SEARCH · PubMed Health

Results for “Condensates”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 127 records · Page 7Linked to original sources

PubMed2007

Connective tissue growth factor (CTGF) acts as a downstream mediator of TGF-beta1 to induce mesenchymal cell condensation.

Mesenchymal cell (MC) condensation or the aggregation of MCs precedes chondrocyte differentiation and is required for subsequent cartilage formation during endochondral ossification. In this study, we used micromass cultures of C3H10T1/2 cells as an in vitro model system for studying MC condensation and the events important for this process. Transforming growth factor beta1 (TGF-beta1) served as the initiator of MC condensation in our model system and we were interested in determining whether CTGF functions as a downstream mediator of TGF-beta1. CTGF is a matricellular protein that has been found to be expressed in MC condensations and in the perichondrium. Micromass cultures of C3H10T1/2 cells condensed under TGF-beta1 stimulation concomitant with dramatic up-regulation of CTGF mRNA and protein levels. CTGF silencing by either CTGF siRNA or CTGF antisense oligonucleotide approaches showed that TGF-beta1-induced condensation was CTGF dependent. Furthermore, silencing of CTGF expression resulted in significant reductions in cell proliferation and migration, events that are crucial during MC condensation. In addition, up-regulation of Fibronectin (FN) and suppression of Sox9 expression by TGF-beta1 was also found to be mediated by CTGF. Immunofluorescence of developing mouse vertebrae showed that CTGF, TGF-beta1 and FN were co-expressed in condensations of MCs, while Sox9 expression was low at this stage. During subsequent chondrogenesis, Sox9 expression was high in chondrocytes while CTGF expression was limited to the perichondrium. Thus, CTGF is an essential downstream mediator of TGF-beta1-induced MC condensation through its effects on cell proliferation and migration. CTGF is also involved in up-regulating FN and suppressing Sox9 expression during TGF-beta1 induced MC condensation.

Animals↗

PubMed1996

DNA digestion and chromatin condensation during nuclear death in Tetrahymena.

DNA fragmentation and nuclear condensation are key features in the regulated cell death of higher animal cells. Nuclear death also occurs as part of a developmentally programmed process during the sexual life cycle of the unicellular organism Tetrahymena. We examined the regulation of nuclear death and the relationship between DNA fragmentation and chromatin condensation in this model system. Nuclear death is accompanied by DNA digestion to low-molecular-weight oligonucleosomal-length fragments, in agreement with a previous study, indicating an endonuclease-like activity typical of apoptosis in higher organisms. Actinomycin D and cycloheximide block DNA digestion as well as nuclear condensation suggesting that nuclear death is under genetic regulation. DNA digestion is completely blocked by aurin, a general nuclease inhibitor. In addition, when DNA fragmentation is blocked, nuclear condensation also fails to occur. Moreover, a kinetic analysis of DNA breakdown, using agarose gels, shows that some DNA digestion occurs before nuclear condensation has taken place. Thus the initiation of DNA digestion may provide conditions necessary for nuclear condensation. Temporary inhibition of nuclear death aborts the death program since after removal of inhibitors cells revert to a vegetative pathway without having eliminated the old or developed the new macronucleus. Zn2+ and EGTA, both of which inhibit apoptosis in some cell types, fail to prevent nuclear condensation or DNA digestion in Tetrahymena, suggesting a requirement here for an endonuclease which is Ca2+-independent and Zn2+-insensitive. With the TUNEL assay, DNA breakdown is detected exclusively in the condensed macronucleus (and occasional micronuclei identified as degenerating haploid products of meiosis), but not in precondensed macronuclei. These studies show that apoptotic-like DNA fragmentation occurs after condensation of the degenerating macronucleus. However, early DNA digestion may be critical for nuclear condensation and subsequent degeneration.

Animals↗

PubMed1984

The contribution of polycyclic aromatic hydrocarbons to the carcinogenic impact of emission condensate from coal-fired residential furnaces evaluated by topical application to the skin of mice.

