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At least 19 recordsLinked to original sources
PubMed1985

Electronic excitations in condensed biological matter.

In living matter, electronic excitations may have a collective character which is reviewed here in simple physical terms. In liquids and ordered solids the collective excitations appear as plasmons or excitons. Plasmons are delocalized electronic perturbations of a huge number of oscillating electrons decaying very quickly into localized electronic perturbations, mainly low-energy ionizations. Excitons are very light, moving quantum quasi-particles carrying energy, charge and information in structured biological systems. In deformable soft structures collective excitations appear as solitons behaving as rather massive quasi-particles of combined quantum and classical character. Solitons are relatively stable micro-objects able to transfer energy, charge, mass, and biological information along such biological structures as (chains of) macromolecules, fibres, membranes and surfaces. Some photobiological and radiation biological consequences of collective electronic excitations are suggested.

Animals↗
PubMed2002

The Claisen condensation in biology.

The mechanism for carbon-carbon bond formation used in the biosynthesis of natural products such as fatty acids and polyketides is a decarboxylating Claisen condensation. The enzymes that catalyze this reaction in various bacterial systems, collectively referred to as condensing enzymes, have been intensively studied in the past several decades, and members of the family have been crystallized. The condensing enzymes share a common 3-dimensional fold, first described for the biosynthetic thiolase I that catalyzes a non-decarboxylating Claisen condensation, although they share little similarity at the amino acid level. Their active sites, however, possess significant similarities. The initiation condensing enzymes use CoA primers and possess a catalytic triad of Cys, His, Asn; and the elongating condensing enzymes that exclusively use ACP thioesters have a triad of Cys, His, His. These active site differences affect the sensitivity of the respective enzymes to the antibiotics thiolactomycin and cerulenin. Different reaction mechanisms have been proposed for the condensing enzymes. This review covers the recent structural and mechanistic data to see if a unifying hypothesis for the reaction mechanism catalyzed by this important family of enzymes can be established.

Animals↗
PubMed1984

The use of peripheral blood mononuclear cell prematurely condensed chromosomes for biological dosimetry.

Even though the premature chromosome condensation (PCC) technique has been shown to be a powerful cytogenetic tool, it has not yet been applied for biological dosimetry purposes. An improved and simple methodology for polyethylene glycol-mediated cell fusion and PCC induction has given the opportunity to explore the use of peripheral blood mononuclear cell prematurely condensed chromosomes as a biological dosimeter of absorbed radiation dose. This new approach offers several advantages, and it is presented as an alternative to the conventional cytogenetic technique. First, the chromosomal damage may be visualized in about 2 hr from the moment a blood sample is available. Consequently, the chances for interphase cell death or chromosomal repair are decreased. Second, the amount of blood required is only 0.5 ml. Third, the PCC analysis of about 100 mononuclear blood cells shows the radiation damage even at low doses, whereas hundreds of lymphocyte metaphases must be analyzed when conventional cytogenetic techniques are applied. Fourth, the linear dose-response relationships obtained may be easily standardized. The methodology used diminishes the possibility of differential results from one laboratory to another by avoiding the variables introduced by the stimulation and culture of lymphocytes required by conventional cytogenetic techniques. Finally, the kinetics of lymphocyte chromosome aberration recovery can be directly examined. This approach provides us, therefore, with a direct and more sensitive method for the estimation of radiation injury and repair.

Animals↗
PubMed2006

Condensin and Repo-Man-PP1 co-operate in the regulation of chromosome architecture during mitosis.

The reversible condensation of chromosomes during cell division remains a classic problem in cell biology. Condensation requires the condensin complex in certain experimental systems, but not in many others. Anaphase chromosome segregation almost always fails in condensin-depleted cells, leading to the formation of prominent chromatin bridges and cytokinesis failure. Here, live-cell analysis of chicken DT40 cells bearing a conditional knockout of condensin subunit SMC2 revealed that condensin-depleted chromosomes abruptly lose their compact architecture during anaphase and form massive chromatin bridges. The compact chromosome structure can be preserved and anaphase chromosome segregation rescued by preventing the targeting subunit Repo-Man from recruiting protein phosphatase 1 (PP1) to chromatin at anaphase onset. This study identifies an activity critical for mitotic chromosome structure that is inactivated by Repo-Man-PP1 during anaphase. This activity, provisionally termed 'regulator of chromosome architecture' (RCA), cooperates with condensin to preserve the characteristic chromosome architecture during mitosis.

Adenosine Triphosphatases↗
PubMed1994

Size dependency of circular dichroism in macroaggregates of photosynthetic pigment-protein complexes.

