scholarly journals The role of tetrahydromethanopterin and cytoplasmic cofactor in methane synthesis

1986 ◽  
Vol 235 (2) ◽  
pp. 453-458 ◽  
Author(s):  
F D Sauer ◽  
B A Blackwell ◽  
S Mahadevan
Keyword(s):  
Experimental Evidence ◽  
Membrane Fraction ◽  
Methanobacterium Thermoautotrophicum ◽  
Supernatant Fraction ◽  
Original Activity ◽  
Methyl Transfer ◽  
14C Labelling ◽  
First Time ◽  
Kinetics Of

A fraction previously isolated from acid-treated supernatant fraction of Methanobacterium thermoautotrophicum by DEAE-Sephadex chromatography [Sauer, Mahadevan & Erfle (1984) Biochem. J. 221, 61-97] which was absolutely required for methane synthesis, has been separated into two compounds, tetrahydromethanopterin (H4MPT) and an as-yet-unidentified cofactor we call ‘cytoplasmic cofactor’. H4MPT was identified by its u.v. spectrum and by 13C- and 1H-n.m.r. spectroscopy. The reduction of 2-(methylthio)ethanesulphonic acid (CH3-S-CoM) to methane by the membrane fraction from M. thermoautotrophicum was completely dependent on the addition of cytoplasmic cofactor. Methane synthesis from CO2, however, was only partially dependent on cofactor addition, and 57% of the original activity was retained in its absence. The kinetics of 14C labelling were consistent with the scheme methyl-H4MPT→CH3-S-CoM→methane, as has been proposed. This is the first time that direct experimental evidence has been presented to show that the proposed methyl transfer from H4MPT to coenzyme M (HS-CoM) actually occurs.

scholarly journals IMMUNE RESPONSES IN VITRO

1971 ◽  
Vol 134 (2) ◽  
pp. 395-416 ◽  
Author(s):  
Carl W. Pierce ◽  
Barbara M. Johnson ◽  
Harriet E. Gershon ◽  
Richard Asofsky
Keyword(s):  
Culture Conditions ◽  
Antibody Concentration ◽  
Spleen Cells ◽  
Immunoglobulin Class ◽  
Cell Densities ◽  
Erythrocyte Antigen ◽  
First Time ◽  
Kinetics Of

We have demonstrated for the first time that mouse spleen cells stimulated in vitro with heterologous erythrocytes developed immunoglobulin class-specific γM, γ1, γ2a+2b, and γA plaque-forming cell (PFC) responses. A modification of the hemolytic plaque technique, the addition of goat anti-mouse µ-chain antibody to the assay preparation, specifically prevented development of all γM PFC and enabled accurate and reproducible enumeration of immunoglobulin class-specific PFC after treatment with appropriate monospecific anti-globulins and complement. Culture conditions, with regard to medium, atmosphere, agitation, and spleen cell densities, were similar to those previously shown to support only γM PFC responses. Evaluation of the kinetics of appearance of PFC showed that γM PFC reached maximum numbers on days 4–5; the magnitude of this response was 3–10 times greater than γ1 γ2a+2b, or γA PFC which reached maximum numbers on days 5–6. Optimal erythrocyte antigen dose for γM PFC responses was 107/culture, whereas a dose of 106 erythrocytes/culture consistently stimulated optimal γ1 γ2a+2b, or γA PFC responses. Investigations of the effects of anti-erythrocyte antibody on γM and γG PFC responses indicated that antibody suppressed these responses by neutralizing the effective antigenic stimulus at the macrophage-dependent phase of the response. At the same antibody concentration, γG PFC responses were more effectively suppressed than γM PFC responses. Further, γG responses could be almost completely suppressed by antibody as long as 48 hr after initiation of cultures, whereas γM PFC responses could only be completely suppressed during the first 24 hr. These results were discusssed in terms of the role of antigen in the stimulation γM and γG antibody.

