Circular dichroism of turnip peroxidases

1977 ◽  
Vol 55 (8) ◽  
pp. 804-811 ◽  
Author(s):  
Dominique Job ◽  
H. Brian Dunford
Keyword(s):  
Active Sites ◽  
Common Property ◽  
Cd Spectra ◽  
Cyanide Binding ◽  
Helical Content ◽  
Japanese Radish ◽  
Plant Peroxidases ◽  
Reduced Forms ◽  
Very High ◽  
Circular Dichroic

Circular dichroic (CD) spectra of two turnip isoperoxidases, P1 and P7, and of their derivatives were measured over the wavelength range of 200 to 650 nm. For the two isoenzymes, it was observed that although the visible and Soret bands are located at similar wavelengths, their ellipticities are different. These results suggest that the active sites are similar but that differences do exist. The results are compared with those reported for Japanese radish peroxidase a and horseradish peroxidase. It appears that a common property of plant peroxidases is the presence of negative CD Soret bands for the reduced forms and their inversion upon cyanide binding. The CD spectra in the far UV region indicate an appreciable helical content for both native enzymes and their various derivatives. The calculated contents of unordered structure are very high (greater than 50% for either P1 or P7), in agreement with other studies on glycoproteins.

Effect of polymerization degree of oligogalacturonates and D-galacturonans on their circular dichroic spectra

1979 ◽  
Vol 44 (1) ◽  
pp. 167-173 ◽  
Author(s):  
Slavomír Bystrický ◽  
Rudolf Kohn ◽  
Tibor Sticzay
Keyword(s):  
Physicochemical Properties ◽  
Aqueous Solutions ◽  
Helical Structure ◽  
Monomeric Unit ◽  
Polymerization Degree ◽  
Cd Spectra ◽  
Circular Dichroic

The CD spectra of aqueous solutions of homopolymeric sodium oligogalacturonates and D-galacturonans of polymerization degree n = 1-64, as well as lower calcium oligogalacturonates (n = 1-5) were measured. Chiroptic properties were correlated with the polymerization degree in terms of optical superposition of monomeric unit increments. Interpretation of obtained data, respecting further physicochemical properties entitles to conclude that the conformation of macromolecules of D-galacturonan in solution is close to helical structure.

Active sites and factors influencing them for efficient oxygen reduction reaction in metal-N coordinated pyrolyzed and non-pyrolyzed catalysts: a review

2017 ◽  
Vol 5 (38) ◽  
pp. 20095-20119 ◽  
Author(s):  
Kiranpal Singh ◽  
Fatemeh Razmjooei ◽  
Jong-Sung Yu
Keyword(s):  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Active Sites ◽  
Reduction Reaction ◽  
Factors Influencing ◽  
Very High

This review outlines the fundamentals of active sites in biomimetic oxidase and M–N/C catalysts, responsible for carrying out oxygen reduction reaction at a very high TOF.

Energetics of ligand and inhibitor interactions with acetylcholinesterase

1987 ◽  
Vol 65 (9) ◽  
pp. 798-802 ◽  
Author(s):  
Y. T. Das ◽  
H. D. Brown ◽  
S. K. Chattopadhyay
Keyword(s):  
Active Sites ◽  
Specific Activity ◽  
Dimethyl Ester ◽  
Cotton Effect ◽  
Irreversible Inhibitor ◽  
Appreciable Change ◽  
Electrophorus Electricus ◽  
Heats Of Reaction ◽  
Normal Enzyme ◽  
Circular Dichroic

