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PubMed2026

Bridging-driven condensation by eukaryotic SMC complexes is a conserved feature of genome organization.

The Structural Maintenance of Chromosome (SMC) protein family plays a central role in higher-order genome organization through ATP-dependent DNA loop extrusion by cohesin and condensin and other processes. Whether these activities fully account for the complexity of chromosome architecture remains unknown. Here, we uncover a conserved ATP-independent mechanism of chromatin condensation by SMC complexes, occurring via biomolecular condensation. Using single-molecule fluorescence imaging, we show that a variety of SMCs form dynamic DNA-bound condensates that exhibit key features of biomolecular condensates, including droplet coalescence, fluorescence recovery after photobleaching, and rapid exchange with free SMC complexes. Atomic force microscopy analysis of human cohesin-DNA assemblies reveals DNA-length-dependent clustering, providing evidence for bridging-driven condensation. Analyses of in vivo super-resolution imaging and high-throughput chromosome conformation capture (Hi-C) data indicate that these condensates form chromatin-associated clusters with multi-loop structures. Together, our results establish that SMC complexes employ ATP-independent phase condensation as well as ATP-dependent activities to shape genome architecture. This work reveals a broadly conserved principle of chromosomal organization across eukaryotes.

Chromosomal Proteins, Non-Histone↗

PubMed2003

In vivo requirements for rDNA chromosome condensation reveal two cell-cycle-regulated pathways for mitotic chromosome folding.

Chromosome condensation plays an essential role in the maintenance of genetic integrity. Using genetic, cell biological, and biochemical approaches, we distinguish two cell-cycle-regulated pathways for chromosome condensation in budding yeast. From G(2) to metaphase, we show that the condensation of the approximately 1-Mb rDNA array is a multistep process, and describe condensin-dependent clustering, alignment, and resolution steps in chromosome folding. We functionally define a further postmetaphase chromosome assembly maturation step that is required for the maintenance of chromosome structural integrity during segregation. This late step in condensation requires the conserved mitotic kinase Ipl1/aurora in addition to condensin, but is independent of cohesin. Consistent with this, the late condensation pathway is initiated during the metaphase-to-anaphase transition, supports de novo condensation in cohesin mutants, and correlates with the Ipl1/aurora-dependent phosphorylation of condensin. These data provide insight into the molecular mechanisms of higher-order chromosome folding and suggest that two distinct condensation pathways, one involving cohesins and the other Ipl1/aurora, are required to modulate chromosome structure during mitosis.

Adenosine Triphosphatases↗

PubMed2006

Condensation phase transitions of symmetric conserved-mass aggregation model on complex networks.

We investigate condensation phase transitions of the symmetric conserved-mass aggregation (SCA) model on random networks (RNs) and scale-free networks (SFNs) with degree distribution P(k) approximately k(-gamma). In the SCA model, masses diffuse with unit rate, and unit mass chips off from mass with rate omega. The dynamics conserves total mass density rho. In the steady state, on RNs and SFNs with gamma > 3 for omega is not equal to infinity, we numerically show that the SCA model undergoes the same type of condensation transitions as those on regular lattices. However, the critical line rho(c)(omega) depends on network structures. On SFNs with gamma < or = 3, the fluid phase of exponential mass distribution completely disappears and no phase transitions occurs. Instead, the condensation with exponentially decaying background mass distribution always takes place for any nonzero density. For the existence of the condensed phase for gamma < or = 3 at the zero density limit, we investigate one lamb-lion problem on RNs and SFNs. We numerically show that a lamb survives indefinitely with finite survival probability on RNs and SFNs with gamma > 3, and dies out exponentially on SFNs with gamma< or = 3. The finite lifetime of a lamb on SFNs with gamma < or = 3 ensures the existence of the condensation at the zero density limit on SFNs with gamma < or = 3, at which direct numerical simulations are practically impossible. At omega = infinity, we numerically confirm that complete condensation takes place for any rho > 0 on RNs. Together with the recent study on SFNs, the complete condensation always occurs on both RNs and SFNs in zero range process with constant hopping rate.

