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971.
Zinc is a multi-functional element that is found in almost 300 enzymes where it performs catalytic, co-catalytic, and/or structural
functions. In 1982, Gordon et al. (Am J Clin Ntr 35:849–857, 1982) found that a low zinc diet caused poor platelet aggregation
and increased bleeding tendency in adult males. This fact drew interest to the role of zinc in blood clotting. It has been
shown that hyperzincemia predisposes to increased coagulability, and hypozincemia to poor platelet aggregation and increased
bleeding time. The blood clotting disturbances can be regressed by appropriate zinc intake management. Considering the importance
of zinc as an essential element, its participation in regulation of the equilibrium between pro- and anti-thrombotic factors
originating in platelets and endothelium prompted further investigations. 相似文献
972.
Edyta Skrzypek Ilona Czyczyło-Mysza Izabela Marcińska Maria Wędzony 《Plant Cell, Tissue and Organ Culture》2008,94(2):131-137
Anthers cultures of six Polish cultivars of pasture lupin (Lupinus L.) were examined for their androgenic response. Anthers with microspores at the uninucleate stage were isolated from flower
buds and cultured in liquid media. Better viability of androgenetic structures was obtained when donor plants had grown under
field as opposed to greenhouse conditions. A density of five anthers per 0.5 ml medium was more conducive to androgenetic
induction than 25 anthers per 0.5 ml medium. Addition of 5% maltose to the induction medium and culture at 25°C without pre-treatment
of flowers, buds or anthers promoted microspore release and division. The greatest frequency of androgenic callus, ~70% was
developed from cvs. Katon, Wat (white lupin), in contrast to cvs. Legat, Juno (yellow lupin), Polonez and Sonet (narrow-leafed
lupin) with callus induction ~30–40%. Despite various combinations of media tested, plant regeneration was not obtained from
anther derived callus. 相似文献
973.
Guranowski A Wojdyła AM Pietrowska-Borek M Bieganowski P Khurs EN Cliff MJ Blackburn GM Błaziak D Stec WJ 《FEBS letters》2008,582(20):3152-3158
We show here that Fhit proteins, in addition to their function as dinucleoside triphosphate hydrolases, act similarly to adenylylsulfatases and nucleoside phosphoramidases, liberating nucleoside 5'-monophosphates from such natural metabolites as adenosine 5'-phosphosulfate and adenosine 5'-phosphoramidate. Moreover, Fhits recognize synthetic nucleotides, such as adenosine 5'-O-phosphorofluoridate and adenosine 5'-O-(gamma-fluorotriphosphate), and release AMP from them. With respect to the former, Fhits behave like a phosphodiesterase I concomitant with cleavage of the P-F bond. Some kinetic parameters and implications of the novel reactions catalyzed by the human and plant (Arabidopsis thaliana) Fhit proteins are presented. 相似文献
974.
Małkowski A Sobolewski K Jaworski S Bańkowski E 《Molecular and cellular biochemistry》2008,311(1-2):137-143
Our previous study reported that TGF-β may be isolated from human Wharton’s jelly (WJ) in a form of soluble, high molecular
complex(es). We decided to study the effect of extracellular matrix degradation and reduction of disulphide bridges reduction
on the release of TGF-β from WJ. The WJ prepared from the umbilical cords of newborns delivered at term by healthy mothers
was homogenised and treated with hyaluronidase, collagenase, heparinase, chondroitinase and β-mercaptoethanol, the resulting
extracts were then submitted to TGF-β immunoassay and SDS/PAGE followed by Western immunoblotting. The effect of metalloproteinase
activation on TGF-β was also studied. Pre-treatment of WJ homogenates with hyaluronidase or collagenase markedly increased
the extractability of TGF-β, but did not dissociate the complexes. In contrast, the action of β-mercaptoethanol resulted in
the release of free TGF-β; but activation of metalloproteinases resulted in the disappearance of this factor. We conclude
that TGF-β1 is bound through disulphide bonds to an extracellular matrix component of WJ. The large amount of collagen fibrils
and hyaluronate molecules which surround the cells scattered in WJ may prevent the access of extracting solution to TGF-β
causing a low extractability of this factor. Although hyaluronate and collagen do not bind TGF-β directly, they may present
a barrier that prevents the diffusion of TGF-β in WJ and results in its concentration around the cells thereby facilitating
its interaction with membrane receptors and subsequent stimulation of cell division and synthesis of extracellular matrix
components. 相似文献
975.
