High Concentrations Of MgCl2 Research Articles

Interactions of pig Fab gamma fragments with protein A from Staphylococcus aureus.

Ninety % of pig serum IgG was bound to protein A-Sepharose. Both individual fractions of the IgG, separated on the basis of their electric charge, were adsorbed on protein A-Sepharose to a similar extent. However, these fractions differed in their elution profile from the protein A-Sepharose when a gradient of increasing molarity of MgCl2 was used. Relative amounts of fractions eluted in higher concentrations of MgCl2 were augmented with the increasing amount of IgG bound to SpA-Sepharose. Not only high proportions of Fc fragments, but also nearly half of Fab fragments reacted with protein A. This latter interaction, confirmed also by affinity electrophoresis, did not have the character of a specific reaction of antibody with antigen.

Raman spectroscopic studies of structural properties of solid and molten states of the magnesium chloride – alkali metal chloride system

Raman spectra have been recorded for solids and melts of composition MgCl2 + nACl (n = 0–4 and A = Cs, Rb, K, Na, Li). Characteristic spectra have been observed for each of the solids predicted from phase diagram studies and an additional two compounds formulated as Rb3MgCl5 and K3MgCl5 were detected. The compounds Cs2MgCl4, Cs3MgCl5, and Rb3MgCl5 contain the discrete MgCl42− tetrahedral ion which has been characterized by its Raman spectrum. These compounds melt with retention of the MgCl42− ion. Most other solids appear to contain distorted network octahedra with face-, edge-, or corner-shared chlorides. These solids melt to give the more stable tetrahedral MgCl42− ion. In melts of high MgCl2 concentration a new peak was detected which appears to be characteristic of the dimeric Mg2Cl73− ion which exists in equilibrium with the MgCl42− ion. The results are compared to similar studies on the better characterized CsCl–AlCl3 system.

Polymorphism at the G6pd and 6Pgd loci in Drosophila melanogaster. III. Developmental and biochemical aspects.

The electrophoretic variants of G6PD and 6PGD isolated from the Bogota Drosophila melanogaster population were characterized developmentally and biochemically. Changes in in vitro enzyme activity during development were comparable to those found for other dehydrogenases: an increase in the larval and adult stage and a decrease in the pupal stage. During the whole life cycle the "S" enzyme of both loci showed a higher activity than the "F" enzyme. MgCl2 had a stimulating effect on the activity of both enzymes whereas their heat stability was decreased. The allozymes of 6PGD had different Vmax's but were comparable with respect to Km values, pH optimum, and stability at 45 C. the allozymes of G6PD showed different Vmax's and differed in stability at 35 C, but had similar Km values and pH optima. As the difference in stability was probably due to differences in molecular structure of the allozymes, the differences in activity found at high pH and high MgCl2 concentration were most probably due to this difference in stability.

Purified Escherichia coli recA protein catalyzes homologous pairing of superhelical DNA and single-stranded fragments.

Purified Escherichia coli recA protein catalyzed ATP-dependent pairing of superhelical DNA and homologous single-stranded fragments. The product of the reaction: (i) was retained by nitrocellulose filters in 1.5 M NaCl/0.15 M Na citrate at pH 7, (ii) was dissociated at pH 12.3 but was not dissociated by heating at 55 degrees C for 4 min or by treatment with 0.2% sodium dodecyl sulfate and proteinase K, (iii) contained covalently closed circular double-stranded DNA (form I DNA), (iv) contained single-stranded fragments associated with replicative form (RF) DNA, and (v) contained a significant fraction of D-loops as judged by electron microscopy. Linear and nicked circular double-stranded DNA did not substitute well for superhelical DNA; intact circular single-stranded DNA did not substitute well for single-stranded fragments. Homologous combinations of single-stranded fragments and superhelical DNA from phages phiX174 and fd reacted, whereas heterologous combinations did not. The reaction required high concentrations of protein and MgCl2. The ATPase activity of purified recA protein was more than 98% dependent on the addition of single-stranded DNA. In 1 mM MgCl2, the ability of superhelical DNA to support the ATPase activity was two-thirds as good as that of single-stranded DNA.

Partial purification and characterization of DNA polymerases from the cauliflower inflorescence.

