scholarly journals Solution properties of polygalacturonic acid

1969 ◽  
Vol 114 (4) ◽  
pp. 863-870 ◽  
Author(s):  
R W Stoddart ◽  
I. P. C. Spires ◽  
K F Tipton
Keyword(s):  
Ph Dependence ◽  
Sedimentation Coefficient ◽  
Ruthenium Red ◽  
Optical Rotatory Dispersion ◽  
Neutral Sugar ◽  
Polygalacturonic Acid ◽  
Specific Viscosity ◽  
Ph Titration ◽  
Titration Curves ◽  
Low Concentrations

1. The specimen of polygalacturonic acid used in these studies was shown to contain very little neutral sugar, methyl ester groups or ash, and only residues of galacturonic acid. Its electrophoretic homogeneity was examined in pyridine–acetic acid buffer at pH6·5 and in borate buffer at pH9·2. The distribution of effective particle weights was shown to be fairly narrow. 2. The pH-titration curve of the polymer gave a pK value of 3·7. 3. The interaction of the polymer with Ruthenium Red was studied and titration curves were obtained for the spectral shifts associated with the formation of a complex. 4. Optical-rotatory-dispersion studies showed that the Drude constant, λc, was dependent on pH. 5. Polygalacturonic acid was shown to display non-Newtonian properties in solution and to have an anomalously high relative specific viscosity at low concentrations. 6. Studies were made of the pH-dependence of the sedimentation coefficient of the polymer. 7. These results are discussed in terms of the structure of the molecule and their relevance to the properties of pectic substances.

scholarly journals The effects of calcium ions and pH on bovine prothrombin fragment 1. Intrinsic fluroescence studies

1979 ◽  
Vol 177 (3) ◽  
pp. 879-886 ◽  
Author(s):  
M E Scott ◽  
K A Koehler ◽  
R G Hiskey
Keyword(s):  
Ph Dependence ◽  
Tight Binding ◽  
Ph Titration ◽  
Prothrombin Fragment ◽  
Ph Values ◽  
Titration Curves ◽  
Or Groups ◽  
Effects Of Ph ◽  
Induced Changes ◽  
Apparent Association

The effects of pH and Ca2+ on the intrinsic fluorescence of bovine prothrombin fragment 1 were investigated to deduce the nature of protein functional groups involved in Ca2+ binding to fragment 1. From pH values of 9 to 3, increasing the H3O+ concentration results in quenching of the fluorescence of fragment 1. Reversible pH-titration curves are obtained which appear to consist of two regions. From pH 4 to pH6.5 a broad titration curve is obtained, whereas from pH6.5 to 9 a more pronounced titration behaviour is evidenced by a group or groups on fragment 1 with an apparent pKa of approx. 7.5. In contrast, the apparent association constant for Ca2+ and fragment 1 shows a sharp pH-dependence in the region between pH7 and 8 with tighter Ca2+ binding at higher pH values. A PKa of approx. 7.5 can be estimated for the group or groups on fragment 1 linked to the tight binding of Ca2+. Both H3O+ and Ca2+ result in blue-shifts in the wave-lengths of fragment-1 emission. These results are interpreted in terms of H+ - and Ca2+ - induced changes in the conformation of fragment 1 as a result of surface-charge neutralization.

scholarly journals Studies of the denaturation and partial renaturation of ovalbumin

1972 ◽  
Vol 129 (3) ◽  
pp. 665-676 ◽  
Author(s):  
J. C. Holt ◽  
J. M. Creeth
Keyword(s):  
Sodium Dodecyl Sulphate ◽  
Sodium Dodecyl ◽  
Sedimentation Coefficient ◽  
Optical Rotatory Dispersion ◽  
Rotatory Dispersion ◽  
Physical Parameters ◽  
Optical Rotatory ◽  
Guanidinium Chloride ◽  
Dispersion Parameters ◽  
Low Concentrations

1. The denaturation of ovalbumin by the reagents sodium dodecyl sulphate and guanidinium chloride was investigated, by following the changes in sedimentation velocity, optical rotatory dispersion and viscosity as a function of denaturant concentration. 2. With sodium dodecyl sulphate both the optical-rotatory-dispersion parameters a0 and b0 become more negative, the sedimentation coefficient decreases and the viscosity increases; significant differences in the denaturation profiles are observed. The change in each parameter is indicative of only limited denaturation. 3. With guanidinium chloride the transition occurs over the concentration range 1–4m: more extensive changes occur in all the physical parameters than with sodium dodecyl sulphate. The values of a0 and b0 are indicative of complete denaturation. Reduction by mercaptoethanol produces only minor further changes. 4. Renaturation was attempted from both denaturants, the removal of reagent being accomplished reversibly by controlled slow dialysis. Partial renaturation was observed, but aggregated or insoluble material was produced in both cases at relatively low concentrations of denaturant. Similar behaviour was observed with fully reduced protein in guanidinium chloride–mercaptoethanol; complete renaturation could not be brought about even at very low protein concentrations.