Dislocations and the thermal reactivity of calcite

1970 ◽  
Vol 314 (1518) ◽  
pp. 429-441 ◽  
Keyword(s):  
Chemical Reactivity ◽  
Previous History ◽  
Strain Fields ◽  
Temperature Range ◽  
Reactivity Of Solids ◽  
Dislocation Movement ◽  
History Of ◽  
First Time ◽  
Kinetics Of

A study has been made of the effect of dislocation movement on the kinetics of thermal decomposition of freshly cleaved calcite crystals. It is shown for the first time that the thermal history of the crystal has a marked effect on its reactivity and two patterns of behaviour have been identified; that in the temperature range up to ca . 700 K in which the kinetics of decomposition are sensitively dependent upon the nature and extent of the crystal’s previous history, and the range above 700 K in which annealing is rapid and reproducible kinetics are obtained for all crystals studied. This effect has not been observed in previous studies of calcite. It is suggested that this is because the experiments were carried out in the temperature range where movement of dislocations is so rapid that the surface structure is virtually constant during the measurements. Tentative correlations are made between the various stages of the observed rates of decomposition and the known dislocation systems in the crystal. The influence of applied stress was studied but because of limitations in the method of stressing the crystal, the amount of plastic deformation was small and its effect on reactivity was not marked. Qualitative consideration is given to the role of dislocations in the reactivity of solids and it is concluded that the elastic energy associated with the strain fields around or at the core of the dislocation cannot be used to promote chemical reactivity but that it is the change in the stereochemical environment of molecules in the dislocated region of the crystal which is important. ‘ . . . a curious illustration of the influence of mechanical forces over chemical affinity. . . ’ M. Faraday (1834)

Evolution of lateral V-defects on InGaN/GaN on Si(111) during PAMBE: the role of strain on defect kinetics

CrystEngComm ◽  
2018 ◽  
Vol 20 (29) ◽  
pp. 4151-4163 ◽  
Author(s):  
Ankush Bag ◽  
Subhashis Das ◽  
Rahul Kumar ◽  
Dhrubes Biswas
Keyword(s):  
Molecular Beam ◽  
Molecular Beam Epitaxial ◽  
Gan On Si ◽  
First Time ◽  
Kinetics Of

In this article, a unique correlation has been established between the defect kinetics of III-nitride adatoms and strain during plasma assisted molecular beam epitaxial (PAMBE) growth of InGaN/GaN heterostructures on silicon(111) for the first time.

THIRD-ORDER NONLINEAR OPTICAL RESPONSE OF A NEW LINEAR POLYMER WITH 4-AMINOAZOBENZENE

2001 ◽  
Vol 10 (03) ◽  
pp. 311-327 ◽  
Author(s):  
A. S. KUTSENKO ◽  
S. M. MALOLETOV ◽  
O. M. BURIN ◽  
V. I. VOLKOV ◽  
A. A. BORSHCH ◽  
...  
Keyword(s):  
Refractive Index ◽  
Relaxation Time ◽  
Nonlinear Refraction ◽  
Nonlinear Behavior ◽  
Polymer Chains ◽  
Azo Compounds ◽  
And Inversion ◽  
First Time ◽  
Kinetics Of

Nonlinear refraction in a new polymer material based on diglycidylether of bisphenol-A and containing 4-aminoazobenzene covalently attached to the polymer chains have been studied. The material was shown to exhibit fast nonlinear response (relaxation time about 20 ns, χ(3)= 5 × 10- 8 esu) together with slow one (relaxation time of the order of tens of hours). This makes it possible to record fast and long life (quasi stationary) phase holograms. An analysis of possible mechanisms for the refractive index nonlinear behavior in the new structure is presented. In particular, a role of electronic, thermal, orientation, and isomerization processes is discussed. It was for the first time shown that the rotational and inversion mechanisms of the cis → trans isomerization of the azo-compounds have determinative effect upon kinetics of the nonlinear refractive index relaxation. For the rotational mechanism the relaxation time was found to be 10-4 s meanwhile for the inversion mechanism it was 105 s.