Journal Article↗

PubMed2003

Efimov states in a Bose-Einstein condensate near a Feshbach resonance.

Recent experiments with Bose-Einstein condensates of 85Rb atoms near a Feshbach resonance have produced evidence for a condensate of diatomic molecules coexisting with the atom condensate. It should also be possible to create condensates of the triatomic molecules predicted by Efimov coexisting with the atom and dimer condensates. The smoking gun for the trimer condensate would be oscillatory dependence of observables on the binding energy of the trimer. It may also be possible to deduce the existence of the trimer condensate from the spectra of the bursts of atoms and dimers created in the disappearance of the trimers.

Journal Article↗

PubMed2005

Nature of the condensate in mass transport models.

We study the phenomenon of real space condensation in the steady state of a class of one-dimensional mass transport models. We derive the criterion for the occurrence of a condensation transition and analyze the precise nature of the shape and the size of the condensate in the condensed phase. We find two distinct condensate regimes: one where the condensate is Gaussian distributed and the particle number fluctuations scale normally as L(1/2) where L is the system size, and the second regime where the particle number fluctuations become anomalously large and the condensate peak is non-Gaussian. We interpret these results within the framework of sums of random variables.

Journal Article↗

PubMed1987

The influence of the condensation instrument on the clinical behaviour of amalgam restorations.

The influence of the condensation instrument on the behaviour of amalgam restorations was investigated in a clinical study for which in a group of forty-nine patients, 125 Class I or II amalgam restorations were made by each of two operators. The restorations were made in series of five per patient. For each restoration within a series, the amalgam was condensed with a different instrument (hand condensation, Amalgam Condensaire, Speedomatic, Bergendal Vibrator and Electro-mallet). For a period of 2.5 years the restorations were checked at half-year intervals for failures. The marginal integrity of the restorations was assessed half-yearly with a six-point photo rating scale. The discolouration, roughness formation and the marginal integrity of the restorations were assessed clinically with four-point rating scales. The number of failures and the assessments were analysed for the effect of the condensation instrument, the patient and the operator. After 2.5 years, 12% of the restorations had failed, which is too few for the tracing of a condensation instrument and a patient effect. The operator, however, had an influence on the failure percentage. The condensation instrument had no influence on the clinical behaviour of the restorations, however the patient had. The operator only had an influence on the marginal integrity. This suggests that clinically the condensation results depend more on the operator rather than the instrument.

Dental Amalgam↗

PubMed1975

[Mechanism for the condensation reaction of fatty-acid biosynthesis (author's transl)].

The spontaneous hydrogen-deuterium exchange of the methylene group of malonyl-thioesters was investigated by nuclear-magnetic-resonance (NMR) spectroscopy using the model compound S-malonyl-N-acetylcysteamine. The half life of the methylene proteins is 12 to 16 min in 0.1 M K-phosphate buffer at pH 6.5 to 7.0 at 25 degrees C, the conditions of maximal activity of fatty acid synthetase from yeast. Proton catalysis was used for the quick preparation of deuterium- and tritium-labeled malonylthioesters. Compared with malonyl-CoA, dideutero-malonyl-CoA had no primary isotope effect on the reaction velocity of the yeast enzyme catalysed fatty acid synthesis, in which the rate limiting step is the condensation reaction. Although deuterium oxide had a solvent isotope effect, there was no difference in reaction velocities between malonyl CoA and dideuteromalonyl CoA in deuterium oxide. The condensation reaction was investiaged separately from the overall fatty acid synthesis using beta-ketoacyl-acyl-carrier-protein (ACP) synthetase (condensing enzyme) of Escherichia coli. The condensation reaction with deuteromalonyl-ACP had no kinetic isotope effect, in agreement with the observations on the overall reaction. However, in this case no solvent isotope effect was observed with 2H2O. When the condensation reaction was carried out in the presence of tritiated water, there was no incorporation of label into the reaction product acetoacetyl-thioester, excluding proton exchange with the solvent. The results exclude a mechanism for the condensation reaction involving a malonyl carbanion and its acylation as intermediates in the sense of an organic-chemical malonic ester synthesis, and they indicate that the condensation reaction follows a concerted mechanism: The formation of the new carbon-carbon bond is coupled with the cleavage of the carboxyl bond of the malonyl group.

