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Using electron spin resonance spectroscopy (ESR), we measure the rotational mobility of probe molecules highly diluted in deeply supercooled bulk water and negligibly constrained by the possible ice fraction. The mobility increases above the putative glass transition temperature of water, [T.sub.g] = 136 K, and smoothly connects to the thermodynamically stable region by traversing the so called 'no man's land' (the range 150-235 K), where it is believed that the homogeneous nucleation of ice suppresses the liquid water. Two coexisting fractions of the probe molecules are evidenced. The 2 fractions exhibit different mobility and fragility; the slower one is thermally activated (low fragility) and is larger at low temperatures below a fragile-to-strong dynamic cross-over at [approximately equal to]225 K. The reorientation of the probe molecules decouples from the viscosity below [approximately equal to]225 K. The translational diffusion of water exhibits a corresponding decoupling at the same temperature [Chen S-H, et al. (2006) The violation of the Stokes-Einstein relation in supercooled water. Proc Natl Acad Sci USA 103:12974-12978]. The present findings are consistent with key issues concerning both the statics and the dynamics of supercooled water, namely the large structural fluctuations [Poole PH, Sciortino F, Essmann U, Stanley HE (1992) Phase behavior of metastable water. Nature 360:324-328] and the fragile-to-strong dynamic cross-over at [approximately equal to]228 K [Ito K, Moynihan CT, Angell CA (1999) Thermodynamic determination of fragility in liquids and a fragile-to-strong liquid transition in water. Nature 398:492-494]. decoupling of transport properties | dynamic cross-over in water | dynamic heterogeneity | supercooled water | polycrystalline materials

A combination of molecular mechanics (MM), electron paramagnetic resonance spectrosocpy (EPR) and spectra simulation (MM-EPR) are used to determine the solution structures of di- and tri-nuclear copper(ll) complexes of melamine-based oligomacrocyclic ligands. The spin Hamiltonian parameters of the mononuclear, melamine-appended macrocyclic ligand copper(II) complex are determined by EPR spectroscopy and were also studied with DFT methods.

An alternative approach that is adapted to the diffusion operator-based stochastic Liouville equation (SLE) formalism that is used to calculate slow-motional electron paramagnetic resonance (EPR) line shapes is presented. This approach would be efficient enough to enable direct iterative refinement of molecular models based on least squares fitting of experimental EPR spectra.

The optical and electron paramagnetic resonance (EPR) properties of InP nanocrystals are studied, in which metallic gold or indium is present as an incorporated part of nanocrystals. The interaction of metal with semiconductor nanocrystals provides new functionalities to the nanostructures and the possibility of charge separation.

Improvements in the purification of methanobactin (mb) from either Methylosinus trichosporium [OB3b.sup.[dagger]] or Methylococcus capsulatus Bath resulted in preparations that stimulated methane-oxidation activity in both whole-cell and cell-free fractions of Methylococcus capsulatus Bath expressing the membrane-associated methane monooxygenase (pMMO). By using washed membrane factions with pMMO activities in the 290 nmol propylene oxidized [min.sup.-1] [(mg protein).sup.-1] range, activities approaching 400 nmol propylene oxidized [min.sup.-1] [(mg protein).sup.-1] were commonly observed following addition of copper-containing mb (Cu-mb), which represented 50-75 % of the total whole-cell activity. The stimulation of methane-oxidation activity by Cu--mb was similar to or greater than that observed with equimolar concentrations of Cu(II), without the inhibitory effects observed with high copper concentrations. Stimulation of pMMO activity was not observed with copper-free mb, nor was it observed when the copper-to-mb ratio was

Site-directed spin labeling (SDSL) electron paramagnetic resonance (EPR) spectroscopy is a powerful technique for characterizing local areas within a large protein structure and to detect and follow changes in local structure due to dynamic interactions. MsbA reconstituted into lipid membranes is evaluated by EPR spectroscopy and it is determined that the Walker A domain forms an alpha-helical structure.

Amyloid-beta (A-beta) peptides of varying length and composition were used in conjunction with tyrosine fluorescence measurements and low temperature electron paramagnetic resonance (EPR) spectroscopy to examine three histidine and one tyrosine coordination environment of Cu(super 2+) in A-beta. Findings reveal that tyrosine fluorescence intensity in A beta is not quenched entirely, as would be expected for direct coordination of the tyrosine phenolic oxygen to Cu(super 2+).

