Addition Of Sodium Molybdate Research Articles

Detection of Hydrogen Bubbles Produced by Corrosion Inhibition of Metal Weldment Using Machine Learning

This study analyzes the corrosion inhibition efficiency of sodium molybdate (SM) solution on weldment specimens in 1 M HCl, based on H2 bubbles detection. The detection of the bubbles produced by the corrosion process is achieved by a YOLOv4 deep learning algorithm. The results indicate that the corrosion rate is higher on the weld metal zone than on the base metal zone in the same solution, which might be attributed to the coarser grain of the weld metal zone and the stability of the produced oxide layer. The addition of sodium molybdate was discovered to boost the stability of the oxide layer, hence enhancing the specimens’ corrosion resistance. The overall inhibitory efficiency of the sodium molybdate solution was 59% for the weld metal (WM) (0.4 g/L), 52% for the heat-affected zone (HAZ) (0.2 g/L), and 37% for the base metal (BM) (0.2 g/L). The object detection algorithm models showed 97% for the mAP and 0.98 for recall. The minimum average bubble detected for the WM was 0.353 /mm2 at an SM concentration of 0.4 g/L, while the HAZ was 0.612 /mm2 at 0.2 g/L, and the BM was 1.055 /mm2 at 0.2 g/L. The results of the bubbles detection appeared to be consistent with the corrosion experiment outcomes obtained by the potentiodynamic polarization and hydrogen volume measurement tests. This experiment validates the distinctiveness of the different weld zones in terms of the inhibitor concentration required for successful corrosion prevention, as well as the potential of analyzing corrosion using machine learning algorithms for object detection.

The Blue Molybdenum Reaction for the Determination of Phosphate in Natural Water and Detergent Samples

Background:
 The ideal reaction conditions for the quantitative detection of phosphate in various natural water and detergent samples were carefully researched in order to produce and preserve the colored complex product. The blue complex was identified using a simple and accurate UV-VIS spectrophotometer with a maximum wavelength of 870 nm.
 Even though phosphate is an essential ingredient for the development of aquatic species, it is important to know exactly how much is present because an excess amount of phosphate can eutrophic water. Since detergents are one of the sources of phosphate in natural water, determining the concentration of phosphate in detergent samples is also essential.
 Materials and Methods:
 The method is based on the addition of sodium molybdate, which causes the interaction of orthophosphate with molybdate to produce an intense, stable, and water-soluble phosphomolybdate blue complex. Then, this combination is reduced using hydrazine hydrate in a sulfuric acid solution.
 Results:
 With a correlation coefficient of 0.9944, the system complies with Lambert-Beer's law at 870 nm in a concentration range of (0.05-9) ppm. Molar absorptivity was determined to be 12.16x103 L mol-1 cm-1 and Sandell's sensitivity was found to be 0.0156 g cm-2. Water samples were collected from Warte, Choman, Jundeyan, and Bexal in Kurdistan's vicinity of Soran. Further, detergent samples that were obtained from the market and their phosphate level were examined. The Bexal waterfall had the lowest concentration of phosphate, 0.18 ppm, while the Warte and Jundeyan water samples had the highest concentrations, 3.31 ppm, and 3.04 ppm, respectively. Moreover, similar phosphate concentrations in the two detergent samples were discovered to be at 20.43 and 24.76 ppm.
 Conclusion:
 The molybdenum blue reaction has been successfully employed to provide a sensitive and quick measuring method to quantify the phosphate content in various water and detergent samples using UV-VIS spectrophotometry by applying the right reaction conditions and reagent quantities.