Two distinct DNA polymerases, designated A and B, have been partially purified from rapidly growing apical tissues of the cauliflower inflorescence (Brassica oleracea, var. botrytis). They were readily separable from each other, because enzyme A was adsorbable on an anion-exchanger, but enzyme B was not. The effects of divalent rations and ionic strength on both enzyme activities were very different. Enzyme A utilized activated DNA well at low concentration of MgCl2 or at low ionic strength, but heat-denatured DNA was utilized more effectively than was activated DNA at high concentration of MgCl2. Enzyme B also utilized much more heat-denatured DNA and poly (rA)•(dT)10 at high ionic strength. Gel chromatography with Sephadex G-200 revealed that enzyme A has a higher molecular weight (approx. 100, 000) than enzyme B (approx. 75, 000). It has been also described that some points of properties in enzyme A and B resemble to those of the two DNA polymerase -α and -β from mammalian cells, respectively. The existence of the third enzyme, designated C, in the fraction with enzyme A was suggested with an assay system using poly (rA)•(dT)10 as the template.

Lipoamide Dehydrogenase Regulation in Rat Brain

The Pyruvate dehydrogenase multienzyme complex (PDHC) purified from rat brain is phosphorylated in the presence of low concentrations of ATP and MgCl2. The phosphorylated PDHC is incapable of catalyzing the oxidative decarboxylation of pyruvate. In the presence of high concentrations (10 mM) of MgCl2, the phosphorylated (inactive) PDHC is converted back to the dephospho-form of PDHC which is catalytically active. The dihydrolipoyl dehydrogenase (LAD) component, E3, of PDHC is inactivated by pyridoxal phosphate (PLP) and the PLP-inactivated LAD can be reactivated by an amino acid, taurine. These results indicate the reversible formation of Schiff base between PLP and LAD. They also provide clear evidence for the involvement of LAD (E3) in the previously reported inactivation of PDHC by PLP.

Modulation of the response of bovine adrenocortical adenylate cyclase to corticotropin

An assessment was made of some of the basic parameters responsible for the modulation of adenylate cyclase activity in a bovine adrenocortical plasma-membrane preparation. When determined at 0.1 mM-ATP, basal adenylate cyclase activity increased with increasing MgCl2 concentrations, whereas in the presence of corticotropin activity was essentially maximal at 10mM-MgCl2; high concentrations (25mM) of MgCl2 inhibited adenylate cyclase activity determined in the presence of both corticotropin and GTP. At all MgCl2 concentrations, corticotropin and GTP activated the enzyme in a synergistic fashion. The magnitude of the stimulation of basal activity produced by corticotropin was a function of Mg2+ concentration, whereas that produced by GTP appeared largely independent of Mg2+ concentration. Adenylate cyclase activity in the bovine adrenal membrane was half-maximally stimulated by corticotropin concentrations in the range 0.3--1.0 nM. The concentration of corticotropin evoking half-maximum response was not significantly affected by raising the free Mg2+ concentration from 0.4 to 4.9 mM, nor by the presence of GTP. In the presence of GTP, high concentrations (over 1 micrometer) of corticotropin inhibited adenylate cyclase activity, although no inhibition was apparent in the absence of guanine nucleotide.

�ber den enzymatischen Abbau von Tripolyphosphat und Diphosphat in zerkleinertem Fleisch

The diphosphatase of comminuted muscle tissue is activated by high MgCl2 concentrations. CaCl2, EDTA and low concentrations of MgCl2 lower the activity. The addition of diphosphate inhibits even after its complete enzymatic hydrolysis the breakdown of additionally added diphosphate; addition of MgCl2 increases the diphosphatase activity again.

Re-activation of the peptidyltransferase centre of rabbit reticulocyte ribosomes after inactivation by exposure to low concentrations of magnesium ion.

