AG1-X8 Resin Research Articles

DTPA(DOTA)-Nimotuzumab Radiolabeling with Generator-produced Thorium for Radioimmunotherapy of EGFR-overexpressing Carcinomas.

The feasibility of preparing the "in-house" generators and the Th- DTPA(DOTA)-Nimotuzumab radioimmunoconjugate was evaluated. 226Th is perspective for TAT, however, due to short half-life it is preferable to apply this radionuclide for readily available epithelial malignancies. Nimotuzumab being specific for EGFR expressing cells as a targeting moiety is considered to be suitable for thorium delivery. TEVA extraction chromatographic resin and anion exchange resin AG 1x8 were used as sorbents for 226Th generator. In order to determine features of labeling by Th4+ we applied 234Th as a longer-lived analog of short-lived 226Th and the immunoconjugates DTPA(DOTA)-Nimotuzumab were used for radiolabeling. The generator on the base of TEVA resin has shown higher volume activity of the product compared to the AG 1x8. The 226Th volume concentration was up to 80%/mL. The radiolabeling of BFCA by thorium radioisotopes reached 95% at the MR(Th:p-SCN-Bn-DTPA) = 1:100 and 86% for MR(Th:p-SCN-Bn-DOTA) = 1:5000 at 90°C. The procedure of Nimotuzumab labeling with Th4+ for radiotherapy of EGFR-overexpressing carcinomas was established. The overall labeling yield in both radioimmunoconjugates - DTPA and DOTA functionalized - was in the range of 45-50%. The immunoconjugate Nimotuzumab-p-SCN-Bn-DTPA was obtained with a molar ratio 1:25 (Nimotuzumab: BFCA), within 1 hour of conjugation at 25°C and labelled via postconjugation approach. Whereas Nimotuzumab-p-SCN-Bn-DOTA was obtained at the same conditions, but radiolabeled by the method of pre-conjugation. Thorium-234 incorporation into both radioimmunoconjugates reached 45-50%. It has been shown that Th-DTPA-Nimotuzumab radioimmunoconjugate specifically bound with EGFR overexpressing epidermoid carcinoma A431 cells.

Determination of the tungsten isotope composition in seawater: The first vertical profile from the western North Pacific Ocean

The stable isotope ratio of W is a new tracer in oceanographic studies and a new proxy in paleoceanographic studies; however, precise data for modern seawater have not been reported to date. Because the concentration of W in seawater is as low as 49 pmol kg−1, an ~3000-fold preconcentration is necessary prior to measurement by multicollector inductivity coupled plasma mass spectrometry (MC-ICP-MS). For the preconcentration, we investigated solid-phase extraction using chelating resins, namely, NOBIAS Chelate-PA1 with ethylenediaminetriacetic acid groups and TSK-8HQ with 8-hydroxyquinolie groups. We report that TSK-8HQ is useful because the effects of the seawater matrix are minor thermodynamically and kinetically. We present a novel method for analysis of the concentrations and isotope ratios of W and Mo in seawater, consisting of solid phase extraction, chromatographic separation using anion exchange resin AG1 X8, and measurement by MC-ICP-MS. Both W and Mo are quantitatively recovered by this method, which was applied to seawater samples collected from the North Pacific Ocean. The measured concentration of W and the concentration and isotope ratio of Mo are consistent with those in the literature. The isotope ratio of W is found to be uniform throughout the water column in the western North Pacific Ocean; δ186/184W is 0.55 ± 0.12‰ (ave ± 2sd, n = 7) using NIST SRM 3163 as a reference for W. On the basis of this data, we determined that the isotopic difference in δ186/184W is ~0.49‰ between seawater and oxic sediments in the modern ocean. This value accords with the reported experimental data for the isotope fractionation of W during adsorption on manganese and iron (oxyhydr)oxides, suggesting the validity of our data.

Quantification of Tl (I) and Tl (III) based on microcolumn separation through ICP-MS in river sediment pore water.

