T4 lysozyme and mutants thereof crystallize in different conformations that are related to each other by a bend about a hinge in the molecule. This observation suggests that the wild type protein may undergo a hinge-bending motion in solution to allow substrate access to an otherwise closed active site cleft… Read More

Site-directed spin labeling of proteins has proven to be a practical means for determining secondary structure and its orientation; surfaces of tertiary interactions; inter-residue distances; chain topology and depth of a given side chain from the membrane/aqueous surface in membrane proteins; and local electrostatic potentials at solvent-exposed sites. Moreover, the… Read More

Thirty single cysteine substitution mutants of T4 lysozyme have been prepared and spin-labeled with a sulfhydryl-specific nitroxide reagent in order to systematically investigate the relationship between nitroxide side-chain mobility and protein structure. The perturbation caused by replacement of a native residue with a nitroxide amino acid was assessed from the… Read More

In this study, we have spin-labeled the lysine and cysteine residues of low-density lipoprotein (LDL) using N-4-(2,2,6,6-tetramethylpiperidinyl-1-oxyl-4-yl) maleimide (MAL-6) and succinimidyl-2,2,5,5-tetramethyl-3-pyrroline-1-oxyl-3-carboxylate (SSL), respectively. The electron spin resonance (ESR) spectrum of SSL bound to LDL indicated that the nitroxide moiety was relatively mobile. In contrast, the ESR spectrum of MAL-6 bound… Read More

The physical and chemical interaction of nitric oxide (NO) with stable nitroxides have been studied in both aqueous and membrane environments. The ESR spectrum of 3-carbamoyl-2,2,5,5-tetramethyl-3-pyrroline-1- yloxy (CTPO) was observed to broaden upon exposure to NO. This effect can be explained by invoking Heisenberg spin exchange as has been previously… Read More

The binding and state of aggregation of cecropin in large unilamellar vesicles of different surface potential and varying acyl chain length were examined using a Cys-33 spin-labeled derivative of cecropin AD (CAD). Association isotherms of the peptide were measured for vesicles of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine (POPC) containing 5, 15, and 30 mol… Read More

A spin-labeled derivative of the ion channel peptide cecropin AD (Fink et al., 1988) was synthesized and used to investigate its aggregation state in water and in the presence of a helix-promoting solvent. A cysteine was introduced at position 33 and spin-labeled using the methanethiosulfonate spin label. In low ionic… Read More

This work demonstrates the use of multiquantum EPR to study the magnetic properties of copper complexes and copper proteins. Pure absorption spectra are obtained because of the absence of field modulation. The signal intensity of 3-quantum spectra is proportional to the spin lattice relaxation time T1, while its linewidth in… Read More

In addition to contributing to lens optical properties, the α-crystallins are small heat shock proteins that possess chaperone activity and are predicted to bind and sequester destabilized proteins to delay cataract formation. The current model of α-crystallin chaperone mechanism envisions a transition from the native oligomer to an activated form… Read More

αA- and αB-crystallins are small heat shock proteins that bind thermodynamically destabilized proteins thereby inhibiting their aggregation. Highly expressed in the mammalian lens, the α-crystallins have been postulated to play a critical role in the maintenance of lens optical properties by sequestering age-damaged proteins prone to aggregation as well as… Read More