Large molecular aggregates, condensed biological macromolecules, intact membrane systems, and cell organelles often exhibit intense anomalous circular dichroism (CD) bands which are absent in systems of lower structural complexity. Theory predicts that in dense, chirally organized macroaggregates the size of the aggregate controls the magnitude of the anomalous CD bands [Keller, D., & Bustamante, C. (1986) J. Chem. Phys. 84, 2972-2979]. Photosynthetic pigment-protein complexes in their native thylakoid membranes and in vitro were used to provide direct experimental evidence of the size dependency of CD in macroaggregates.

Chlorophyll↗
PubMed2001

Synthesis and biological evaluations of condensed pyridine and condensed pyrimidine-based HMG-CoA reductase inhibitors.

A series of 3,5-dihydroxyheptenoic acid derivatives containing pyrazolopyridine, isoxazolopyridine, thienopyridine, and pyrazolopyrimidine as a key scaffold was synthesized from condensed pyridine and condensed pyrimidine carboxylic acid esters by homologation, aldol condensation with ethyl acetoacetate dianion, and stereoselective reduction of the 5-hydroxyketone. Several compounds in the series were found to have potent HMG-CoA reductase inhibitory activities in vitro and marked cholesterol biosynthesis inhibitory activities in vivo. It has been shown that these scaffolds can be used as a suitable replacement for the hexahydronaphthalene ring present in naturally occurring HMG-CoA reductase inhibitors.

Administration, Oral↗
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↗
PubMed2003

Condensin and biological role of chromosome condensation.

Mitotic chromosome condensation is an essential cellular function ensuring proper compaction and segregation of sister chromatids during cell division. Condensin, a five-subunit complex, conserved among eukaryotes, is the key molecular machine of chromosome condensation. Recent advances in the structural biology and functional analysis of condensin demonstrate the unique nature and indispensable biological role of this complex. Condensin functions span chromosome dynamics during mitotic cell division, cell-cycle feedback control mechanisms, as well as formation and maintenance of interphase chromosome structure. Being at the intersection of several cell-cycle regulatory networks condensin is a promising therapeutic target for control over cell proliferation.

Adenosine Triphosphatases↗
PubMed1982

Synthesis of some benzofuran and furocoumarin derivatives for possible biological activity.

Condensation of 5-formyl-6-methoxy-2,3-diphenylbenzofuran (I) and 6-formyl-5-methoxy-2,3-diphenylbenzofuran (II) with aliphatic or aromatic primary amines led to the formation of the corresponding anils (IIIa-k and IVa-c). The anils (IIIa,f,k or IVa-c) reacted with ethyl cyanoacetate, ethyl acetoacetate, or diethyl malonate to form the respective esters (Va-c or VIa-c). When Va-c or VIa-c were treated with pyridine hydrochloride, demethylation occurred followed by cyclization to form the corresponding furocoumarins (VIIa-c or VIIIa-c). Reduction of the anils using sodium borohydride furnished the corresponding Mannich bases (Xa-d and XI). The antimicrobial activity of compounds IIIi, IVc, Va, VIa, and VIIIa was investigated.

Anti-Bacterial Agents↗
PubMed1977

Reactions of hydroxybenzofurans. VI. Syntheses of benzofuran chalcones, hydrazones and pyrazolines of potential biological activity.

Condensation of 5-acetyl-6-methoxy- (I) and 6-acetyl-5-methoxy-2,3-diphenylbenzofuran (II) with aromatic aldehydes gave the chalcones IIIa--f and IVa--f, respectively. Reaction of the chalcones IIIa--f and IVa--f with hydrazine hydrate-acetic acid mixture yielded the corresponding N-acetyl pyrazolines Va--f and VIa--f. The chalcones IIIa--f and IVa--f reacted with phenylhydrazine in ethanol to yield the corresponding phenylhydrazones VIIa--f and VIIIa--f. The latter hydrazones cyclize easily with boiling glacial acetic acid to the corresponding pyrazoline derivatives (IXa--f and Xa--f). The antibacterial activity of the chalcones and pyrazolines was investigated.

Bacteria↗
PubMed2004

Biological removal of methanol from process condensate for the purpose of reclamation.

The biological removal of methanol from condensate of ammonia manufacturing processes for the purpose of reclamation using contact type reactor was studied. Methanol of 60 mg/L was removed completely under an HRT of 1.12 h. Optimal inorganic nutrient dose was determined on evaluating methanol removal performance and dehydrogenase activities (DHA) under different nutrition doses. The optimal inorganic nutrient dose only gave an increase of conductivity of ca. 10 micros/cm2 in the effluent on treating synthetic condensate containing methanol of 30 mg/L. The results demonstrated that biological removal of methanol was effective for the purpose of recovering the methanol-bearing condensate.

Ammonia↗