Surface properties of AZ91 magnesium alloy after PEO treatment using molybdate salts and low current densities

Plasma electrolytic oxidation (PEO) process is a recently developed electrochemical method used to produce on the surface of various metals oxide ceramic coatings that improve corrosion and wear properties of the substrate. In this work, PEO process was applied on AZ91 magnesium alloy using low current densities (0.05A/cm2) and an alkaline solution of silicates with different concentrations of sodium molybdate (0.3–3g/l). The effect of the low current densities of process and of molybdate salts on the corrosion resistance of the coatings was studied with potentiodynamic polarization tests and electrochemical impedance spectroscopy (EIS) in chloride and sulfate environment.The morphology, the phases and the chemical composition of the coatings were examined using a scanning electron microscope equipped with EDS, X-ray diffraction, secondary ion mass spectrometry and X-ray photoelectron spectroscopy.The corrosion properties of the PEO coated samples were remarkably improved if compared with the uncoated samples. The addition of sodium molybdate, in determinate conditions, had a positive effect on the characteristics of the coatings in terms of corrosion resistance.

Corrosion Inhibition of Self-assembled Monolayer of Phytic Acid for HAl77-2 Brass

The effect of phytic acid concentration, self-assembling time and concentration of sodium molybdate on the corrosion inhibition of the selfassembled monolayer of phytic acid for HAl77-2 brass was investigated by using potentiodynamic polarization curves, electrochemical impedance spectroscopy (EIS) and dezincification factor analysis etc. The results showed that with the increase of phytic acid concentration, the corrosion current density of HAl77-2 brass decreased first and then increased; with the increase of assembling time, the phytic acid layeron HAl772 brass became denser, however with further increase of time (for example upto 16 h), the self-assembled layer of phytic acid turned to be aged and spalled off, correspondingly, the corrosion current density increased and the impedance arc radius decreased for the brass electrode. The corrosion inhibition of the phytic acid on HAl77-2 brass was significantly increased with the addition of sodium molybdate. Besides, the synergistic action of phytic acid and sodium molybdate can weaken the dezincification of brass obviously. These results provide theoretical support for the application of 定稿日期:2014-09-21 基金项目:国家科技支撑计划项目 (2013BAJ09B04)资助 作者简介:宋芳,女,1988年生,硕士生 通讯作者:陈友媛,E-mail:youyuan@ouc.edu.cn,研究方向为地下水资源利用 DOI:10.11902/1005.4537.2014.176

Functional activity of the modA 2 gene in Methylobacterium dichloromethanicum DM4

The putative METDI2644 (modA2) gene of Methylobacterium dichloromethanicum DM4, present in the 126-kbp chromosomal fragment associated with dichloromethane (DCM) degradation was investigated. While this gene is presumed to encode the periplasmic substrate-binding subunit of the molybdate ABC transporter, its conceptual translation also exhibits similarity to the proteins containing the ostA conservative domain and responsible for resistance of gram-negative bacteria to organic solvents. Reverse transcription polymerase chain reaction (RT-PCR) revealed the RNA transcripts of this gene in the cells grown on either DCM or methanol. The mobilizable suicide vector pK18mob was used to obtain a knockout mutant with the METDI2644 gene inactivated by insertion of the gentamycin cassette. The mutant pregrown on methanol exhibited lower growth rate on DCM than the wild-type strain DM4. The difference was not alleviated by addition of sodium molybdate. Our results suggest that the METDI2644 gene product plays a role in cell adaptation to DCM degradation.

Nutrient enrichment in tropical wetlands: shifts from autotrophic to heterotrophic nitrogen fixation

We used established long-term experimental P-amended plots in freshwater marshes of northern Belize to determine the impact of P input on nitrogen (N) fixation. Marshes with different conductivities and sulfate concentrations were selected to elucidate the effect of salinity and the contribution of sulfur reducing bacteria to the overall N fixation. Rates of N fixation in sediment, roots, and cyanobacterial mats was measured in laboratory incubation experiments (acetylene reduction assay calibrated by 15N2 reduction assay) with and without the addition of sodium molybdate (sulfur reducing bacteria inhibitor). P has increased macrophyte primary production significantly, which led to the rapid elimination of cyanobacterial mats and the elimination of autotrophic N fixation. P addition enhanced heterotrophic N fixation in both the sediments and rhizosphere due primarily to increased C supply to the sediment. When expressed on a dry weight basis, root associated N fixation was higher than sediment N fixation, but the contribution of the root associated fixation to the total N fixation was small when expressed per square meter. Sulfur reducing bacteria were an important component of N fixation, contributing from 20 to 53% to the overall N fixation. A simple N budget was created to determine if N demands are met following P addition. The heterotrophic N fixation substituted in part for autotrophic cyanobacterial N fixation when P limitation was alleviated.

