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PubMed2002

[Study on the effects of cooking oil fume condensate on the DNA integrity].

The aim of this study was to study the DNA damage mechanisms of cooking oil fumes (COF) in vitro. The colorimetric MTT reduction assay was adopted to measure the effects of the cytotoxicity of COF condensate on type II pneumocytes from the lungs in the rats. The condensate of COF was of the dose-responsive effect on cell-inhibit rate to some extent (r = 0.943, P < 0.01). There is distinctive cytotoxicity on type II pneumocytes when concentration is higher than 20 micrograms/ml. The genotoxicities of COF condensate to type II pnemocytes were studied by modified alkaline single-cell gel using a electrophoresis(SCGE) assay(comet assay), the maximum concentration of condensate is below the concentration of cytotoxicity. The results showed that the condensate of COF was of the dose-responsive effect on the type II pneumocytes DNA damage to some extent(r = 0.918, P < 0.05) at the dosage of 0-5 micrograms/ml. The DNA damage reach to the maximum at the dosage of 10 micrograms/ml. The damaged DNA could be restored after been cultured for 2 hours. Calf thymus DNA cross-link after the administration of COF condensate were measured with ethidium bromide assay. It was found that condensate of COF was of the dose-responsive effect on the calf thymus DNA cross-links to some extent(r = 0.963, P < 0.01). The above results suggested that cooking oil fume condensate could induce DNA damage at much lower dosage and result in the increase of DNA cross-links in a certain concentration.

Air Pollution, Indoor↗

PubMed1987

Contribution of polycyclic aromatic hydrocarbons and polar polycyclic aromatic compounds to the carcinogenic impact of flue gas condensate from coal-fired residential furnaces evaluated by implantation into the rat lung.

For identification of the substances chiefly responsible for the carcinogenic action of the emission condensate from coal-fired residential furnaces, the implantation method was used as a carcinogen-specific bioassay for comparison of the carcinogenic effect of various fractions with that of a total sample of flue gas condensate tested in 2 or 3 different doses. After implantation into the lungs of Osborne-Mendel rats, the condensate from coal-fired residential furnaces, a fraction containing polycyclic aromatic hydrocarbons (PAHs) and thiaarenes [sulfur-containing polycyclic aromatic compounds (S-PACs)] with 4-7 rings, as well as fraction containing more polar polycyclic aromatic compounds (PACs) and PAHs with higher molecular weight, induced lung carcinomas and sarcomas. According to probit analysis, the fraction containing PAHs plus S-PACs with 4-7 rings accounted for about 68.2% of the total carcinogenicity of flue gas condensate, whereas the fraction containing more polar PACs and higher PAHs accounted for about 54.6%. All other fractions, such as nonaromatic compounds and PACs with 2 and 3 rings, constituting about 70% of the weight of the total condensate, seemed not to be carcinogenic. Only 1.4% of the total carcinogenicity of the flue gas condensate was found to be attributable to the amount of benzo[a]pyrene (CAS: 50-32-8) present in the condensate (1.14 mg/g condensate). The contribution of more than 100% of both active fractions to the total carcinogenicity (68.2 and 54.6%) may suggest an interrelation of the fractions.

Air Pollutants↗

PubMed1985

Cell proliferation in condensing scleral ectomesenchyme associated with the conjunctival papillae in the chick embryo.

The role of cell proliferation in the formation of scleral ectomesenchymal condensations underlying the conjunctival papillae was examined with in vivo tritiated thymidine labelling in chick embryos ranging in age from 8 days 0 h to 10 days 12 h. Percentages of labelled nuclei were determined in both ectomesenchyme and the deeper fibrous sclera for short-term and continuous tritiated thymidine incubations. During formation of the ectomesenchymal condensations the percentages of labelled nuclei were consistently higher within the condensations than in corresponding non-condensing ectomesenchyme between papillae. The consistent differences of labelling percentages observed within the condensing versus non-condensing ectomesenchyme were not found in the fibrous sclera at any stage. All areas of both the ectomesenchyme and fibrous sclera showed decreases in the percentages of labelled nuclei from 8 days 0 h to 10 days 12 h, although the decline in the ectomesenchymal condensations beneath papillae occurred more slowly than in areas between papillae. The data suggest that the conjunctival papillae directly influence the proliferation in the subjacent condensing ectomesenchyme but have no effect on the ectomesenchyme between papillae or any region of the deeper fibrous sclera. The observations of this investigation are discussed in relation to other studies of the development of the pre-ossicular mesenchyme.

