scholarly journals Extraction of Reduced Wool Proteins by Solutions of Salts

1969 ◽  
Vol 22 (4) ◽  
pp. 1081 ◽  
Author(s):  
JA Maclaren ◽  
DJ Kilpatrick
Keyword(s):  
Aqueous Solution ◽  
Solvent System ◽  
Disulphide Bonds ◽  
Wool Proteins

It has been shown earlier that the disulphide bonds in wool fibres are reduced specifically and almost quantitatively in aqueous solution using toluene-w-thiol (Maclaren 1962) or tributyl phosphine (Sweetman and Maclaren 1966; Maclaren, Kilpatrick, and Kirkpatrick 1968). The next step was to find a suitable solvent system to extract the proteins from the reduced fibre.

The Dissociation of Anilinium Ions in Aqueous Dimethylsulfoxide

1972 ◽  
Vol 50 (4) ◽  
pp. 474-478 ◽  
Author(s):  
Keith Yates ◽  
Graeme Welch
Keyword(s):  
Aqueous Solution ◽  
Solvent System ◽  
Ionization Mechanism ◽  
Normal Order ◽  
Aqueous Dimethylsulfoxide

The pKa values often substituted primary anilines and six substituted tertiary anilines have been determined in 70% DMSO–water. The ΔpKa values relative to those in aqueous solution indicate that DMSO is about 2 log units stronger as a base than H2O. The normal order of basicity (tertiary > primary) is inverted in this solvent system and the Hammett ρ values for the two series provide evidence for a different ionization mechanism than that in water.

scholarly journals The Effect of Reduction of The Disulphide Bond on the Fluorescence of High-Sulphur Wool Proteins

1968 ◽  
Vol 21 (6) ◽  
pp. 1325 ◽  
Author(s):  
GM Bhatnagar ◽  
LC Gruen
Keyword(s):  
Protein Conformation ◽  
Fluorescence Emission ◽  
Disulphide Bond ◽  
Thiol Groups ◽  
Quenching Effect ◽  
Tyrosine Fluorescence ◽  
Disulphide Bonds ◽  
Wool Proteins ◽  
Made In ◽  
Model Peptides

Reduction of the disulphide bonds affects the fluorescence emission from many proteins; this change is generally correlated with a change in the protein conformation (Cowgill 1964, 1966; Stryer, Holmgren, and Reichard 1967). Cowgill (1967) has reported the quenching effect of disulphide and thiol groups on the tryptophan and tyrosine fluorescence from model peptides when the quenching moiety is present in the same molecule as the chromophore. Similar observations have been made in this laboratory using a high-sulphur fraction extracted from wool protein.

scholarly journals Solvent kinetic isotope effects of human placental alkaline phosphatase in reverse micelles

1998 ◽  
Vol 330 (1) ◽  
pp. 267-275 ◽  
Author(s):  
Ter-Mei HUANG ◽  
Hui-Chih HUNG ◽  
Tsu-Chung CHANG ◽  
Gu-Gang CHANG
Keyword(s):  
Aqueous Solution ◽  
Isotope Effect ◽  
Reverse Micelles ◽  
Kinetic Isotope Effect ◽  
Isotope Effects ◽  
Solvent System ◽  
Placental Alkaline Phosphatase ◽  
K Value ◽  
Kinetic Isotope ◽  
Human Placental Alkaline Phosphatase