Binding Sites↗

PubMed2002

Condensate removal mechanisms in a constrained vapor bubble heat exchanger.

Microgravity experiments on the constrained vapor bubble heat exchanger (CVB) are being developed for the space station. Herein, ground-based experimental studies on condensate removal in the condenser region of the vertical CVB were conducted and the mechanism of condensate removal in microgravity was found to be the capillary force. The effects of curvature and contact angle on the driving forces for condensate removal is studied. The Nusselt correlations are derived for the film condensation and the flow from the drop to the meniscus at the moment of merging. These new correlations scale as forced convection with h proportional to L(1/2) or h proportional to L(1/2)(cd). For the partially wetting ethanol system studied, the heat transfer coefficient for film condensation was found to be 4.25 x 10(4) W/m(2)K; for dropwise condensation at moment of merging it was found to be 9.64 x 10(4) W/m(2)K; and for single drops it was found to be 1.33 x 10(5) W/m(2)K.

Journal Article↗

PubMed2000

Condensation in a steady-flow thermoacoustic refrigerator.

Condensation may occur in an open-flow thermoacoustic cooler with stack temperatures below the saturation temperature of the flowing gas. In the experimental device described here the flowing gas, which is also the acoustic medium, is humid air, so the device acts as a flow-through dehumidifier. The humid air stream flows through an acoustic resonator. Sound energy generated by electrodynamic drivers produces a high-amplitude standing wave inside of the resonator, which causes cooling on a thermoacoustic stack. Condensation of water occurs as the humid air passes through the stack and is cooled below its dew point, with the condensate appearing on the walls of the stack. The dry, cool air passes out of the resonator, while the condensate is wicked away from the end of the stack. Thermoacoustic heat pumping is strongly affected by the form of the condensate inside of the stack, whether condensed mostly on the stack plates, or largely in the form of droplets in the gas stream. Two simple models of the effect of the condensate are matched to a measured stack temperature profile; the results suggest that the thermoacoustic effect of droplets inside the stack is small.

Acoustics↗

PubMed1993

Effects of Condensed Tannins on Endoglucanase Activity and Filter Paper Digestion by Fibrobacter succinogenes S85.

The effect of condensed tannins from birdsfoot trefoil (Lotus corniculatus L.) on the cellulolytic rumen bacterium Fibrobacter succinogenes S85 was examined. Condensed tannins inhibited endoglucanase activity in the extracellular culture fluid, at concentrations as low as 25 mug ml. In contrast, cell-associated endoglucanase activity increased in concentrations of condensed tannins between 100 and 300 mug ml. Inhibition of endoglucanase activity in both the extracellular and the cell-associated fractions was virtually complete at 400 mug of condensed tannins ml. Despite the sharp decline in extracellular endoglucanase activity with increasing concentrations of condensed tannins, filter paper digestion declined only moderately between 0 and 200 mug of condensed tannins ml. However, at 300 mug ml, filter paper digestion was dramatically reduced and at 400 mug ml, almost no filter paper was digested. F. succinogenes S85 was seen to form digestive grooves on the surface of cellulose, and at 200 mug ml, digestive pits were formed which penetrated into the interior of cellulose fibers. Cells grown with condensed tannins (100 to 300 mug ml) possessed large amounts of surface material, and although this material may have been capsular carbohydrate, its osmiophilic nature suggested that it had arisen from the formation of tannin-protein complexes on the cell surface. The presence of electron-dense extracellular material suggested that similar complexes were formed with extracellular protein.