Animals↗

PubMed1984

Contribution of polycyclic aromatic hydrocarbons to the carcinogenic impact of gasoline engine exhaust condensate evaluated by implantation into the lungs of rats.

An attempt was made to identify the substances chiefly responsible for the carcinogenicity of gasoline engine exhaust condensate. A carcinogen-specific bioassay was performed by a comparison of the carcinogenic effect of various fractions with that of a total sample of automobile exhaust condensate, tested in two or three different doses. The results were examined by Probit analysis. After implantation into the lungs of OM rats, the condensate emitted from a gasoline-driven automobile and the fraction of polycyclic aromatic compounds consisting of more than 3 rings induced lung carcinomas and sarcomas. The tumor incidence demonstrated a clear-cut dose-response relationship. The fraction of polycyclic aromatic hydrocarbons (PAH) consisting of more than 3 rings accounted for about 81% of the total carcinogenicity of automobile exhaust condensate. This fraction represented only 2.8% by weight of the condensate. The content of benzo[a]pyrene (CAS: 50-32-8; 0.483 mg/g condensate) accounted for 2.4% of the total carcinogenicity of automobile exhaust condensate. Regarding the minor effect of the PAH-free fraction (approximately equal to 87% by wt), no evidence of cocarcinogenic activity was observed, since the total condensate as well as the PAH fraction consisting of more than 3 rings applied proportionally caused about the same tumor incidence.

Animals↗

PubMed1981

Distribution of endogenous beta-galactoside-specific lectin, fibronectin and type I and III collagens during dermal condensation in chick embryos.

The distribution of endogenous beta-galactoside-specific lectin, fibronectin, type I and III collagens was studied by the indirect immunofluorescence method during the formation of dermal condensation in the feathered region (dorsal skin) of a chick embryo. Endogenous beta-galactoside specific lectin was concentrated in the condensed dermal region, coinciding with the formation of condensation of dermal cells. It was also detected in epidermal placodes. Fibronectin was weakly stained in dermis prior to the formation of dermal condensation but not in epidermis. Condensation of dermal cells resulted in the formation of thicker fibrils of fibronectin in the condensed region. Distribution of type I collagen was found to be very different from that of endogenous beta-galactoside-specific lectin and fibronectin. Type I collagen in dermis decreased along with the formation of dermal condensation. Epidermis had no type I collagen. Type III collagen was not found in dorsal skin. Relationship found between these distribution patterns and dermal condensation in the embryonic chick skin is discussed.

Animals↗

PubMed2004

Ion condensation and signal transduction.

Many abiotic and other signals are transduced in eukaryotic cells by changes in the level of free calcium via pumps, channels and stores. We suggest here that ion condensation should also be taken into account. Calcium, like other counterions, is condensed onto linear polymers at a critical value of the charge density. Such condensation resembles a phase transition and has a topological basis in that it is promoted by linear as opposed to spherical assemblies of charges. Condensed counterions are delocalised and can diffuse in the so-called near region along the polymers. It is generally admitted that cytoskeletal filaments, proteins colocalised with these filaments, protein filaments distinct from cytoskeletal filaments, and filamentous assemblies of other macromolecules, constitute an intracellular macromolecular network. Here we draw attention to the fact that this network has physicochemical characteristics that enable counterion condensation. We then propose a model in which the feedback relationships between the condensation/decondensation of calcium and the activation of calcium-dependent kinases and phosphatases control the charge density of the filaments of the intracellular macromolecular network. We show how condensation might help mediate free levels of calcium both locally and globally. In this model, calcium condensation/decondensation on the macromolecular network creates coherent patterns of protein phosphorylation that integrate signals. This leads us to hypothesize that the process of ion condensation operates in signal transduction, that it can have an integrative role and that the macromolecular network serves as an integrative receptor.

Animals↗

PubMed1995

Chromosome condensation induced by fostriecin does not require p34cdc2 kinase activity and histone H1 hyperphosphorylation, but is associated with enhanced histone H2A and H3 phosphorylation.