Human placental alkaline phosphatase was embedded in a reverse micellar system prepared by dissolving the surfactant sodium bis(2-ethylhexyl) sulphosuccinate (Aerosol-OT) in 2,2,4-trimethylpentane. This microemulsion system provides a convenient instrumental tool to study the possible kinetic properties of the membranous enzyme in an immobilized form. The pL (pH/p2H) dependence of hydrolysis of 4-nitrophenyl phosphate has been examined over a pL range of 8.5-12.5 in both aqueous and reverse micellar systems. Profiles of log V versus pL were Ha-bell shaped in the acidic region but reached a plateau in the basic region in which two pKa values of 9.01-9.71 and 9.86-10.48, respectively, were observed in reverse micelles. However, only one pKa value of 9.78-10.27 in aqueous solution was detected. Profiles of log V/K versus pL were bell-shaped in the acidic region. However, they were wave-shaped in the basic region in which a residue of pKa 9.10-9.44 in aqueous solution and 8.07-8.78 in reverse micelles must be dehydronated for the reaction to reach an optimum. The V/K value shifted to a lower value upon dehydronation of a pKa value of 9.80-10.62 in aqueous solution and 11.23-12.17 in reverse micelles. Solvent kinetic isotope effects were measured at three pL values. At pL 9.5, the observed isotope effect was a product of equilibrium isotope effect and a kinetic isotope effect; at pL 10.4, the log V/K value was identical in water and deuterium. The deuterium kinetic isotope effect on V/K was 1.14 in an aqueous solution and 1.16 in reverse micelles. At pL 11.0 at which the log V values reached a plateau in either solvent system, the deuterium kinetic isotope effect on V was 2.08 in an aqueous solution and 0.62 in reverse micelles. Results from a proton inventory experiment suggested that a hydron transfer step is involved in the transition state of the catalytic reaction. The isotopic fractionation factor (ϕ) for deuterium for the transition state (ϕT) increased when the pH of the solution was raised. At pL 11.0, the ϕT was 1.07 in reverse micelles, which corresponds to the inverse-isotope effect of the reaction in this solvent system. Normal viscosity effects on kcat and kcat/Km were observed in aqueous solution, corresponding to a diffusional controlled physical step as the rate-limiting step. We propose that the rate-limiting step of the hydrolytic reaction changes from phosphate releasing in aqueous solution to a covalent phosphorylation or dephosphorylation step in reverse micelles.

scholarly journals Catalytic Hydrolysis of Phosphate Monoester by Supramolecular Complexes Formed by the Self-Assembly of a Hydrophobic Bis(Zn2+-cyclen) Complex, Copper, and Barbital Units That Are Functionalized with Amino Acids in a Two-Phase Solvent System

Micromachines ◽  
2019 ◽  
Vol 10 (7) ◽  
pp. 452
Author(s):  
Yuya Miyazawa ◽  
Akib Bin Rahman ◽  
Yutaka Saga ◽  
Hiroki Imafuku ◽  
Yosuke Hisamatsu ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Amino Acids ◽  
Active Site ◽  
Self Assembly ◽  
Hydrolytic Activity ◽  
Solvent System ◽  
Supramolecular Complexes ◽  
Artificial System ◽  
Two Phase ◽  
Hydrolysis Of

We previously reported on the preparation of supramolecular complexes by the 2:2:2 assembly of a dinuclear Zn2+-cyclen (cyclen = 1,4,7,10-tetraazacyclododecane) complex having a 2,2′-bipyridyl linker equipped with 0~2 long alkyl chains (Zn2L1~Zn2L3), 5,5-diethylbarbituric acid (Bar) derivatives, and a copper(II) ion (Cu2+) in aqueous solution and two-phase solvent systems and their phosphatase activities for the hydrolysis of mono(4-nitrophenyl) phosphate (MNP). These supermolecules contain Cu2(μ-OH)2 core that mimics the active site of alkaline phosphatase (AP), and one of the ethyl groups of the barbital moiety is located in close proximity to the Cu2(μ-OH)2 core. The generally accepted knowledge that the amino acids around the metal center in the active site of AP play important roles in its hydrolytic activity inspired us to modify the side chain of Bar with various functional groups in an attempt to mimic the active site of AP in the artificial system, especially in two-phase solvent system. In this paper, we report on the design and synthesis of new supramolecular complexes that are prepared by the combined use of bis(Zn2+-cyclen) complexes (Zn2L1, Zn2L2, and Zn2L3), Cu2+, and Bar derivatives containing amino acid residues. We present successful formation of these artificial AP mimics with respect to the kinetics of the MNP hydrolysis obeying Michaelis–Menten scheme in aqueous solution and a two-phase solvent system and to the mode of the product inhibition by inorganic phosphate.

scholarly journals Glycerin/NaOH Aqueous Solution as a Green Solvent System for Dissolution of Cellulose

Polymers ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 1735
Author(s):  
Ke Li ◽  
Huiyu Yang ◽  
Lang Jiang ◽  
Xin Liu ◽  
Peng Lang ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Solvent System ◽  
Industrial Applications ◽  
Degree Of Polymerization ◽  
Green Solvent ◽  
Mixed Aqueous Solution ◽  
Before And After ◽  
Solvent Systems ◽  
The Difference ◽  
Ubbelohde Viscometer

Dissolving cellulose in water-based green solvent systems is highly desired for further industrial applications. The green solvent glycerin—which contains hydrogen-bonding acceptors—was used together with NaOH and water to dissolve cellulose. This mixed aqueous solution of NaOH and glycerin was employed as the new green solvent system for three celluloses with different degree of polymerization. FTIR (Fourier-transform infrared), XRD (X-ray diffractometer) and TGA (thermogravimetric analysis) were used to characterize the difference between cellulose before and after regenerated by HCl. A UbbeloHde viscometer was used to measure the molecule weight of three different kinds of cellulose with the polymerization degree of 550, 600 and 1120. This solvent system is useful to dissolve cellulose with averaged molecule weight up to 2.08 × 105 g/mol.