1. The larger subrivosomal particles of rabbit reticulocytes retained full activity in the puromycin reaction and in poly(U)-directed polyphenylalanine synthesis after 4h at 0 degrees C when buffered 0.5M-NH4Cl/10-30mM-MgCl2 was the solvent. 2. Activity in the puromycin reaction was diminished to approx 10% after 15-30 min at 0 degrees C when the concentration of MgCl2 was lowered to 2mM. 3. Activity was not restored when the concentration of MgCl2 was raised from 2mM to 10-30 mM at 0 degrees C. However, activity was recovered as measured by both assay systems when the ribosome fraction was heated to 37 degrees C at the higher concentrations of MgCl2. 4. Recovery of activity was noted during the course of the polyphenylalanine synthesis in 50 mM-KCl/5mM-MgCl2/25mM-Tris/HCl, pH 7.6, at 37 degrees C. Re-activation was slow at 20 degrees C and below. 5. No more than about 5% of the protein moiety of the subparticle was lost in 0.5M-NH4Cl on decreasing MgCl2 concentration from 10mM to 2mM. No proteins were detected in the supernatant fractions by gel electrophoresis after ribosomes were separated by differential centrifugation. The supernatant fraction was not essential for the recovery of activity. However, at higher (e.g. 1M) concentrations of NH4Cl, proteins were split from the subparticle. 6. The loss and regain of activity found on lowering and restoring the concentration of MgCl2 at 0.5M-NH4Cl appears to arise from a conformational change that does not seem to be associated with a loss and regain of particular proteins. 7. A 2% decrease in E260 was noticed when the concentration of Mg2+ was restored, and the change in the spectrum indicated a net increase of approx. 100A-U base-pairs per subribosomal particle. 8. When the concentration of Mg2+ was restored, S20,W of the subparticle remained at 52+/- 1S until the sample was incubated at 37 degrees C when S20,W increased to 56 +/- 1S compared with the value of 58 +/- 1S for the subparticle as originally isolated.

Characterization of calcium binding to adipocyte plasma membranes.

Calcium binding to adipocyte plasma membranes has been assessed by equilibrium dialysis and by membrane filtration techniques. Calcium binding was specific and saturable, displaying two distinct classes of binding sites. The affinity constants and maximum binding capacities in the presence of 0.1 M KCl were 4.5 X 10(4) M-1 and 1.8 nmol/mg of protein and 2.0 X 10(3) M-1 and 13.7 nmol/mg for the high and low affinity sites, respectively. Bound calcium was totally dissociated in the presence of excess calcium within 11.0 min in two distinct phases corresponding to the two classes of sites. Association and dissociation rate constants for the high affinity sites were 7.7 X 10(2) M-1S-1 and 9.2 X 10(-3S-1 respectively. Free energy changes at 24 degrees were +6.4 kcal mol-1 for the high affinity sites and +4.5 kcal mol-1 for the low affinity sites. The high affinity sites demonstrated a pH optimum of 7.0 whereas the binding to the low affinity sites progressively increased between pH 6.0 and 9.0. Low concentrations of MgCl2 (less than 300 muM) enhanced calcium binding slightly, whereas high concentrations of KCl and MgCl2 were noncompetitive inhibitors of calcium binding. Procaine and ruthenium red had no effect on calcium binding and lanthanum was a poor inhibitor of calcium binding. This represents the first report of calcium binding to adipocyte plasma membranes and the first kinetic analysis of calcium binding to biological membranes. The specificity of this calcium-binding system in adipocyte plasma membranes suggests its importance in cellular bioregulation.

The pre-steady state of Na+-K+-dependent ATPase after addition of Na+ ions. Transition of the phosphorylated intermediate from an ADP-sensitive to an ADP-insensitive form.

Na+-K+-Dependent ATPase [EC 3.6.1.3] was preincubated with ATP in the presence of a high concentration of MgCl2, and the phosphorylated intermediate, EP, was formed by adding a high concentration of NaCl. The following results showed that EP was converted from an ADP-sensitive to an ADP-insensitive form by a single turnover of the ATPase reaction. 1. After initiating the reaction by adding NaCl, almost all the EP was at first sensitive to added ADP, but its sensitivity to ADP decreased with increase in the time interval between the additions of NaCl and of ADP. 2. Both in the presence and absence of KCl, the time course of the replacement of ADP-sensitive EP by ADP-insensitive EP coincided with the time course of the decomposition of EP after addition of EDTA.