The objective of this investigation was to identify the substances chiefly responsible for the carcinogenicity of the emission condensate from coal-fired residential furnaces. To realize this, the carcinogenic effect of various fractions was compared with that of an unseparated sample of emission condensate, tested in different doses. The probit and Weibull analysis of the results showed: (1) The condensate emitted from a coal fired residential furnace as well as the reconstituted condensate combining all fractions, provoked local tumors after repeated application to the dorsal skin of mice. The tumor incidence exhibited a clear cut dose-response relationship. (2) The fraction of polycyclic aromatic hydrocarbons (PAH) and thiaarenes with more than three rings accounted for almost the total carcinogenicity (109-118% compared with the total condensate) of the emission condensate from the coal-fired residential furnace. (3) The fraction containing azaarenes and nitroarenes (NO2-PAH) accounted only for 4-7% of the total carcinoma incidence of the emission condensate. (4) The content of benzo[a]pyrene (0.702 mg/g condensate) contributes 10-11% to the total carcinogenicity of the emission condensate. (5) The PAH-free fraction and the fraction containing PAH with 2 and 3 rings (together about 77% by wt) were almost ineffective. No cocarcinogenic activity of this fraction was obtained, since the total condensate, as well as the PAH-fraction consisting of more than three rings applied proportionally provoked about the same carcinoma incidence.

Administration, Topical↗

PubMed1995

DNA condensation by the rat spermatidal protein TP2 shows GC-rich sequence preference and is zinc dependent.

Transition protein-2 (TP2), isolated from rat testes, was recently shown to be a zinc metalloprotein. We have now carried out a detailed analysis of the DNA condensing properties of TP2 with various polynucleotides using circular dichroism spectroscopy. The condensation of the alternating copolymers by TP2 (incubated with 10 microM ZnSO4), namely, poly(dG-dC).poly(dG-dC) and poly(dA-dT).poly(dA-dT), was severalfold higher than condensation of either of the homoduplexes poly(dG).poly-(dC) and poly(dA).poly(dT) or rat oligonucleosomal DNA. Between the two alternating copolymers, poly(dG-dC).poly(dG-dC) was condensed 3.2-fold more effectively than poly(dA-dT).poly(dA-dT). Preincubation of TP2 with 5 mM EDTA significantly reduced its DNA-condensing property. Interestingly, condensation of the alternating copolymer poly(dI-dC).poly(dI-dC) by TP2 was much less as compared to that of poly(dG-dC).poly(dG-dC). The V8 protease-derived N-terminal fragment (88 aa) condensed poly(dA-dT).poly(dA-dT) to a very small extent but did not have any effect on poly(dG-dC).poly-(dG-dC). The C-terminal fragment (28 aa) was able to condense poly(dA-dT).poly(dA-dT) more effectively than poly(dG-dC).poly(dG-dC). These results suggest that TP2 in its zinc-coordinated form condenses GC-rich polynucleotides much more effectively than other types of polynucleotides. Neither the N-terminal two-thirds of TP2 which is the zinc-binding domain nor the C-terminal basic domain are as effective as intact TP2 in bringing about condensation of DNA.

Amino Acid Sequence↗

PubMed2004

Evidence that both kinetic and thermodynamic factors govern DNA toroid dimensions: effects of magnesium(II) on DNA condensation by hexammine cobalt(III).

Millimolar concentrations of divalent cations are shown to affect the size of toroids formed when DNA is condensed by multivalent cations. The origins of this effect were explored by varying the order in which MgCl(2) was added to a series of DNA condensation reactions with hexammine cobalt chloride. The interplay between Mg(II), temperature, and absolute cation concentration on DNA condensation was also investigated. These studies reveal that DNA condensation is extremely sensitive to whether Mg(II) is associated with DNA prior to condensation or Mg(II) is added concurrently with hexammine cobalt(III) at the time of condensation. It was also found that, in the presence of Mg(II), temperature and dilution can have opposite effects on the degree of DNA condensation. A systematic comparison of DNA condensates observed in this study clearly illustrates that, under our low-salt conditions, toroid size is determined by the kinetics of toroid nucleation and growth. However, when Mg(II) is present during condensation, toroid size can also be limited by a thermodynamic parameter (e.g., undercharging). The path dependence of DNA condensation presented here illustrates that regardless of which particular factors limit toroid growth, toroids formed under the various conditions of this study are largely nonequilibrium structures.