Influence of molybdate species on the tartaric acid/sulphuric acid anodic films grown on AA2024 T3 aerospace alloy

AA2024 T3 alloy specimens have been anodised in tartaric acid/sulphuric media and tartaric acid/sulphuric media containing sodium molybdate; molybdate species were added to the anodising bath to enhance further the protection provided by the porous anodic film developed over the macroscopic alloy surface. Morphological characterisation of the anodic films formed in both electrolytes was undertaken using scanning electron and transmission electron microscopies; the chemical compositions of the films were determined by Rutherford backscattering spectroscopy that was complemented by elemental depth profiling using rf-glow discharge optical emission spectrometry. The electrochemical behaviour was evaluated using potentiodynamic polarisations and electrochemical impedance spectroscopy; the corrosion performance was examined after salt spray testing. The porous anodic film morphology was little influenced by the addition of molybdate salt, although thinner films were generated in its presence. Chemical composition of the anodic film was roughly similar; however, addition of sodium molybdate in the anodizing bath resulted in residues of molybdate species in the porous skeleton and improved corrosion resistance measured by electrochemical techniques that was confirmed by salt spray testing.

Nitrogen Fixation in Microbial Mat and Stromatolite Communities from Cuatro Cienegas, Mexico

Nitrogen fixation (nitrogenase activity, NA) of a microbial mat and a living stromatolite from Cuatro Cienegas, Mexico, was examined over spring, summer, and winter of 2004. The goal of the study was to characterize the diazotrophic community through molecular analysis of the nifH gene and using inhibitors of sulfate reduction and oxygenic and anoxygenic photosynthesis. We also evaluated the role of ultraviolet radiation on the diazotrophic activity of the microbial communities. Both microbial communities showed patterns of NA with maximum rates during the day that decreased significantly with 3-3,4-dichlorophenyl-1',1'-dimethylurea, suggesting the potential importance of heterocystous cyanobacteria. There is also evidence of NA by sulfur-reducing bacteria in both microbial communities suggested by the negative effect exerted by the addition of sodium molybdate. Elimination of infrared and ultraviolet radiation had no effect on NA. Both microbial communities had nifH sequences that related to group I, including cyanobacteria and purple sulfur and nonsulfur bacteria, as well as group II nitrogenases, including sulfur reducing and green sulfur bacteria.

Sgt1p Is a Unique Co-chaperone That Acts as a Client Adaptor to Link Hsp90 to Skp1p

Sgt1p is a conserved, essential protein required for kinetochore assembly in both yeast and animal cells. Sgt1p has homology to both TPR and p23 domains, sequences often found in proteins that interact with and regulate the molecular chaperone, Hsp90. The presence of these domains and the recent findings that Sgt1p interacts with Hsp90 has led to the speculation that Sgt1p and Hsp90 form a co-chaperone complex. To test this possibility, we have used purified recombinant proteins to characterize the in vitro interactions between yeast Sgt1p and Hsp82p (an Hsp90 homologue in yeast). We show that Sgt1p interacts directly with Hsp82p via its p23 homology region in a nucleotide-dependent manner. However, Sgt1p binding does not alter the enzymatic activity of Hsp82p, suggesting that it is distinct from other co-chaperones. We find that Sgt1p can form a ternary chaperone complex with Hsp82p and Sti1p, a well characterized Hsp90 co-chaperone. Sgt1p interacts with its binding partner Skp1p through its TPR domains and links Skp1p to the core Hsp82p-Sti1p co-chaperone complex. The multidomain nature of Sgt1p and its ability to bridge the interaction between Skp1p and Hsp82p argue that Sgt1p acts as a "client adaptor" recruiting specific clients to Hsp82p co-chaperone complexes.