Acetylcholinesterase (AChE, EC 3.1.1.7) from Electrophorus electricus, purified by affinity chromatography to a specific activity of 7000 – 10000 U/mg protein, was studied at 27 °C in conduction-type microcalorimeters for the heats of reaction, with the subsite-specific cationic ligands edrophonium and propidium and with the irreversible inhibitor diisopropylfluorophosphate (DFP), in an ion-free aqueous medium. Edrophonium and propidium, each at 0.5 × 10−5 M, yielded reaction heats of +3.2 and –1.5 kcal/mol (1 kcal = 4.184 J) respectively, with 1.3 × 10−5 M AChE active sites. DFP (1.3 × 10−5 M) reacted exothermically yielding −0.5 kcal/mol at stoichiometric level with AchE active sites. Circular dichroic spectra showed that a ternary complex of AChE (6.5 × 10−7 M active sites) and the two ligands (each at 1 × 10−3 M) in 1 mM Tris–HCl buffer (pH 8.0) had a positive Cotton effect at 235 nm. Neither DFP nor phosphoric acid 2,2-dichloroethenyl dimethyl ester (DDVP) caused any appreciable change. DFP–AChE, however, behaved like a normal enzyme in showing a positive Cotton effect in association with the two ligands. DDVP–AChE showed an increase in negative ellipticity at 287 nm in the presence of the two ligands. Another cationic ligand, d-tubocurarine, when present together with edrophonium, increased negative ellipticity at 302 nm and blue-shifted a 265-nm peak of the normal AChE. DFP interactions with AChE appear to be energetically different from those of edrophonium, the latter of which is believed to associate with the acetylcholine-binding subsite.

scholarly journals CONVERSION OF STYRENE INTO BENZALDEHYDE AND STYRENE EPOXIDE OVER MgCoAl-LDH CATALYSTS

2017 ◽  
Vol 55 (4) ◽  
pp. 403 ◽  
Author(s):  
Nguyen Tien Thao ◽  
Dang Van Long ◽  
Dinh Minh Hoan
Keyword(s):  
Active Sites ◽  
Styrene Oxide ◽  
Metal Salts ◽  
Experimental Conditions ◽  
Cobalt Ions ◽  
Styrene Epoxide ◽  
Co Precipitation ◽  
Double Hydroxide ◽  
Very High ◽  
Styrene Conversion

Co-containing hydroxides have been successfully synthesized by the co-precipitation of starting-metal salts. The obtained materials were characterized by some physical means including XRD, EDS, BET… It is found that Co2+ ions are present in the layered double hydroxide (LDH) sheets. The presence of cobalt ions in LDH plays as active sites for the oxidation of styrene with air. The catalysts exhibited a very high activity in the conversion of styrene into two main products (benzaldehyde and styrene oxide). The highest styrene conversion is about 90-95% and the total selectivity to benzaldehyde and styrene oxide is in the range of 80-85% under reported experimental conditions.

Effects on breathing of rostral pons glutamate injection during opossum development

1990 ◽  
Vol 69 (1) ◽  
pp. 189-195 ◽  
Author(s):  
J. P. Farber
Keyword(s):  
Active Sites ◽  
Excitatory Amino Acid ◽  
Thiobarbituric Acid ◽  
Initial Response ◽  
Diving Response ◽  
Trigeminal Nuclei ◽  
High Incidence ◽  
Very High ◽  
Amino Acid Glutamate ◽  
Diaphragm Activity

To determine whether pathways from the rostral pons, capable of influencing breathing, were present in immature mammals, the excitatory amino acid glutamate (sodium salt) was pressure injected in very small volumes into the rostral pons of suckling and adult opossums. The youngest animals tested were approximately 3 wk old (1.5-2.9 g). Animals were anesthetized with the thiobarbituric acid derivative, Inactin, and the electromyogram of the diaphragm was used to assess changes in breathing rhythm and ventilatory output. Glutamate concentrations of 50, 150, and 1,000 mM were injected into the rostral pons. Active sites were generally located between parabrachial and either lateral lemniscal or trigeminal nuclei. Effects of glutamate in opossums of all ages included changes in diaphragm activity and respiratory timing over several breaths. In the youngest animals, a very high incidence of apnea occurred as an initial response (17 of 20 sites) at the 1,000 mM concentration. The high incidence of apneic response in the youngest animals suggests that strong activation of rostral pontine neurons can more easily disrupt respiratory output; a physiological circumstance of such activation might include a diving response stimulated by trigeminal afferents.