Cations, Divalent↗

PubMed2001

Factors influencing breath condensate volume.

Analysis of breath condensate (BC) has received interest recently due to the need for easy and repetitive monitoring or airway and pulmonary disease. While many authors have used custom built systems, commercial systems are now available and will probably be used more widely. Early studies of markers and mediators in BC have reported concentrations following varying periods of sampling time. However, factors that influence the generation of BC have not been analysed and it is unclear whether breathing rate, tidal volume, lung function, body weight, height or age influence the amount of BC collected. We therefore studied the influence of these factors on breath condensate volume and breath condensate urea and protein concentrations in 22 healthy volunteers and 23 COPD patients. A strong correlation of total respired volume and breath condensate volume was observed for both groups (volunteers: r=0.952, p < 0.0001, COPD: r=0.883, p < 0.001) while no significant correlation existed for breath condensate volume and TLC, RV, Vc, FEV1, R(tot), height or body weight, As long as ventilation remained fairly constant, breath condensate volume increased linearly with time. The fraction of breath condensate extracted from total vapour contained in the exhalate was estimated by measuring relative atmospheric humidity before and after the collecting tube. The amount calculated by the change in temperature and saturation corresponded closely to the amount actually collected. We conclude from these results that breath condensate volume is primarily dependent on V(E), and does not seem to depend on lung function parameters. For standardisation it is suggested to report breath condensate measurements per volume respired. Both, urea and protein are present in measurable quantities in breath condensate and protein as well as BCV may be helpful denominators for comparison with e.g. cytokines in lung disease.

Asthma↗

PubMed2026

Integrative chemical genetics platform identifies condensate modulators linked to neurological disorders.

Dysregulation of biomolecular condensates is implicated across multiple neurological disorders. However, approaches to systematically identify their modulators remain limited. Here, we expand the utility of MLF2 as a versatile condensate biomarker and develop CondenScreen, an integrated high-content screening and bioinformatics pipeline enabling identification of condensate modulators across chemical and genetic space. Screening 1760 bioactive compounds in a cellular DYT1 dystonia model, we validate the platform for condensate-targeted drug discovery, identifying drugs that prevent the accumulation of the MLF2 reporter into nuclear envelope condensates. In parallel, a genome-wide CRISPR/Cas9 screen correlates nuclear condensate abundance with genes implicated in microcephaly and over eight additional neurodevelopmental disorders. Machine learning and confocal imaging resolve distinct condensate phenotypes, with RNF26 deletion provoking nuclear envelope condensates that phenocopy hallmarks of torsin deficiency. Our study provides a scalable platform for identifying modulators of condensates and establishes a correlative connection between nuclear condensate accumulation and genes implicated in neurodevelopmental disorders.

Humans↗

PubMed1997

Nanoscopic structure of DNA condensed for gene delivery.

Scanning force microscopy was used to examine DNA condensates prepared with varying stoichiometries of lipospermine or polyethylenimine in physiological solution. For the first time, individual DNA strands were clearly visualized in incomplete condensates without drying. Using lipospermine at sub-saturating concentrations, discrete nuclei of condensation were observed often surrounded by folded loops of DNA. Similar packing of DNA loops occurred for polyethylenimine-induced condensation. Increasing the amount of the condensing agent led to the progressive coalescence or aggregation of initial condensation nuclei through folding rather than winding the DNA. At over-saturating charge ratios of the cationic lipid or polymer to DNA, condensates had sizes smaller than or equal to those measured previously in electron micrographs. Polyethylenimine condensates were more compact than lipospermine condensates and both produced more homogeneously compacted plasmids when used in a 2-4-fold charge excess. The size and morphology of the condensates may affect their efficiency in transfection.

