Physicochemical studies on the aggregation of bovine cardiac tropomyosin with ionic strength

1969 ◽  
Vol 47 (4) ◽  
pp. 411-413 ◽  
Author(s):  
William D. McCubbin ◽  
Cyril M. Kay
Keyword(s):  
Ionic Strength ◽  
High Ionic Strength ◽  
Optical Rotatory Dispersion ◽  
Rotatory Dispersion ◽  
Sedimentation Equilibrium ◽  
Velocity Sedimentation ◽  
Optical Rotatory ◽  
Dispersion Parameters ◽  
Tertiary Structures ◽  
The Individual

The aggregation of bovine cardiac tropomyosin as a function of ionic strength has been studied by the techniques of sedimentation velocity, sedimentation equilibrium, osmometry, viscometry, and optical rotatory dispersion. The measurements indicate that in aqueous buffers at neutral pH and at ionic strengths below 0.6, cardiac tropomyosin is heterogeneous and consists of a monomer in equilibrium with its aggregates. Dissociation of the aggregates occurs on dilution to yield a molecular weight species of approximately 70 000, in very good agreement with the value obtained at high ionic strength. These observations essentially parallel similar findings noted for the polymerization of skeletal tropomyosin, with the exception that the cardiac protein shows no tendency to polymerize at high ionic strength. The virtual constancy of all the optical rotatory dispersion parameters with polymerization suggests that the association is probably linear rather than lateral, with no accompanying changes in secondary and tertiary structures of the individual monomers.

scholarly journals Oligonucleotide studies. Optical rotatory dispersion of five homodinucleotides

1969 ◽  
Vol 113 (5) ◽  
pp. 843-851 ◽  
Author(s):  
Yasuo Inoue ◽  
Kimihiko Satoh
Keyword(s):  
Ionic Strength ◽  
Salt Concentration ◽  
Equilibrium Mixture ◽  
Cotton Effect ◽  
Phosphate Group ◽  
Optical Rotatory Dispersion ◽  
Rotatory Dispersion ◽  
Optical Rotatory ◽  
Ionization State ◽  
Terminal Phosphate Group

1. The optical rotatory dispersion (ORD) of five homodinucleotides, ApAp(3′), CpCp(3′), GpGp(3′), IpIp(3′) and UpUp(3′) (where A, C, G, I and U represent adenosine, cytidine, guanosine, inosine and uridine respectively, and p to the left of a nucleoside symbol indicates a 5′-phosphate and to the right it indicates a 3′-phosphate), were measured as a function of pH, ionic strength and Mg2+ concentration. 2. The ORD titrations of ApAp(3′) and CpCp(3′), which were made by measuring the ORD curves at closely spaced pH intervals, exhibit a maximum at approx. pH5·0 and 5·7 for ApAp(3′) and CpCp(3′) respectively in the profile of the magnitude of the first Cotton effect versus pH. The results indicate that the conformational rigidity of these dinucleotides depends on the ionization state of a 3′-terminal phosphate group. 3. ApAp(3′) was shown to exist as an approximately 1:1 equilibrium mixture of the two major ionic species represented by Ap(−1)Ap(−1) and Ap(−1)Ap(−2) at pH6·16, whereas at pH7·5 it exists exclusively as a form of Ap(−1)Ap(−2). 4. To ascertain the effects of the presence of a terminal phosphate group and of the ionization of the secondary phosphate on the conformation of adenylate dimer, we measured the ORD of ApA, ApAp(3′)CH3 and ApAp(2′). The rotatory power of the first Cotton effect in the above series of dinucleotides decreased at 20° in the order ApA> ApAp(3′)CH3≈ApAp(3′)(−1)> ApAp(2′) at pH7> ApAp(3′) at pH7. 5. The pH–rotation profiles were also obtained for ApAp(2′), CpCp(2′) and UpUp(3′), but no corresponding maximum was observed. Although simple nearest-neighbour calculations based on the ORD data of IpIp(3′) and 5′-IMP account for the observed ORD spectrum of polyinosinic acid at low salt concentration, there were large discrepancies between calculated and experimental results of the polyguanylic acid ORD even at low ionic strength. 6. The extent to which the amplitude of the Cotton effects of IpIp(3′) increases with salt concentration, especially by the addition of Mg2+, was much greater than that observed for ApAp(3′). The implication of such salt effects on the ORD is considered.

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.

On the use of the n-propylammonium and n-butylammonium salts of d-10-camphorsulfonic acid for the calibration of spectropolarimeters: the concentration and solvent dependency of the optical rotatory dispersion parameters

1976 ◽  
Vol 54 (20) ◽  
pp. 3200-3202
Author(s):  
Yasushi Nakagawa ◽  
Michael F. Gillen ◽  
Ross E. Williams
Keyword(s):  
Ammonium Salts ◽  
Optical Rotatory Dispersion ◽  
Rotatory Dispersion ◽  
Optical Rotatory ◽  
Dispersion Parameters ◽  
Camphorsulfonic Acid ◽  
Concentration Dependency ◽  
Circular Dichroic

The utility of the title ammonium salts for the calibration of ord spectropolarimeters has been investigated. The solvent and concentration dependency of the measured specific molar rotations at 306 and 270 nm suggest that they may be used for calibration purposes only under well-defined conditions. The results of the Kramers–Kronig transformation of their circular dichroic spectra are presented and compared with the measured ord spectra.

scholarly journals Sedimentation Equilibrium Studies on Protein From Kookaburra Beak

1976 ◽  
Vol 29 (6) ◽  
pp. 481
Author(s):  
EF Woods
Keyword(s):  
Molecular Weight ◽  
Optical System ◽  
Optical Rotatory Dispersion ◽  
Rotatory Dispersion ◽  
Sedimentation Equilibrium ◽  
Optical Rotatory ◽  
Equilibrium Studies ◽  
Aqueous Buffer ◽  
Random Coils ◽  
Equilibrium Sedimentation

Fractionated samples of the soluble S-carboxymethyl proteins from kookaburra beak (Frenkel and Gillespie 1976) were examined by equilibrium sedimentation. The molecular weight was found to be 11 300 when the photoelectric scanning absorption optical system was employed and 13 700 when Rayleigh interference optics were used. Possible explanations for this difference are considered and it is concluded that it must arise from heterogeneity of the protein. Optical rotatory dispersion measurements indicate that the proteins probably exist as random coils in dilute aqueous buffer.

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