A study of ultraviolet light-induced electron-hole excitations in anatase TiO2 powders is presented by a combination of electron paramagnetic resonance and infrared spectroscopy measurements. It is concluded that under high vacuum conditions, the major fraction of photoexcited electrons remains in the conduction band.

The domain formation in sphingomyelin(SM)/Cholesterol (Chol) mixed membranes are explored by using electron spin resonance spectroscopy. The experimental data demonstrates that for lipid bilayers consisting of palmitoyl-SM and Chol in multilamellar vesicle in excess water, gel, and L(sub o) phases coexist at temperatures up to 30 degree celsius, that is, below the gel - fluid transition of palmitoyl-SM.

Nitric oxide (NO) production in the rat placenta was monitored and quantified by electron paramagnetic resonance (EPR) spectroscopy with hemoglobin and an Fe-N-(dithiocarboxy)sarcosine (DTCS) complex as NO-trapping reagents. Expression of nitric oxide synthase (NOS) isoforms was also examined by quantitative RT-PCR analysis. The EPR spectrum of the placenta with hemoglobin trapping showed a three-line hyperfine structure (g = 2.008 and a = 1.66-mT). The EPR signal was diminished after the placenta was homogenized or the NOS inhibitor L-NAME was administered to pregnant rats. Therefore, the specific signal was definitely identified as being derived from endogenous NO spin-trapped by hemoglobin, and the EPR spectrum showed that the NO adduct existed as a pentacoordinate [alpha]-NO heme species. The EPR spectrum of the placenta with Fe-DTCS trapping showed a triplet signal (g = 2.038) derived from an NO-Fe-DTCS complex. The height of the triplet signal did not vary significantly with gestational stage during the last few days of gestation. At the gestational stages examined, the level of NOS II mRNA expression was significantly higher than that of NOS III mRNA. NOS II expression in term (day 21.5) placenta was significantly increased compared with that in preterm (day 19.5) placenta (P < 0.01, n = 4 or 5). These results suggest that NOS II is the predominant producer of NO in the placenta and that NOS II-generated NO plays significant roles in the maintenance of placental functions immediately before birth. electron paramagnetic resonance; spin trapping; reverse transcriptase-mediated polymerase chain reaction; nitrosyl-hemoglobin; Fe-N-(dithiocarboxy)sarcosine

Electron paramagnetic resonance (EPR) studies reveal that the steric interaction between the methyl hydrogens on a tert-butoxy substituent and the cyclooctatetraene (COT) ring system sterically induces a puckering of the eight-membered ring in the anion radical of tert-butoxy-COT. The conclusion suggests that the alkoxy-COT anion radical system, having a narrower and lower barrier, is more susceptible to tunneling than is [4]annulene.

W-band time-resolved electron paramagnetic resonance (TREPR) spectroscopy was used in observing the lowest excited doublet (D1) in solution. Also observed were the doublet (D0) and quartet (Q1) ground states in an axial-ligating p-pyridylnitronylnitroxide radical and a MgTPPn complex. Two electron spin polarization mechanisms were established in a radical-triplet pair, namely, radical-triplet pair and ESP transfer mechanisms. The capacity of TREPR spectroscopy to allow the separate observation of D1 from D0 and Q1 affirms its effectiveness in the observation of the D1 state of a radical-triplet pair in solution.

The total dose response of Si/Si[O.sub.2] structures with ultrathin (20-40 [Angstrom]) thermal oxide layers grown on porous silicon substrates has been studied by Electron Paramagnetic Resonance (EPR) spectroscopy. The modification of the interface defect passivation and the generation of oxide defects have been analysed as a function of dose for three series of samples with different initial hydrogen passivation states.

Illuminating [Ca.sup.2+]-depleted photosystem (PS) II membranes generated two new EPR signals at g = 11 and 15 by perpendicular and parallel polarization modes, respectively. Two turnovers of the oxygen evolving center (OEC) beyond the modified [S.sub.2[prime]] state are required for the appearance of these signals. The formation of the signals correlated with that of an asymmetric (singlet-like) EPR signal observed at g [approximately equal to] 2. Spectral simulation indicated that both signals arose from a transition between [where] [2.sup.[+ or -][greater than]] levels with intradoublet splitting of [Delta] = 0.276 [cm.sup.-1] in an S = 2 spin system. Furthermore, the two signals in parallel and perpendicular modes were formed at the same time, indicating that the same metal center was responsible. The molecular z-axis of the S = 2 spin system for the signals was almost parallel to the plane of thylakoid membranes. These results indicate that the Mn cluster in the photosynthetic oxygen evolving center is the source of the new EPR species which may be a Mn(IV)-Mn(IV) or Mn(III)-Mn(III) dimer or a Mn(III) monomer. Redox events of the Mn cluster in the [Ca.sup.2+]-depleted PS II are discussed based on these observations.