Thallium (Tl) is a typical toxic element, whose biological effects and geochemical behavior are closely related with its chemical speciation in the environment. In this context, the objective of the present study was to develope an effective method for separation of Tl (I) and Tl (III) based on solid-phase extraction (SPE) using anion exchange resin AG1-X8 as a sorbent and ICP-MS measurement. In this proposed method, Tl (I) and Tl (III) could be separated by selective adsorption of Tl (III)-DTPA in the resin, while Tl (III) was eluted by the solution mixed with HCl and SO2. The validity of this method was confirmed by assays of standard solutions of Tl (I) and Tl (III), as well as with spike of contaminated samples. The present study results revealed that higher concentration of Tl (I) (245.48μg/l) and Tl (III) (20.92μg/l) had been found near the acid mine drainage (AMD) sample of sediment pore water. The results revealed that Tl (I) of 61.47μg/l and Tl (III) of 9.73μg/l were present in the river water contaminated by acid mine drainage. This thallium speciation analysis implied that the dominant Tl (I) species in the river water studied might be due to the weathering of sulfide mineral-bearing rocks, mining, and smelting activities in the studied area.

Precise analysis of the concentrations and isotopic compositions of molybdenum and tungsten in geochemical reference materials

Molybdenum (Mo) is a redox-sensitive element and its concentrations and stable isotope compositions are widely used as a redox proxy in paleoceanography. Tungsten (W) is an emerging new isotope proxy, which has potential as a tracer for hydrothermal and early diagenetic processes. We present a new method for the precise and accurate analysis of Mo and W concentrations and isotope compositions from one single sample aliquot, thus saving mass of a sample and making the results directly comparable without concerns related to analytical or natural sample heterogeneity. After acid digestion, Mo and W are separated from the sample matrix using chelating resin NOBIAS Chelate-PA1 and anion exchange resin AG1 X8. Matrix removal is highly efficient: the remaining percentage is 10−2 to 10−5% with respect to the initial weight. Subsequently, samples are measured for Mo and W concentrations and isotope compositions using multi-collector inductivity coupled plasma mass spectrometry (MC-ICP-MS). For mass bias correction and determination of concentrations, we use standard-sample bracketing and in addition an external correction method employing ruthenium (Ru) for Mo and rhenium (Re) for W. This double correction approach results in an external reproducibility of or below 0.10‰ (2SD) for δ98Mo and 0.05‰ for δ186W based on ICP standard solutions (NIST SRM 3134 lot No. 130418 for Mo and NIST SRM 3163 lot No. 080331 for W). We present data for Mo and W in 12 geological reference materials including igneous rocks, sedimentary rocks, marine sediments, and manganese nodules. For Mo our method reproduces published values for the geological standard materials within analytical error of published values. For W, although published data do not always agree for a given geological standard material, our data agree within error with more recent data. We interpret a cause of the deviations is due to unknown effects of a desolvating nebulizer for MC-ICP-MS.

Study on the removal of interferences for the determination of ⁸⁷Sr/⁸⁶Sr isotopic ratio in petroleum drill-hole water samples using isotope dilution – inductively coupled plasma mass spectrometry (ID – ICP-MS)

87Sr/86Sr isotopic ratio is one of the useful tools that can authenticate the original source of the natural products from the earth-created and/or geological processes. However, the effect of interferences in petroleum drill-holes water sample such as thickness of sample matrix or isotopic signal of 87Rb might cause the low precision of 87Sr/86Sr determination using quadrupole inductively coupled plasma spectrometry (ICP-MS). The elimination of these mentioned effects was thus studied by using the ion - exchange chromatography. Calcium in sample matrix was separated on anionite column (Bio-Rad AG1-X8 resin) in methanol medium with the high efficiency while rubidium was removed from strontium on cation exchange resin (Bio-Rad AG50-X8) with strontium recovery over 99%. The isotope dilution technique with 86Sr - enriched isotopic standard solution was used for the control of separation process. The 87Sr/86Sr isotopic ratio was thus determined using ICP-MS with the signal correction by a strontium isotopic ratio standard reference material (NIST SRM 987).

A modified method of separating Tl(I) and Tl(III) in aqueous samples using solid phase extraction

In spite of the development of new measurement techniques in recent years, the rapid and accurate speciation of thallium in environmental aqueous samples remains a challenge. In this context, a novel method of solid phase extraction (SPE), involving the anion exchange resin AG1-X8, is proposed to separate Tl(I) and Tl(III). In the presence of diethylene triamine pentacetate acid (DTPA), Tl(III) and Tl(I) can be separated by selective adsorption of Tl(III)-DTPA onto the resin, Tl(III) is then eluted by a solution of HCl with SO2. The validity of this method was confirmed by assays of standard solutions of Tl(I) and Tl(III). The proposed method is shown to have an outstanding performance even in solutions with a high ratio of Tl(I)/Tl(III), and can be applied to aqueous samples with a high concentration of other electrolytes, which could interfere with the measurement. Portable equipment and reagents make it possible to use the proposed method routinely in the field.

