Spin Form Research Articles

Role of the Oxyferrous Heme Intermediate and Distal Side Adduct Radical in the Catalase Activity of Mycobacterium tuberculosis KatG Revealed by the W107F Mutant

Catalase-peroxidase (KatG) is essential in Mycobacterium tuberculosis for oxidative stress management and activation of the antitubercular pro-drug isoniazid. The role of a unique distal side adduct found in KatG enzymes, involving linked side chains of residues Met255, Tyr229, and Trp107 (MYW), in the unusual catalase activity of KatG is addressed here and in our companion paper (Suarez, J., Ranguelova, K., Jarzecki, A. A., Manzerova, J., Krymov, V., Zhao, X., Yu, S., Metlitsky, L., Gerfen, G. J., and Magliozzo, R. S. (2009) J. Biol. Chem. 284, in press). The KatG[W107F] mutant exhibited severely reduced catalase activity yet normal peroxidase activity, and as isolated contains more abundant 6-coordinate heme in high spin and low spin forms compared with the wild-type enzyme. Most interestingly, oxyferrous heme is also found in the purified enzyme. Oxyferrous KatG[W107F] was prepared by photolysis in air of the carbonyl enzyme or was generated using hydrogen peroxide decayed with a t1/2 of 2 days compared with 6 min for wild-type protein. The stability of oxyenyzme was modestly enhanced in KatG[Y229F] but was not affected in KatG[M255A]. Optical stopped-flow experiments showed rapid formation of Compound I in KatG[W107F] and facile formation of oxyferrous heme in the presence of micromolar hydrogen peroxide. An analysis of the relationships between catalase activity, stability of oxyferrous enzyme, and a proposed MYW adduct radical is presented. The loss of catalase function is assigned to the loss of the MYW adduct radical and structural changes that lead to greatly enhanced stability of oxyenzyme, an intermediate of the catalase cycle of native enzyme.

Spinning and flow forming hard-to-deform metal alloys

The increasing requirements of industry concerning products of hard-to-deform materials result in growing interest in the technologies of spinning and flow forming. Moreover, the tendency to manufacture short series makes those technologies more and more attractive in the case of axisymmetrical products. The paper presents works involved in the preparation of manufacture of new axisymmetrical products of hard-to-deform metal alloys. Those products often have complex shapes, difficult to obtain by the traditional methods of stamping. The elaboration of the new technologies has been preceded by material and technological investigation.

Spin needlets for cosmic microwave background polarization data analysis

Scalar wavelets have been used extensively in the analysis of cosmic microwave background (CMB) temperature maps. Spin needlets are a new form of (spin) wavelets which were introduced in the mathematical literature by Geller and Marinucci (2008) as a tool for the analysis of spin random fields. Here we adopt the spin needlet approach for the analysis of CMB polarization measurements. The outcome of experiments measuring the polarization of the CMB are maps of the Stokes Q and U parameters which are spin two quantities. Here we discuss how to transform these spin two maps into spin two needlet coefficients and outline briefly how these coefficients can be used in the analysis of CMB polarization data. We review the most important properties of spin needlets, such as localization in pixel and harmonic space and asymptotic uncorrelation. We discuss several statistical applications, including the relation of angular power spectra to the needlet coefficients, testing for non-Gaussianity on polarization data, and reconstruction of the E and B scalar maps.

Two-photon exchange contribution to proton form factors in the time-like region

We estimate the two-photon exchange contribution to the process ${e}^{+}+{e}^{\ensuremath{-}}\ensuremath{\rightarrow}p+\overline{p} $. The two-photon exchange corrections to double spin polarization observables and form factors in the time-like region are calculated. The corrections are found to be small in magnitude but with a strong angular dependence at fixed momentum transfer. These two features are the same as those in the space-like region. In future experiments, the double spin polarization observable ${P}_{z}$ deserves to be considered.

Study of spin and orbital magnetic form factors of CeRh3B2by X-ray magnetic diffraction

Study of spin and orbital magnetic form factors of CeRh₃B₂by X-ray magnetic diffraction

Spin form factors of the samarium ions in SmAl2

Spin form factors of the samarium ions in SmAl₂

Mg<sub>65</sub>Cu<sub>25</sub>Gd<sub>10</sub> BMG Rod and Ribbon and Composite Synthesized via Spray Forming

Mg bulk metallic glass rod, ribbon and composite plate were synthesized via injection casting, melt spinning, and spray forming, respectively. The BMG composite plate has various microstructure combinations, from fully amorphous phase to mixture of nanocrystals, crystals and amorphous phase. XRD analyses were done on the rod and ribbon and throughout the vertical locations of the plates at the maximum thickness. Glass transition temperature (Tg) and onset crystallization temperature (Tx) were measured with DSC, and GFA (Glass Forming Ability) was estimated with various GFA models. The microhardness of the spray-formed Mg-Cu-Gd layered composite plate at various positions and Mg-Cu-Gd rod and ribbon were measured.

