Data between 6.0 and 2.4 A resolution, collected at 253 K, wer used to refine a revised atomic model of muscle phosphoglucomutase: final crystallographic R factor = 16.3% (Rfree = 19.1%); final r.m.s. deviations from ideal bond lengths and angles = 0.018 A and 3.2 degrees, respectively. Features of the protein that were recognized only in the revised model include: the disposition of water molecules within domain-domain interfaces; two ion pairs buried in domain-domain interfaces, one of which is a structural arginine around which the active-site phosphoserine loop is wound; the basic architecture of the active-site 'crevice', which is a groove in a 1(1/3)-turn helix, open at both ends, that is produced by the interfacing of the four domains; the distorted hexacoordinate ligand sphere of the active-site Mg2+, where the enzymic phosphate group acts as a bidentate ligand; a pair of arginine residues in domain IV that form part of the enzymic phosphate-binding site (distal subsite) whose disposition in the two monomers of the asymmetric unit is affected unequally by distant crystallographic contacts; structural differences throughout domain IV, produced by these differing contacts, that may mimic solution differences induced by substrate binding; large differences in individually refined Debye-Waller thermal factors for corresponding main-chain atoms in monomers (1) and (2), suggesting a dynamic disorder within the crystal that may involve domain-size groups of residues; and a 'nucleophilic elbow' in the active site that resides in a topological environment differing from previous descriptions of this type of structure in other proteins.

This paper employs continuum principles combined with van der Waals theory to estimate the thermal contact resistance between nanowires and planar substrates. This resistance is modeled using elastic deformation theory and thermal resistance relations. The contact force between a nanowire and substrate is obtained through a calculation of the van der Waals interaction energy between the two. The model estimates numerical values of constriction and gap resistances for several nanowire-substrate combinations with water and air as the surrounding media. The total interface resistance is almost equal to the gap resistance when the surrounding medium has a high thermal conductivity. For a low-conductivity medium, the interface resistance is dominated by the constriction resistance, which itself depends significantly on nanowire and substrate conductivities. A trend observed in all calculations is that the interface resistance increases with smaller nanowires, showing that interface resistance will be a significant parameter in the design and performance of nanoelectronic devices.

Abstract. The large amount of soil carbon in boreal forest ecosystems has the potential to influence the climate system if released in large quantities in response to warming. Thus, there is a need to better understand and represent the environmental sensitivity of soil carbon decomposition. Most soil carbon decomposition models rely on empirical relationships omitting key biogeochemical mechanisms and their response to climate change is highly uncertain. In this study, we developed a multi-layer microbial explicit soil decomposition model framework for boreal forest ecosystems. A thorough sensitivity analysis was conducted to identify dominating biogeochemical processes and to highlight structural limitations. Our results indicate that substrate availability (limited by soil water diffusion and substrate quality) is likely to be a major constraint on soil decomposition in the fibrous horizon (40–60% of soil organic carbon (SOC) pool size variation), while energy limited microbial activity in the amorphous horizon exerts a predominant control on soil decomposition (>70% of SOC pool size variation). Elevated temperature alleviated the energy constraint of microbial activity most notably in amorphous soils, whereas moisture only exhibited a marginal effect on dissolved substrate supply and microbial activity. Our study highlights the different decomposition properties and underlying mechanisms of soil dynamics between fibrous and amorphous soil horizons. Soil decomposition models should consider explicitly representing different boreal soil horizons and soil–microbial interactions to better characterize biogeochemical processes in boreal forest ecosystems. A more comprehensive representation of critical biogeochemical mechanisms of soil moisture effects may be required to improve the performance of the soil model we analyzed in this study.

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