scholarly journals Gravity Affects the Closure of the Traps inDionaea muscipula

2014 ◽  
Vol 2014 ◽  
pp. 1-5 ◽  
Author(s):  
Camilla Pandolfi ◽  
Elisa Masi ◽  
Boris Voigt ◽  
Sergio Mugnai ◽  
Dieter Volkmann ◽  
...  
Keyword(s):  
Parabolic Flight ◽  
Large Diameter ◽  
Carnivorous Plant ◽  
Venus Flytrap ◽  
Dionaea Muscipula ◽  
Fast Movement ◽  
First Time ◽  
Kinetics Of

Venus flytrap (Dionaea muscipulaEllis) is a carnivorous plant known for its ability to capture insects thanks to the fast snapping of its traps. This fast movement has been long studied and it is triggered by the mechanical stimulation of hairs, located in the middle of the leaves. Here we present detailed experiments on the effect of microgravity on trap closure recorded for the first time during a parabolic flight campaign. Our results suggest that gravity has an impact on trap responsiveness and on the kinetics of trap closure. The possible role of the alterations of membrane permeability induced by microgravity on trap movement is discussed. Finally we show how the Venus flytrap could be an easy and effective model plant to perform studies on ion channels and aquaporin activities, as well as on electrical activityin vivoon board of parabolic flights and large diameter centrifuges.

A kinetic study of the phase transformations in Al2O3 and Na2O · 6Al2O3 by a combined use of 27Al MAS NMR spectroscopy and x-ray diffraction: Importance of nucleation

1991 ◽  
Vol 6 (12) ◽  
pp. 2701-2705 ◽  
Author(s):  
S. Prabakar ◽  
K.J. Rao ◽  
C.N.R. Rao
Keyword(s):  
Nmr Spectroscopy ◽  
Phase Transformations ◽  
Mas Nmr ◽  
X Ray Diffraction ◽  
X Ray ◽  
Combined Use ◽  
27Al Mas Nmr ◽  
First Time ◽  
Kinetics Of

Phase transformations of Al2O3 and Na2O · 6Al2O3 prepared by the gel route have been investigated for the first time by 27Al MAS NMR spectroscopy in combination with x-ray diffraction. Of particular interest in the study is the kinetics of the γ → α and γ → β transformations, respectively, in these two systems. Analysis of the kinetic data shows the important role of nucleation in both these transformations.

scholarly journals Violaxanthin conversion by recombinant diatom and plant de-epoxidases, expressed in Escherichia coli – comparative analysis

2019 ◽  
Author(s):  
Monika Olchawa-Pajor ◽  
Monika Bojko ◽  
Wojciech Strzałka ◽  
Kazimierz Strzałka ◽  
Dariusz Latowski
Keyword(s):  
Escherichia Coli ◽  
Open Reading Frames ◽  
Amino Acid Residues ◽  
Metal Affinity ◽  
Comparable Activity ◽  
First Time ◽  
Kinetics Of ◽  
Reading Frames

The purpose of this research was to obtain recombinant violaxanthin de-epoxidases (VDEs) from two species. The first one was VDE of Arabidopsis thaliana (L.) Heynh. (WT Columbia strain) (AtVDE) which in vivo catalyzes conversion of violaxanthin (Vx) to zeaxanthin (Zx) via anteraxanthin (Ax). The second one was VDE of Phaeodactylum tricornutum Bohlin, 1897 (CCAP 1055/1 strain) (PtVDE) which is responsible for de-epoxidation of diadinoxanthin (Ddx) to diatoxanthin (Dtx). As the first step of our experiments, open reading frames coding for studied enzymes were amplified and subsequently cloned into pET-15b plasmid. For recombinant proteins production Escherichia coli Origami b strain was used. The molecular weight of the produced enzymes were estimated approximately at 45kDa and 50kDa for AtVDE and PtVDE, respectively. Both enzymes, purified under native conditions by immobilized metal affinity chromatography, displayed comparable activity in assay mixture and converted up to 90% Vx in 10 min in two steps enzymatic de-epoxidation, irrespective of enzyme origin. No statistically significant differences were observed when kinetics of the reactions catalyzed by these enzymes were compared. Putative role of selected amino-acid residues of AtVDE and PtVDE was also considered. The significance of the first time obtained recombinant PtVDE as a useful tool in various comparative investigations of de-epoxidation reactions in main types of xanthophyll cycles existing in nature are also indicated.