Enzymatic hydrolysis of β-lactam antibiotics at low pH in a two-phase "aqueous solution - water-immiscible organic solvent" system

2002 ◽  
Vol 80 (6) ◽  
pp. 699-707 ◽  
Author(s):  
Ghermes G Chilov ◽  
Vytas K Švedas
Keyword(s):  
Aqueous Solution ◽  
Enzymatic Hydrolysis ◽  
Organic Solvent ◽  
Solvent System ◽  
Low Ph ◽  
Thermodynamic Evaluation ◽  
Two Phase ◽  
Suggested Approach ◽  
Hydrolysis Of ◽  
Organic Solvent System

The application of the two-phase "aqueous solution – water-immiscible organic solvent" system is suggested not for effective biocatalytic synthesis, but for hydrolytic purposes. Enzymatic hydrolysis of benzylpenicillin and N-phenylacetamidodesacetoxycephalosporanic acid to corresponding antibiotic nuclei 6-aminopenicillanic and 7-aminodesacetoxycephalosporanic acids in a two-phase water–butylacetate system at pH 3–4 is proposed as an alternative to the biocatalytic hydrolysis in an alkaline medium. An experimental study has been performed and a model has been developed, which describes the influence of pH, phase volume ratio, thermodynamic constants, and initial antibiotic concentration on the effectiveness of their hydrolysis in a two-phase "aqueous solution – water-immiscible organic solvent" system. The thermodynamic evaluation of penicillin G and 7-phenylacetamidodesacetoxycephalosporanic acid hydrolysis at low pH in a two-phase aqueous solution – water-immiscible organic solvent system has demonstrated high practical potential. The suggested approach allows for the exclusion of several technological steps during the transformation of natural β-lactam antibiotics to their semi-synthetic analogues: alkaline extraction of the biosynthetic antibiotic from butylacetate followed by its enzymatic hydrolysis at pH 7.5–8.0 and further acidification of the reaction mixture, which results in the precipitation of the antibiotic nucleus. Experimental observations also revealed a specific feature of this process: the kinetic supersaturation of the antibiotic nucleus slows down the attainment of the equilibrium, which should be taken into account when further developing this approach.Key words: enzymatic hydrolysis, β-lactam antibiotic nuclei, two-phase systems, supersaturation, penicillin acylase.

Structures Formed by Cryoprotective Agents Used in Freezc-Etching

1971 ◽  
Vol 29 ◽  
pp. 448-449
Author(s):  
G. G. Cocks ◽  
C. E. Cluthe
Keyword(s):  
Aqueous Solution ◽  
Polyethylene Oxide ◽  
Liquid Nitrogen Temperature ◽  
Ice Crystals ◽  
Etching Technique ◽  
Structural Constituent ◽  
Cryoprotective Agents ◽  
Quick Freezing ◽  
Freeze Etching ◽  
Fractured Surface

The freeze etching technique is potentially useful for examining dilute solutions or suspensions of macromolecular materials. Quick freezing of aqueous solutions in Freon or propane at or near liquid nitrogen temperature produces relatively large ice crystals and these crystals may damage the structures to be examined. Cryoprotective agents may reduce damage to the specimem, hut their use often results in the formation of a different set of specimem artifacts.In a study of the structure of polyethylene oxide gels glycerol and sucrose were used as cryoprotective agents. The experiments reported here show some of the structures which can appear when these cryoprotective agents are used.Figure 1 shows a fractured surface of a frozen 25% aqueous solution of sucrose. The branches of dendritic ice crystals surrounded hy ice-sucrose eutectic can be seen. When this fractured surface is etched the ice in the dendrites sublimes giving the type of structure shown in Figure 2. The ice-sucrose eutectic etches much more slowly. It is the smooth continuous structural constituent surrounding the branches of the dendrites.

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