Masłyk M Kochanowicz E Zieliński R Kubiński K Hellman U Szyszka R 《Molecular and cellular biochemistry》2008,312(1-2):61-69
Since Svf1 is phosphoprotein, we investigated whether it was a substrate for protein kinase CK2. According to the amino acid
sequence Svf1 harbours 20 putative CK2 phosphorylation sites. Here, we have reported cloning, overexpression, purification
and characterization of yeast Svf1 as a substrate for three forms of yeast CK2. Svf1 serves as a substrate for both the recombinant
CK2α (K
m 0.35 μM) and CK2α′ (K
m 0.18 μM) as well as CK2 holoenzyme (K
m 1.1 μM). Different K
m values argue that CK2β(β′) subunit has an inhibitory effect on the activity of both CK2α and CK2α′ towards surviving factor
Svf1. Reconstitution of α′2ββ′ isoform of CK2 holoenzyme shows that β/β′ subunits have regulatory effect depending on the kind of CK2 catalytic subunit.
This effect was not observed in the case of α2ββ′ isoform, which may be due to interaction between Svf1 and regulatory CK2β subunit (shown by co-immunoprecipitation experiments).
Interactions between CK2 subunits and Svf1 protein may have influence on ATP as well as ATP-competitive inhibitors (TBBt and
TBBz) binding. CK2 phosphorylates up to six serine residues in highly acidic peptide K199EVIPESDEEESSADEDDNEDEDEESGDSEEESGSEEESDSEEVEITYED248 of the Svf1 protein in vitro. Presented data may help to elucidate the role of protein kinase CK2 and Svf1 in the regulation
of cell survival pathways. 相似文献
976.
Zgoła-Grześkowiak A Grześkowiak T Zembrzuska J Frańska M Frański R Lukaszewski Z 《Biodegradation》2008,19(3):365-373
Aerobic biodegradation of tripropylene glycol (PG3) was investigated under the conditions of the OECD screening test 301E
and the Continuous Flow Activated Sludge Simulation test (CFAS). A modified two-chamber facility with a denitrification stage
was used for the CFAS test. Primary PG3 biodegradation was measured by the HPLC with fluorimetric detection and analyte derivatisation.
Metabolites were identified by LC-MS with electrospray ionisation and GC-MS with electron impact ionisation, as well as semiquantitatively
determined by the LC-MS technique. PG3 was found to be inherently biodegradable and it exhibits a strong poisonous effect
on activated sludge after exceeding the threshold concentration (10 mg l−1). Metabolite accumulation onto the activated sludge is probably responsible for this poisonous effect. Probable biotransformation
products of tripropylene glycol under the aerobic conditions include metabolites with a single terminal aldehyde or a ketone
group and metabolites with two terminal aldehyde or ketone groups. Their concentration rises at the end of the OECD screening
test. 相似文献
977.
Valery A. Isidorov Paweł Lech Anna Żółciak Magdalena Rusak Lech Szczepaniak 《Trees - Structure and Function》2008,22(4):531-542
An investigation was carried out of the composition of metabolites in pine seedlings tissues at the initial stages of the
infectious process caused by pathogenic fungi Armillaria ostoyae, which causes a root rot of trees and degradation of forest resources. With the help of successive extraction with organic
solvents of different polarity, more than 190 metabolites were extracted from the needles and roots of the seedlings and then
identified by GC–MS method. The composition of the extracts from control plants and those inoculated with Armillaria ostoyae were compared. It was established that part of secondary metabolites (glucosamines and free amino acids, carbohydrates raffinose
and trehalose) were present only in the tissues of inoculated plants. Possible roles of some of these compounds appearing
in the roots of seedlings infected with the fungus are also discussed in the paper. 相似文献
978.