Aluminum Silicates↗

PubMed2004

Ionizing radiation induces frequent translocations with delayed replication and condensation.

Certain chromosome rearrangements display a significant delay in replication timing that is associated with a delay in mitotic chromosome condensation. Chromosomes with delay in replication timing/delay in mitotic chromosome condensation participate in frequent secondary rearrangements, indicating that cells with delay in replication timing/delay in mitotic chromosome condensation display chromosomal instability. In this report, we show that exposing cell lines or primary blood lymphocytes to ionizing radiation results in chromosomes with the delay in replication timing/delay in mitotic chromosome condensation phenotype, and that the delay in replication timing/delay in mitotic chromosome condensation phenotype occurs predominantly on chromosome translocations. In addition, exposing mice to ionizing radiation also induces cells with delay in replication timing/delay in mitotic chromosome condensation chromosomes that persist for as long as 2 years. Cells containing delay in replication timing/delay in mitotic chromosome condensation chromosomes frequently display hyperdiploid karyotypes, indicating that delay in replication timing/delay in mitotic chromosome condensation is associated with aneuploidy. Finally, using a chromosome engineering strategy, we show that only a subset of chromosome translocations displays delay in replication timing/delay in mitotic chromosome condensation. Our results indicate that specific chromosome rearrangements result in the generation of the delay in replication timing/delay in mitotic chromosome condensation phenotype and that this phenotype occurs frequently in cells exposed to ionizing radiation both in vitro and in vivo.

Cell Line↗

PubMed2002

Dilution of respiratory solutes in exhaled condensates.

Most exhaled water is produced as gaseous water vapor, which can be collected in cooled condensers. The presence of nonvolatile solutes in these condensates suggests that droplets of respiratory fluid (RF) have also been collected. However, calculation of RF solute concentrations from condensates requires estimation of the dilution of RF droplets by water vapor. We used condensate electrolyte concentrations to calculate the dilution of RF droplets in condensates from 20 normal subjects. The total ionic concentration (conductivity) was 497 plus minus 68 (mean plus minus SEM) muM. Of this, 229 plus minus 43 muM was NH(4)(+), but little NH(4)(+) was collected from subjects with tracheostomies, indicating oral formation. The Na+ concentration in condensate ([Na+](cond)) averaged 242 plus minus 43 muM. Large variations in [Na(+)](cond) correlated well with variations of K+ in condensate ([K+](cond)) and Cl-) in condensate ([Cl-](cond)), and were attributed to differences in respiratory droplet dilution. Dividing condensate values of ([Na+] + [K+] ) by those of plasma indicated that RF represented between 0.01% and 2.00% of condensate volumes. Calculated values for Na+, K+, Cl-, lactate, and protein in RF were [Na+](RF) = 91 +/- 8 mM, [K+](RF) = 60 +/- 11 mM, [Cl-](RF) = 102 +/- 17 mM, [lactate](RF) = 44 +/- 17 mM, and [protein](RF) = 7.63 +/- 1.82 g/dl, respectively.

Acid-Base Equilibrium↗

PubMed1983

The origin of the ectomesenchymal condensations which precede the development of the bony scleral ossicles in the eyes of embryonic chicks.

The origin of neural crest-derived ectomesenchymal condensations located subjacent to scleral papillae and the development of the more deeply situated scleral ossicles were investigated in scleral tissues explanted from the eyes of chick embryos at Hamburger & Hamilton (1952) stages 30-38 (6 1/2-12 days of incubation). Explants were pulse labelled with [3H]thymidine for 4h in vitro. Nuclear counts and % labelling indices were calculated for standardized areas within and between the condensations. At all stages exhibiting condensations, the % labelling indices were higher within the condensations than in tissues between condensations. % labelling declined with maturity, but the decline was greater between than within condensations. Regional differences in intensity of proliferation in the ectomesenchyme centred about the scleral papillae seemed to be the best explanation for the development of these condensations. The condensations disappeared concomitant with the complete degeneration of the adjacent papillae. A new distribution of labelled nuclei 70-100 micrometer deep in the tissue and beneath the original sites of the condensations preceded the appearance of ossicle primordia. The roles of the scleral papillae, the ectomesenchymal condensations and deeper primordia in the development of scleral ossicles are discussed.

