The solution structure of clip domains from Manduca sexta prophenoloxidase activating proteinase-2.

Clip domains are structural modules found in arthropod serine proteinases and some proteolytically inactive homologues, which mediate extracellular signaling pathways of development and immunity. While little is known about their structures or functions, clip domains are proposed to be sites for interactions of proteinases with their activators, cofactors, and substrates. Here we report the solution structure of dual clip domains from Manduca sexta prophenoloxidase activating proteinase-2. Each domain adopts a new mixed alpha/beta fold (a three-stranded antiparallel beta-sheet flanked by two alpha-helices), and the architecture provides structural information on clip domains from a catalytically active proteinase for the first time. Examination of the structure in conjunction with a multiple sequence alignment of the clip domains from different groups suggests a substrate-binding site, a bacteria-interacting region, and a surface for specific interactions. In summary, our results provide insights into the structural basis of clip domain functions and this structure may represent the prototype of group-2 clip domains.

Sulfoalkyl ether-alkyl ether cyclodextrin derivatives, their synthesis, NMR characterization, and binding of 6alpha-methylprednisolone.

The objective of this study is to see if random alkyl ethers of various sulfoalkyl ether cyclodextrins can be synthesized and characterized. The purpose of the alkylation was to test the hypothesis that an increase in the "height" of a cyclodextrins cavity would help in the binding/complexation of larger more structurally complex molecules. The synthesis of new cyclodextrin derivatives comprising a mixture of sulfoalkyl ether and alkyl ether substituents on the same cyclodextrin ring was performed in aqueous alkaline solutions using various sultones and alkylsulfates. The method presented provided an easy and efficient way to modify cyclodextrins avoiding the use of organic solvents and high quantities of alkylating agents and could be carried out in either a two step or "one pot" single step process. Purification was by neutralization followed by ultrafiltration. The derivatives were characterized by 1D, ((1)H and (13)C), and a 2D NMR technique (HMQC, Heteronuclear Multiple Quantum Coherence). The combination of these techniques allowed an analysis of the degree of substitution and the site of substitution on the cyclodextrin (CD) nucleus. For both beta- and gamma-CD, sulfoakylation was preferred on the 2 > 3 > 6 hydroxyls while alkylation was preferred 6 > 2 > 3. Due to the simultaneous presence of short alkyl ether chains and negatively charged sulfoalkyl ether chains, these mixed water-soluble cyclodextrin derivatives, especially those of gamma-cyclodextrin, should be able to bind more complex drugs. The improved binding capacity of these new modified CDs with the model drug 6alpha-methylprednisolone is reported.

The metathesis-facilitated synthesis of terminal ruthenium carbide complexes: a unique carbon atom transfer reaction.

Ruthenium benzylidene metathesis catalysts react with 2,3-dicarbomethoxymethylene-cyclopropane, eliminating styrene and dimethyl fumarate, and producing the first terminal ruthenium carbide complexes. The products are diamagnetic, air-stable, and moderately soluble in hydrocarbon solvents. An X-ray study of Ru(C:)Cl2(P(C6H11)3) (1,3-dimesityl-4,5-dihydroimidazol-2-ylidene) shows a Ru-C distance of 1.650(2) A, consistent with the presence of a very short Ru-C triple bond.

Conformational Analysis of the ß-amyloid Peptide Fragment, ß(12-28).

Abstract NMR and CD spectroscopy have been used to examine the conformation of the peptide, ß(12-28), (VHHQKLVFFAEDVGSNK) in aqueous and 60% TFE/40% H(2)0 solution at pH 2.4. In 60% TFE solution, the peptide is helical as confirmed by the CD spectrum and by the pattern of the NOE cross peaks detected in the NOESY spectrum of the peptide. In aqueous solution, the peptide adopts a more extended and flexible conformation. Broadening of resonances at low temperature, temperature-dependent changes in the chemical shifts of several of the CH(α) resonances and the observation of a number of NOE contacts between the hydrophobic side-chain protons of the peptide are indicative of aggregation in aqueous solution. The behavior of ß(12-28) in 60% TFE and in aqueous solution are consistent with the overall conformation and aggregation behavior reported for the larger peptide fragment, ß(1-28) and the parent ß-amyloid peptide.