Results of a study that used electron spin resonance spectroscopy on TiMCM-41 molecular sieve offers further confirmation of the isomorphous substitution of Ti(IV) into this material. This research compared synthesized TiMCM-41 material, where Ti is thought to be in a framework tetrahedral site, with Ti ion-exchanged Ti-AlMCM-41 material, where Ti is in an ion-exchangeable extra-framework site. The discoveries made in this study are discussed.

Electron Paramagnetic Resonance (EPR) imaging techniques show that chemical vapour disposition diamond growth is impacted by nitrogen incorporation. The distribution of a single substitutional nitrogen impurity in diamond film thickness involving the use of an Electron Paramagnetic Resonance imaging probe is established. EPR imaging will probably be used frequently in future research to establish differential nitrogen incorporation.

Using electron spin polarized paramagnetic resonance (ESP EPR) spectroscopy, an investigation was made on the effect of the rate of primary charge separation, metal-site occupancy, and H-subunit content on the observed P865+QsubAsup- charge-separated state. Fe-removed and Zn-substituted reaction centers from Rhodopseudomonas sphaeroides R-26 were utilized to observe specific electron transfer rates (kQ) from the intermediate acceptor H- to the primary acceptor QA. Correlation of the transient EPR and optical results showed that the slow KQ rate in Fe-removed RCs was not dependent on the occupancy of the H-subunit or Fe-site.

The two crystalline forms of the six-coordinate complex [Fe-(TpivPP)(NO2)(NO)]- synthesis and characterization were investigated. New (porphinato)-iron(II) complexes having nitric oxide and nitrite were examined to determine their bonding and electronic structure. Iron(II) nitrite derivatives starts the syntheses of {FeNO}7 complexes characterized by a combination of spectroscopic methods and X-ray diffraction studies. Results demonstrate the relative importance of the relative effects of axial ligand orientation in defining electronic structure in iron porphyrins.

The nanosecond kinetics of the hydrated electron generated by laser excitation of phenothiazine in the presence of quinone in SDS solution were investigated. The results of Fourier transform electron paramagnetic resonance spectroscopy showed that idebenone with the long alkyl chain at the 6-position quenches the hydrated electron. The homologue CoQ0 without the long chain is reduced by the trapping hydrated electron.

Time domain pulsed saturation recovery and electron-electron double resonance spectroscopies were used to measure the spin-lattice relaxation rates of the electron and the nitrogen nucleus in nitroxide spin labels in [...]

The selectivity of the two nitrone spin traps, 4-(2- ethoxycarbonyl ethyl)-3,3,5,5-tetramethyl-1-pyrroline N-oxide and 4-(2- ethoxycarbonyl ethyl)5,5-di(2H3 methyl)-3,3-dimethyl-1-pyrrolidine N-oxide, toward superoxide and hydroxyl radicals have been examined. The spin trapping studies reveal that the first nitrone compound forms a more stable nitroxide structure with hydroxyl radicals than DMPO-OH spin adducts. The nitrone-hydroxyl radical reaction, which remains unaffected with the increase in nitrone bulkiness, occurs at near diffusion controlled rates.

The detection of a new electron paramagnetic resonance (EPR) signal that suggests the existence of a paramagnetic intermediate in the resting state of the photosynthetic oxygen-evolving complex is reported. The signal is detected by using parallel polarization EPR. The newly detected signal provides an additional spectroscopic probe for the understanding of the structure and mechanism of the complex.

Equations were developed to describe the saturation-recovery transient of a 'slow' relaxing spin when its spin-lattice relaxation is perturbed by pairwise interactions with a 'fast' relaxing spin. These were quantitatively applied to the case of the tyrosine radical in photosystem II. In addition, the effect of dipole-dipole induced relaxation on progressive power saturation measurements of the tyrosine radical was analyzed.