Reference measurements of cadmium and lead contents in candidates for new environmental certified materials by isotope dilution inductively coupled plasma mass spectrometry

The analytical procedures for the reference measurements of cadmium and lead concentrations in four candidates for new environmental certified reference materials were developed. Cadmium and lead content was determined in bottom sediment (M-2 BotSed), Baltic herring tissue (M-3 HerTis), cormorant tissue (M-4 CormTis) and codfish tissue (M-5 CodTis). The measurements were carried out with the use of a direct isotope dilution inductively coupled plasma mass spectrometry (ID ICP-MS). The isotope dilution approach and the combined uncertainty of results are based on the mathematical equations as from definition of a primary method of measurement. All factors influencing the final results included: the procedural blank, the moisture content in the materials, the factors affecting the blend ratio measurements (instrumental background, spectral interferences, dead time, mass discrimination effects and the repeatability of measured isotopic ratios) as well as the isotopic equilibrium were systematically investigated and included in the uncertainty budget. The content of cadmium in candidates for new environmental reference materials, after correction for moisture contents, matrix separation on ion-exchange resin AG1-X8 of the blended samples and after using for the ICP-MS measurements ratio of pair of isotopes n(110Cd)/n(111Cd) was found to be: (2.18 ± 0.06) μg g−1 in M-2 BotSed, (337 ± 2) ng g−1 in HerTis, (16.4 ± 0.6) ng g−1 in CormTis) and (2.7 ± 0.4) ng g−1 in CodTis, respectively. The content of lead in candidates for new environmental reference materials, after correction for moisture contents, matrix separation on ion-exchange resin AG1-X8 of the blended samples and after using for the ICP-MS measurements ratio of pair of isotopes n(208Pb)/n(207Pb) was found to be: (108 ± 5) ng g−1 in M-3 HerTis, (2.34 ± 0.12) μg g−1 in M-4 CormTis and (43 ± 2) ng g−1 in M-5 CodTis, respectively. The Cd and Pb contents determined in this work were used as a contribution of the Faculty of Chemistry, Biological and Chemical Research Centre University of Warsaw in the characterisation of the abovementioned candidates for new certified reference materials in the frame of the Inter-Laboratory Comparison, organized by the Institute Nuclear Chemistry and Technology (Warsaw, Poland). The obtained excellent agreement within uncertainties with the reference values further validated the methods developed in this study.

Radiochemical Separation and Measurement by Mass Spectrometry with Magnetic Sector with Inductively Coupled Plasma source (ICP-SFMS) of Plutonium Isotopes in Soil Samples

The aim of this work is twofold: to optimize the radiochemical separation of Plutonium (Pu) from soil samples, and to measure the Pu concentration. Soil samples were prepared using acid digestion assisted by microwaves; then, Pu purification was carried out with Pu AG1X8 resin. Pu isotopes were measured using Mass Spectrometry with Magnetic Sector with Inductively Coupled Plasma source (ICP-SFMS). In order to reduce the interference due to the presence of 238UH+ in the samples a desolvation system (Apex) was used. The limit of detection (LOD) of Pu was determined. The efficiency of Pu recovery from soil samples varies from 70 to 93%.

Reference measurements for total mercury and methyl mercury content in marine biota samples using direct or species-specific isotope dilution inductively coupled plasma mass spectrometry

