The littoral zone of shallow water bodies in the Czech Republic has been studied quite consistently at several fishponds. The use of algae, especially diatoms, for the monitoring of the state of lotic freshwater also has a long tradition. The main objective of the presented paper is to validate the feasibility of the use of littoral periphyton comunities for the biomonitoring of standing waters. At the investigated sites, littoral periphytic diatoms were studied together with selected enviromental variables (pH, conductivity, nutrients – especially total phosphorus) on three types of natural substrates (epilithon, epiphyton, epipelon). The evaluation of the diatom community was performed on the basis of the checklists of algal indicator species published by authors from the Czech Republic, Austria and the Netherlands. The data were subjected to statistical software NCCS 2000 (GLM Anova and ``Ward's minimum'' variance cluster analysis). Littoral periphytic diatoms appear to be good indicators of the fishpond water quality. The selected substrates show non-significant differences therefore the average values from all substrates were used. The best indicatory system for evaluation of Czech fishponds was van Dam's index.
Summary NMR pulse sequences for measuring coupling constants in 13C, 15N-labeled proteins are presented. These pulse sequences represent improvements over earlier experiments with respect to resolution and number of radiofrequency pulses. The experiments are useful for measuring JNH, JNCO, JNC, JHNCO and JHNH. Applications to chymotrypsin inhibitor 2 (CI-2) are shown. 相似文献
The staining mechanism of van Gieson's picrofuchsin was studied by use of simple protein model systems and tissue sections, and by spectrophotometry and dialysis experiments. At the endpoint of the staining reaction (equilibrium) cytoplasm is yellow. Dye dilution experiments demonstrated that the highest affinity in the tissue section — picrofuchsin system is between binding sites in cytoplasmic protein and acid fuchsin. Nevertheless sections that were first stained in acid fuchsin (AcF) and then in picrofuchsin ended up with cytoplasm stained yellow. It was concluded that differences in the dye diffusion rates and differences in the permeability of tissue components cannot be invoked to explain the differential staining result. Model experiments with dissolved proteins demonstrated a positive relationship between protein concentration and uptake of picric acid (PA) from picrofuchsin. From this and experiments with additives (sodium dodecylsulphate, urea etc.) and organic solvents, it is proposed that coagulant interchain cross-linking at the high protein concentration of the cytoplasm masks potential dye-binding sites. This affects high affinity dyes with multiple binding sites more than small dyes, and so puts AcF at a disadvantage compared to PA. Staining of non-collagen proteins is mainly by hydrophobic bonding, involving ionic attractions, apolar bonds, and release of water. This mode of binding is relatively strong, decreases swelling and leads to slow dye exchange. Dye binding to collagen is mostly by hydrogen bonds, but in aqueous dye solvent nonpolar residues and charged residues may also participate. This structure remains relatively open during and after dye-binding, and the bound dye ions are therefore easily exchanged for other dye ions.
Address at which the main part of the investigation was carried out 相似文献
During the production by mammalian cells of recombinant factor VIII from which the B domain was deleted (rFVIII), proteolytic
cleavages in the C-terminal part of the heavy chain were observed (Kjalke et al., 1995). By radioactive pulse labelling it
was investigated whether the cleavages took place inside the cells during protein synthesis or after release in the medium.
The rFVIII-producing CHO (Chinese hamster ovary) cells were cultured in the presence of 35S-methionine and then the cell lysate and the conditioned media were immunoprecipitated and analyzed by electrophoresis. By
pulse labelling and chasing for various time periods, it was shown that the cleavages only took place after secretion of the
protein from the cells. Adding cell lysate to uncleaved rFVIII caused cleavage of the heavy chain, as seen by loss of binding
to a monoclonal antibody specific for intact rFVIII, indicating that the cleavage was performed by proteinase(s) released
from the lysed cells. By incubating intact rFVIII with the multicatalytic proteinase (proteasome) present in cytoplasm and
nucleus of eukaryotic cells, loss of binding to the monoclonal antibody was observed. This indicates that the multicatalytic
proteinase, released from lysed rFVIII producing cells, could be responsible for the cleavage of rFVIII. Among several protease
inhibitors tested, only bacitracin was found to diminish the extent of cleavage. Phosphatidylserine also protected rFVIII
against cleavage, probably by binding to rFVIII.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
Prostaglandins of the E-type (PGE's) were found to react or combine with a urinary metabolite of Halothane yielding products which left unrecovered during the purification procedure preceeding specific radioimmunoassay of PGE2. The products were retained on sephadex LH-20 columns, and showed on thin layer silica gel plates (TLC) Rf values lower than those of the parent PGE-compounds. The product formation is supposed to involve the β-hydroxyketone system of PGE, since PG's of the F and A type were unaffected. The product formation could be avoided by inducing anaesthesia with Hexobarbitone and maintaining the anaesthesia with Halothane-nitrous oxide or it could be reveresed by adding barbiturates to urine samples obtained from animals anaesthetized with Halothane- nitroux oxide alone. The barbiturates effectively competed with PGE for the metabolite leaving PGE to behave normally on sephadex LH-20 and TLC, thus enabling us to evaluate correctly the PGE2 content by RIA. 相似文献
A structural component of mitotic chromosomes that partially explains the compaction of DNA within mitotic chromosomes is suggested on the basis of the occurrence of long, regular cylindrical structures in preparations of isolated human chromosomes. These structures, unit fibers, of a rather constant diameter of about 4,000 Å have been postulated to be formed by coiling of the 250T2–300 Å solenoid chromatin fiber that itself is formed by coiling of the 100 Å string of nucleosome fiber. The human chromatid would thus be composed by a hierarchy of helices with contraction ratios for DNA at each level of coiling of 7 (string of nucleosomes), 5 (solenoid) and 40 (4,000 Å unit fiber or super-solenoid) which results in an overall contraction ratio for DNA in the unit fiber structures of about 1,400, which is approximately 5-fold less than the final contraction of DNA in intact chromatids of condensed metaphase chromosomes. The present report concerns more detailed studies with respect to the dimensions and cytochemical properties of the unit fiber structures observed in preparations of isolated human mitotic chromosomes that provide direct and indirect evidence in support of their super-solenoid structure and relate to known properties of human mitotic chromosomes. 相似文献