Animals↗

PubMed1997

DNA condensation by multivalent cations.

In the presence of multivalent cations, high molecular weight DNA undergoes a dramatic condensation to a compact, usually highly ordered toroidal structure. This review begins with an overview of DNA condensation: condensing agents, morphology, kinetics, and reversibility, and the minimum size required to form orderly condensates. It then summarizes the statistical mechanics of the collapse of stiff polymers, which shows why DNA condensation is abrupt and why toroids are favored structures. Various ways to estimate or measure intermolecular forces in DNA condensation are discussed, all of them agreeing that the free energy change per base pair is very small, on the order of 1% of thermal energy. Experimental evidence is surveyed showing that DNA condensation occurs when about 90% of its charge is neutralized by counterions. The various intermolecular forces whose interplay gives rise to DNA condensation are then reviewed. The entropy loss upon collapse of the expanded wormlike coil costs free energy, and stiffness sets limits on tight curvature. However, the dominant contributions seem to come from ions and water. Electrostatic repulsions must be overcome by high salt concentrations or by the correlated fluctuations of territorially bound multivalent cations. Hydration must be adjusted to allow a cooperative accommodation of the water structure surrounding surface groups on the DNA helices as they approach. Undulations of the DNA in its confined surroundings extend the range of the electrostatic forces. The condensing ions may also subtly modify the local structure of the double helix.

Cations↗

PubMed2002

Alterations in the spatiotemporal expression pattern and function of N-cadherin inhibit cellular condensation and chondrogenesis of limb mesenchymal cells in vitro.

Cartilage formation in the embryonic limb is presaged by a cellular condensation phase that is mediated by both cell-cell and cell-matrix interactions. N-Cadherin, a Ca(2+)-dependent cell-cell adhesion molecule, is expressed at higher levels in the condensing mesenchyme, followed by down-regulation upon chondrogenic differentiation, strongly suggesting a functional role in the cellular condensation process. To further examine the role of N-cadherin, we have generated expression constructs of wild type and two deletion mutants (extracellular and intracellular) of N-cadherin in the avian replication-competent, RCAS retrovirus, and transfected primary chick limb mesenchymal cell cultures with these constructs. The effects of altered, sustained expression of N-cadherin and its mutant forms on cellular condensation, on the basis of peanut agglutinin (DNA) staining, and chondrogenesis, based on expression of chondrocyte phenotypic markers, were characterized. Cellular condensation was relatively unchanged in cultures overexpressing wild type N-cadherin, compared to controls on all days in culture. However, expression of either of the deletion mutant forms of N-cadherin resulted in decreased condensation, with the extracellular deletion mutant demonstrating the most severe inhibition, suggesting a requirement for N-cadherin mediated cell-cell adhesion and signaling in cellular condensation. Subsequent chondrogenic differentiation was also affected in all cultures overexpressing the N-cadherin constructs, on the basis of metabolic sulfate incorporation, the presence of the cartilage matrix proteins collagen type II and cartilage proteoglycan link protein, and alcian blue staining of the matrix. The characteristics of the cultures suggest that the N-cadherin mutants disrupt proper cellular condensation and subsequent chondrogenesis, while the cultures overexpressing wild type N-cadherin appear to condense normally, but are unable to proceed toward differentiation, possibly due to the prolonged maintenance of increased cell-cell adhesiveness. Thus, spatiotemporally regulated N-cadherin expression and function, at the level of both homotypic binding and linkage to the cytoskeleton, is required for chondrogenesis of limb mesenchymal cells.