A novel structure calculation scheme is described that has combined structural restrains derived from pulsed EPR and NMR spectroscopy in order to characterize the structural states of partially folded proteins. The protein-micelle interactions are understood by showing that helix dynamics of sodium lauroyl sarcosinate (SLAS)-bound [alpha]-synuclein has correlated with the degree of protein-induced departures from free micelles dimensions.

The EPR spectra of the trigonally symmetric Mo(III) coordination compounds [HIPT[N.sub.3]NMoL (L = [N.sub.2], CO, N[H.sub.3], [HIPT[N.sub.3]N]Mo = [[(3,5-[(2,4,6-i-[Pr.sub.3][C.sub.6][H.sub.2]).sub.2][C.sub.6][H.sub.3]NC[H.sub.2]C[H.sub.2]).sub.3]N]Mo) and their temperature and solvent dependencies are interpreted within a formal etwo-orbitalE model that has reflected the ground-state configuration. The studies have provided new insights into the role of trigonal coordination, as imposed by the [[HIPT[N.sub.3]N].sup.3-] ligand, in activating the Mo ion for the binding and reduction of [N.sub.2].

The samples of the wild type and various mutants of human sulfite oxidase (SO) that are depleted of chloride are prepared and purified. The studies have shown that the depletion of chloride has no effect on the formation of the high-pH (hpH) species.

Pulsed electron double resonance (PELDOR)/double electron?electron resonance (DEER) spectra at Q-band (34 GHz) is obtained and compared to X-band (9.4 GHz) to understand the substantial increase in DEER sensitivity. The availability of Q-band DEER spectroscopy could have a major impact on studies related structural biology using site-directed spin labeling EPR techniques.

The rapid-mix freeze-quench (RMFQ) methods and electron paramagnetic resonance (EPR) spectroscopy are used to characterize the steady-state radical in the deamination of ethanolamine catalyzed by adenosylcobalamin (AdoCb1)-dependent ethanolamine ammonia-lyase (EAL). The enzyme-bound AdoCbl cleaved to cob(II)-alamin provide insight into the C-N bond in the substrate radical, which is a significant barrier in the overall reaction.

The rapid scan electronic absorption spectrophotometry and multifrequency (9-295 GHz) electron paramagnetic resonance (EPR) spectroscopy is combined to determine the electronic nature of the intermediates in milk lactoperoxidase. The studies have shown that the identification of the ABTS binding site is a valuable tool in rational drug design.

The stability of point defects in SrTi[O.sub.3] (STO) during thin film processing is addressed by using electron paramagnetic resonance (EPR) spectroscopy. The results have shown that oxygen treatment has altered the electrical charge state of the vacancy, while exposure to vacuum causes different changes, either conversion to a different charge state or creation of the vacancy.

The dynamic electron-spin-resonance (ESR) spectra are examined across three different magnetic ordering states in a [La.sub.1.2][Sr.sub.1.8][Mn.sub.2][O.sub.7] (LSMO) single crystal. The studies have shown that the ferromagnetic (FM) and paramagnetic domains have coexisted in this compound throughout a wide range of temperature and that the FM correlations have persisted up to 335 K.

Weakly concentrated 'as-grown' and reduced SrTi[O.sub.3]:Mn crystals and ceramics are examined by using electron paramagnetic resonance (EPR) to understand the Mn substitution in the strontium titanate structure. The temperature dependence of [Mn.sup.2+] and [Mn.sup.4+] EPR spectra has indicated the formation of Mn[O.sub.2] or MnO small particles to be the favored configuration for the Mn insertion in SrTi[O.sub.3].

The structure and magnetic properties of [Zn.sub.1-x][Mn.sub.x]O (0.01 less than or equal to x < 0.10) were analyzed using the Raman and electron paramagnetic resonance spectroscopies, respectively. Evidence of pure paramagnetic behavior instead of the expected ferromagnetic character, was observed in samples with x less than or equal to 0.05, which can be attributed to a probable lack of free carries.

Perdeuterated all trans beta-carotene imbedded in activated Cu-MCM-41 was examined by electron paramagnetic resonance (EPR) and electron spin-echo envelope modulation (ESEEM) spectroscopies. ESEEM and pulse electron nuclear double resonance (ENDOR) studies of Cu(super 2+)-Car (carotenoids) complex in Cu-MCM-41 provided new information about the interaction between transition-metal ion and carotenoids.

