Herein we describe semiempirical molecular orbital calculations of serine protease catalyzed hydrolysis of amides and esters. We found that attack of the substrate by the active site serine to form the tetrahedral intermediate was the rate-limiting step with both substrates. The lowest energy path for formation of the tetrahedral intermediate was for Ser to approach the substrate, followed by coupled heavy atom movement and proton transfer to complete the reaction. The effect of the environment on catalysis was estimated by calculating molecular mechanical interaction energies in both a noncovalent trypsin-peptide complex and a model for the transition state in which a covalent bond is imposed between of the serine and the carbonyl carbon of the substrate. We found that the environment itself was important in stabilizing the transition state compared to the Michaelis complex in addition to stabilization by the asparatic acid of the catalytic triad and the oxyanion hole. A molecular dynamics simulation was also performed of the noncovalent complex to test the importance of motion in the active site in the early stages of catalysis.

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The MASCOT Camera (MasCam) is part of the Mobile Asteroid Surface Scout (MASCOT) lander's science payload. MASCOT has been launched to asteroid (162173) Ryugu onboard JAXA's Hayabusa 2 asteroid sample return mission on Dec 3rd, 2014. It is scheduled to arrive at Ryugu in 2018, and return samples to Earth by 2020. MasCam was designed and built by DLR's Institute of Planetary Research, together with Airbus-DS Germany. The scientific goals of the MasCam investigation are to provide ground truth for the orbiter's remote sensing observations, provide context for measurements by the other lander instruments (radiometer, spectrometer and magnetometer), the orbiter sampling experiment, and characterize the geological context, compositional variations and physical properties of the surface (e.g. rock and regolith particle size distributions). During daytime, clear filter images will be acquired. During night, illumination of the dark surface is performed by an LED array, equipped with 4 × 36 monochromatic light-emitting diodes (LEDs) working in four spectral bands. Color imaging will allow the identification of spectrally distinct surface units. Continued imaging during the surface mission phase and the acquisition of image series at different sun angles over the course of an asteroid day will contribute to the physical characterization of the surface and also allow the investigation of time-dependent B R. Jaumann

The potential energy surfaces of four cyclic alkanes have been examined using molecular mechanics, semiempirical, and ab initio methods to determine if they produce mutually consistent results and investigate the source of any errors between the methods. The C5 -CR cyclic alkanes were chosen since these structures present a finite set of conformations and transition-state geometries and are still within the computational time and memory limits of the quantum mechanical approaches. We also examined several conformations of 1 ,Z-dideoxyribose to determine the effect of heteroatoms on the results for the 5-membered ring. The molecular mechanics and ab initio calculations are consistent in the relative energies and geometries determined for the conformers of all ring systems. While the semiempirical calculations yielded geometries consistent with the other methods (except for 5-membered rings), the relative energies often deviated substantially. A decomposition analysis of the semiempirical and molecular mechanics energies revealed that the disparities are mainly due to errors in the 1-center energies of the semiempirical calculations. The 2-center bonding and nonbonding energies followed reasonable trends for the conformers. The core-repulsion function, however, is suspected of producing anomalies. A minimum in the attractive Gaussian of this term at 2.1 A for H-H interactions partly explains the propensity of the 5-membered rings to optimize to near planarity (decreasing 12-diaxial hydrogen distances to 2.3 A) and the underestimation of the relative energy of the boat structure of cyclohexane.