Animals↗

PubMed1995

Different roles for fibronectin in the generation of fore and hind limb precartilage condensations.

Fibronectin expression and spatiotemporal distribution were examined in relation to the distinctive patterns of mesenchymal condensation and chondrogenesis seen in high-density serum-free cultures of chicken wing and leg bud precartilage cells. More fibronectin protein was produced on a per cell basis by leg than by wing mesenchyme, both in freshly isolated tissue and during the prechondrogenic condensation period in culture, where the difference was twofold. The quantitative difference in fibronectin expression in freshly isolated wing and leg mesenchyme was also seen at the level of total and poly (A)+ RNA. During the condensation phase, fibronectin was distributed in the wing and leg mesenchymal cultures in a way that prefigured the eventual distribution of cartilage in these cultures: in wing cultures condensations were broad and flat, and rich in diffusely organized fibronectin; in leg cultures, condensations were compact and spheroidal, and contained abundant deposits of fibronectin. In addition, the leg condensations were connected by long fibronectin-rich fibers. Transient treatment with TGF-beta early during the culture period led to increase in fibronectin production and expansion of condensations in both wing and leg cultures. Leg mesenchyme was more responsive to transforming growth factor-beta than wing mesenchyme with respect to fibronectin production, and this was reflected in a greater enhancement of cartilage formation in later cultures. Treatment of cultures with monoclonal antibody 304 directed against the amino-terminal heparin-binding domain of fibronectin inhibited condensation formation and reduced chondrogenesis in wing mesenchyme, but left these two processes unchanged in leg mesenchyme, despite disruption by the antibody of the leg-specific fibronectin fibers. These studies indicate that for both wing and leg mesenchyme the morphology, extent, and spatiotemporal regulation of precartilage condensation and subsequent chondrogenesis closely parallels the deposition of fibronectin. But whereas the interaction between cells and fibronectin in wing bud mesenchyme is mediated in part by the protein's amino-terminal domain, this domain does not appear to be involved in analogous interactions in leg bud mesenchyme.

Animals↗

PubMed1978

Ion-molecule condensation reactions: a mechanism for organic synthesis in ionized reducing atmospheres.

The CH3+ ion, formed in ionized methane, undergoes consecutive eliminative condensation reactions with methane to form the carbonium ions C2H5+, i-C3H7+ and t-C4H9+. At T smaller than 500 degrees K, NCH4 greater than 10(16) cm-3 these ions react with NH3 in competitive condensation -- H+ transfer reactions, e.g. C2H5 + NH3 M leads to C2H5NH3+ leads to NH4+ + C2H4 At particle densities of NCH4 smaller than 10(16) cm-3 proton transfer is the only significant reaction channel. At NCH4 greater than 10(17) cm-3 condensation constitutes 5--20% of the overall reactions. The product of the condensation reaction further associates with CO2 to form C2H5NH3+ . CO2; the atomic composition of this cluster ion is identical with the protonated amino acid alanine. The carbonium ions i-C3H7+ and t-C4H9+ condense also with HCN to yield protonated isocyanides. HCNH% also appears to condense with HCN at T greater than 570 degrees K, and form cluster ions with HCN at lower temperatures. The rate constants of the condensation reactions vary with temperature and pressure in a complex manner. Under conditions similar to those on Titan at an altitude of 100 km (T = 100--150 degrees K, NCH4 approximately 10(18) cm-3), with a methane atmosphere containing 1% H2 and traces of NH3 and H2O, ion-molecule condensation reactions followed by H+ transfer are expected to lead to the atmospheric synthesis of C2H6, C3H8, CH3OH, C2H5OH and the terminal ions NH4+, CH3NH3+ and C2H5NH3+. At higher temperatures (250 degrees K smaller than T smaller than 400 degrees K), the synthesis of i-C4H10, i-C3H7OH and t-C4H9OH and of the ions i-C3H7NH3+ and t-C4H9NH3+ is also expected. Electron recombination of the terminal ions may yield amines, imines and nitriles. Cycles of protonation and dissociative recombination of the alkanes and alcohols produced in condensation reactions will also produce unsaturated hydrocarbons, ketones and aldehydes in the ionized atmosphere.