Arabski M Gwoździński K Sudak B Kaca W 《Zeitschrift für Naturforschung. C, Journal of biosciences》2008,63(5-6):460-468
The effects of O33 and O49 P. mirabilis lipopolysaccharides (LPSs) on human erythrocyte membrane properties were examined. Physical parameters of the plasma membrane, such as membrane lipid fluidity, physical state of membrane proteins, and osmotic fragility, were determined. The fluidity of the lipids was estimated using three spin-labeled stearic acids of doxyl derivatives: 5-doxylstearic acid, 12-doxylstearic acid, and 16-doxylstearic acid. All the applied labels locate to different depths of the lipid layer and provide information on the ordering of phospholipid fatty acyl chain mobility. LPSs O49 increased the membrane lipid fluidity in the polar region of the lipid bilayer as indicated by spin-labeled 5-doxylstearic acid. An increase in fluidity was also observed in the deeper region using 12-doxylstearic acid only for O33 LPSs. The highest concentration of O33 LPSs (1 mg/ml) increased the motion of membrane proteins detected by the spin-label residue of iodoacetamide. These results showed different actions of O33 and O49 LPSs on the plasma membrane due to the different chemical structures of O-polysaccharides. P. mirabilis O33 and O49 LPSs did not induce changes in the membrane cytoskeleton, osmotic fragility and lipid peroxidation of erythrocytes. On the other hand a rise in the content of carbonyl compounds was observed for the highest concentrations of O33 LPS. This result indicated protein oxidation in the erythrocyte membrane. Lipid A, the hydrophobic part of LPS, did not change the membrane lipid fluidity and osmotic fragility of erythrocytes. Smooth and rough forms of P. mirabilis LPSs were tested for their abilities for complement-mediated immunohemolysis of erythrocytes. Only one out of seven LPSs used was a potent agent of complement-mediated hemolysis. It was rough, Ra-type of P. mirabilis R110 LPS. The O-polysaccharide-dependent scheme of reaction is presented. 相似文献
979.
Understanding chlorophylls: central magnesium ion and phytyl as structural determinants 总被引:1,自引:0,他引:1
Fiedor L Kania A Myśliwa-Kurdziel B Orzeł Ł Stochel G 《Biochimica et biophysica acta》2008,1777(12):1491-1500
Phytol, a C20 alcohol esterifying the C-17(3) propionate, and Mg2+ ion chelated in the central cavity, are conservative structural constituents of chlorophylls. To evaluate their intramolecular structural effects we prepared a series of metal- and phytyl-free derivatives of bacteriochlorophyll a and applied them as model chlorophylls. A detailed spectroscopic study on the model pigments reveals meaningful differences in the spectral characteristics of the phytylated and non-phytylated pigments. Their analysis in terms of solvatochromism and axial coordination shows how the central Mg and phytyl residue shape the properties of the pigment. Surprisingly, the presence/absence of the central Mg has no effect on the solvatochromism of (bacterio)chlorophyll pi-electron system and the hydrophobicity of phytyl does not interfere with the first solvation shell of the chromophore. However, both residues significantly influence the conformation of the pigment macrocycle and the removal of either residue increases the macrocycle flexibility. The chelation of Mg has a flattening effect on the macrocycle whereas bulky phytyl residue seems to control the conformation of the chromophore via steric interactions with ring V and its substituents. The analysis of spectroscopic properties of bacteriochlorophyllide (free acid) shows that esterification of the C-17(3) propionate is necessary in chlorophylls because the carboxyl group may act as a strong chelator of the central Mg. These observations imply that the truncated chlorophylls used in theoretical studies are not adequate as models of native chromophores, especially when fine effects are to be modeled. 相似文献
980.
Czogalla A Grzymajło K Jezierski A Sikorski AF 《Biochimica et biophysica acta》2008,1778(11):2612-2620
The region of beta-spectrin that is responsible for interactions with ankyrin was shown to comprise an ankyrin-sensitive lipid-binding site. Structural studies indicate that it exhibits a mixed 3(10)/alpha helical conformation and is highly amphipathic. These features together with the distinctively conserved sequence of the lipid-binding site motivated us to explore the mechanism of its interactions with biological membranes. A series of singly and doubly spin-labeled erythroid beta-spectrin-derived peptides was constructed, and the spin-label mobility and spin-spin distances were analyzed via electron paramagnetic resonance spectroscopy and two different calculation methods. The results indicate that in beta-spectrin, the lipid-binding domain, which is part of the 14(th) segment, has the topology of typical triple-helical spectrin repeat. However, it undergoes significant changes when interacting with phospholipids or detergents. A mechanism for these interactions is proposed in this paper. 相似文献