Chromosome condensation at mitosis correlates with the activation of p34cdc2 kinase, the hyperphosphorylation of histone H1 and the phosphorylation of histone H3. Chromosome condensation can also be induced by treating interphase cells with the protein phosphatase 1 and 2A inhibitors okadaic acid and fostriecin. Mouse mammary tumour FT210 cells grow normally at 32 degrees C, but at 39 degrees C they lose p34cdc2 kinase activity and arrest in G2 because of a temperature-sensitive lesion in the cdc2 gene. The treatment of these G2-arrested FT210 cells with fostriecin or okadaic acid resulted in full chromosome condensation in the absence of p34cdc2 kinase activity or histone H1 hyperphosphorylation. However, phosphorylation of histones H2A and H3 was strongly stimulated, partly through inhibition of histone H2A and H3 phosphatases, and cyclins A and B were degraded. The cells were unable to complete mitosis and divide. In the presence of the protein kinase inhibitor starosporine, the addition of fostriecin did not induce histone phosphorylation and chromosome condensation. The results show that chromosome condensation can take place without either the histone H1 hyperphosphorylation or the p34cdc2 kinase activity normally associated with mitosis, although it requires a staurosporine-sensitive protein kinase activity. The results further suggest that protein phosphatases 1 and 2A may be important in regulating chromosome condensation by restricting the level of histone phosphorylation during interphase, thereby preventing premature chromosome condensation.

Alkaloids↗

PubMed1998

Major changes in chromatin condensation suggest the presence of an apoptotic pathway in plant cells.

A large decrease in fluorescence intensity of propidium iodide (PI)-stained nuclei is observed during senescence of plant cells. The phenomenon reflects a decrease in accessibility of DNA to this fluorochrome and is a consequence of chromatin condensation. This decrease is substantially greater than usually found in animal nuclei whose chromatin undergoes condensation, e.g., during differentiation or quiescence. Chromatin condensation was confirmed by analyses of (i) DNA accessibility to DNase I, (ii) histone disassociation induced by HCl, (iii) saturation of binding sites by the PI fluorochrome (iv), and (v) visual inspection by fluorescence and confocal microscopy. The extent of changes revealed by these assays was used to map progressive changes in chromatin condensation which allowed us to identify different stages in an apoptosis-like pathway in plants. The initial step of chromatin condensation which occurred prior to endonucleolytic DNA degradation was detected by fluorescence and confocal microscopy and confirmed by a variety of assays employing flow cytometry. The initial chromatin condensation appears to be a reversible step in the early stage of apoptosis. The loss of reversibility of chromatin condensation observed subsequently may be a critical point in the cascade of apoptotic events, leading to further irreversible changes during apoptosis in plants.

Acids↗

PubMed1999

Critical Condensate Saturation in Porous Media.

The understanding of gas and condensate flow in porous media is critical to the optimum exploitation of gas-condensate reservoirs. Critical condensate saturation and relative permeabilities are the key parameters for the evaluation of possible recovery strategies. This work is aimed at developing a mechanistic network model for the critical condensate saturation in which phase trapping and connectivity in the pore corners are critically examined. Porous media are modeled by networks of pore bodies interconnected by pore throats. Bodies and throats are characterized by their connectivity, shapes, and radii distributions. Pore-level laws are identified from micromodel experiments with near-critical fluids. A nonzero critical condensate saturation can be obtained in the absence of contact angle hysteresis due to the converging-diverging nature of the throats. The critical saturation at which the condensate flows is found to be a function of pore geometry, water saturation, and interfacial tension (or the Bond number). The modified sphere-pack model underpredicts the critical condensate saturation of typical sandstones. The cubic model adequately predicts the critical saturation and its experimentally observed trends. Copyright 1999 Academic Press.

Journal Article↗

PubMed1988

Acetaldehyde and its condensation products as markers in alcoholism.