Friction Stir Welding of GRCop-84 for Combustion Chamber Liners

GRCop-84 is a copper-chromium-niobium alloy developed by the Glenn Research Center for liquid rocket engine combustion chamber liners. GRCop-84 exhibits superior properties over conventional copper-base alloys in a liquid hydrogen -oxygen operating environment. The Next Generation Launch Technology program has funded a program to demonstrate scale-up production capabilities of GR -Cop 84 to levels suitable for main combustion chamber production for the prototype rocket engine. This paper describes a novel method of manufacturing the main combustion chamber liner. The process consists of several steps: extrude the GR -Cop 84 powder into billets, roll the billets into plates, bump form the plates into cylinder halves and friction stir weld the halves into a cylinder. The cylinder is then metal spun formed to near net liner dimensions followed by finish machining to the final configuration. This paper describes the friction stir weld process development including tooling and non-destructive inspection techniques, culminating in the successful production of a liner pre-form completed through spin forming.

A non-volatile-memory device on the basis of engineered anisotropies in (Ga,Mn)As

The rich anisotropic transport behaviour shown by ferromagnetic semiconductors arises from a complex interplay of their electronic density of states and magnetic response. Such behaviour promises to enable devices whose ability to manipulate information in the form of electronic spin goes well beyond the now ubiquitous spin-valve read heads of magnetoelectronics, and on a platform that is compatible with conventional complementary metal oxide semiconductor technology. Most ferromagnetic semiconductor devices so far have relied on the bulk anisotropic behaviour of their constituent layers. Recent improvements in lithographic patterning enable the fabrication of a novel class of devices in which the anisotropy of many individual elements can be independently engineered. Here we demonstrate the first such device consisting of two nanobars with mutually orthogonal easy axes linked by a constriction. It behaves as a non-volatile memory element, where information can be written by setting the relative orientation of the magnetization of the nanobars, and read by measuring the constriction resistance.

Dynamic finite element modeling for the conventional spinning process

The process of spin forming is frequently used for manufacturing the axial symmetric products. The spinning process is a transient dynamic contact problem, and is difficult to solve by the quasi‐static theory. It is also found that the literature contains few studies of spinning simulation modeling. The present study deals with the dynamic FEM code, LS‐DYNA, to simulate the conventional spinning processes based on the updated Lagrangian formulation. The applications of the mass scaling technique and contact algorithm between the roller and sheet are modeled. The modeling also considers the elasto‐plastic material and Coulomb friction conditions. With the differences being variations in the rotation speed of the mandrel, the feed rate of the roller, and the material density. The predicted load‐deformation relationships, the strain energy distributions, the full history of deformation states, and the influence and usage of the mass scaling factor are assessed. Some defects in the simulations are observed, and proper solution models are suggested. Besides, some results of the die‐less spinning process using a cylindrical mandrel are compared with the conventional spinning process. The proposed models and techniques are helpful for the analysis of the spinning process, and will be a good approach for industrial metal forming simulation.

Analysis on folding defects of inner grooved copper tubes during ball spin forming

This paper mainly focuses on the folding which is the main defect on the inner surface of the inner grooved copper tube during ball spin forming. The material model and two-dimensional geometrical model of finite element simulation of multi-step ball spinning for forming inner grooved copper tubes have been built. The folding defects formed both on one side of the fin and on the bottom of inner grooves of the copper tubes had been analyzed according to the finite element results such as strain distribution, metal flow and contact state between the copper tube and the plug. Efficient measures have been proposed to prevent the folding defects. The SEM observation on the inner surface of the finished inner grooved copper tubes has been performed to illustrate the folding distribution and shape. Metallographic observation on the microstructure of cross-section of the copper tubes has been performed to analyze the forming process of folding. The results of the finite element simulation agree well with the experimental observation of the folding defects on the inner surface and the microstructure of cross-section of the inner grooved copper tubes.

Spin form factor of gadolinium in GdAl 2

X-ray diffraction experiments with white synchrotron radiations were carried out on single-crystal samples of GdAl 2 in order to observe the spin form factor of the gadolinium ion. The ( h 0 0), ( h h 0), and ( h h h) reflections for sin θ/ λ>0.5 Å −1 were measured at several temperatures. The form-factor data of each ( h 0 0), ( h h 0), and ( h h h) series are found to agree with the theoretical 4f radial integral 〈 j 0〉 for a free ion using much smaller value of a spin magnetic moment than is estimated from bulk magnetization measured at the same temperature. The temperature dependence of the atomic spin-scattering amplitudes for the ( h h h) reflections is peculiar while that for the ( h 0 0) and ( h h 0) ones seems to be consistent with the magnetization versus temperature curve.