MICROBIAL Fe(III) REDUCTION IN ACIDIC MINING LAKE SEDIMENTS AFTER ADDITION OF AN ORGANIC SUBSTRATE AND LIME

To elucidate the role of Fe(III) reduction in mining lake sediments amended with organic substrates, we performed a large (10 m diameter) enclosure experiment in which sediments were amended with Carbokalk, a waste product from sugar industry containing organic carbon and lime. Fe(III) reduction rates were determined monthly by measuring the accumulation of Fe(II) in the sediments in the field. Fe(III) reduction rates were also determined by incubating sediment samples with synthetic Fe(III) oxyhydroxide under in situ temperature in the laboratory. Sulfate reduction was selectively inhibited in the Fe(III) reduction experiments by addition of sodium molybdate. Sulfate reduction was measured by accumulation of reduced inorganic sulfides in the field and by 35S radiotracer using a core injection technique. Sediment incubation and determination of sulfate reduction rates with radiotracer showed that sulfate reduction and direct microbial Fe(III) reduction occured simultaneously in the upper centimeters of the sediments and that both processes contributed to alkalinity generation. However, Fe(III) reduction was the initial process and rates were at least 3.5 fold higher than sulfate reduction rates. The results indicate that the presence of suitable anions for Fe(II) precipitation as carbonate or sulfide is needed in order to prevent loss of potential alkalinity by Fe(II) diffusion and reoxidation in the water column.

Effect of various anionic species on net methane production in flooded rice soils

In a laboratory incubation study, effect of various anions on net methane production in two rice soils (alluvial and acid sulphate) under flooded conditions was examined. Methane production was considerable in alluvial soil and almost negligible in acid sulphate soil, albeit with a higher density of viable methanogens, during 30-day incubation without salts. Sodium salts of hydroxide and phosphate further stimulated methane production in alluvial soil and marginally in acid sulphate soil. But, addition of sodium molybdate, a selective inhibitor of sulphate-reducing bacteria, increased the production of methane in acid sulphate soil. In contrast, nitrite, nitrate, sulphite and sulphate suppressed the production of methane in both soils. Acetate served as an excellent substrate for methanogenesis in alluvial soil, but not in acid sulphate soil. Succinate and citrate also stimulated methane production especially in alluvial soil, but after a longer lag. In acid sulphate soil, most of the added carbon in the form of sodium salts of carboxylic acids was converted to CO2 and not methane, which is consistent with their preferential use by the sulphate-reducing bacteria. In general, none of the amendments could increase production of methane in acid sulphate soil to the same level as in alluvial soil.

Corrosion inhibition by molybdate/polymaliate mixtures

The inhibition of the corrosion of mild steel in continuously aerated potable water by the addition of sodium molybdate, Na 2MoO 4, was examined by two independent techniques. The first involved the measurement of open circuit potentials of coupons as a function of time till steady-state, constant potentials, E st, were established. The plot of E st as a function of the logarithm of [MoO 4 2−] disclosed consecutive domains of active corrosion, localized (pitting) corrosion and full passivation. The curve did not allow, however, the evaluation of corrosion rates. This information was ascertained from weight loss determination. The rate of corrosion/log [MoO 4 2−] was mirror image of the potential curve. BELGARD EV® (BELEV), a polymeric maleic anhydride preparation used as an anti-scalant, acted in the neutralized state as a moderate adsorption inhibitor affecting anodic sites. Complete surface coverage was ensured in the presence of ca 100 ppm inhibitor in solution. Mixtures of molybdate and BELEV exhibited inhibition synergism. The combined effect of the mixture exceeded the sum produced by the two individual agents. Differences in behaviour was noted between solutions containing low (30 ppm) and high (≥50 ppm) BELEV. The former solutions failed to inhibit corrosion completely whatever the concentration of MoO 4 2− was. With higher BELEV additions inhibition was achieved at definite [MoO 4 2−]/[BELEV] ratios. These were the compositions which raised the metal potential to or above that characterizing a pitting attack in MoO 4 2− solutions only. Visual observation of the metal coupons and test solutions confirmed the above conclusion. Successful mixtures of MoO 4 2− and BELEV could be worked out which ensured complete inhibition and substantial cost savings.

