Low-temperature thermal conductivity of an amorphous palladium silicon alloy

The thermal conductivity of a glassy PdSi alloy has been measured in the temperature range 0.1–30 K. The thermal conductivity contributed by the phonons has the same anomalous behavior as found for all non-metallic amorphous materials. Heat treatment increases the phonon thermal conductance by ～50%, a change which does not appear to be related to partial crystallization.     

Green's function for a third-order generalized right focal problem

We determine the Green's function for the third-order three-point generalized right focal boundary value problem

     

A property of weakly Krull domains

We show that a weakly Krull domain satisfies : for every pair there is an such that is -invertible. For Noetherian, satisfies if and only if every grade-one prime ideal of is of height one. We also show that a modification of can be used to characterize Noetherian domains that are one-dimensional.

     

Synthesis and characterization of ammonioundecafluoro-closo-dodecaborates(1-). New superweak anions

The ammonioborane monoanion H(3)NB(12)H(11)(-) was per-B-fluorinated with elemental fluorine in liquid hydrogen fluoride to yield the first member of a new class of weakly coordinating anions, H(3)NB(12)F(11)(-) (isolated as [N(n-Bu)(4)](2)[H(2)NB(12)F(11)] in 41% yield). The pK(a) of the H(3)NB(12)F(11)(-) anion is 9.6. Several salts of the tri-N-alkylated anions Me(3)NB(12)F(11)(-) and Dd(3)NB(12)F(11)(-) (Dd = n-C(12)H(25)) were also prepared. The structure of [CPh(3)][Me(3)NB(12)F(11)] was determined by single-crystal X-ray diffraction: monoclinic, space group P2(1)/c, a = 18.053(3) A, b = 33.139(5) A, c = 9.600(2) A, beta = 91.459(4) degrees, V = 5742(2) A(3), Z = 8, T = 173(2) K, R(1) = 0.045. It revealed that the only direct interactions between the undecafluoroammonioborate monoanions and the trityl cations in the two independent ion pairs were long and weak BF...CPh(3) interactions of 2.992(6) and 2.942(6) A. Salts of the new anions were chemically, electrochemically, and thermally stable. The conductivity of Li(Me(3)NB(12)F(11)) in dimethoxyethane was comparable to that of LiPF(6) but less than half the value of Li(1-Me-CB(11)F(11)).     

Efficient syntheses of benzothiazepines as antagonists for the mitochondrial sodium-calcium exchanger: potential therapeutics for type II diabetes

Type II diabetes mellitus is a chronic metabolic disorder that can lead to serious cardiovascular, renal, neurologic, and retinal complications. While several drugs are currently prescribed to treat type II diabetes, their efficacy is limited by mechanism-related side effects (weight gain, hypoglycemia, gastrointestinal distress), inadequate efficacy for use as monotherapy, and the development of tolerance to the agents. Consequently, combination therapies are frequently employed to effectively regulate blood glucose levels. We have focused on the mitochondrial sodium-calcium exchanger (mNCE) as a novel target for diabetes drug discovery. We have proposed that inhibition of the mNCE can be used to regulate calcium flux across the mitochondrial membrane, thereby enhancing mitochondrial oxidative metabolism, which in turn enhances glucose-stimulated insulin secretion (GSIS) in the pancreatic beta-cell. In this paper, we report the facile synthesis of benzothiazepines and derivatives by S-alkylation using 2-aminobenzhydrols. The syntheses of other bicyclic analogues based on benzothiazepine, benzothiazecine, benzodiazecine, and benzodiazepine templates are also described. These compounds have been evaluated for their inhibition of mNCE activity, and the results from the structure-activity relationship (SAR) studies are discussed.     

A snapshot of enzyme catalysis using electrospray ionization mass spectrometry

Insights into the early molecular events involving protein-ligand/substrate interactions such as protein signaling and enzyme catalysis can be obtained by examining these processes on a very short, millisecond time scale. We have used time-resolved electrospray mass spectrometry to delineate the catalytic mechanism of a key enzyme in bacterial lipopolysaccharide biosynthesis, 3-deoxy-d-manno-2-octulosonate-8-phosphate synthase (KDO8PS). Direct real-time monitoring of the catalytic reaction under single enzyme turnover conditions reveals a novel hemiketal phosphate intermediate bound to the enzyme in a noncovalent complex that establishes the reaction pathway. This study illustrates the successful application of mass spectrometry to reveal transient biochemical processes and opens a new time domain that can provide detailed structural information of short-lived protein-ligand complexes.