scholarly journals Vasopressin-dependent Myogenic Cell Differentiation Is Mediated by Both Ca2+/Calmodulin-dependent Kinase and Calcineurin Pathways

2005 ◽  
Vol 16 (8) ◽  
pp. 3632-3641 ◽  
Author(s):  
Bianca Maria Scicchitano ◽  
Lucia Spath ◽  
Antonio Musarò ◽  
Mario Molinaro ◽  
Nadia Rosenthal ◽  
...  
Keyword(s):  
Transcriptional Activation ◽  
Nuclear Translocation ◽  
Myogenic Cell ◽  
Specific Gene ◽  
Myocyte Enhancer Factor 2 ◽  
First Time ◽  
Kinetics Of ◽  
Enhancer Factor ◽  
Formation Of Complexes

Arg8-vasopressin (AVP) promotes the differentiation of myogenic cell lines and mouse primary satellite cells by mechanisms involving the transcriptional activation of myogenic bHLH regulatory factors and myocyte enhancer factor 2 (MEF2). We here report that AVP treatment of L6 cells results in the activation of calcineurin-dependent differentiation, increased expression of MEF2 and GATA2, and nuclear translocation of the calcineurin target NFATc1. Interaction of these three factors occurs at MEF2 sites of muscle specific genes. The different kinetics of AVP-dependent expression of early (myogenin) and late (MCK) muscle-specific genes correlate with different acetylation levels of histones at their MEF2 sites. The cooperative role of calcineurin and Ca2+/calmodulin-dependent kinase (CaMK) in AVP-dependent differentiation is demonstrated by the effect of inhibitors of the two pathways. We show here, for the first time, that AVP, a “novel” myogenesis promoting factor, activates both the calcineurin and the CaMK pathways, whose combined activation leads to the formation of multifactor complexes and is required for the full expression of the differentiated phenotype. Although MEF2–NFATc1 complexes appear to regulate the expression of an early muscle-specific gene product (myogenin), the activation of late muscle-specific gene expression (MCK) involves the formation of complexes including GATA2.

scholarly journals Efficacy Analysis and Kinetics of 3-Component Photopolymerization by Visible-LED/Coumarin and Enhanced by Additives of Iodonium Salt and Amine

2021 ◽  
Author(s):  
Jui-Teng Lin ◽  
Jacques Lalevee ◽  
Da-Chun Cheng
Keyword(s):  
Dual Function ◽  
Photo Oxidation ◽  
Efficacy Analysis ◽  
System A ◽  
Component Systems ◽  
Analytical Formulas ◽  
Iodonium Salt ◽  
First Time ◽  
Kinetics Of

This article presents, for the first time, the kinetics and the general conversion features of free radical polymerization (FRP) in a 3-component system (A/B/N), with [A] being the initiator, and [B] and [N] are additives, based on the proposed mechanism of Rahal et al. Higher FRP can be achieved by additives [B] and [N], via the dual function of (i) regeneration [A], and (ii) generation of extra radicals (R) via the radicals (S' and S) produced by N.The initiator (coumarin) shows a dual photo-oxidation and photo-reduction character for high efficacy. The FRP conversion efficacy (CE) depends not only on the property of the initiator [A], the additives [B] and [N}, but also the types of monomers. For example, when [A]=CoumC, [A]/NPG is more efficient than [A]/Iod, but revserse trend occurs in some monomers. However, 2-component systems (with CE=0% to 80%) are always less efficient than that of 3-component systems (with CE=70% to 86%, in TMPTA). Specific systems with [A]=coumarins, [B]=Iodonium salt, and N=NPG are analyzed. Analytical formulas for the role of each component concentration, light intensity and coupling rates on the conversion efficacy are derived.

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