Binding of [3H]triamcinolone acetonide to glucocorticoid receptors in brain cytosol fractions of rats with intact adrenals.

Binding of [3H]triamcinolone acetonide (TA) increased with prolongation of incubation periods of up to 5 h after the onset of incubation at 2 degrees C, with a plateau thereafter persisting for at least up to 48 h in brain cytosol fractions of rats with intact adrenals. Elevation of incubation temperature to 30 degrees C resulted in a marked reduction of the binding at equilibrium which persisted for only 1 to 2 h with complete abolition thereafter. The addition of sodium molybdate was effective in doubling the maximal value at 30 degrees C without markedly affecting the binding at 2 degrees C. [3H]TA binding at equilibrium determined at 2 degrees C was a reversible, saturable and structure selective process with uneven distribution profiles in rat brain. Among a variety of steroid hormones tested, TA was the most potent displacer with progressively less potent displacement by dexamethasone, deoxycorticosterone, progesterone, prednisolone, hydrocortisone and corticosterone. Among discrete brain regions examined, the highest density was detected in the cerebellum followed by the hippocampus, cerebral cortex, midbrain, striatum, hypothalamus and medulla-pons in a rank order of decreasing density. In contrast, both the cerebellum and medulla-pons had significantly higher affinities for [3H]TA than the cerebral cortex. Moreover, the binding was markedly inhibited by Zn2+ ions at 10 microM due to a decrease in the affinity. These results suggest that [3H]TA labels a ligand recognition domain on the cytoplastic glucocorticoid receptor complex with different affinities in rat brain.

The nontransformed progesterone and estrogen receptors in gastric cancer

Contents of the progesterone receptors (PgR) and estrogen receptors (ER) in 18 gastric adenocarcinoma tissues were determined using both the dextran-coated charcoal (DCC) assay and enzyme immunoassay (EIA). PgR were found in 15 cancer tissues (range, 1.0–58.8 fmol/mg protein) and 12 normal mucosal tissues (range, 1.4–26.8 fmol/mg protein) by DCC assay, whereas only 6 cancer tissues (ranged, 0.2–3.3 fmol/mg protein) and 7 normal mucosal tissues (range, 0.1–0.8 fmol/mg protein) had measurable PgR by EIA analysis. Similar results were observed for ER. DCC assay found ER in 12 cancer tissues (range, 2.9–112.6 fmol/mg protein) and 12 normal mucosal tissues (range, 1.2–36.6 fmol/mg protein), whereas EIA measured ER in 16 cancer tissues (range, 0.1–3.5 fmol/mg protein) and 15 normal mucosal tissues (range, 0.1–4.8 fmol/mg protein). No significant correlation between DCC and EIA was observed for either PgR or ER. DCC assay and its modified procedures including 5% DCC stripping of cytosol and/or the addition of sodium molybdate in buffer were simultaneously measured in 5 gastric adenocarcinoma tissues and 1 gastritis cystica polyposa tissue (a precancerous lesion). Higher receptor levels were found by the modified procedures than by conventional method. Using the DCC procedure with addition of sodium molybdate in buffer for receptor analysis, PgR and ER were found in gastric tissues in six patients, with significantly increased levels of measurable PgR. The results suggest that PgR and ER may be involved in the physiology of normal and gastric cancer tissues; their clinical implications are worthy of further study.