scholarly journals The isocitrate dehydrogenases of Acinetobacter lwoffi. Separation and properties of two nicotinamide–adenine dinucleotide phosphate-linked isoenzymes

1972 ◽  
Vol 130 (1) ◽  
pp. 211-219 ◽  
Author(s):  
Colin H. Self ◽  
P. David J. Weitzman
Keyword(s):  
Molecular Weight ◽  
Ph Dependence ◽  
Gel Filtration ◽  
Deae Cellulose ◽  
Nicotinamide Adenine Dinucleotide Phosphate ◽  
Molecular Size ◽  
Ion Exchange Chromatography ◽  
Exchange Chromatography ◽  
Low Concentrations ◽  
Stimulation Of

Two isoenzymes of NADP-linked isocitrate dehydrogenase have been identified in Acinetobacter lwoffi and have been termed isoenzyme-I and isoenzyme-II. The isoenzymes may be separated by ion-exchange chromatography on DEAE-cellulose, by gel filtration on Sephadex G-200, or by zonal ultracentrifugation in a sucrose gradient. Low concentrations of glyoxylate or pyruvate effect considerable stimulation of the activity of isoenzyme-II. The isoenzymes also differ in pH-dependence of activity, kinetic parameters, stability to heat or urea and molecular size. Whereas isoenzyme-I resembles the NADP-linked isocitrate dehydrogenases from other organisms in having a molecular weight under 100000, isoenzyme-II is a much larger enzyme (molecular weight around 300000) resembling the NAD-linked isocitrate dehydrogenases of higher organisms.

Compositional and structural heterogenicity of the cardiac jelly of the chick embryo tubular heart: a TEM, SEM and histochemical study

Development ◽  
1980 ◽  
Vol 56 (1) ◽  
pp. 211-223
Author(s):  
J. M. Hurle ◽  
J. M. Icardo ◽  
J. L. Ojeda
Keyword(s):  
Alcian Blue ◽  
Regional Differences ◽  
Histochemical Study ◽  
Cetylpyridinium Chloride ◽  
Ruthenium Red ◽  
Heart Tube ◽  
Fibrillar Material ◽  
Low Concentrations ◽  
Dorsal Mesocardium ◽  
Myocardial Layer

The hearts of chick embryos of stages 9–13 were subjected to SEM, TEM and histochemical studies to ascertain possible regional differences in the structure and composition of the cardiac jelly. Two distinct regions, the cardiac jelly filling the space located between the myocardium and the endocardium (MECJ) and the cardiac jelly filling the dorsal mesocardium (EECJ), were distinguished by their structural and histochemical properties. MECJ is formed by amorphous and fibrillar material arranged between the endocardial and myocardial layer. The amount of its components increases when cetylpyridinium chlorideis introduced into the fixative, and it appears intensely stained by ruthenium red and alcian blue at low concentrations of MgCl2. The amount and arrangement of its componentsincrease during the beginning of the looping process of the heart tube. The EECJ is very rich in ruthenium-red-positive basal-lamina-like material and the addition of cetylpyridinium chloride to the fixative does not modify its appearance. It also appears poorly stained by alcian blue at low concentrations of MgCl2 and its arrangement undergoes modifications closely associated with the events of endocardial fusion. The possible significance of these results in the early morphogenesis of the heart is discussed.

Ionic Equilibria and pH

2021 ◽  
pp. 276-312
Author(s):  
Christopher O. Oriakhi
Keyword(s):  
Worked Examples ◽  
Ionization Constants ◽  
Acid Base ◽  
Buffer Solution ◽  
Ph Titration ◽  
Titration Curves ◽  
Ionic Equilibria ◽  
Common Ion ◽  
The Common ◽  
Hasselbalch Equation

Ionic Equilibria and pH reviews the quantitative aspects of aqueous acid-base chemistry. Definitions and concepts are presented and appropriate worked examples illustrate calculations of concentration, pH and ionization constants. Acid-base properties of salts (salt hydrolysis) is introduced and explained along with the common-ion effect and calculation of hydrolysis constants. Equilibria of acid-base buffers with respect to buffer preparation, calculating the pH of a buffer solution and application of the Henderson-Hasselbalch equation, buffer range and buffer capacity is discussed. Determining the pH during acid-base titrations, selecting the appropriate acid-base indicators, and generating pH titration curves are explained.

