A xylobiose-derived isofagomine lactam glycosidase inhibitor binds as its amide tautomer

The atomic-resolution structure of a xylobiose-derived isofagomine lactam in complex with the xylanase Xyn10A from Streptomyces lividans reveals that the lactam is bound to the enzyme as the amide tautomer, with "reversed" protonation-states for nucleophile and acid-base.     

Chloropalladated propargyl amine: a highly efficient phosphine-free catalyst precursor for the Heck reaction

[reaction: see text] The palladacycle (Pd[k(1)-C, k(1)-N-C=(C(6)H(5))C(Cl)CH(2)NMe(2)](mu-Cl))(2) 1 derived from the chloropalladation of 3-(dimethylamino)-1-phenyl-1-propyne promotes the arylation of olefins under relatively mild reaction conditions. The coupling of iodoarenes and activated bromoarenes with n-butylacrylate and styrene occurs at room temperature. Turnover numbers of up to 85 000 have been achieved with deactivated bromoarenes and up to 1000 for activated chloroarenes at higher temperatures (80-150 degrees C).     

Dilogarithm identities in conformal field theory and group homology

Recently, Rogers' dilogarithm identities have attracted much attention in the setting of conformal field theory as well as lattice model calculations. One of the connecting threads is an identity of Richmond-Szekeres that appeared in the computation of central charges in conformal field theory. We show that the Richmond-Szekeres identity and its extension by Kirillov-Reshetikhin (equivalent to an identity found earlier by Lewin) can be interpreted as a lift of a generator of the third integral homology of a finite cyclic subgroup sitting inside the projective special linear group of all 2×2 real matrices viewed as adiscrete group. This connection allows us to clarify a few of the assertions and conjectures stated in the work of Nahm-Recknagel-Terhoven concerning the role of algebraic K-theory and Thurston's program on hyperbolic 3-manifolds. Specifically, it is not related to hyperbolic 3-manifolds as suggested but is more appropriately related to the group manifold of the universal covering group of the projective special linear group of all 2×2 real matrices viewed as a topological group. This also resolves the weaker version of the conjecture as formulated by Kirillov. We end with a summary of a number of open conjectures on the mathematical side.To Professor C. N. Yang for his 70^th birthdayThis work was partially supported by grants from the Statens Naturvidenskabelige Forskningsraad and the Paul and Gabriella Rosenbaum Foundation     

EXHAUSTIBLE RESOURCES,LEARNING, AND THE THEORY OF THE SECOND BEST

We formulate and characterize the solutions to optimal control models of social welfare maximization in a resource industry composed of two parts — conventional, with unit cost that increases with cumulative production, and backstop, whose unit cost decreases with cumulative production, due to learning. Since marginal cost pricing leads to losses in backstop operations, we consider three “second best” constraints that ensure non-negative profits. These constraints introduce distortions away from marginal cost pricing. Two constraints cause a discontinuous upward jump in price at the time of transition from conventional to backstop, and a supply side distortion-violation of cost minimization to meet demand.