Induction of aryl hydrocarbon hydroxylase and demonstration of a specific nuclear receptor for 2,3,7,8-tetrachlorodibenzo- p-dioxin in two human hepatoma cell lines

Two established human hepatoma cell lines, Hep3B and HepG2, were examined for aryl hydrocarbon (benzo[ a]pyrene) hydroxylase (AHH) induction and for the presence of the murine-equivalent aromatic hydrocarbon ( Ah) receptor. Both cell lines demonstrated polycyclic aromatic hydrocarbon (PAH)-induced AHH activity; however, assay conditions for induction were different than those established for the control mouse hepatoma cell line, Hepa c1–9. When cytosols from either cell line were exposed to tritiated 2,3,7,8-tetrachlorodibenzo- p-dioxin ([ 3H]TCDD) and analyzed on sucrose gradients with or without prior charcoal treatment, two peaks were observed at positions corresponding to 4–5 S and 8–9 S. The 8–9 S peak was identified as the probable human Ah receptor equivalent since, like the mouse Ah receptor, this peak: (a) was eliminated only by cytochrome P 1-450 inducers; (b) was sensitive to protease digestion; and (c) was thermolabile. Levels of TCDD specifically bound in the 8–9 S peak for HepG2 and Hep3B were 27 and 34 fmol/mg cytosolic protein respectively. The level of TCDD specifically bound was not affected by charcoal treatment or by the addition of sodium molybdate, which is known to stabilize ligand binding to steroid receptors. Incubation of Hep3B or HepG2 cells with [H]TCDD at 37° for 1 hr effected a redistribution of binding from the cytosol 8–9 S peak to a nuclear 6 S peak. The nuclear peaks from both human cell lines demonstrated similar sedimentation properties, temperature-dependence and inducer-specificity, as for the mouse nuclear Ah receptor. Appearance of nuclear 6 S binding is consistent with a temperature-dependent translocation process, supporting the observation that these human hepatoma cell lines contain a binding component which is similar to the mouse Ah receptor in structure and function during AHH induction.

Molybdate stabilizes soluble [ 3H]dexamethasone binding sites in rat brain tissue in incubations at room temperature (22 °C)

We have described an in vitro procedure for the measurement of glucocorticoid receptor concentrations in soluble fractions prepared from rat brain tissue using a relatively short incubation period of 1 h at room temperature (22 °C). Using [ 3H]dexamethasone as ligand we found that, with the addition of sodium molybdate (Na 2MoO 4) to the buffer, estimates of receptor-binding parameters derived from Scatchard analysis ( K dandB max ) did not differ significantly between assays using 4–5 h incubations at 0–4 °C and those using a 1 h incubation performed at room temperature (22 °C). The use of molybdate was critical; 1 h incubations at 22 °C in the absence of molybdate resulted in a substantial (∼ 65%) loss of [ 3H]dexamethasone binding.

Studies on Estramustine-Binding Protein in the Human Prostate

In the present study, size exclusion HPLC was used to analyse the properties of Estramustine-binding protein (EMBP) in the cytosol of human benign prostatic hypertrophy (BPH). The typical size exclusion HPLC separation profile of 3H-Estramustine-labelled cytosol of BPH showed four radioactive peaks that corresponded to the V0, 250K, 68K and 45K protein regions. The specific binding protein for Estramustine is contained mainly in the 250K protein region and in part in the V0 region. In the presence of sodium molybdate, the specific Estramustine binding to a 250K protein was increased to a level which was about 2.5 times as much as the value in the absence of sodium molybdate. The specific Estramustine binding to a 250K protein under the condition of no DCC treatment and the addition of sodium molybdate was 600% of the value obtained under the condition of DCC treatment and no addition of sodium molybdate. These results suggested that sodium molybdate stabilized the specific Estramustine-binding activity to a 250K protein and that specific Estramustine binding to a 250K protein seemed to be weaker than the binding of androgen to androgen receptor.

