mais divergentes e, consequentemente, como um dos auxiliares na seleção de genitores mais divergentes em soja.<br>Heterosis has been reported for grain yield in soybeans, and despite the fact that hybrid cultivars have not been used yet, the knowledge of heterosis magnitude is very important for a previous selection of crosses, since heterosis is related to parental divergence. However, the obtention of enough F1 seeds for experimental evaluation in plots is a time-consuming task, and thus, other indicators of the occurrence of heterosis could be very useful. The objective of this work was to evaluate heterosis and its relationship with AFLP molecular genetic distance (DG). Six F1 hybrids, derived from parents with different levels of genetic distances (DG) and their respective parents, were evaluated in completely randomized block designs, with four replications. Heterosis estimates were very different among different crosses, varying from 6.29 to 56.50% for mid-parent heterosis (h mg) and from -0.34 to 51.30% for high-parent heterosis (h gs). Besides, the correlation between heterosis and genetic distances (DG) were very high (0.83 and 0.60,respectively, for h mg and h gs), which indicates that DG can be used as indicative of more divergent crosses, and thus, as one criterion for selection of more divergent parents

Guidelines for the use and interpretation of assays for monitoring autophagy

In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process vs. those that measure flux through the autophagy pathway (i.e., the complete process); thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from stimuli that result in increased autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field. © 2012 Landes Bioscience