Journal Article↗

PubMed2004

Chromosome condensation in mitosis and meiosis of rye (Secale cereale L.).

Structural investigation and morphometry of meiotic chromosomes by scanning electron microscopy (in comparison to light microscopy) of all stages of condensation of meiosis I + II show remarkable differences during chromosome condensation in mitosis and meiosis I of rye (Secale cereale) with respect to initiation, mode and degree of condensation. Mitotic chromosomes condense in a linear fashion, shorten in length and increase moderately in diameter. In contrast, in meiosis I, condensation of chromosomes in length and diameter is a sigmoidal process with a retardation in zygotene and pachytene and an acceleration from diplotene to diakinesis. The basic structural components of mitotic chromosomes of rye are "parallel fibers" and "chromomeres" which become highly compacted in metaphase. Although chromosome architecture in early prophase of meiosis seems similar to mitosis in principle, there is no equivalent stage during transition to metaphase I when chromosomes condense to a much higher degree and show a characteristic "smooth" surface. No indication was found for helical winding of chromosomes either in mitosis or in meiosis. Based on measurements, we propose a mechanism for chromosome dynamics in mitosis and meiosis, which involves three individual processes: (i) aggregation of chromatin subdomains into a chromosome filament, (ii) condensation in length, which involves a progressive increase in diameter and (iii) separation of chromatids.

Chromosomes, Plant↗

PubMed2002

Differential regulation of maternal and paternal chromosome condensation in mitotic zygotes.

A-kinase anchoring protein AKAP95 is implicated in somatic mitotic chromosome condensation by recruiting the condensin complex. Here, we report a differential regulation of condensation of maternal and paternal chromosomes mediated by AKAP95 in mitotic mouse zygotes. AKAP95 is synthesized upon oocyte activation, targeted to the female pronucleus and specifically associates with maternal chromosomes at mitosis. AKAP95 mRNA is highly restricted to the vicinity of the meiotic spindle in metaphase II oocytes. In vivo displacement of endogenous AKAP95 in female pronuclei by microinjection of competitor peptides and rescue experiments show that AKPA95 is required for recruitment of the mCAP-D2 condensin subunit to, and condensation of, maternal chromosomes. In contrast, AKAP95 is dispensable for mCAP-D2 recruitment to, and condensation of, paternal chromosomes. Our results indicate that at first embryonic mitosis, paternal chromosomes target condensins and condense independently of AKAP95, whereas maternal chromosomes require AKAP95 for condensin recruitment and condensation. We propose a concept whereby condensation of chromosomes in gametes, zygotes and somatic cells involves related but distinct mechanisms.

Adenosine Triphosphatases↗

PubMed2006

Identification of compounds associated with testosterone depressions in fish exposed to bleached kraft pulp and paper mill chemical recovery condensates.

In previous experiments, bleached kraft chemical recovery condensates generated during softwood pulp production have been identified as a primary source of substances causing testosterone depressions in mummichog (Fundulus heteroclitus). Recent toxicity identification evaluations have encountered inconsistencies in the potential of condensates and fractions to reduce steroid concentrations between three repeated exposures. To assess the sources of these inconsistencies, temporal assessments of condensate extractives and analytical methodologies were evaluated. Condensates were collected during a six-month period, extracted by solid-phase extraction (SPE), and analyzed by gas chromatography-mass spectrometry and gas chromatography-flame photometric detection. All unique extractives were cataloged by mass spectra, peak area, and gas chromatographic retention time, and nine were confirmed and quantified against authentic standards. Confirmed components included phenolic guaiacyl-based lignin degradation products, sulfur (S9), three diterpenoids, and a dimethoxy stilbene. Concentrations of confirmed condensate extractives were consistent in all samples collected. Spiking experiments of confirmed extractives revealed substantial losses following high-pressure liquid chromatographic fractionation and three different methods of fraction preparation. In an effort to propose chemical classes associated with biological activity, all unique condensate extractives in previously established bioactive and inactive fractions were classified based on their potential to depress testosterone in mummichog. Of 39 unique components in bioactive SPE extracts of condensates, six were associated with hormonal activity. Mass spectral interpretation indicated hydroxylated diterpenoids, sesquiterpenoids, and a lignin-derived stilbene as classes of chemicals associated with steroid depressions.

