Form Of C2 Research Articles

Unraveling the Structure Transition and Peroxidase Mimic Activity of Copper Sites Over Atomically Dispersed Copper-Doped Carbonized Polymer Dots.

The lack of systematic structural resolution makes it difficult to build specific transition metal atoms-doped carbonized polymer dots(TMAs-doped-CPDs). Herein, the structure-activity relationship between Cu atoms and CPDs was evaluated by studying the peroxidase-like properties of Glu-Cu-CPDs prepared by using copper glutamate (Glu) with Cu-N2O2 initial structure. The results showed that the Cu atoms bound to Glu-Cu-CPDs in the form of Cu-N2C2, indicating that Cu-O bonds changed into Cu-C bonds under hydrothermal conditions. This phenomenon was also observed in other Cu-doped-CPDs. Moreover, the carboxyl and amino groups content decreased after Cu-atom doping. Theoretical calculations revealed a dual-site catalytic mechanism for catalyzing H2O2. Eventually, the detection of intracellular H2O2 suggested their application prospects. Our work provides an in-depth understanding on the formation and catalysis mechanism of TMAs-doped-CPDs, allowing for building specific TMAs-doped-CPDs.

A Comparative Study of Different Schemes Based on Bézier-like Functions with an Application of Craniofacial Fractures Reconstruction

Cranial implants, especially custom made implants, are complex, important and necessary in craniofacial fracture restoration surgery. However, the classical procedure of the manual design of the implant is time consuming and complicated. Different computer-based techniques proposed by different researchers, including CAD/CAM, mirroring, reference skull, thin plate spline and radial basis functions have been used for cranial implant restoration. Computer Aided Geometric Design (CAGD) has also been used in bio-modeling and specifically for the restoration of cranial defects in form of different spline curves, namely C1,C2,GC1GC2, rational curves, B-spline and Non-Uniform Rational B-Spline (NURBS) curves. This paper gives an in-depth comparison of existing techniques by highlighting the limitations and advantage in different contexts. The construction of craniofacial fractures is made using different Bézier-like functions (Ball, Bernstein and Timmer basis functions) and is analyzed in detail. The C1,GC1 and GC2 cubic Ball curves are performed well for construction of the small fractured part. Any form of fracture is constructed using this approach and it has been effectively applied to frontal and parietal bone fractures. However, B-spline and NURBS curves can be used for any type of fractured parts and are more friendly user.

C2 weakens the turnover frequency during the melting of FexCy: insights from reactive MD simulations

The carbon accumulation in the form of C2 on the surface at high temperatures blocks the surface catalytic active sites, reducing the activity of melted FexCy nanoparticles.

Holographic dark energy model with Hubble horizon as an IR cut-off

The main task of this paper is to realize a cosmic observational compatible universe in the framework of holographic dark energy model when the Hubble horizon H is taken as the role of an IR cut-off. When the model parameter c of a time variable cosmological constant (CC) Λ(t) = 3c2H2(t) becomes time or scale dependent, an extra term enters in the effective equation of sate (EoS) of the vacuum energy weffΛ = −c2−dln c2/3dln a. This extra term can make the effective EoS of time variable CC cross the cosmological boundary and be phantom-like at present. For the lack of a first principle and fundamental physics theory to obtain the form c2, we give a simple parameterized form of c2 as an example. Then the model is confronted by the cosmic observations including SN Ia, BAO and CMB shift parameter R. The result shows that the model is consistent with cosmic observations.

Plasmon Waveguide Resonance Spectroscopic Evidence for Differential Binding of Oxidized and Reduced Rhodobacter capsulatus Cytochrome c2 to the Cytochrome bc1 Complex Mediated by the Conformation of the Rieske Iron−Sulfur Protein

