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81.
Nataša Tomášková Rastislav Varhač Gabriel Žoldák Lenka Olekšáková Dagmar Sedláková Erik Sedlák 《Journal of biological inorganic chemistry》2007,12(2):257-266
The alkaline isomerization of horse heart ferricytochrome c (cyt c) has been studied by electronic absorption spectroscopy in the presence of the Hofmeister series of anions: chloride, bromide,
rhodanide and perchlorate. The anions significantly affect the apparent pK
a value of the transition in a concentration-dependent manner according to their position in the Hofmeister series. The Soret
region of the absorption spectra is not affected by the presence of the salts and shows no significant structural perturbation
of the heme crevice. In the presence of perchlorate and rhodanide anions, the cyanide exchange rate between the bulk solvent
and the binding site is increased. These results imply higher flexibility of the protein structure in the presence of chaotropic
salts. The thermal and isothermal denaturations monitored by differential scanning calorimetry and circular dichroism, respectively,
showed a decrease in the conformational stability of cyt c in the presence of the chaotropic salts. A positive correlation between the stability, ΔG, of cyt c and the apparent pK
a values that characterize the alkaline transition indicates the presence of a thermodynamic linkage between these conformational
transitions. In addition, the rate constant of the cyanide binding and the partial molar entropies of anions negatively correlate
with the pK
a values. This indicates the important role of anion-induced solvent reorganization on the structural flexibility of cyt c in the alkaline transitions.
Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users. 相似文献
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Despite iodine being one of the most abundant of the minor elements in oxic seawater, the principal processes controlling
its interconversion from iodate to iodide and vice versa, are still either elusive or largely unknown. The two major hypotheses
for iodate reduction involve either phytoplankton growth in primary production, or bacteria during regeneration. An earlier
study intended to exploit the unusual nature of anchialine environments revealed that iodide is oxidised to iodate in the
bottom of such caves, whereas reduction of iodate occurs in the shallower parts of the water column. This investigation was
made on the hypothesis that study of the nitrogen and phosphorus nutrient systems within the caves might offer a bridge between
the iodine chemistry and the marine bacteria which are assumed to be the agent of change of the iodine in the caves. Accordingly,
the hydrography, the nutrient chemistry, and some further iodine studies were made of two anchialine caves on the east coast
of the Adriatic Sea in Croatia. Iodate and iodide were determined by differential pulse voltammetry and cathodic stripping
square-wave voltammetry, respectively. Total iodine was determined indirectly, as iodate, after oxidation of reduced iodine
species with UV irradiation and strong chemical oxidants. Nutrient concentrations were measured by spectrophotometry. Nutrient
profiles within the well stratified water columns indicate a relatively short-lived surface source of nitrate and phosphate
to the caves, with a more conventional, mid-water, nutrient regeneration system. The latter involves nitrite and ammonium
at the bottom of the halocline, suggestive of both autotrophic and heterotrophic microbial activity. High iodate/low iodide
deep water, and conservative behaviour of total inorganic iodine were confirmed in both systems. Iodate is reduced to iodide
in the hypoxic region where nutrient regeneration occurs. The concentrations of organic iodine were surprisingly high in both
systems, generally increasing toward the surface, where it comprised almost 80% of total iodine. As with alkalinity and silica,
the results suggest that this refractive iodine component is liberated during dissolution of the surrounding karst rock. A
major, natural flushing of one of the caves with fresh water was confirmed, showing that the cave systems offer the opportunity
to re-start investigations periodically. 相似文献
84.
Petr Žalud Jiřina Száková Jiřina Sysalová Pavel Tlustoš 《Central European Journal of Biology》2012,7(3):519-530
The contents of cadmium, iron, lead and zinc in the biomass of two species of leafy vegetables after urban particulate matter
(PM) application was investigated in lettuce (Lactuca sativa var. capitata) and chard (Beta vulgaris var. cicla). The experimental design consisted of four variables: i) two different soil types, ii) two vegetables, iii) two size fractions
of contaminated particulate matter (PM) (0.063–0.119 mm, and <0.063 mm), and iv) foliar and soil application of the PM. The
aliquots of the PM samples were applied to the soil before the experiment and as a foliar suspension during plant growth.
The element uptake by plant biomass was significantly higher via foliar application, simulating the atmospheric deposition, than via the roots from the soil application treatment. The content in plants increased rapidly compared to the control treatment
for the elements iron, lead and zinc. Gently washing the leaves only slightly reduced the amounts of Fe and Zn. However, the
majority of Pb was removed by washing with the concentration dropping from 3000% to 500%. The effect of PM application on
Cd contents in plant leaves was negligible, in most cases. Lettuce exhibited higher element uptake compared to chard. No adverse
effects of PM application on growth parameters of the vegetables were observed. No significant differences were reported for
particle size fractions of PM. Fluvisol soils had a higher element uptake via roots than Chernozem soils. Moreover, the addition of PM into the Fluvisol altered the sorption properties of the soil resulting
in a lower Cd uptake by plants growing in PM amended Fluvisols. 相似文献
85.
Valdemaras Žiliukas Vida Žiliukienė Rimantas Repečka 《Central European Journal of Biology》2012,7(5):858-866
The aim of this study was to assess juvenile fish communities in terms of species composition, fish diversity and density in the littoral zone of the Kaunas reservoir before (in 1989–1990, period I) and after (in 1999–2000, period II, and in 2006–2007, period III) launching the Kruonis hydroelectric pumped plant (Kruonis HPP). During the whole research period, 20 fish species were caught. According to the frequency of occurrence, the three-spined stickleback Gasterosteus aculeatus, European perch Perca fluviatilis and roach Rutilus rutilus were regarded as constant species in all investigated periods. Significant differences were established in juvenile fish community density between period I and periods II and III, whereas species richness (S) and species diversity indices (H′, J′) did not change significantly. The density of the shoreline community in period III was more than two times lower than in period I, probably due to higher fluctuations in water level of the reservoir, resulting from the Kruonis HPP operation. 相似文献
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Naugžemys Donatas Lambertini Carla Patamsytė Jolanta Butkuvienė Jurgita Khasdan Vadim Žvingila Donatas 《Hydrobiologia》2021,848(14):3317-3330
Hydrobiologia - Like in many other parts of the world, Phragmites australis distribution and abundance are changing in Lithuania because of the impact of human activities on aquatic habitats. We... 相似文献
89.
Several synthetic plant growth regulators (PGRs), including prohexadione-calcium (ProCa), paclobutrazol (PBZ), and chlormequat
chloride (CCC), known for their ability to inhibit gibberellin (GA) biosynthesis, were investigated for their influence on
Populus tremula L. (aspen) shoots grown in vitro. Changes in plant growth induced by these inhibitors were compared to the effects of exogenous
gibberellins (GA3 and GA4/7). All PGRs were added to the nutrient medium at concentrations of either 1 or 5 μM. Stem segments with and without apical
buds were excised from in vitro-grown shoot culture, and these explants were incubated either in test tubes or Petri dishes.
In the presence of 5 μM ProCa, shoot growth and rooting were inhibited when grown in test tubes, while shoots grown in Petri
dishes exhibited strongly enhanced shoot and root growth. PBZ suppressed shoot development both in test tubes and Petri dishes,
although 1 μM PBZ promoted adventitious root formation when shoots were grown in test tubes. Five micromolars CCC suppressed
shoot and root development in test tubes, but promoted shoot growth in Petri dishes. 相似文献