The circular dichroism of ovoverdin and other carotenoproteins from the lobster Homarus americanus

1983 ◽  
Vol 61 (9) ◽  
pp. 1018-1024 ◽  
Author(s):  
N. Martin Young ◽  
Ross E. Williams
Keyword(s):  
Visible Region ◽  
Homarus Americanus ◽  
Cd Spectra ◽  
Visible Absorption ◽  
Cd Spectrum ◽  
Negative Band ◽  
Shell Protein ◽  
Fitting Procedures ◽  
Positive Feature ◽  
Circular Dichroic

The circular dichroic (CD) spectra of the α-, β′-, and γ-crustacyanins, ovoverdin, and the yellow lobster-shell protein were measured in the region 200–750 nm, for comparison with the CD spectrum of the free carotenoid astaxanthin. The two carotenoid chromophores of ovoverdin gave a CD spectrum with a series of bands of alternating sign and ellipticities up to 1.9 × 105 degree∙cm2∙dmol−1, comparable to the low temperature CD spectrum of astaxanthin in the UV region. The visible region of ovoverdin also contained strong CD bands where astaxanthin itself has very weak ones. The blue (640 nm) chromophore of ovoverdin gave a broad negative CD feature quite different from the blue chromophores of the three crustacyanins. The crustacyanins have a broad positive feature between 400 and 610 nm with ellipticities up to 2 × 105 degree∙cm2∙dmol−1, followed at higher wavelengths by a negative band with an ellipticity up to 1 × 105 degree∙cm2∙dmol−1. Gaussian curve-fitting procedures showed the positive features to consist of a minimum of two or three CD bands. In addition to the exciton bands at the main visible absorption, the yellow lobster-shell protein had a pair of CD bands of equal but opposite ellipticity associated with an absorption band between 250 and 340 nm. The UV regions of the CD spectra of the five carotenoproteins have bands from both carotenoid and protein chromophores, and possible assignments of these bands to one or the other of the two types of chromophore are proposed.

Process Optimization with Acid Functionalised Activated Carbon derived from Corncob for Production of 4-Hydroxymethyl-2,2-Dimethyl-1,3-Dioxolane and5-Hydroxy-2,2-Dimethyl-1,3-Dioxane

2021 ◽  
Author(s):  
Jaspreet Kaur ◽  
Anil Sarma ◽  
Prof Mithilesh K Jha ◽  
Poonam Gera
Keyword(s):  
Active Sites ◽  
High Surface ◽  
High Surface Area ◽  
Reaction Parameters ◽  
Glycerol Conversion ◽  
Acidic Catalyst ◽  
The Face ◽  
Structural Deformity ◽  
Very High

Abstract This study focuses on the application of the corncob derived base (NaOH) activated and acid (H2SO4) functionalized carbons for the glycerol valorization to produce 2,2-Dimethyl-1,3-dioxolane-4-methanol (solketal), an oxygenated additive to fuel. The two derived catalysts viz., AAC-CC and AC-CC were subjected to various techniques for the determination of their structural properties and their comparison is made on the basis of characteristics and conversion into the final product. The conjugated boat structure of AAC-CC resulted very high surface area (779.8 m2/g) and higher pore volume (0.428cc/g) of AAC-CC that unveil its suitability as better among the two catalytic pathways during the solketal production. The acidic catalyst shows the highest catalytic activity as compared to basic due to the availability of the more active sites to the catalyst that will help in the reaction for higher conversion. The face cantered composite design (FCCD) of RSM was applied for the optimization of the reaction parameters for the ketalisation reaction. From the optimized results, the acidic catalyst AAC-CC gives higher glycerol conversion, i.e. 80.3% than the basic catalyst AC-CC i.e. 72.12% under the actual laboratory experiment. Moreover, the catalyst could be reused for three consecutive batch reactions without (< 5%) much reduction of activity and no distinctive structural deformity.