The dissociation constants for the binding of Rhodobacter capsulatus cytochrome c2 and its K93P mutant to the cytochrome bc1 complex embedded in a phospholipid bilayer were measured by plasmon waveguide resonance spectroscopy in the presence and absence of the inhibitor stigmatellin. The reduced form of cytochrome c2 strongly binds to reduced cytochrome bc1 (Kd = 0.02 microM) but binds much more weakly to the oxidized form (Kd = 3.1 microM). In contrast, oxidized cytochrome c2 binds to oxidized cytochrome bc1 in a biphasic fashion with Kd values of 0.11 and 0.58 microM. Such a biphasic interaction is consistent with binding to two separate sites or conformations of oxidized cytochrome c2 and/or cytochrome bc1. However, in the presence of stigmatellin, we find that oxidized cytochrome c2 binds to oxidized cytochrome bc1 in a monophasic fashion with high affinity (Kd = 0.06 microM) and reduced cytochrome c2 binds less strongly (Kd = 0.11 microM) but approximately 30-fold more tightly than in the absence of stigmatellin. Structural studies with cytochrome bc1, with and without the inhibitor stigmatellin, have led to the proposal that the Rieske protein is mobile, moving between the cytochrome b and cytochrome c1 components during turnover. In one conformation, the Rieske protein binds near the heme of cytochrome c1, while the cytochrome c2 binding site is also near the cytochrome c1 heme but on the opposite side from the Rieske site, where cytochrome c2 cannot directly interact with Rieske. However, the inhibitor, stigmatellin, freezes the Rieske protein iron-sulfur cluster in a conformation proximal to cytochrome b and distal to cytochrome c1. We conclude from this that the dual conformation of the Rieske protein is primarily responsible for biphasic binding of oxidized cytochrome c2 to cytochrome c1. This optimizes turnover by maximizing binding of the substrate, oxidized cytochrome c2, when the iron-sulfur cluster is proximal to cytochrome b and minimizing binding of the product, reduced cytochrome c2, when it is proximal to cytochrome c1.

Forme respiratoire néonatale létale de la maladie de Niemann-Pick C2 et diagnostic anténatal par l'étude des mutations du gène HE1 /NPC2

We report the fifth case of neonatal form of type C2 (NP-C2) Niemann-Pick disease with early and fatal respiratory distress. Eleven families presenting such cases are known to date in the world. Since December 2000, isolation of the underlying gene HE1 /NPC2 and its mutations has allowed major advances in diagnosis. Case report. – Elisa was born in May 2000. NP-C2 disease was associated with severe respiratory distress leading to death at the age of four months. On the next pregnancy in September 2000, prenatal diagnosis was performed by means of biological tests that required four weeks response time. In December 2000, isolation of the HE1 /NPC2 gene located to 14q24.3 and of some of its mutations allowed to characterize the patient as being homozygote for the nonsense mutation E20X. On the the two next pregnancies, prenatal diagnosis was performed at 12 SA, in 48 hours, by the means of mutation analysis. The last fetus was heterozygote for the mutation E20X, allowing the birth at term of a healthy male newborn baby. Conclusion. – Niemann-Pick type C disease is a rare lysosomal lipid storage disease with severe prognosis. It is characterized by abnormalities of intracellular transport of endocytosed cholesterol. Diagnosis relies on biological tests that require cultured cells. Genetic heterogeneity defines two different genetic complementation groups C1 and C2. Severe and early respiratory distress is more likely to be associated with the rare type C2. Since December 2000, after identification of the disease-causing mutations in the proband, mutation analysis of gene HE1 /NPC2 on direct chorionic villus samples allows early and fast (48 hours) prenatal diagnosis.

Theoretical and experimental examination of -caprolactam dimer stability

The cyclic dimer of ε-caprolactam (C2) is a very stable compound as indicated by its high melting point (347 °C), low solubility in most solvents, and relatively low reactivity toward hydrolysis. FTIR measurements in solid state confirmed the existence of hydrogen bonds between NH protons and CO groups. Upon heating to 200 °C these bonds are not broken, but are merely weakened. This is shown by shifts of the NH stretching band toward higher wave numbers as well as by shifts of other characteristic bands. Temperature controlled NMR measurements on 0.3 and 30% C2 solutions in formic acid gave temperature coefficients of NH proton signals of −0.006 and −0.009 ppm/K, respectively, strongly indicating intermolecular hydrogen bonding. In the same concentration range signals for NH protons and CO carbons were shifted toward higher fields with higher C2 concentration. Using density functional theory (DFT) calculations it was not possible to successfully perform geometry optimization on any C2 structure with intramolecular hydrogen bonds. The trans form of C2 was found to be 7.0 kcal/mol lower in energy than the cis form. Symmetrical structures of C2 based on published trans X-ray structures were found to have comparable energies. Hydrogen bonds between trans C2 and discrete molecules of formic acid, water and N-methylacetamide, as model for solvents and a neighboring C2 molecule, were found to be comparable in energy. Full geometry optimization of a dimer of trans C2 gave energy stabilization of 8.25 kcal/mol per H-bond. These results show C2-C2 polar interactions to be comparable with polar interactions of C2 with solvents. The stability of C2, however, cannot be explained only by hydrogen bonding. It is likely that nonpolar interactions between C2 molecules complement the stabilization by hydrogen bonding. Optimized dimer of two trans cyclic-ε-caprolactam-dimer molecules (Etot = −1 461.0682582 H).