Failure Behavior of Pressurized Spherical Tanks Depending on Manufacturing Method

There are numerous applications of pressure vessels in aerospace field for storing liquid or gaseous media. Generally the metallic vessels have been manufactured by welding two hemispheres, which are machined or spin-formed. In this study, the solid state bonding method was utilized with blow forming to manufacture aerospace titanium tanks. This solid state joining technology replaced the welding process and without any secondary material or liquid phases in bonding process, homogeneous microstructure was obtained at bonding interface. Using this method, a titanium tank of a space vehicle was manufactured and during a hydraulic pressurizing test, the strain and acoustic emission signals are observed to investigate the effect of solid state bonding method on the failure mode and performance of the tank.. This result was compared with the one made by conventional method of spin forming and welding. The result shows that the pressurization rate and the acoustic emission signal increasing rate provide a similar tendency for a vessel of integrity, while the signal increasing rate is much higher than the pressurization rate for a vessel with welding defects. It is clear that the failure mode of the solid state bonded tank is different from the welded tank due to the completely united interface by diffusion process.

Sugar-derived Glasses Support Thermal and Photo-initiated Electron Transfer Processes over Macroscopic Distances

Trehalose-derived glasses are shown to support long range electron transfer reactions between spatially well separated donors and protein acceptors. The results indicate that these matrices can be used not only to greatly stabilize protein structures but also to facilitate both thermal and photo-initiated hemeprotein reduction over large macroscopic distances. To date the promise of exciting new protein-based technologies that can harness the exceptional tunability of protein functionality has been significantly thwarted by both intrinsic instability and stringent solvent/environment requirements for the expression of functional properties. The presented results raise the prospect of overcoming these limitations with respect to incorporating redox active proteins into solid state devices such as tunable batteries, switches, and solar cells. The findings also have implications for formulations intended to enhance long term storage of biomaterials, new protein-based synthetic strategies, and biophysical studies of functional intermediates trapped under nonequilibrium conditions. In addition, the study shows that certain sugars such as glucose or tagatose, when added to redox-inactive glassy matrices, can be used as a source of thermal electrons that can be harvested by suitable redox active proteins, raising the prospect of using common sugars as an electron source in solid state thermal fuel cells.

A Weak Fe–O Bond in the Oxygenated Complex of the Nitric-oxide Synthase of Staphylococcus aureus

Little is known about the intermediates formed during catalysis by nitric-oxide synthase (NOS). We report here the characterization by resonance Raman spectroscopy of the oxygenated complex of the NOS from Staphylococcus aureus (saNOS) as well as the kinetics of formation and decay of the complex. An oxygenated complex transiently formed after mixing reduced saNOS with oxygen and decayed to the ferric enzyme with kinetics that were dependent on the substrate L-arginine and the cofactor H(4)B. The oxygenated complex displayed a Soret absorption band centered at 430 nm. Resonance Raman spectroscopy revealed that it can be described as a ferric superoxide form (Fe(III)O(2)(-)) with a single nu(O-O) mode at 1135 cm(-1). In the presence of L-arginine, an additional nu(O-O) mode at 1123 cm(-1) was observed, indicating an increased pi back-bonding electron donation to the bound oxygen induced by the substrate. With saNOS, this is the first time that the nu(Fe-O) mode of a NOS has been observed. The low frequency of this mode, at 517 cm(-1), points to an oxygenated complex that differs from that of P450(cam). The electronic structure of the oxygenated complex and the effect of L-arginine are discussed in relation to the kinetic properties of saNOS and other NOS.

Flow equations for uplifting half-flat to Spin(7) manifolds

In this supplement to the paper by Franzen et al. [Fortschr. Phys. (to be published)], we discuss the uplift of half-flat sixfolds to Spin(7) eightfolds by fibration of the former over a product of two intervals. We show that the same can be done in two ways—one, such that the required Spin(7) eightfold is a double G2 sevenfold fibration over an interval, the G2 sevenfold itself being the half-flat sixfold fibered over the other interval, and second, by simply considering the fibration of the half-flat sixfold over a product of two intervals. The flow equations one gets are an obvious generalization of the Hitchin’s flow equations [to obtain sevenfolds of G2 holonomy from half-flat sixfolds [Hitchin (2001)]]. We explicitly show the uplift of the Iwasawa using both methods, thereby proposing the form of new Spin(7) metrics. We give a plausibility argument ruling out the uplift of the Iwasawa manifold to a Spin(7) eightfold at the “edge,” using the second method. For Spin(7) eightfolds of the type X7×S1, X7 being a sevenfold of SU(3) structure, we motivate the possibility of including elliptic functions into the “shape deformation” functions of sevenfolds of SU(3) structure of Franzen et al. via some connections between elliptic functions, the Heisenberg group, theta functions, the already known D7-brane metric [Greene et al., Nucl. Phys. B 337, 1 (1990)], and hyper-Kähler metrics obtained in twistor spaces by deformations of Atiyah-Hitchin manifolds by a Legendre transform [Chalmers, Phys. Rev. D 58, 125011 (1998)].

