Probing hydrocarbon dynamics at asphaltene/maltene interfaces for the global characterization of bitumen.

Hypothesis: The objective is to noninvasively probe the local hydrocarbon dynamics at asphaltene/maltene interfaces to reveal the global characteristics of bitumen at increasing temperatures and under various mechanical constraints.

Experiments: We propose multidimensional (1D and 2D) nuclear magnetic relaxation (NMR) experiments to characterize the dynamic properties of hydrocarbons for a set of bitumen from 40 to 180 °C. The convergence towards universal theoretical modelling of NMR relaxation experiments gives a comprehensive understanding of hydrocarbon transport in these very weakly permeable samples.

Backbone ¹H, ¹³C and ¹⁵N assignments of yeast Ump1, an intrinsically disordered protein that functions as a proteasome assembly chaperone.

Eukaryotic proteasome assembly is a highly organized process mediated by several proteasome-specific chaperones, which interact with proteasome assembly intermediates. In yeast, Ump1 and Pba1-4 have been identified as assembly chaperones that are dedicated to the formation of the proteasome 20S catalytic core complex. The crystal structures of Pba chaperones have been reported previously, but no detailed information has been provided for the structure of Ump1.

Backbone and side chain 1H, 13C, and 15N assignments of the ubiquitin-like domain of human HOIL-1L, an essential component of linear ubiquitin chain assembly complex.

HOIL-1L and its binding partner, HOIL-1L interacting protein (HOIP), are essential components of linear ubiquitin (Ub) chain assembly complex (LUBAC), a 600-kDa enzyme complex catalyzing elongation of a tandemly connected Ub chain, which serve as a regulator of NF-κB activation. Specific interaction between the N-terminal Ub-like domain (UBL) of HOIL-1L and the Ub-associated domain (UBA) located at the central region of HOIP is shown to be involved in the formation of LUBAC. For better understanding of the mechanisms underlying the generation of the linear Ub chains by LUBAC, it is necessary to characterize the UBL-UBA interaction on the basis of structural data, which, however, is not available to date.

Conformational dynamics of wild-type Lys-48-linked diubiquitin in solution.

Proteasomal degradation is mediated through modification of target proteins by Lys-48-linked polyubiquitin (polyUb) chain, which interacts with several binding partners in this pathway through hydrophobic surfaces on individual Ub units. However, the previously reported crystal structures of Lys-48-linked diUb exhibit a closed conformation with sequestered hydrophobic surfaces. NMR studies on mutated Lys-48-linked diUb indicated a pH-dependent conformational equilibrium between closed and open states with the predominance of the former under neutral conditions (90% at pH 6.

Redox-dependent domain rearrangement of protein disulfide isomerase coupled with exposure of its substrate-binding hydrophobic surface.

Protein disulfide isomerase (PDI) is a major protein in the endoplasmic reticulum, operating as an essential folding catalyst and molecular chaperone for disulfide-containing proteins by catalyzing the formation, rearrangement, and breakage of their disulfide bridges. This enzyme has a modular structure with four thioredoxin-like domains, a, b, b', and a', along with a C-terminal extension. The homologous a and a' domains contain one cysteine pair in their active site directly involved in thiol-disulfide exchange reactions, while the b' domain putatively provides a primary binding site for unstructured regions of the substrate polypeptides.