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A novel tripeptide, milnamide A, and a Choristida sponge ketide amino acid, jasplakinolide, were cytotoxic constituents of the Axinellide sponge, Auletta cf constricta. 1H NMR spectroscopy, which was used to study the tripeptide's structure, revealed light methyl groups and a tert-butyl group. Jasplakinolide, which also exhibited a tert-butyl group, did not demonstrate a tyrosine moiety.

A pulse sequence for recording pure absorption gradient enhanced heteronuclear single quantum correlation (HSQC) spectra with coherence transfer selection achieved using gradients was described. The gradient version of the enhanced sensitivity HSQC experiment gives sensitivity gains relative to the nongradient version of the same experiment. This gain in sensitivity can be significant for application to moderately sized proteins.

A new type of functional nanosystem known as polymer micelles with cross-linked ionic cores is developed using block ionomer complexes as a micellar template. The resulting micelles are hydrophilic nanospheres that combine several key structural features such as a cross-linked ionic core, a hydrophilic poly(ethylene oxide) PEO shell and a nanoscale size, making these systems very beneficial for effective drug delivery.

Various combinations of nine different solid-phase synthesis (SPS) resins and seven different solvents have been investigated for their ability to generate 1H NMR spectra having narrow line widths. The results showed the influence structure of the SPS resin and solvent on NMR spectral quality. Tentagel resins exhibited the best overall NMR data in various solvents while the solvents DMF, CD2Cl2 and DMSO generated the best NMR data.

A nuclear magnetic resonance method is developed for the specific identification of a chemical compound bound to a solid-phase-synthesis resin bead. The method employs isotope-filtered H NMR (HMQC) in a two-coil high-resolution magic-angle spinning probe, which prevents ambiguous bound compound identity. The technique exhibited efficient applications for such a structural characterization.

A new method uses magic angle spinning in a conventional spectrometer to derive 1H NMR spectra of organic compounds covalently linked to solid-phase synthesis beads. Qualitative and quantitative advantages of this method enable 1H NMR as an efficient analytical tool for solid-phase organic synthesis. This new method is nondestructive compared to 'cleave and characterize' methods associated with solid-phase organic synthesis.

The solution form of IIANtr from Escherichia coli and its interaction with its partner protein, NPr, were characterized by nuclear magnetic resonance (NMR) spectroscopy. The diffusion coefficient of the protein (1.13 × 10−6 cm/sec) falls between that of HPr (′9 kDa) and the N-terminal domain of E. coli enzyme I (∼30 kDa), indicating that the functional form of IIANtr is a monomer (∼18 kDa) in solution. Thus, the dimeric structure of the protein found in the crystal is an artifact of crystal packing. The residual dipolar coupling data of IIANtr (covering residues 11-155) measured in the absence and presence of a 4% polyethyleneglycol-hexanol liquid crystal alignment medium fit well to the coordinates of both molecule A and molecule B of the dimeric crystal structure, indicating that the 3D structures in solution and in the crystal are indeed similar for that protein region. However, only molecule A possesses an N-terminal helix identical to that derived from chemical shifts of IIANtr in solution. Further, the 15N heteronuclear nuclear Overhauser effect (NOE) data also support molecule A as the representative structure in solution, with the terminal residues 1-8 and 158-163 more mobile. Chemical shift mapping identified the surface on IIANtr for NPr binding. Residues Gly61, Asp115, Ser125, Thr156, and nearby regions of IIANtr are more perturbed and participate in interaction with NPr. The active-site His73 of IIANtr for phosphoryl transfer was found in the Nδ1-H tautomeric state. This work lays the foundation for future structure and function studies of the signal transducing proteins from this nitrogen pathway. [ABSTRACT FROM AUTHOR]

Diacyl phosphatidylglycerols (PG) are the major anionic lipids in the Escherichia coli membrane. Short‐chain dihexanoyl phosphatidylglycerol (DHPG) was previously utilized for the structural determination, by NMR spectroscopy, of the peptide corresponding to the N‐terminal membrane anchor of the glucose‐specific enzyme IIA (IIAGlc) from E. coli. This study explores the possible use of lipid micelles of dioctanoyl phosphatidylglycerol (DOPG) and didecanoyl phosphatidylglycerol (DDPG) as alternatives to DHPG. At a peptide concentration of 1 mM, the minimum peptide/lipid molar ratios required for the formation of the lipid‐binding amphipathic helix are approximately 1 :40, 1 :5, and 1 :5 for DHPG, DOPG, and DDPG, respectively. Based on the lipid titration, the critical micelle concentration (CMC) of DHPG was estimated to be ∼50 mM. The 1H spectral linewidths of the peptide bound to a variety of lipid micelles decrease in the following order: DDPG > DOPG > DHPG. The helical regions of the peptide in different anionic lipids were elucidated based on chemical shift indexes (CSI). Residues Leu2‐Leu9, Leu2‐Val10, and Leu2‐Val10 were found to be helical in DHPG, DOPG, and DDPG, respectively, indicating that the lipid chain length had only a subtle effect on the amphipathic helix of the peptide. In light of the minimum peptide/lipid ratio and the spectral linewidth, and the CSI‐derived peptide structure, DOPG is proposed as a good compromise for structural studies of this membrane‐associated peptide by solution NMR spectroscopy. [ABSTRACT FROM AUTHOR]