Ribulose diphosphate carboxylase/oxygenase. III. Isolation and properties

Similarities in properties of ribulose diphosphate carboxylase and oxygenase activities further substantiate the hypothesis that the same protein catalyzes both reactions. The Km (ribulose diphosphate) is 0.33 mM for the ribulose diphosphate oxygenase, when assayed in air with an oxygen electrode. Maximum activity is obtained with 10 to 35 mM MgCl2. Higher MgCl2 concentrations are inhibitory, but they shift the pH optimum from 9.3 or 9.4 to 8.7 or 9.0. MnCl2 is an effective cofactor of the oxygenase and some activity is obtained with CoCl2. Both the ribulose diphosphate carboxylase and oxygenase activity of the purified protein from spinach leaves are slowly inactivated by storage at 0 degrees and reactivated in 10 min at 50 degrees, provided both 25 mM MgCl2 and 1 mM dithiothreitol are present. The sulfhydryl groups of the enzyme which react rapidly with 5,5'-dithiobis(2-nitrobenzoic acid) are approximately 4 at pH 7.8 and 11 at pH 9.4. At both pH values ribulose diphosphate prevents two of these sulfhydryl groups from reacting with this reagent. About 50% inhibition of the oxygenase activity at pH 9.0 occurs with 50 mM bicarbonate in the presence of 3 mM ribulose diphosphate, and from variations in these parameters the inhibition is attributed to the CO2 species. The purified enzyme of acrylamide gels prevented the reduction of nitroblue tetrazolium in the presence of the superoxide radical, but the enzyme in solution did not react as a superoxide dismutase.

Alkali burns of the rabbit cornea. II. A histochemical study of glycosaminoglycans.

In alkali burned rabbit cornea the stainability of glycosaminoglycans in cold microtome setions was investigated. Staining by Alcian blue in 3% acetic acid, Alcian blue in various MgCl2 concentration and toluidine blue (pH 4.5) was employed. From the 1st to the 4th experimental day the intensity of reactions was decreased. This is most probably due to an increased hydration of the corneal stroma. On the 7th day hydration was markedly suppressed and reached nearly the normal level. In this time interval a decreased stainability of glycosaminoglycans was seen accompanied by a complete loss of staining in the marginal zone. On the 14th day the stainability in the traumatized area began to restore and in the marginal zone appeared. On the 32nd day the staining intensity of both areas was normalised, however when lower concentrations of MgCl2 were used; in the presence of higher concentrations of MgCl2 the decreased staining intensity persisted and points to a lower sulfatation of glycosaminoglycans. This was particularly remarkable in the area bordering the injured zone. This decrease runs parallel to the increased activities of acid glycosidases (especially of acid beta-galactosidase) which were reported previously.

Histochemical studies on the distribution of acidic glycosaminoglycans in human rib cartilage during the aging process

In human cadevers of different age five zones of basic substances can be distinguished around the cartilage cell by using hyaluronidase digestion and Alcian blue stain combined with various MgCl 2-concentrations. This treatment produces different reactions in the various zones. The zones are numbered according to their distance from the cell; thus zone 1 (Z1 = pericellular zone) is the nearest to the cell. Z 1 and Z 2 (inner territorial zone) contain hyaluronidase-digestible substance but Z 1 strains at higher electrolyte concentrations than does Z 2. The third zone (Z 3 = outer territorial zone) which first appears in childhood always contains hyaluronidase-resistant material and, besides, hyaluronidase-digestible material in adolescence. Since the distance between the cells increases with the proceeding process of aging, Z 4 (periterritorial zone) and Z 5 (interterritorial zone) appear in the cartilage centre. In adolescence only Z 5 can be found; it is slightly hyaluronidase-sensitive and stains even at high MgCl 2-concentrations. In adult and old cartilage a weakly basophilic zone 4 appears. The comparison of fixed and unfixed tissues renders the distinction between the zones feasible as the hyalurinodase resistance is increased in fixed tissue and, on the other hand, the structures appear less outlined in unfixed tissue. As far as the distribution of acidic glycosaminoglycans (GAG) is concerned the territories and interterritories are not clearly defined units, for part of the zones mentioned above can be arranged circumcellularly or, in addition, interstitially depending on the various cartilage regions and on the different periods of life. We assume that the pericellular as well as the inner and outer territorial zones belong to the cell itself and that their step by step appearance is due to a process of development whereas the periterritorial and interterritorial zones result from cell degeneration caused by aging, and expand, mainly, wihtout cellular control.

Purification and regulatory properties of phosphoribulokinase from Hydrogenomonas eutropha H 16.

