The 1.7 Å resolution crystal structure of recombinant family G/11 b-1,4-xylanase (rXynA) from Bacillus subtilis 1A1 shows a jellyroll fold in which two curved b-sheets form the active-site and substrate-binding cleft. The onset of thermal denaturation of rXynA occurs at 328 K, in excellent agreement with the optimum catalytic temperature. Molecular dynamics simulations at temperatures of 298-328 K demonstrate that below the optimum temperature the thumb loop and palm domain adopt a closed conformation. However, at 328 K these two domains separate facilitating substrate access to the active-site pocket, thereby accounting for the optimum catalytic temperature of the rXynA.

Background: The molecular basis of increased protein stability by N-glycosylation is incompletely understood. Results: Glycosylation position rather than number is more important for protein thermostability in the xylanase A from Bacillus subtilis. Conclusion: Glycans contribute both to stabilizing protein-glycan and less favorable glycan-glycan interactions. An extensive protein-glycan interface favors protein stability. Significance: Formation of a protein-glycan interface provides a conceptual framework to understand glycoprotein stabilization.

These results call for a revision of both the "hinge-bending" model for the activity of group 11 xylanases, and the role of Tyr69 in the catalytic mechanism.

The binding constant and stoichiometry ratio for the formation of iron(II)−(1,10-phenanthroline) or iron(II)−o-phenanthroline complexes has been determined by a combination of a low-cost analytical method using a smartphone and a molecular modeling method as a laboratory experiment designed for analytical and physical chemistry courses. Intensity values were obtained from the digital images by measuring the RGB (red, green, blue) values (on a scale of 0−255 in intensity) of the samples between Fe(II) and ophenanthroline using a digital camera from a smartphone. The R channel showed the best linearity for predicting the binding constant. For computational studies, iron(II) complexes using water molecules and 1,10-phenanthroline were used to evaluate the stability of the complex by varying the number of ligands. Complexes have been optimized by reaching a minimum amount of energy. It was possible to observe how stable the complexes are from the optimization calculations, including aspects about the achieved geometries. The approach provides a simple method for performing stability constants over a wide range of complexes, from the undergraduate chemistry laboratories, in the field, and in the research laboratory.