Theories of the neurobiology of episodic memory predominantly focus on the contributions of medial temporal lobe structures, based on extensive lesion, electrophysiological, and imaging evidence. Against this backdrop, functional neuroimaging data have unexpectedly implicated left posterior parietal cortex (PPC) in episodic retrieval, revealing distinct activation patterns in PPC subregions as...

Orientation is a fundamental mental function that processes the relations between the behaving self to space (places), time (events), and person (people). Behavioral and neuroimaging studies have hinted at interrelations between processing of these three domains. To unravel the neurocognitive basis of orientation, we used high-resolution 7T functional MRI as...

This study reveals that the entry into World War I in 1917 indexed the decisive transition to the modern period in American political consciousness, ushering in new objects of political discourse, a more rapid pace of change of those objects, and a fundamental reframing of the main tasks of governance....

In 2006, a deadly Escherichia coli O157:H7 outbreak in bagged spinach was traced to California’s Central Coast region, where >70% of the salad vegetables sold in the United States are produced. Although no definitive cause for the outbreak could be determined, wildlife was implicated as a disease vector. Growers were...

Diverse motivations for preserving nature both inspire and hinder its conservation. Optimal conservation strategies may differ radically depending on the objective. For example, creating nature reserves may prevent extinctions through protecting severely threatened species, whereas incentivizing farmland hedgerows may benefit people through bolstering pest-eating or pollinating species. Win-win interventions that...

Integrating accurate air quality modeling with decision making is hampered by complex atmospheric physics and chemistry and its coupling with atmospheric transport. Existing approaches to model the physics and chemistry accurately lead to significant computational burdens in computing the response of atmospheric concentrations to changes in emissions profiles. By integrating...

Regime shifts triggered by human activities and environmental changes have led to significant ecological and socioeconomic consequences in marine and terrestrial ecosystems worldwide. Ecological processes and feedbacks associated with regime shifts have received considerable attention, but human individual and collective behavior is rarely treated as an integrated component of such...

Global temperatures are rising. So are the oceans. Climate change has become inevitable and irreversible. To NASA climate scientist Josh Willis that sounds like the setup for a joke. “Greenland’s been on Jenny Craig,” he quipped at a public lecture in February. “It’s lost a couple trillion tons.” Climate scientist...

Journal of the American Chemical SocietyDOI: 10.1021/jacs.5b07228

Journal of the American Chemical SocietyDOI: 10.1021/jacs.5b05890

Journal of the American Chemical SocietyDOI: 10.1021/jacs.5b07438

Abstract

In nitrogen fixation by Azotobacter vinelandii nitrogenase, the iron protein (FeP) binds to and subsequently transfers electrons to the molybdenum–FeP, which contains the nitrogen fixation site, along with hydrolysis of two ATPs. However, the nature of the reduced state cluster is not completely clear. While reduced FeP is generally thought to contain an [Fe4S4]1+ cluster, evidence also exists for an all-ferrous [Fe4S4]0 cluster. Since the former indicates a single electron is transferred per two ATPs hydrolyzed while the latter indicates two electrons could be transferred per two ATPs hydrolyzed, an all-ferrous [Fe4S4]0 cluster in FeP is potenially two times more efficient. However, the 1+/0 reduction potential has been measured in the protein at both 460 and 790 mV, causing the biological significance to be questioned. Here, “density functional theory plus Poisson Boltzmann” calculations show that cluster movement relative to the protein surface observed in the crystal structures could account for both measured values. In addition, elastic network mode analysis indicates that such movement occurs in low frequency vibrations of the protein, implying protein dynamics might lead to variations in reduction potential. Furthermore, the different reductants used in the conflicting measurements of the reduction potential could be differentially affecting the protein dynamics. Moreover, even if the all-ferrous cluster is not the biologically relevant cluster, mutagenesis to stabilize the conformation with the more exposed cluster may be useful for bioengineering more efficient enzymes.

Journal of the American Chemical SocietyDOI: 10.1021/jacs.5b07398

Journal of the American Chemical SocietyDOI: 10.1021/jacs.5b06413

Journal of the American Chemical SocietyDOI: 10.1021/jacs.5b07394

Journal of the American Chemical SocietyDOI: 10.1021/jacs.5b03135

Journal of the American Chemical SocietyDOI: 10.1021/jacs.5b04802

Journal of the American Chemical SocietyDOI: 10.1021/jacs.5b07678

Journal of the American Chemical SocietyDOI: 10.1021/jacs.5b06791

Journal of the American Chemical SocietyDOI: 10.1021/jacs.5b06847