1. Phosphoribulokinase was purified 286-fold from extracts of autotrophically grown cells. 2. The enzyme had a molecular weight of 237000 and showed a pH optimum of 9.0 in both crude extracts and purified preparation. MgCl(2) was required for activity; full activation was obtained at 5mm-MgCl(2) and the K(m) was approx. 0.5mm. 3. The ATP-saturation curve was sigmoidal and the degree of positive co-operativity increased at higher MgCl(2) concentrations. The ATP-binding sites appeared to be non-interacting at low ribulose 5-phosphate concentrations. 4. Lineweaver-Burk plots for ribulose 5-phosphate showed abrupt transitions between apparently linear sections. The apparent K(m) and V(max.) values increased with increasing concentrations of ribulose phosphate. The transitions may be explained by a sequence of negative and positive co-operativity in the catalytic rate constants. 5. Phosphoribulokinase activity was inhibited by AMP and phosphoenolpyruvate and was activated by NADH. The presence of AMP or phosphoenolpyruvate increased s(0.5) (substrate concentration required for half-maximal velocity) for both ribulose 5-phosphate and ATP but V(max.) was not changed. The sigmoidicity of the ATP-saturation curve increased in the presence of AMP but was not affected by phosphoenolpyruvate. The transitions in the ribulose 5-phosphate-saturation curves were more abrupt in the presence of either inhibitor. NADH lowered the s(0.5) for both ribulose 5-phosphate and ATP. The activator did not affect the degree of positive co-operativity between ATP-binding sites, but the ribulose 5-phosphate-binding sites appeared to be non-interacting in its presence. 6. A sequence of positive and negative co-operativity in the interactions of AMP-binding sites was suggested by the Hill plots. In the presence of NADH (and phosphoenolpyruvate) the sensitivity to inhibition by AMP was less below a certain AMP concentration and increased above that concentration. 7. Examination of the interactions between ligands indicated that phosphoribulokinase can be regulated effectively by changes in effector concentrations similar to those reported to occur in vivo.

Salt-induced alterations of the fluorescence yield and of emission spectra in <italic>Chlorella pyrenoidosa</italic>

(1) The addition of salts to the suspending medium induces a decrease in the yield of chlorophyll a fluorescence in normal and DCMU-poisoned intact algal cells of Chlorella pyrcnoidosa. Potassium and sodium acetate cause a pronounced lowering of the fluorescence at relatively low concentrations (0.01-0.1 M). MgClj and KC1 cause a similar lowering of fluorescence but at much higher concentrations (0.1-0.4 u). In contrast to sodium acetate, ammonium acetate does not cause any significant change in the fluorescence transient. (2) Unlike the case in isolated chloroplasts, MgClj decreases the ratio of short wavelength (mainly system 2) to long wavelength (mainly system 1) emisiion bands in both DCMU poisoned and normal cells. Since these salt-induced changes do not appear to be related to the redox reactions of photosynthesis, the salts might have caused a decrease in the mutual distance between the two photosystems by changing the microstructure of the chloroplasts in vivo thereby facilitating the spillover of excitation energy from strongly fluorescent system 2 to weakly fluorescent system 1. (3) The light induced turbidity changes in intact algal cells, as measured by the increase in optical density at 540 nm, is reduced in the presence of these salts. However, MgClj produces the greatest reduction while Na acetate the least, even though both of these salts (at the concentrations used) cause large suppression of the fluorescence transient. Moreover, the light induced turbidity changes were, essentially irreversible. (4) As high concentrations of salts increase the osmotic potential of the bathing medium, it seems that the osmotic changes as well as the ionic changes in the intact algal cells are responsible for the fluorescence quenching and changes in the mode of excitation transfer observed in this study. In the case of low concentrations of salts (e.g., 0.1 u Na or K acetate) the effects are predominantly ionic, and in the case of very high concentrations of MgCl2 (0.4 M), die osmotic effects play a much larger role.

MECHANISM OF ACTION OF WASHOUT SOLUTIONS FOR KIDNEY PRESERVATION

SUMMARY We have investigated the effect of inhibition of cellular swelling on subsequent renal function in the presence of marked loss of tissue potassium during 24 hr of simple cold storage of dog kidneys. This was done by initially perfusing kidneys with a solution which contains 130 HIM sucrose and 5 m potassium. Postoperative renal function was equal to that achieved with the “intracellular” solution, C3, which contains 140 DIM glucose and 115 m potassium. Analysis of tissue electrolytes and water showed that the cortex of kidneys stored in the sucrose solution lost the same amount of potassium as the cortex of kidneys stored in lactated Ringer's solution. But while the cortex of kidneys stored in lactated Ringer's solution was swollen by 30%, sucrose cortex, like C3 cortex, lost weight. We also compared the osmotic effect of glucose and sucrose on the water content of anoxic slices of renal cortex at 4 C. Sucrose was the more effective osmotic agent. Finally, we studied the effect of high concentrations of MgSO4 and MgCl2 on changes in cortical potassium and water. Magnesium did not prevent the loss of potassium. But magnesium as well as sulfate did inhibit cellular swelling. We conclude that, during storage, cellular swelling, and not potassium loss or sodium gain, is the primary cause of poor renal function after transplantation. Because “intracellular” C3 solution contains in high concentration several nonpermeable solutes such as gluocse, sulfate, and magnesium, its main beneficial effect during renal storage is not maintenance of cellular potassium, but is, instead, inhibition of cellular swelling.