Circular dichroism studies on Mengo virus variants and their constituent ribonucleates

1970 ◽  
Vol 48 (8) ◽  
pp. 940-943 ◽  
Author(s):  
Cyril M. Kay ◽  
John S. Colter ◽  
Kimio Oikawa
Keyword(s):  
Amino Acids ◽  
Viral Protein ◽  
Small Amplitude ◽  
Helical Content ◽  
Mengo Virus ◽  
Α Helix ◽  
The Right ◽  
Circular Dichroïsm ◽  
Circular Dichroic

A comparison of the circular dichroic spectra of three variants of Mengo virus and their constituent ribonucleates shows that the curves are essentially identical to one another, with respect to crossover points and the positions and amplitudes of troughs and peaks. This would suggest that the manner in which the proteins are arranged around the RNA chain in the virus is precise and similar in all three cases, and that there are no significant differences in the density of packing among the virions. By subtracting the RNA contribution from that of the virus, the circular dichroic curve of the protein in situ was obtained. The small amplitude of the ellipticity bands at ~205 and 220 mμ (transitions characteristic of the right-handed α-helix) suggests that the protein, as it exists in the virion, possesses a low α-helical content. This observation is consistent with the fact that the viral protein contains a large content of proline and non-α-helix-forming amino acids.

scholarly journals Kinetic studies on the binding of cyanide to oxygenated cytochrome c oxidase

1976 ◽  
Vol 155 (2) ◽  
pp. 453-455 ◽  
Author(s):  
T Brittain ◽  
C Greenwood
Keyword(s):  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Kinetic Studies ◽  
Binding Properties ◽  
Cyanide Concentration ◽  
Cyanide Binding ◽  
Single Process ◽  
Reduced Forms

The reaction of cyanide with oxygenated cytochrome c oxidase was followed by means of flow-flash techniques. The oxygenated form, produced after photolysis of the partially reduced CO complex in the presence of cyanide and O2, shows cyanide-binding properties distinct from those of both the oxidized and the reduced forms of the protein. The binding is a single process (k = 22M-1-S-1) linearly dependent on cyanide concentration to as high as 75 mM. It is suggested that the oxygenated form is a conformational variant of the oxidized protein.

scholarly journals Biological and physiological properties of reverse ankyrin engineered for dimer construction to enhance HIV-1 capsid interaction

2021 ◽  
Author(s):  
On-anong Juntit ◽  
Umpa Yasamut ◽  
Supachai Sakkhachornphop ◽  
Koollawat Chupradit ◽  
Weeraya Thongkum ◽  
...  
Keyword(s):  
Active Sites ◽  
Sandwich Elisa ◽  
Binding Activity ◽  
Gag Protein ◽  
Linker Peptide ◽  
C Terminus ◽  
Physiological Properties ◽  
Helical Content ◽  
Binding Avidity ◽  
Hiv 1

Assembly and budding in the late-stage of human immunodeficiency virus type 1 (HIV-1) production relies on the polymerization of Gag protein at the inner leaflet of the plasma membrane. We previously generated an ankyrin repeat protein (Ank1D4) that specifically interacts with the CAp24 protein. This study aimed to improve the binding activity of Ank1D4 by generating two platforms for the Ank1D4 dimer. The design of these constructs featured a distinct orientation of monomeric Ank1D4 connected by a linker peptide (G S) . The binding surfaces in either dimer generated from the C-terminus of the Ank1D4 monomer linked with the N-terminus of another monomer (Ank1D4 ) or its inverted form (Ank1D4 ), similar to monomeric Ank1D4. The interaction of Ank1D4 with CAp24 from capture ELISA was significantly greater than that of Ank1D4 and the parental Ank1D4. The bifunctional characteristic of Ank1D4 was further demonstrated using sandwich ELISA. The binding kinetics of these ankyrins were evaluated using bio-layer interferometry analysis. The K of Ank1D4 , Ank1D4 and monomeric Ank1D4 was 3.5 nM, 53.7 nM, and 126.2 nM, respectively. The dynamics of the interdomain linker and the behavior of ankyrin dimers were investigated in silico. Upon the binding distance calculation from the candidate structures, the achievement in obtaining double active sites is more possible in Ank1D4 . The CD spectroscopic data indicated that secondary structure of dimer forms resemble Ank1D4 monomer α-helical content. This finding confers the strategy to generate dimer from rigid scaffold for acquiring the binding avidity.

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