The distance between the two metal binding sites of human serum transferrin is calculated from measurements made of the paramagnetic broadening of the EPR spectrum of Cu2+ bound at the NH2-terminal (B) site from Fe3+ bound at the COOH-terminal (A) site. Complexes of monoferric(A)-monocupric(B) transferrin, monocupric(B) transferrin, and monogallium(A)-monocupric(B) transferrin were prepared und...

Triton-fractionated photosystem-I particles poised at -625 mV, where the two bound iron-sulfur proteins are reduced, have been studied by optical and electron paramagnetic resonance spectroscopies from 293 to 5 K. At 5-9 K, these particles exhibit two decay components with lifetimes of 1.3 and 130 msec in the laser pulse-induced absorption and electron paramagnetic resonance signal changes. Spe...

We introduce a mechanism for ion sensing by MRI in which analytes compete with paramagnetic ions for binding to polydentate chelating agents. Displacement of the paramagnetic ions results in alteration of solvent interaction parameters and consequent changes in relaxivity and MRI contrast. The MRI changes can be tuned by the choice of chelator. As an example, we show that calcium-dependent disp...

Chromium(VI) compounds are known to be potent toxic and carcinogenic agents. Because chromium(VI) is easily taken up by cells and is subsequently reduced to chromium(III), the formation of paramagnetic chromium such as chromium(V) and chromium(III) is believed to play a role in the adverse biological effects of chromium(VI) compounds. The present report, uses electron spin resonance (ESR) spect...

Paramagnetic changes occurring during tumor develop ment were studied in the mouse AKR leukemia (trans planted) model system using electron spin resonance. Para magnetic changes were found only in blood and in organs directly involved by the leukemic cells. The change in blood consisted of an increase in a paramagnetic transition element complex, and occurred prior to the tissue changes. In the...

We present a new approximate learning algorithm for Boltzmann Machines, using a systematic expansion of the Gibbs free energy to second order in the weights. The linear response correction to the correlations is given by the Hessian of the Gibbs free energy. The computational complexity of the algorithm is cubic in the number of neurons. We compare the performance of the exact BM learning algor...

We study the magneto-elastic coupling behavior of paramagnetic chains in soft polymer gels exposed to external magnetic fields. To this end, a laser scanning confocal microscope is used to observe the morphology of the paramagnetic chains together with the deformation field of the surrounding gel network. The paramagnetic chains in soft polymer gels show rich morphological shape changes under o...

A variety of mechanisms have been proposed for detecting inorganic ions using magnetic resonance imaging (MRI) contrast agents. In the most widely explored approach, analyte binding to a paramagnetic metal chelate withdraws ligand(s), increasing the number (q) of inner sphere sites available for water coordination at the paramagnetic center. As a consequence, the longitudinal relaxivity (r1) of...

The susceptibility of ~Sm0.65Sr0.35!MnO3 shows an unusual temperature dependence above the Curie temperature which is attributed to the presence of small manganese-ion clusters with S'9. A field-induced transition is observed in the paramagnetic state, which corresponds to a doubling of the cluster size and an increase of the strength of the interaction between them. The continuous transition f...

We have used density functional theory methods to investigate the solid-state "magic-angle" spinning (MAS) NMR and single-crystal NMR/ENDOR spectra of paramagnetic organometallic complexes and metalloporphyrins. The solid-state MAS NMR chemical shifts (including both diamagnetic and hyperfine contributions) are predicted with a slope of 1.007 and an R2 = 0.967, corresponding to a 28 ppm (or 6.3...