The effect of molybdate on the intracellular distribution of estrogen receptor in mammary tumors.

The addition of sodium molybdate (20 mM) to human breast tumor homogenates results in an increased yield of estrogen receptor sites in the cytosol, but reduces the number of sites detectable in salt extracts of purified nuclei. Only about 25% of the increase in cytosol receptor can be accounted for by the loss of nuclear sites. Addition of molybdate to isolated nuclear salt extracts has no inhibitory effect on the estrogen receptor assay, but addition of the oxyanion to the cytosol after separation of the initial nuclear pellet still gives a significant increase in estradiol binding capacity. Furthermore, addition of molybdate to the suspension from the first nuclear pellet still results in loss of binding sites in the nuclear salt extract. This rules out the possibility that the negative effect of molybdate on nuclear receptor recovery is by its inhibition of cytosol receptor activation and translocation during tissue preparation. The number of nuclei isolated from estrogen receptor-containing tumors does not differ significantly in the presence or absence of molybdate. Estrogen receptor-negative tumors however yield fewer nuclei, particularly when they are processed in the presence of molybdate. We conclude that when homogenization of tumors is carried out in the presence of molybdate, a significant fraction of estrogen receptor which would normally be present in purified nuclei is lost, perhaps by leakage through the nuclear membrane.

Rapid changes in specific estrogen binding elicited by cGMP or cAMP in cytosol from human endometrial cells.

Addition of cGMP to cytosol of human endometrium or to cells of the endometrial cancer line HEC-1 produced severalfold increases in specific estrogen binding (EB) levels. This effect was maximal with 1 microM cGMP in the presence of 0.1 mM isobutylmethylxanthine (a phosphodiesterase inhibitor) during incubations with [3H]estradiol. In contrast, cAMP decreased EB levels under similar conditions. The effects of cyclic nucleotides on EB levels were complete in less than 15 min in the presence of Mg2+, Mn2+, or Ca2+. The EB sites generated by the addition of cGMP during labeling of cytosol with 10 nM [3H]estradiol were found to sediment in the 8S and 4S regions of low-salt glycerol gradients. No changes in EB levels were observed when cyclic nucleotides were added to cytosol depleted of ATP by preincubation at 4 degrees C for 3 hr, but responsiveness was restored by addition of exogenous ATP. The ATP requirement and the pattern of dependence of cyclic nucleotide actions on divalent cation concentrations suggest that cGMP and cAMP effects may be mediated by kinases and may involve phosphorylations. Another possibility is that the cyclic nucleotides interact allosterically with the binder in the presence of ATP. Addition of sodium molybdate, ATP, and GTP to homogenates of endometrial tissue or HEC-1 cells produces increases in EB levels similar to those obtained by the addition of cGMP. However, these compounds are much less active when added to cytoplasm or cytosol. On the basis of these and other observations, it is hypothesized that molybdate, ATP, and GTP affect EB levels primarily by increasing cGMP concentrations through processes involving a plasma membrane-bound guanylate cyclase.

Increase in the estrogen binding capacity of breast cancer cytosols following limited proteolysis with trypsin

When small amounts of trypsin were added to prelabelled estrogen receptors in 24 human breast cancer cytosols there was a substantial increase in the binding capacity [79 ± 11 (SE) %]. At the same time the affinity of the hormone receptor interaction was maintained at a very high level or even increased. This finding is discussed in relation to previous results where a diisopropylfluorophosphate (DFP) inhibitable protease activity was shown to cause a similar augmentation of estrogen binding sites in human myometrial cytosols. Addition of sodiummolybdate at or immediately after homogenization led to a similar increase in estrogen binding sites. Because these two effects were not additive we propose that the limited trypsin treatment reactivates the binding sites previously inactivated through a mechanism which can be inhibited by sodiummolybdate.