The correlation of lipid release and photochemical activities in isolated spinach chloroplasts.

Purified isolated spinach chloroplasts were suspended in media of different pH and the extracts obtained after centrifugation were analyzed for their lipid composition. The quantity of lipids present in the supernatant increased considerably by lowering the proton concentration. Under alkaline conditions more than 30% of the phospho- and sulfolipids were released from the thylakoid membranes. A stabilization was achieved when higher concentrations of MgCl2 were present. Photochemical activities showed an uncoupling of photophosphorylation at pH 8.5 and 8.9, and a stabilization at pH 5.5. The correlation between phosphorylation and the release of lipids was further demonstrated in the presence of MgCl2 when the ATP-formation was protected under alkaline conditions. From the comparison of the lipid composition in the extracts obtained from broken chloroplasts and from fragments after sonication, the conclusion can be drawn that part of the phospho- and sulfolipids and monogalactolipids are located at the surface of the membrane. The majority of lipids released are bound to particles as demonstrated by the sedimentation in the ultracentrifuge.

An induced mitochondrial DNA polymerase from Tetrahymena.

The activity of mitochondrial DNA polymerase from Tetrahymena pyriformis can be induced up to 50‐fold by several kinds of DNA damage (irradiation, thymine starvation etc.). The induced mitochondrial enzyme has been purified more than 5900‐fold based on whole treated cells. The purification procedure involved the following steps: (a) isolation of mitochondria from cells with induced enzyme; (b) extraction of the polymerase; (c) chromatography on two columns of phosphocellulose at different pH. Homogeneity studies of the purified polymerase indicate that the enzyme is more than 50% pure.The purified polymerase is able to use both native and heat‐denatured DNA as primer, although the optimal ion concentrations differ quite considerably with the primer. At low Mg2+ concentrations (5–12 mM) optimal conditions are observed for the reaction with heat‐denatured DNA, while the reaction with native DNA primer demonstrates optimum around 45 mM MgCl2. In the reaction with native DNA primer the high MgCl2 concentrations can be partially substituted by high KCl concentrations of same ionic strength. The reactions with the bihelical polymers poly[d(A‐T)] · poly[d(A‐T)] and poly[d(I‐C)] · poly[d(I‐C)] demonstrate optima similar to those found for the reaction with heat‐denatured DNA.The purified DNA polymerase has a temperature optimum around 28°C and heat‐inactivation experiments demonstrate that the enzyme is very labile at the high Mg2+ concentrations required for the reaction with native DNA.

Length distribution of F-actin transformed from Mg-polymer.

Abstract The length distribution of F-actin produced from Mg-polymer formed in the presence of β-actinin was investigated in detail by electron microscopy. When Mg-polymer was formed at a low MgCl2 concentration (approx. 1 mM), where a fairly large amount of G-actin coexisted with Mg-polymer, and was transformed into F-actin by the addition of KCl at a fairly high temperature (45 °C), the length distribution of F-actin was of a Poisson type. The number average length was approximately 0.6 μm. On the other hand, the formation of Mg-polymer at a high MgCl2 concentration (approx. 2mM), where only a small amount of G-actin remained, resulted in a simple exponential distribution of particle length of the transformed F-actin and its average lengths became shorter. Moreover, when the amount of G-actin coexisting with Mg-polymer was increased by the addition of G-actin to the Mg-polymer solution and transformation then induced, the average length of the resultant F-actin was increased and the length distribution became more homogeneous. These results are explained by the theories of polymerization in systems with a fixed number of polymers. The amount of G-actin coexisting with Mg-polymer also increased with increase of total actin concentration. However, in this case, the average lengths were not significantly changed after its transformation into F-actin. When the transformed F-actin solution was left standing for a long time, the length distribution gradually changed from the Poisson type to the simple exponential type. This was probably due to the fact that a re-arrangement of the preformed F-actin took place. The relaxation time for such redistribution was about 25 h at 35 °C. Both β-actinin and ATP were indispensable for the transformation of Mg-polymer into the F-actin particles having a homogeneous length distribution.