F-electron correlations in nonmagnetic Ce studied by means of spin-resolved resonant photoemission

We have studied the spin-spin coupling between two $f$ electrons of nonmagnetic Ce by means of spin-resolved resonant photoemission using circularly polarized synchrotron radiation. The two $f$ electrons participating in the $3{d}_{5∕2}\ensuremath{\rightarrow}4f$ resonance process are coupled in a singlet while the coupling is veiled in the $3{d}_{3∕2}\ensuremath{\rightarrow}4f$ process due to an additional Coster-Kronig decay channel. The identical singlet coupling is observed in the $4d\ensuremath{\rightarrow}4f$ resonance process. Based on the Ce measurements, it is argued that spin-resolved resonant photoemission is one approach to study the correlation effects, particularly in the form of spin, in the rare earths.

An experimental and analytical study on dome forming of seamless Al tube by spinning process

The thickness distribution of a spin formed dome in an Al pressure vessel was studied experimentally and a simple formulation to predict the thickness distribution of the dome was proposed. The ends of the seamless Al tubes, which are widely used as liners in high pressure FRP composite vessels, were closed by spin forming. The thickness of the boss part of the dome may not be sufficient after forming operations, especially for high pressure vessels in which a deep thread cut is necessary for accommodating a pressure gas valve. Thus, a two-step spin forming of the Al tube end closure was proposed to improve and thicken the boss. First, the boss was deformed to a diameter smaller then the desired one. Later the dome was modified to obtain a greater boss diameter. The second forming provided a greater and better thickness distribution around the boss. Experimental work was carried out to compare the thickness distribution obtained with the conventional process and using the proposed two-step spin forming process. The ends of Al 6061-O tubes were deformed to dome shapes at an elevated temperature using a spinning machine. A simple analytical model, which was based on geometrical shape changes and an assumption of material constancy during forming, was formulated to predict the final thickness distribution of the dome. The results indicate that the proposed two-step spin forming provides a greater boss thickness than that of conventional forming.

A DFT computational study of spin crossover in iron(iii) and iron(ii) tripodal imidazole complexes. A comparison of experiment with calculations

B3LYP* functionals were used to model the sixteen iron(II) (1A, LS and 5T, HS) and iron(III) (2T, LS and 6A, HS) complexes of the 1:3 Schiff base condensate of tris(2-aminoethyl)amine and imidazole-4-carboxaldehyde, H3L1, and its deprotonated forms, [H2L1]1-, [HL1]2-, and [L1]3-. This ligand system is unusual in that [FeH3L1]3+, [FeH3L1]2+ and [FeL1]- all exhibit a spin crossover between 100-300 K. This makes these complexes ideal for a hybrid DFT computational approach and provides an opportunity to refine the value of the exact exchange admixture parameter, c3, and to predict properties of partially protonated complexes that are not experimentally available. The accepted value of 0.20 is larger than the value of approximately 0.13 that was found to best reproduce experimental data in terms of spin state predictions. With iron(III) B3LYP calculations showed that all of the complexes were low spin at 298 K with the exception of [FeH3L1]3+ which is spin crossover in agreement with experimental results. It was also shown for iron(III) that the ligand field increased as the number of protons decreased. In contrast all of the iron(II) complexes were close to the spin crossover region regardless of protonation state. Experimental structures are fairly well modeled by this system in regard to the key structural indicators of spin state, which are the bite and trans angles. The calculated iron to nitrogen atom distances are always larger in the high spin form than the low spin form but all iron to nitrogen bond distances are larger than the experimental values. In general non-bonded interactions are not well modeled by this methodology.

Absence of a Detectable Intermediate in the Compound I Formation of Horseradish Peroxidase at Ambient Temperature*

A microsecond-resolved absorption spectrometer was developed to investigate the elementary steps in hydrogen peroxide (H(2)O(2)) activation reaction of horseradish peroxidase (HRP) at ambient temperature. The kinetic absorption spectra of HRP upon the mixing with various concentrations of H(2)O(2) (0.5-3 mm) were monitored in the time range from 50 to 300 mus. The time-resolved spectra in the Soret region possessed isosbestic points that were close to those between the resting state and compound I. The kinetic changes in the Soret absorbance could be well fitted by a single exponential function. Accordingly, no distinct spectrum of the putative intermediate between the resting state and compound I was identified. These results were consistent with the proposal that the O-O bond activation in heme peroxidases is promoted by the imidazolium form of the distal histidine that exists only transiently. It was estimated that the rate constant for the breakage of the O-O bond in H(2)O(2) by HRP is significantly faster than 1 x 10(4) s(-1).