Pentane interference

Abstract: Three stable conformations of salts formed from 3,6-diguanidino-1,2,4,5-tetrazine-1,4-di-N-oxide (DTDO) and HNO3 and HN(NO2)2 were studied using the density functional theory. For two salts, free energies (Gs) and total energies (Es) of the three conformations increase in the same order. Intramolecular interactions in the three conformations, such as the hydrogen bonding interaction (E H), the charge transfer (q), the binding energy (E b), the dispersion energy (E dis) and the second-order perturbation energy (E 2), decrease in completely opposite order to that of Gs and Es. Different conformations have distinct effects on the chemical stabilities and UV stabilities of two salts. Aromaticities of tetrazine in different conformations are slightly different. Although stabilities of the three conformations are different, their values are comparable.

Abstract: Supersonic molecular jet laser spectroscopy is used to observe the individual conformations of a number of aryl methyl ethers in the gas phase and to establish their planar conformations.

Abstract: Minimum perturbation mapping reveals that five side chain conformations of tryptophan-59 can potentially pack in the hydrophobic core of ribonuclease T1. In the crystallographic structure tryptophan-59 is in the trans perpendicular conformation. The other four wells in the tryptophan-59 (chi) 1 x (chi) 2 torsion space minimum perturbation mapping are trans antiperpendicular, gauche+ antiperpendicular, gauche+ perpendicular, and guache- perpendicular. The point mutations V33I and V33L are predicted to stabilize the trans antiperpendicular over the perpendicular conformation by 1.3 and 0.6 kcal/mol, respectively. The three gauche conformations require the creation of a new pocket within the protein core. The Mutation F80G creates the pocket for the gauche+ antiperpendicular tryptophan-59 conformation. The additional mutation V78A makes a more generous pocket for this conformation. The three mutation A19G, V78G and F80L creates the pocket for the gauche+ perpendicular conformation. A slightly more generous mutation at residue 80 may be required to fully stabilize this conformation. It does not appear possible to create a pocket that fits the gauche- perpendicular conformation better than the other two gauche conformations. The expression of ribonuclease-T1 mutants with tryptophan-59 in a gauche conformation probably requires filling in the crystallographic tryptophan-59 pocket. The mutations A22F, V33F, or V67F are all promising possibilities for this purpose.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.