Helen S. M. Lu

Protein Design: A Hierarchic Approach

The de novo design of peptides and proteins has recently emerged as an approach for investigating protein structure and function. Designed, helical peptides provide model systems for dissecting and quantifying the multiple interactions that stabilize secondary structure formation. De novo design is also useful for exploring the features that specify the stoichiometry and stability of α-helical coiled coils and for defining the requirements for folding into structures that resemble native, functional proteins. The design process often occurs in a series of discrete steps. Such steps reflect the hierarchy of forces required for stabilizing tertiary structures, beginning with hydrophobic forces and adding more specific interactions as required to achieve a unique, functional protein.

Suppression of Metallic Conductivity of Single-Walled Carbon Nanotubes by Cycloaddition Reactions

The high carrier mobility of films of semiconducting single-walled carbon nanotubes (SWNTs) is attractive for electronics applications, but the presence of metallic SWNTs leads to high off-currents in transistor applications. The method presented here, cycloaddition of fluorinated olefins, represents an effective approach toward converting the “as grown” commercial SWNT mats into high-mobility semiconducting tubes with high yield and without further need for carbon nanotube separation. Thin-film transistors, fabricated from percolating arrays of functionalized carbon nanotubes, exhibit mobilities >100 square centimeters per volt-second and on-off ratios of 100,000. This method should allow for the use of semiconducting carbon nanotubes in commercial electronic devices and provide a low-cost route to the fabrication of electronic inks.

Prianosin A, a novel antileukemic alkaloid from the okinawan marine sponge Prianos melanos

Abstract A novel alkaloid, prianosin A (1), with potent antineoplastic activity has been isolated from the Okinawan marine sponge Prianos melanos. Its absolute stereostructure was determined by single crystal x-ray diffraction analysis.

The structure of a new nucleoside antibiotic, capuramycin

Summary The structure of capuramycin has been determined to be an uracil nucleoside with a caprolactam substituent as shown in Fig. 5 by NMR spectral analysis, chemical degradation and X-ray analysis.

Pyrenoline-A and -B, two new phytotoxins from Pyrenophora teres

Two novel isoquinoline fungal derivatives, pyrenoline-A and -B, were isolated from the culture fluid of Pyrenophora teres, a pathogen of barley, and characterized by spectroscopic and X-ray diffraction techniques.

Further structural studies on the 2-methyl-3(2H)-furanone derived metabolites of the marine alga Laurencia chilensis

Abstract Chilenone B was isolated from the red marine alga Laurencia chilensis, and its structure was determined by x-ray diffraction and spectroscopic techniques. Chilenone B is a trimer of 2-methyl-3(2H)-furanone.

Structural revision of aspirochlorine (=antibiotic A30641), a novel epidithiopiperazine-2, 5-dione produced byaspergillus SPP.

Abstract The structure of aspirochlorine has been revised to the novel epidithiopiperazine-2, 5-dione1 on the basis of chemical, spectroscopic, and x-ray crystallographic experiments.