scholarly journals Increase in the apparent intercalation ability of a platinum complex via multivalency by installation into the sidechain of a graft copolymer and observation of structural changes in the intercalated DNA

RSC Advances ◽  
2019 ◽  
Vol 9 (45) ◽  
pp. 26429-26434 ◽  
Author(s):  
Shigehito Osawa ◽  
Riichi Takahashi ◽  
Remi Watanabe ◽  
Sayaka Kubo ◽  
Hidenori Otsuka
Keyword(s):  
Graft Copolymer ◽  
Binding Constant ◽  
Structural Changes ◽  
Platinum Complex ◽  
Apparent Binding Constant ◽  
Multivalent Effect

Pt complexes increase their apparent binding constant by grafting on sidechains of polymer segments via multivalent effect.

Effect of Concentration of KI and of Temperature on Shortening of Glycerol-Treated Muscle Fibers in KI Solutions

1956 ◽  
Vol 185 (1) ◽  
pp. 92-94 ◽  
Author(s):  
W. J. Bowen ◽  
K. Laki
Keyword(s):  
Binding Constant ◽  
Muscle Fibers ◽  
Component Analysis ◽  
Contractile Protein ◽  
Temperature Dependent ◽  
Molecular Rearrangement ◽  
Previous Conclusion ◽  
Apparent Binding Constant ◽  
Speed Of Shortening

Experiments reported here further support the previous conclusion that the shortening of glycerol-treated muscle caused by neutral Nessler's reagent (HgI2 in KI solution) is essentially due to the KI component. Analysis of the data obtained indicates that the apparent binding constant of KI to the contractile protein is 5 or 6 m/l. The same value for the binding ATP is about 10,000. The extent and speed of shortening in HgI2-KI solution are temperature dependent. The molecular rearrangement which results in the shortening of glycerol-treated fibers is considered to be directly related to the binding KI to the protein.

scholarly journals Characterization of 83-kilodalton nonmuscle caldesmon from cultured rat cells: stimulation of actin binding of nonmuscle tropomyosin and periodic localization along microfilaments like tropomyosin.

1988 ◽  
Vol 106 (6) ◽  
pp. 1973-1983 ◽  
Author(s):  
S Yamashiro-Matsumura ◽  
F Matsumura
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Actin Filaments ◽  
Binding Constant ◽  
Reducing Agents ◽  
Actin Binding ◽  
Low Molecular Weight ◽  
Tropomyosin Isoforms ◽  
Apparent Binding Constant ◽  
Stimulation Of

Nonmuscle caldesmon purified from cultured rat cells shows a molecular weight of 83,000 on SDS gels, Stokes radius of 60.5 A, and sedimentation coefficient (S20,w) of 3.5 in the presence of reducing agents. These values give a native molecular weight of 87,000 and a frictional ratio of 2.04, suggesting that the molecule is a monomeric, asymmetric protein. In the absence of reducing agents, the protein is self-associated, through disulfide bonds, into oligomers with a molecular weight of 230,000 on SDS gels. These S-S oligomers appear to be responsible for the actin-bundling activity of nonmuscle caldesmon in the absence of reducing agents. Actin binding is saturated at a molar ratio of one 83-kD protein to six actins with an apparent binding constant of 5 X 10(6) M-1. Because of 83-kD nonmuscle caldesmon and tropomyosin are colocalized in stress fibers of cultured cells, we have examined effects of 83-kD protein on the actin binding of cultured cell tropomyosin. Of five isoforms of cultured rat cell tropomyosin, tropomyosin isoforms with high molecular weight values (40,000 and 36,500) show higher affinity to actin than do tropomyosin isoforms with low molecular weight values (32,400 and 32,000) (Matsumura, F., and S. Yamashiro-Matsumura. 1986. J. Biol. Chem. 260:13851-13859). At physiological concentration of KCl (100 mM), 83-kD nonmuscle caldesmon stimulates binding of low molecular weight tropomyosins to actin and increases the apparent binding constant (Ka from 4.4 X 10(5) to 1.5 X 10(6) M-1. In contrast, 83-kD protein has slight stimulation of actin binding of high molecular weight tropomyosins because high molecular weight tropomyosins bind to actin strongly in this condition. As the binding of 83-kD protein to actin is regulated by calcium/calmodulin, 83-kD protein regulates the binding of low molecular weight tropomyosins to actin in a calcium/calmodulin-dependent way. Using monoclonal antibodies to visualize nonmuscle caldesmon along microfilaments or actin filaments reconstituted with purified 83-kD protein, we demonstrate that 83-kD nonmuscle caldesmon is localized periodically along microfilaments or actin filaments with similar periodicity (36 +/- 4 nm) as tropomyosin. These results suggest that 83-kD protein plays an important role in the organization of microfilaments, as well as the control of the motility, through the regulation of the binding of tropomyosin to actin.