Several studies show that recently abstaining alcoholics generate higher circulating levels of acetaldehyde than nonalcoholics following ethanol administration. It is conceivable that levels of stable adducts (tetrahydroisoquinolines and tetrahydro-beta-carbolines) derived from acetaldehyde condensations with biogenic amines also might be increased in alcoholics consuming ethanol, thus serving in body fluids as chemical markers that are more persistent than acetaldehyde itself. Limited human and rat studies indicate that urinary excretion of an oxidized tryptamine condensation product (harmane) and of an acetaldehyde/serotonin condensation product is elevated by chronic ethanol. Salsolinol, the derivative of acetaldehyde and dopamine, does not appear to be a meaningful urinary marker, but levels of the related pyruvic acid/dopamine product may be increased by ethanol. Blood assays of condensation products have been limited in number and equivocal. Condensation product measurements are complicated not only by artifacts (formation during analyses), but by other inherent problems. Products of interest often are constituents of diets and alcoholic beverages. For this and perhaps endogenous metabolic reasons, traces of condensation products are normally excreted by nondrinking individuals. Furthermore, the assays require high sensitivity and specificity and are not easily adapted to routine use. Thus, although several condensation products have initial appeal as clinical or pathological indicators in chronic alcoholism, thorough and statistically sound studies are needed before conclusions can be reached concerning any particular biogenic amine-derived product.

Acetaldehyde↗

PubMed1984

Description of a chromosome replication unit in individual prematurely condensed human S-phase chromosomes.

Mammalian chromosome replication was studied by the aid of premature chromosome condensation (PCC). After induction of PCC the sites of DNA replication appear as "gaps" between condensed chromosomal regions. These condensed particles are unineme before and bineme after DNA replication. The two phases are due mainly to the unineme or bineme nature of the particles. During early S-phase almost all particles are unimene, during late S-phase they are bineme and there is only one transitory stage between these two main stages. Premature chromosome condensation was studied in detail on a specific human chromosome 22 which is marked by its heterochromatin constitution. This led to easy identification of these elements in S-phase PCC (S-PCC) preparations. For each stage of the S-phase there was a reproducible pattern of condensed chromosomal particles making up the whole chromosome. The number of these particles was rather limited and a complementary pattern was found in early versus late S-phase. The pattern of early S-PCC corresponded to the banding pattern of G-banded prometaphase chromosomes; the pattern of late S-PCC, to R-banded prometaphase chromosomes. Thus, "gaps" and condensed particles as observed after PCC induction are obviously homologous to chromosome replication units. Replication of constitutive heterochromatin occurred during the very late S-phase. During this stage PCC induction led to condensation of the heterochromatin into several small, highly fluorescent particles.

Cell Line↗

PubMed1999

Meiotic events at the centromeric heterochromatin: histone H3 phosphorylation, topoisomerase II alpha localization and chromosome condensation.

Mechanisms of chromosome condensation and segregation during the first meiotic division are not well understood. Resolution of recombination events to form chiasmata is important, for it is chiasmata that hold homologous chromosomes together for their oppositional orientation on the meiotic metaphase spindle, thus ensuring their accurate segregation during anaphase I. Events at the centromere are also important in bringing about proper attachment to the spindle apparatus. This study was designed to correlate the presence and activity of two proteins at the centromeric heterochromatin, topoisomerase II alpha (TOP2A) and histone H3, with the processes of chromosome condensation and individualization of chiasmate bivalents in murine spermatocytes. We tested the hypothesis that phosphorylation of histone H3 is a key event instigating localization of TOP2A to the centromeric heterochromatin and condensation of chromosomes as spermatocytes exit prophase and progress to metaphase. Activity of topoisomerase II is required for condensation of chromatin at the end of meiotic prophase. Histone H3 becomes phosphorylated at the end of prophase, beginning with its phosphorylation at the centromeric heterochromatin in the diplotene stage. However, it cannot be involved in localization of TOP2A, since TOP2A is localized to the centromeric heterochromatin throughout most of meiotic prophase. This observation suggests a meiotic function for TOP2A in addition to its role in chromatin condensation. The use of kinase inhibitors demonstrates that phosphorylation of histone H3 can be uncoupled from meiotic chromosome condensation; therefore other proteins, such as those constituting metaphase-promoting factor, must be involved. These results define the timing of important meiotic events at the centromeric heterochromatin and provide insight into mechanisms of chromosome condensation for meiotic metaphase.

Animals↗

PubMed2001

Murine recombinant prion protein induces ordered aggregation of linear nucleic acids to condensed globular structures.