Synthesis ofRhodobacter sphaeroidescytochromec2inEscherichia coli

The cytochrome c2 structural gene, cycA, from Rhodobacter sphaeroides was expressed in Escherichia coli. CycA-specific mRNA was detected in E. coli both under aerobic and anaerobic conditions with trimethylamine-N-oxide as electron acceptor. However mature holocytochrome c2 was only detected in anaerobically-grown cells. The mature form of cytochrome c2 (Mr= 12,500) was secreted into the periplasm of E. coli suggesting that the signal polypeptide was processed. The cytochrome c2 synthesized in E. coli exhibited absorbance maxima in the reduced from at 550 nm (α-band) and 521 nm (β-band) and contained covalently attached haem c. The results indicate that a foreign c-type cytochrome can be secreted and assembled in E. coli under anaerobic conditions.

Synthesis of Rhodobacter sphaeroides cytochrome c2 in Escherichia coli

The cytochrome c2 structural gene, cycA, from Rhodobacter sphaeroides was expressed in Escherichia coli. CycA-specific mRNA was detected in E. coli both under aerobic and anaerobic conditions with trimethylamine-N-oxide as electron acceptor. However mature holocytochrome c2 was only detected in anaerobically-grown cells. The mature form of cytochrome c2 (Mr = 12,500) was secreted into the periplasm of E. coli suggesting that the signal polypeptide was processed. The cytochrome c2 synthesized in E. coli exhibited absorbance maxima in the reduced form at 550 nm (alpha-band) and 521 nm (beta-band) and contained covalently attached haem c. The results indicate that a foreign c-type cytochrome can be secreted and assembled in E. coli under anaerobic conditions.

Isolation and characterization of a novel plasma protein which binds to activated C4 of the classical complement pathway

We report here the isolation and partial characterization of a previously unrecognized protease-sensitive plasma protein identified during the development of a novel protocol for the purification of the second component of human complement (C2). This new protein is physicochemically similar to C2. It coprecipitates with C2 on polyethylene glycol fractionation and specifically binds, like C2, to Sepharose-bound iC4/C4b. Binding occurs both in the presence and absence of C2. The purified protein has a chain structure similar to C2 as determined by sodium dodecyl sulfate-gel electrophoresis in the presence or absence of reducing agent and has a molecular mass of 120 kDa, only somewhat greater than C2 at 95 kDa. Both proteins radioiodinate under similar conditions to the same specific activities with each of two different methods that yield 10-fold disparate results. Quantitative Mancini analysis identifies 300 micrograms/ml of the 120-kDa protein in plasma and serum. The protein is present at normal concentrations in serum from individuals genetically deficient in C2, has no C2 functional activity, and is not cleaved as is C2 when serum complement is activated. Potent monospecific polyclonal anti-serum to each do not cross-immunoprecipitate using standard gel techniques. However, these anti-sera identify epitopes in common by Western blotting. The data presented indicate that the 120-kDa protein is a distinct plasma component and suggest that the protein is not an "immature" form of C2. Initial experiments to delineate a functional role for the 120-kDa protein have demonstrated a consistent inhibition of C1 site generation on EAC4b which is dose-dependent and reversible. Thus, this protein appears to be a new complement regulatory factor.

Distinct primary translation products from human liver mRNA give rise to secreted and cell-associated forms of complement protein C2.

The second component of complement (C2), is a class III major histocompatibility complex gene product and a glycoprotein in the classical complement activating system. Synthesis in the human hepatoma-derived cell line HepG2 results in three intracellular forms: an 84-kDa form secreted in 1-2 h; 79-kDa and 70-kDa forms that remain cell-associated for intervals up to 12 h. All three forms are C2 polypeptides as demonstrated by inhibition of immunoprecipitation with unlabeled C2 and the presence of common major peptide fragments following chymotryptic digestion. The cell-associated forms of C2 are not products of proteolysis as demonstrated by experiments with multiple proteinase inhibitors and by observations of the kinetics of synthesis. Inhibition of core glycosylation by tunicamycin and deglycosylation by acid hydrolysis indicate that the three intracellular C2 polypeptides are glycosylated to a similar extent. Although the 84-kDa form of C2 is susceptible to C1s cleavage, the two cell-associated forms are not. Cell-free biosynthesis by mRNA from HepG2 or human liver results in three primary translation products corresponding to the three unglycosylated forms of C2. These results indicate that HepG2 cells synthesize C2 protein in both secreted and cell-associated forms and that each form is derived from a separate primary translation product.

The effects of iodine and thiol-blocking reagents on complement component C2 and on the assembly of the classical-pathway C3 convertase.