Animals↗

PubMed2000

Evaluation of the measurement of leukotriene B4 concentrations in exhaled condensate as a noninvasive method for assessing mediators of inflammation in the lungs of calves.

OBJECTIVE: To determine whether measurement of an inflammatory mediator in exhaled condensate could provide a noninvasive method for evaluating lungs of calves. ANIMALS: 84 calves < or = 2 months old. PROCEDURE: Concentration of leukotriene B4 (LTB4) was evaluated in the exhaled condensate of healthy calves and calves with experimentally induced respiratory tract infections. For collection of samples of exhaled condensate, the total amount of exhaled air was directed into a cooled double-jacketed tube. Each tube was sealed and stored at -80 C. The LTB4 concentration was measured, using an ELISA. RESULTS: In exhaled condensates of clinically healthy calves, normally distributed and highly reproducible LTB4 concentrations (mean +/- SD, 116.1 +/- 55.4 pg/ml) were measured. After experimentally induced infection with Pasteurella multocida serovar D, LTB4 in exhaled condensate increased significantly (mean, 179% increase), compared with basal concentrations before infection; this increase in LTB4 was significantly correlated with deterioration in lung function. In 2 of 4 calves experimentally infected with bovine respiratory syncytial virus, the LTB4 concentration in exhaled condensate increased (300 to 400% increase), compared with baseline values, which was associated with development of bronchial hyperresponsiveness after infection. CONCLUSIONS AND CLINICAL RELEVANCE: Collection of exhaled condensate is tolerated well by calves and is an acceptable method for obtaining fluid from exhaled air originating from the lungs. This method provides alternatives for diagnosing and evaluating treatment of naturally acquired and experimentally induced diseases of the lungs and airways in calves.

Animals↗

PubMedDate not supplied

Predictive value of sperm chromatin condensation (aniline blue staining) in the assessment of male fertility.

A case control study was carried out to determine the value of sperm chromatin condensation in the assessment of male fertility. A total of 165 semen samples from 90 patients (cases) and 75 healthy donors (control) were examined for chromatin condensation (aniline blue staining), as well as conventional sperm parameters, notably sperm morphology, sperm count, and progressive motility. Whereas only 55 +/- 12.0% of the samples from the infertile patients were unstained by aniline blue (chromatin condensed), 78 +/- 19.0% of the samples in the control group did not take up the stain (chromatin condensed). A significant difference (p < .001) was observed between the two groups. Similarly, the difference between the mean percentage of morphologically normal spermatozoa for the infertile patients (12.1 +/- 1.2%) and the control (23.9 +/- 1.9%) was very significant (p < .001). In addition, only 50 out of the 90 patients (55.5%) had a normal sperm count, whereas all the 75 (100%) were normal in the control group. By comparing between the two groups a significant difference (p < .001) was also observed. Furthermore, a significant difference (p < .001) was also found between the cases and the control with regard to the percentage of spermatozoa illustrating linear progressive motility (40 +/- 9.7% vs. 70 +/- 12.3%). However, no correlation was found between sperm chromatin condensation and morphology, count, and motility. This study suggests that chromatin condensation constitutes a valuable parameter in the assessment of male fertility, completely independent of conventional sperm parameters. Consequently, the inclusion of chromatin condensation to routine laboratory investigations of semen prior to assisted reproduction is strongly recommended.