Interaction between nucleic acid and recombinant murine prion protein, MoPrPC resulted in a time-dependent change in the nucleic acid morphology revealed by electron microscopy. After the addition of the protein to DNA, association of small number of nucleic acid molecules (nucleo-protein complex) was followed by aggregation of large number of them still retaining their initial linear morphology. With increase in the incubation time, ordered aggregation resulted in small condensed spherical globules. Subsequently, the formation of large condensed particles took place either by fusion of the already formed small globules or by accumulation of more nucleic acid molecules on them. The condensed nucleic acid structures observed here were different from other known morphologically altered nucleic acid structures induced by different cellular proteins. The condensed nucleic acid structures dissociated spontaneously. The formation of the prion protein-induced condensed nucleic acid structures resembled the human immunodeficiency virus 1 nucleocapsid protein NCp7-induced condensed ordered aggregates of nucleic acids. In the latter system, both the processes of condensation and dissociation of the nucleoprotein complex are believed to be responsible for the functional properties of the HIV-1 virus. Demonstration of functional activity of the prion protein-nucleic acid complex would be relevant for a role of nucleic acid in prion diseases.

Animals↗

PubMed2006

Histone deacetylase activity is necessary for chromosome condensation during meiotic maturation in Xenopus laevis.

Chromosome condensation is thought to be an essential step for the faithful transmission of genetic information during cellular division or gamete formation. The folding of DNA into metaphase chromosomes and its partition during the cell cycle remains a fundamental cellular process that, at the molecular level, is poorly understood. Particularly, the role of histone deacetylase (HDAC) activities in establishing and maintaining meiotic metaphase chromosome condensation has been little documented. In order to better understand how metaphase chromosome condensation is achieved during meiosis, we explored, in vivo, the consequences of HDAC activities inhibition in a Xenopus oocyte model. Our results show that deacetylase activity plays a crucial role in chromosome condensation. This activity is necessary for correct chromosome condensation since the earlier stages of meiosis, but dispensable for meiosis progression, meiosis exit and mitosis entry. We show that HDAC activity correlates with chromosome condensation, being higher when chromosomes are fully condensed and lower during interphase, when chromosomes are decondensed. In addition, we show that, unlike histone H4, Xenopus maternal histone H3 is stored in the oocyte as a hypoacetylated form and is rapidly acetylated when the oocyte exits meiosis.

Animals↗

PubMed1991

Propionyl-CoA condensing enzyme from Ascaris muscle mitochondria. II. Coenzyme A modulation.

The propionyl-CoA condensing enzyme which catalyzes the first step in the biosynthesis of 2-methylbutyrate and 2-methylvalerate by Ascaris muscle appears to exist in at least three forms in the mitochondria of this parasitic nematode. Two forms, A and B, were separated by ion exchange chromatography on CM-Sephadex. Chromatography on phosphocellulose resulted in the recovery of one minor peak (I) and two major peaks with activity (II and III). A and B as well as I, II, and III differed in their specific activities. Forms B and III were the most retained by their resins, and were the most active forms of the enzyme in each case. Inhibition studies with metabolites from Ascaris mitochondria indicate that CoASH, a product of the condensation reaction, and acetyl-CoA are effective inhibitors of the condensing and thiolytic activities of the Ascaris enzyme, respectively. Incubation of the active enzyme form B for 2 h with 0.1 mM CoASH at room temperature under nitrogen caused the loss of 92% of the propionyl-CoA condensing activity and 67% of the thiolase activity when assayed in standard mixtures. The propionyl-CoA condensing enzyme exhibited a hyperbolic dependence of the condensation velocity to changes in substrate concentration. However, in the presence of CoASH the Michaelis-Menten kinetics was transformed into a sigmoidal kinetics indicating a deviation from a simple product inhibition. Inactivation of the most active forms of the enzyme with CoASH was accompanied by (a) a change in the chemical reactivity of the protein toward p-chloromurcuribenzoate, (b) a change in the uv-visible spectrum of the protein, and (c) a change in the elution patterns from both CM-Sephadex and phosphocellulose column chromatography, where-upon one, two, or more protein peaks were obtained. The several protein peaks resolved by rechromatography of the [14C]CoASH-inactivated enzyme III on phosphocellulose had different CoASH contents. The elution positions were correlated with the less active forms (I and II) having increased [14C]CoASH activities. Similarly, the two peaks isolated upon rechromatography of the CoASH-partially inactivated enzyme B on CM-Sephadex had different isotope contents and the elution position of enzyme A corresponded to the less active form. The results described indicate that the CoASH modification of Ascaris propionyl-CoA condensing enzyme may be responsible for the existence of several forms of the enzyme and might represent a mode of control by chemically modulating the amount of the active forms of the enzyme.