Amines↗

PubMedDate not supplied

Possible prebiotic significance of polyamines in the condensation, protection, encapsulation, and biological properties of DNA.

Some properties of DNA condensed with spermidine have been compared with the properties of DNA condensed with Co3+(NH3)6 to determine whether condensation of DNA with these trivalent cations protects DNA against the action of DNase I and increases transcription and encapsulation of DNA into liposomes. It was shown that DNA condensed with Co3+(NH3)6 was resistant to the action of the endonuclease DNase I such as DNA condensed with spermidine was. However, DNA condensed with Co3+(NH3)6 was significantly less active in transcription with the E. coli RNA polymerase than DNA-spermidine condensed forms. In addition, it was demonstrated that both compacted forms of DNA were more efficiently encapsulated into neutral liposomes; however, negatively, charged liposomes were scarcely formed in the presence of DNA condensed with Co3+(NH3)6. These experiments and the well documented properties of polyamines increasing the resistance to radiations and hydrolysis of nucleic acids, as well as their biological activities, such as replication, transcription, and translation, together with the low concentration of Co3+ in the environment, lead us to propose spermidine as a plausible prebiotic DNA condensing agent rather than Co3+ and the basic proteins proposed by other authors. Then, we consider the possible role and relevance of the polyamine-nucleic acids complexes in the evolution of life.

Animals↗

PubMed2005

Fluorescence dynamics of DNA condensed by the molecular crowding agent poly(ethylene glycol).

Condensation of extended DNA into compact structures is encountered in a variety of situations, both natural and artificial. While condensation of DNA has been routinely carried out by the use of multivalent cations, cationic lipids, detergents, and polyvalent cationic polymers, the use of molecular crowding agents in condensing DNA is rather striking. In this work, we have studied the dynamics of plasmid DNA condensed in the presence of a molecular crowding agent, polyethylene glycol (PEG). Steady-state and time-resolved fluorescence of the recently established condensation-indicating DNA binder, YOYO-1 [G. Krishnamoorthy, G. Duportail, and Y. Mely (2002), Biochemistry 41, 15277-15287] was used in inferring the dynamic aspects of DNA condensates. It is shown that DNA condensed by PEG is more flexible and less compact when compared to DNA condensed by binding agents such as polyethyleneimine. The relevance of such differences in dynamics toward functional aspects of condensed DNA is discussed.

Benzoxazoles↗

PubMed1979

Reduction in mutagenicity of cigarette smoke condensate by added sugars.

The effects of adding sugars to high- and low-tar cigarettes on the mutagenicity of their smoke condensates were studied using Salmonella typhimurium TA100 and TA98 with and without metabolic activation. The sugars tested were glucose, fructose, galactose, sorbitol, sucrose and lactose. The lowest mutagenicities observed with these sugars per mg of smoke condensate assayed on TA98 with metabolic activation were 37% (high-tar cigarettes) and 22% (low-tar cigaretts) of that of smoke condensate from untreated cigarettes. Addition of sugars increased the total amounts of smoke condensates, but the mutagenicities of the total condensates were also decreased by all the sugars, the lowest values being 35% (high-tar cigarettes) and 36% (low-tar cigarettes) of that of smoke condensates from cigarettes without added sugar. On assay with TA100 with metabolic activation, decreases in both specific and total mutangenicities of condensates of high-tar cigarettes were observed with all the sugars tested except galactose and sucrose. Treatment with glucose, fructose or sorbitol decreased the specific mutagenicity of condensates of low-tar cigarettes and glucose and fructose reduced also their total mutagenicity. The effects of added sugars were more marked when assayed on TA98 than on TA100 and of the sugars tested fructose and sorbitol had the greatest effects. Addition of sugars had no effect of the mutagenicity of cigarette-smoke condensate without metabolic activation.

Carbohydrates↗