I2 can react with complement component C2 in a two-stage process. In the first stage, a form of C2 with enhanced haemolytic activity is produced. This form of C2 is cleaved to C2a and C2b by C1s at the same rate as native C2. The enhanced C2 haemolytic activity correlates with the ability to form a stable fluid-phase C3 convertase on addition of the C2 to C4b and C1s. It reflects an increased affinity for C4b of C2a formed from I2-treated C2, although the affinity for C4b of I2-treated C2 itself is not markedly increased. The specific activity of C3 convertase formed from I2-treated C2 is the same as that formed from native C2. The second stage of the reaction with I2, which is favoured at high pH or in the presence of excess I2, inactivates C2 on production of a species that cannot be cleaved by C1s. The presence of a single free thiol group in C2, which is the site of modification by I2, was confirmed by titration with p-chloromercuribenzoate, iodoacetamide and 5,5'-dithiobis-(2-nitrobenzoic acid). A single thiol group is also present in Factor B, and the cysteine residue, like that in C2, requires denaturation of the protein before reaction with iodoacetamide and 5,5'-dithiobis-(2-nitrobenzoic acid) but not p-chloro- mercuribenzoate .

Dynamic changes of multiple forms of serum immunoactive relaxin during pregnancy in the rat.

Relaxin isolated from the ovaries of pregnant rats has a mol wt of 6,500. This study determined the size(s) of the relaxin-immunoactive component(s) in the serum of rats during pregnancy. Peripheral sera from rats on days 15, 17, 19, and 21 of pregnancy were filtered through Sephacryl S-200 columns at 37 C and 4 C. Relaxin immunoactivity eluted in three components designated C1, C2, and C3, which had mol wts of approximately 60,000, 13,000 and 6,500, respectively. The distribution of relaxin immunoactivity among C1, C2, and C3 changed with the day of pregnancy. On day 15 of pregnancy essentially all relaxin immunoactivity was associated with C1. By day 17 approximately 20% of the relaxin immunoactivity was in C2 plus C3, and by day 21 the percentage in each of these two components increased to about 25%. C1 appears to possess relaxin bioactivity since the frequency of intrauterine pressure cycles in nonpregnant rats declined during cross-circulation with day 15 pregnant rats. C1 may not be attributable to the binding of 6,500 mol wt relaxin to a binding protein(s) since relaxin immunoactivity remained associated with a component(s) having a mol wt greater than 28,000 after incubation and gel filtration of day 15 serum in the presence of 2.0 M potassium thiocyanate at 37 C. Moreover, the levels of C1 as well as those of C2 and C3 were markedly increased in the peripheral serum of day-21 rats within 15 min of LH administration. C3 may be the 6,500-mol wt form of relaxin and C2 may be an intermediate in the processing of the 20,000-mol wt rat relaxin precursor to the 6,500-mol wt form of relaxin. The physiological significance, if any, of the multiplicity of relaxin-immunoactive components is unknown.

Influence of iron deficiency on the cytochromes of Rhodopseudomonas spheroides.

Rhodopseudomonas spheroides Y cells were grown photosynthetically in a denned medium supplemented with either a limiting amount of iron or with an excess of iron. Soluble and bound cytochromes were determined in both cases.The composition of the soluble cytochromes was not altered qualitatively by iron deficiency. In both culture conditions, a number of cytochromes were isolated by chromatography and purified to various extents: cytochromes c‐550 (c2 type), c′, c‐551, c‐552, and b‐559. In normal cells cytochrome c2, and to a lesser extent cytochrome c′ predominated whereas the amounts of both were greatly lowered in iron deficiency.Bound cytochromes were detected by difference spectroscopy of particles after chemically or light‐induced oxidoreductions. When iron was not limiting, cells were also grown in presence of diphenylamine, which inhibited carotenoid synthesis and facilitated detection of cytochromes. Particles from those cells, as well as particles from uninhibited cells contained cytochrome c‐551 (bound form of cytochrome c2), cytochrome b‐560, and a minor component, possibly b‐type. All reacted to illumination. In iron‐deficient cells, the bound heme b was almost completely suppressed; difference spectra suggested the presence only of cytochrome c2 and c′.

Investigation of the energy and impurity content of a crossed-field plasma gun

The downstream energy and impurity content of the plasma produced by a pulsed crossed-field source is investigated. With a positive center electrode and an optimum neutral gas loading, the source ionizes and accelerates 7×1017 protons containing 140 J of energy to the end of a 2-m-long axial magnetic guide field. This energy is distributed equally between axial motion and gyromotion. The dominant acceleration method is the −μ·∇B force resulting from a gradient in the axial magnetic field within the source. Impurities, in the form of C2+ and O2+ ions, account for about 10% of the plasma. Reversing the source polarity results in a lower energy efficiency and the appearance of Fe2+ ions in the downstream plasma.