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Research has been conducted on the hydrophobic core of ribonuclease T1. The use of the differential scanning calorimetry, urea denaturation and X-ray crystallography in investigating the structural and energetic results of the hydrophobic core's engineered cavity refilling with CH (sub)3, SH and OH groups is described.

Summary: This paper presents the design, testing, and validation of a ultra‐wideband (UWB) wireless solution to replace wired intra‐spacecraft communications with wireless communications. The system requirements are provided in the framework of the Eu:CROPIS mission and the wired intra‐spacecraft communication system is replaced with a two‐segment wireless network. As such, distinct sets of UWB gateways and nodes are prototyped to interface with the on‐board entities and properly handle the data transmission in the resulting spacecraft and payload wireless networks. To accomplish these tasks, a custom radio module integrated into the prototypes was designed to provide the appropriate UWB RF front‐end and run a custom‐built communication stack. The viability of the solution was tested in laboratory conditions. For the test scenarios, sensor data are acquired in the payload network and forwarded as SpaceWire packets over the spacecraft network. Experimental test results indicate the suitability of the proposed solution in terms of delay and data integrity for implementing intra‐spacecraft wireless communications. [ABSTRACT FROM AUTHOR]

Results demonstrate that nucleoside hydrolase of Trypanosoma vivax displays burst kinetics with half-of-the-sites reactivity. The enzyme exhibits a complex multistep mechanism with a rate limiting slow isomerization between a tight and a loose enzyme-ribose complex, which accumulates during the enzyme hydrolysis of purine nucleosides.

The nucleoside hydrolase of Trypanosoma vivax hydrolyzes the N-glycosidic bond of purine nucleosides. Structural and kinetic studies on this enzyme have suggested a catalytic role for a flexible loop in the vicinity of the active sites. Here we present the analysis of the role of this flexible loop via the combination of a proline scan of the loop, loop deletion mutagenesis, steady state and pre-steady state analysis, and x-ray crystallography. Our analysis reveals that this loop has an important role in leaving group activation and product release. The catalytic role involves the entire loop and could only be perturbed by deletion of the entire loop and not by single site mutagenesis. We present evidence that the loop closes over the active site during catalysis, thereby ordering a water channel that is involved in leaving group activation. Once chemistry has taken place, the loop dynamics determine the rate of product release. [ABSTRACT FROM AUTHOR]

In the crystalline state, ribonuclease T1 binds calcium ions at different lattice-dependent positions. In solution, its conformational stability is also remarkably increased in the presence of divalent metal ions. Combining urea unfolding studies and X-ray crystallography, we compared the presence of several metal ions at specific sites in the protein to their contribution to the overall stabilizing effect in solution. We constructed thermodynamic cycles involving particular metal ions and specific carboxylate functions. The resulting coupling energies indicate that some (but not all) metal ions found at lattice contacts in crystal structures may indeed significantly contribute to stability enhancement in the presence of metal ions in solution. [ABSTRACT FROM AUTHOR]

In the crystalline state, ribonuclease T1 binds calcium ions at different lattice-dependent positions. In solution, its conformational stability is also remarkably increased in the presence of divalent metal ions. Combining urea unfolding studies and X-ray crystallography, we compared the presence of several metal ions at specific sites in the protein to their contribution to the overall stabilizing effect in solution. We constructed thermodynamic cycles involving particular metal ions and specific carboxylate functions. The resulting coupling energies indicate that some (but not all) metal ions found at lattice contacts in crystal structures may indeed significantly contribute to stability enhancement in the presence of metal ions in solution. [ABSTRACT FROM AUTHOR]

The nucleoside hydrolases (NHs) are a family of nucleoside-modifying enzymes. They play an important role in the purine-salvage pathway of many pathogenic organisms which are unable to synthesize purines de novo. Although well characterized in protozoan parasites, their precise function and mechanism remain unclear in other species. For the first time, NHs from Caenorhabditis elegans and Campylobacter jejuni, which are representatives of mesozoa and bacteria, respectively, have been cloned and purified. Steady-state kinetics indicate a different substrate-specificity profile to previously described hydrolases. Native diffraction data sets were collected from crystals of NH from each organism. The hexagonal crystals (space group P6[SUB2]22 or P6[SUB4]22) of NH from C. elegans diffracted to a resolution of 2.8 Å, while the data set from the orthorhombic crystals (space group I222 or I2[SUB1]2[SUB1]2[SUB1]) of NH from C. jejuni could be processed to 1.7 Å resolution. The unit-cell parameters were a = b = 102.23, c = 117.27 Å in the former case and a = 110.13, b = 100.13, c = 81.37 Å in the latter. [ABSTRACT FROM AUTHOR]