Inhibition by Tetranitromethane of Photosynthetic Electron Transport from Water to Photosystem II in Chloroplasts

1980 ◽  
Vol 35 (3-4) ◽  
pp. 293-297 ◽  
Author(s):  
P. V. Sane ◽  
Udo Johanningmeier
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Electron Flow ◽  
Ph Dependence ◽  
Photosynthetic Electron Transport ◽  
Donor Side ◽  
Ps Ii ◽  
Diphenyl Carbazide ◽  
Low Concentrations ◽  
Sh Group

Abstract Low concentrations (10 µM) of tetranitromethane inhibit noncyclic electron transport in spinach chloroplasts. A study of different partial electron transport reactions shows that tetranitromethane primarily interferes with the electron flow from water to PS II. At higher concentrations the oxidation of plastohydroquinone is also inhibited. Because diphenyl carbazide but not Mn2+ ions can donate electrons efficiently to PS II in the presence of tetranitromethane it is suggested that it blocks the donor side of PS II prior to donation of electrons by diphenyl carbazide. The pH dependence of the inhibition by this protein modifying reagent may indicate that a functional-SH group is essential for a protein, which mediates electron transport between the water splitting complex and the reaction center of PS II.

The multiple dissociation constants of glutathione disulfide: interpreting experimental pH-titration curves with ab initio MD simulations

2019 ◽  
Vol 21 (18) ◽  
pp. 9212-9217 ◽  
Author(s):  
Vaishali Arunachalam ◽  
Anil Kumar Tummanapelli ◽  
Sukumaran Vasudevan
Keyword(s):  
Complex Systems ◽  
Ab Initio ◽  
Dissociation Constants ◽  
Md Simulations ◽  
Glutathione Disulfide ◽  
Ph Titration ◽  
Titration Curves ◽  
Ab Initio Md

Dissociation constants calculated from ab initio MD simulations can aid the interpretation of the pH-titration curves of complex systems.

scholarly journals The loss of rapidly labelled ribonucleic acid from isolated HeLa cell nuclei

1969 ◽  
Vol 112 (1) ◽  
pp. 71-79 ◽  
Author(s):  
J. W. Watts
Keyword(s):  
Hela Cell ◽  
Incubation Medium ◽  
Sedimentation Coefficient ◽  
Cell Nuclei ◽  
Isolated Nuclei ◽  
Bivalent Cations ◽  
Low Concentrations ◽  
Nuclear Rna ◽  
And Diffusion

1. The loss of nucleic acids and protein from isolated HeLa-cell nuclei was studied. During 4hr. incubation at 37° DNA was conserved, but appreciable amounts of RNA and protein were lost. 2. Two classes of nuclear RNA were distinguished: at least 75% of the RNA was lost from the nuclei relatively slowly through degradation to acid-soluble fragments; the rest of the RNA was lost much more rapidly, not only through degradation to acid-soluble fragments but also through diffusion of RNA out of the nuclei into the incubation medium. 3. The RNA that was preferentially lost was the fraction of nuclear RNA that was rapidly labelled when intact HeLa cells were grown in a medium containing radioactive precursors of RNA. 4. The RNA appearing in the incubation medium was apparently partially degraded and had a sedimentation coefficient of about that of transfer RNA. 5. Both the degradation of RNA and the loss of RNA from the nuclei were sensitive to bivalent cations. Low concentrations of Mg2+ and Mn2+ greatly increased the rate of degradation of the rapidly labelled RNA to acid-soluble fragments, and produced a corresponding decrease in the amount of RNA diffusing into the medium. At higher concentrations they suppressed both degradation and diffusion of RNA. The cations Ca2+, Cu2+, Zn2+ and Ni2+ all progressively inhibited both forms of loss of RNA. 6. Salts of univalent cations produced appreciable effects only at ionic strengths of about 0·2, when degradation to acid-soluble fragments was preferentially inhibited. 7. Both ADP and ATP inhibited loss of RNA at about 30mm. 8. It was concluded that the diffusion of rapidly labelled RNA out of the isolated nuclei was not related to the movement of RNA from nucleus to cytoplasm in vivo, but reflected the ease with which the rapidly labelled RNA detached from the chromatin and the permeability of the membranes of isolated nuclei.

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