Adsorption of Amines to Thylakoid Surfaces and Estimations of ΔpH

1985 ◽  
Vol 12 (1) ◽  
pp. 9 ◽  
Author(s):  
AB Hope ◽  
DB Matthews
Keyword(s):  
Steady State ◽  
Fluorescence Quenching ◽  
Binding Constant ◽  
Protonated Form ◽  
Proton Motive Force ◽  
Amine Concentration ◽  
Apparent Binding Constant ◽  
Mgcl2 Concentration ◽  
A Charge ◽  
Good Agreement

The adsorption of the fluorescent, weak amine ΔpH indicators 9-aminoacridine and N-(1-naphthyl)ethylenediamine to thylakoids of pea chloroplasts in the dark was measured as a function of amine concentration, at several pH's between 8 and 5, and with varied MgCl2 concentration. It was concluded that it was the protonated form of the amine that was adsorbed. Maximum amounts adsorbed, saturation occurring at about 1 mM amine concentration in the presence of 5 mM KCl and 10 mM MgCl2, were up to 1 mol (mol Chl)-1. This was calculated as exceeding the number of available surface negative charges (0.26 for a charge density of 0.025 C m-2). An apparent binding constant of 400-500 μM (concentration for half saturation) was noted for both amines under the above conditions. A model was developed that enabled the estimation of the relative amounts of amine bound to the inside and outside thylakoid surfaces in the steady state, in the light. By this means corrections to the apparent ΔpH calculated from fluorescence quenching of the amines could be established. These corrections amounted to about 1 pH unit for the diamine and more for 9-aminoacridine. The predictions of the model were in good agreement with experimental relations between estimated, light-induced ΔpH values and amine concentration. The implications of a lower ΔpH for earlier estimations of proton motive force in relation to photophosphorylation are briefly considered.

scholarly journals Calorimetric studies of the N-terminal half-molecule of transferrin and mutant forms modified near the Fe3+-binding site

1993 ◽  
Vol 293 (2) ◽  
pp. 517-522 ◽  
Author(s):  
L N Lin ◽  
A B Mason ◽  
R C Woodworth ◽  
J F Brandts
Keyword(s):  
Binding Affinity ◽  
Binding Constant ◽  
Conformational Stability ◽  
High Sensitivity ◽  
Single Amino Acid ◽  
Iron Binding ◽  
Scanning Calorimetry ◽  
Apparent Binding Constant ◽  
Binding Cleft ◽  
Calorimetric Studies

The effects of single amino acid substitution on the thermal stability of the N-terminal half-molecule of human transferrin and its iron-binding affinity have been studied by high-sensitivity scanning calorimetry. All site-directed mutations are located on the surface of the binding cleft, and they are D63-->S, D63-->C, G65-->R, H207-->E and K206-->Q. Differential scanning calorimetry results show that the mutations do not significantly alter the conformational stability of the apo-forms of the proteins. The changes in free energy of unfolding relative to the wild-type protein range from 0.83 to -2.4 kJ/mol. The D63-->S, G54-->R and H207-->E mutations slightly destabilize the apo-protein, while the D63-->C and K206-->Q mutations increase its stability by a small amount. However, there are large compensating enthalpy-entropy changes caused by all mutations. All mutants bind ferric ion, but with different affinities. Replacement of Asp-63 by either Ser or Cys decreases the apparent binding constant by 5-6 orders of magnitude. The G65-->R mutation also decreases the apparent binding constant by 5 orders of magnitude. The K206-->Q mutation increases the apparent binding constant by 20-fold, while the H207-->E mutation does not significantly change the apparent iron-binding affinity of the half-molecule.

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