The analogous C-H bond activation was described through electron addition in the pi-stacked polyfluorenes. This results in an exchange 'aromatic C-H' hydrogens between adjacent fluorene moieties.

The investigation of the interactions between the V- and Ti-containing centers and/or the OH of water or the silica support with the emphasis on the use of electron paramagnetic resonance (EPR) spectroscopy is reported. The local environment of the VO(super 2+) complexes in the noncalcined precursors of the TiO(sub x)-VO(Sub x)SBA-15 mixed-oxide catalysts is studied by means of continuous wave and pulse EPR spectroscopy.

The photolyzation of a number of 2,4- and 2,6-diazidopyridine derivatives is presented. Their X-band electron spin resonance spectra (ESR) is investigated.

A study of electron paramagnetic resonance (EPR) spectra from the oriented cytochrome (cyt) b6f complex shows that the Rieske iron-sulfur protein (ISP) is in distinct orientations, depending on the stoichiometry of the inhibitor at the Q(sub 0) site, was conducted. Implications of the results are discussed in the context of the X-ray crystal structures of the chicken mitochondrial cyt bc1 complex and the M. laminosus and C. reinhardtii cyt b6f complexes.

A method for site-directed spin labeling of oligonucleotides with TPA and a precise 4-pulse electron double resonance (PELDOR) based nanometer distance ruler, in the range from 19 to 53 A for folded DNA/RNA in aqueous buffer solution, is presented.

The experimental data shows that, in the radical cations of oligoanilines 1-7, electron delocalization occurs only to a small extent. The paramagnetic stages of dimers, tetramers, and hexamers are studied by EPR/ENDOR spectroscopy in fluid solution and DFT calculations.

Quantitative information is obtained on the structure, dynamics, and spatial distribution of contact ion pairs formed by site binding of divalent counterions to a polyelectrolyte. The experiment provides an estimate of 20 % site-bound and 80 % territorially bound divalent counterions in glycerol/water glassy frozen solution.

The synechocystis PCC6803 catalase-peroxidase forms the typical Compound I intermediate [Fe(IV)=O por.(super +)] of catalases and peroxidases, and two subsequent protein based radical intermediates. The radicals are identified as a Tyr and a Trp by using a combination of multifrequency EPR spectroscopy, isotope labeling and site directed mutagenesis.

The site-directed spin labeling (SDSL) and EPR spectroscopy is used to show that the conformation of the N-terminal energy-coupling motif of BtuB in micelles or bicelles differs from its structure in a bilayer phase. It is found that relatively mild detergents such as OG and DM can alter the conformation of membrane proteins, and that detergents are not necessarily a substitute for a membrane environment.

The photolytic degradation and radical production rates in TATB are studied as a function of 24 different combinations of humidity, temperature, and illumination. A substantial amount of radicals can be generated with UV light, and efforts are being made to modify EPR spectrometer so that TATB can be irradiated in the EPR cavity to measure the initial rates of radical production.

High-field electron paramagnetic resonance (EPR) was used for examining the g-tensors and hyperfine tensors of the S = 1/2 ground state of the mixed valence [LMn(III)-(mu-O)2Mn(IV)L](super +3) complex (L = N,N'-dimethyl-N,N'-bis(2-pyridylmethyl)ethane-1,2-diamine) in the solid-state and frozen acetonitrile solution. A spin-spin interaction between the neighboring binuclear complexes was revealed by the temperature dependence of the high-field EPR spectra of the polycrystalline powder.

The electronic interactions between organic molecules and metals in codeposited films to clarify the properties of the organic/metal interface are investigated using various spectroscopic techniques. An obvious electronic interaction between naphthalene tetracarboxylic anhydride (NTCDA) and idium was identified in ultra violet- vis and ESR spectra.

The g(sub z) directions of the hydrated and the full dehydrated copper species was determined by comparing the EPR spectrum of a powder sample with that of microcrystals assembled on glass plates. The results showed that the g(sub z) direction of Cu(super 2+) species D is not compatible with site II in the six-ring plane.

The experimental and theoretical investigations of fluorine hyperfine coupling constants (hfcc's) in the anion and cation radicals of a number of fluorinated benzenes, naphthalenes, and anthracenes, which provide important information about the electronic structure, and properties of organic radicals are reported.