Acetyl-CoA C-Acetyltransferase↗

PubMed1989

The mechanism of precartilage mesenchymal condensation: a major role for interaction of the cell surface with the amino-terminal heparin-binding domain of fibronectin.

Using low magnification Hoffman Modulation Contrast microscopy to rapidly identify precartilage mesenchymal condensations in chick limb bud cultures, we have determined the effect on condensation number of treatments disruptive of the interaction of cell surface components with endogenously produced fibronectin. A monoclonal antibody directed against the amino-terminal heparin-binding domain of fibronectin reduced the number of condensations by more than 50%, as did the oligopeptide gly-arg-gly, which is a repeated motif in that fibronectin domain. In contrast, monoclonal antibodies directed against the collagen- and integrin-binding domains of fibronectin, or oligopeptides containing the fibronectin integrin-recognition sequence arg-gly-asp-ser, had no significant effect on condensation number. Addition of Flavobacterium heparinase to cultures also reduced condensation number by more than 50%. Alcian blue staining of sulfated proteoglycan was greatly reduced in differentiated cultures that had been exposed to treatments that reduced condensation number. Taken together with the accompanying study, which directly demonstrates an adhesive interaction between the amino-terminal domain of extracellular fibronectin and heparin-like molecules on the surfaces of latex bead probes, the data presented here strongly indicate a major role for the corresponding cell-matrix interaction in mediating precartilage condensation in limb mesenchyme.

Amino Acid Sequence↗

PubMed1990

Teniposide, a topoisomerase II inhibitor, prevents chromosome condensation and separation but not decondensation in fertilized surf clam (Spisula solidissima) oocytes.

DNA topoisomerase II has been implicated in regulating chromosome interactions. We investigated the effects of the specific DNA topoisomerase II inhibitor, teniposide on nuclear events during oocyte maturation, fertilization, and early embryonic development of fertilized Spisula solidissima oocytes using DNA fluorescence. Teniposide treatment before fertilization not only inhibited chromosome separation during meiosis, but also blocked chromosome condensation during mitosis; however, sperm nuclear decondensation was unaffected. Chromosome separation was selectively blocked in oocytes treated with teniposide during either meiotic metaphase I or II indicating that topoisomerase II activity may be required during oocyte maturation. Teniposide treatment during meiosis also disrupted mitotic chromosome condensation. Chromosome separation during anaphase was unaffected in embryos treated with teniposide when the chromosomes were already condensed in metaphase of either first or second mitosis; however, chromosome condensation during the next mitosis was blocked. When interphase two- and four-cell embryos were exposed to topoisomerase II inhibitor, the subsequent mitosis proceeded normally in that the chromosomes condensed, separated, and decondensed; in contrast, chromosome condensation of the next mitosis was blocked. These observations suggest that in Spisula oocytes, topoisomerase II activity is required for chromosome separation during meiosis and condensation during mitosis, but is not involved in decondensation of the sperm nucleus, maternal chromosomes, and somatic chromatin.

Animals↗

PubMed1987

Influence of DNA length on spermine-induced condensation. Importance of the bending and stiffening of DNA.

Using DNA restriction fragments of 258 to 4362 base-pairs, we have investigated the influence of the DNA length on the condensation process induced by spermine, with the aid of electric dichroism measurements. The 258- and 436 bp fragments condensed into rod-like particles, while the fragments of 748 bp or more condensed into torus-shaped particles. Our results suggest that a DNA molecule longer than the circumference of the toroids observed previously (680 bp) is required to serve as a nucleus for the growth of the condensed particles. The toroids were more stable in the electric field than the rod-shaped particles, suggesting that rapid fluctuations of the bound spermine counterions can provide one of the main attractive forces yielding to the condensation process. Relaxation time data for the 436 bp fragment revealed that the structure of DNA was altered at a spermine concentration as low as one-tenth of that required for condensation: the DNA became bent in the presence of spermine. Moreover, the field strength dependence of the relaxation times, as well as the fitting of the decay curves at 12.5 kV/cm, showed an increase of the stiffness of the DNA double helix upon spermine addition. We estimated that, in the case of DNA condensation by spermine, a decrease in the measured persistence length may occur, irrespective of the DNA flexibility, owing to the bending of the DNA molecule.

Base Composition↗