Adult↗

PubMed1975

The sterochemistry at carbon 3 of pyruvate lyase condensation products. 2-Keto-3-deoxygluconate 6-phosphate and 2-keto-3-deoxygalactonate-6-phosphate aldolase of Pseudomonas saccharophila.

In Pseudomonas saccharophila 2-keto-3-deoxygalactonate-6-P aldolase (EC 4.1.2.21) is induced by growth on galatose while 2-keto-3-deoxygluconate-6-P aldolase (EC 4.1.2.14) is constitutive. These enzymes catalyze identical reactions except for the configuration fixed at C-4 during the condensation reaction. It was found with each enzyme that in a condensation between [3-3H3]pyruvate and D-glyceraldehyde-3-P, the respective condensation products were formed 8 to 10 times faster than tritium was released to water. Since pyruvate deprotonation is obligatory for condensation, the above result requires a hydrogen isotope effect in enolpyruvate formation, which must be then at least partially rate limiting for C--C synthesis. Further, condensation between D-glyceraldehyde-3-P and (3R)-[3-3H, 2H,H]pyruvate or (3S)-[3-3H, 2H,H]pyruvate, as catalyzed by each enzyme, enriched for (3R)- and (3S)-3-3H, 2H-labeled condensation product, respectively. Thus, each enzyme catalyzes C--C and C--H synthesis with retention of configuration at C-3. This shows that the active sites of both enzymes are asymmetric since solutes can only approach a single face of the bound pyruvyl enolate. In addition, the respective aldehyde specific portions of the two active sites must have opposite chiralities, with respect to each other, for correctly orienting the carbonyl faces of the incoming D-glyceraldehyde-3-P, to generate the correct configuration at C-4 of the respective condensation products.

Aldehyde-Lyases↗

PubMed2003

Comparison of exhaled breath condensate from nasal and oral collection.

BACKGROUND: Analysis of exhaled breath condensate may provide new insights into pulmonary inflammatory processes. A new collection method via suction of nasally expired air especially suitable for younger children was presented recently. Here we compare this nasal suction method with the more widely used oral collection method regarding the amount of condensate collected as well as the concentrations of hydrogen peroxide (H2O2), nitrite and nitrate, respectively. MATERIALS AND METHODS: Exhaled breath condensate was collected from 11 healthy adults for the measurements of the amount of condensate and H2O2 concentration and from 17 children for the measurements of nitrite and nitrate. Condensate was collected via nasal suction and oral exhalation from each subject. RESULTS: Overall, no differences between both collection methods were found for all variables assessed except the concentration of H2O2, whereas the latter closely correlated (Spearman r = 0.88, p = 0.0007) between both collection methods. No correlation was found for the amount of condensate collected and the concentration of nitrite and nitrate. The Bland-Altman limits of agreement scattered over a wide range with clinical impact, proving significant differences between both collection methods for all variables measured. CONCLUSIONS: Although nasal and oral collection method proved again suitable for the collection of exhaled breath condensate, the variability of the results obtained precludes the interchangeable usage of the inflammatory markers assessed here.

Adult↗

PubMed2003

[Analysis of the effect on the stress of root canal wall by vertical and lateral condensation procedures].

OBJECTIVE: To analyse the stress variations of root canal wall that resulted from vertical and lateral condensation. METHODS: On the basis of the finite-element model of the mandibular first molar that modified by step-back technique, mesial-buccal root canal was chosen as tested root canal and simulated the procedure of vertical and lateral condensation. The maximal stress of root canal wall and its position were calculated by special software upon different loading condition. RESULTS: Stress of root canal wall caused by vertical condensation was higher than that by lateral condensation on the same loading condition. Maximal stress of vertical condensation was located on loading section and one of lateral condensation was located on coronal and middle 1/3 of root. The lower the position that was loaded, the higher the stress of wall of root canal. CONCLUSION: Lateral condensation will not bring on vertical root fracture directly,but over-force and improper operation are both dangerous that gives rise to vertical root fracture with whichever method.

Dental Pulp Cavity↗