The analytical procedures for reference measurements of the total Hg and methyl mercury (MeHg) mass fractions at various concentration levels in marine biota samples, candidates for certified reference materials (oyster and clam Gafrarium tumidum), were evaluated. Two modes of application of isotope dilution inductively coupled plasma mass spectrometry method (ID ICP-MS), namely direct isotope dilution and species-specific isotope dilution analysis with the use of two different quantification mass spectrometry techniques were compared.The entire ID ICP-MS measurement procedure was described by mathematical modelling and the combined uncertainty of measurement results was estimated. All factors influencing the final results as well as isotopic equilibrium were systematically investigated. This included the procedural blank, the moisture content in the biota samples and all factors affecting the blend ratio measurements (instrumental background, spectral interferences, dead time and mass discrimination effects as well as the repeatability of measured isotopic ratios). Modelling of the entire measurement procedures and the use of appropriate certified reference materials enable to assure the traceability of obtained values to the International System of Units (SI): the mole or the kilogram.The total mass fraction of mercury in oyster and clam biota samples, after correction for moisture contents, was found to be: 21.1 (1.1) 10−9 kg kg−1 (U =5.1% relative, k=2) and 390.0 (9.4) 10−9 kg kg−1 (U=2.4% relative, k=2), respectively. For the determination of mercury being present as methyl mercury, the non-chromatographic separation on anion-exchange resin AG1-X8 of the blended samples was applied. The content of MeHg (as Hg) in oyster sample was found: 4.81 (24) 10−9kgkg−1 (U=5.0%, k=2) and 4.84 (21) 10−9kgkg−1 (U=4.3%, k=2) with the use of quadrupole (ICP QMS) or sector field (ICP SFMS) inductively coupled plasma mass spectrometers, respectively. In the case of clam sample, the concentration of MeHg (as Hg) was found to be: 61.0 (2.3) 10−9kgkg−1 (U=3.8%, k=2) and 61.3 (2.2) 10−9kgkg−1 (U=3.6%, k=2), respectively.The mass fractions for total Hg and MeHg determined in this study were used as a contribution of the International Atomic Energy Agency (IAEA) Environment Laboratories in the characterisation of the IAEA 461 and IAEA 470 certified reference materials. The obtained good agreement with the reference values further validated the methods developed in this study.

Monazite ID-TIMS U-Pb geochronology in the LAGIR laboratory, Rio de Janeiro State University: protocols and first applications to the assembly of Gondwana supercontinent in SE-Brazil

The chemical and spectrometric procedures of the U-Pb geochronology method on monazites, recently installed in the LAGIR laboratory, are described in detail. In addition, preliminary results on monazite samples from the Brasília and Ribeira belts are reported and discussed in the context of the regional geology. Several experiments for calibration of ion exchange chromatographic columns with the AG-1x8 resin, were performed with HCl, using dissolved natural monazite samples. The Pb blanks of reagents are ∼0.5 pg/g in acids and ∼1 pg/g in H2O. The total Pb blanks in chemical procedures were below 22 pg. Preliminary results are presented from three case studies related to Brasiliano orogenic belts of SE-Brazil, which correlate very well with previous age determinations from literature: two sub-concordant grains from an Araxá Group quartzite (southern Brasília belt) define a concordia age of 602.6 ±1.4 Ma; a -0.8% discordant grain from a quartzite of the São Fidelis Group (Costeiro Domain, central Ribeira belt) yielded a concordia age of 535.3 ± 2.4 Ma; two 0.4 % and 1.3 % discordant monazite grains from the post-collisional Itaoca Granite (Costeiro Domain, central Ribeira belt) define a concordia age of 476.4 ± 1.8 Ma.

Determination of weight distribution ratios of Pa(V) and Np(V) with some extraction chromatography resins and the AG1-X8 resin

Literature data on distribution ratios (Dw) of Np(V) and Pa(V) for the AG1-X8 resin are scarce whereas those related on resin capacity factors (k′) values for TEVA, TRU and U/TEVA resins are absent. Therefore, batch extraction experiments for Pa(V) and Np(V) from HCl and HNO3 media were realized, at tracer scale, with AG1-X8 and EIChroM resins (TEVA, TRU and U/TEVA). Based on the new Dw and k′ values obtained in this study, a new protocol for Pa/Np separation has been developed leading to a better separation factor of 105 and a chemical yield of 97±3% and 99±1% for Pa and Np, respectively. A separation of 231Pa from uranium matrix was successfully tested.

Brewers draff as a new low-cost sorbent for chromium (VI): Comparison with other biosorbents

In this study, used brewers draff was investigated as a novel sorbent for Cr(VI) and compared with other biosorbents (grape waste, peat moss, and sawdust). FTIR–ATR, BET analysis, and pHPZC determination were used to characterize the sorbents. Kinetic and equilibrium experiments were performed, and two empirical models, Langmuir and Freundlich, were used to describe Cr adsorption. Additionally, packed bed column experiments were also performed. In order to identify possible reduction processes, ion exchange separation on the AG1-X8 resin was used to separate the anionic Cr(VI) and the reduced cationic Cr(III) from the aqueous phase after biosorption. Cr(VI) removal was pH-dependent and fitted well both the Langmuir and the Freundlich isotherm models. The ion exchange separation showed that Cr(VI) reduction had occurred in the solution during biosorption. The efficiency of draff as a biosorbent was comparable (or even higher) to highly organic materials (e.g., composted peat), showing its potential application for Cr(VI) decontamination.

New low cost sorbents for Cr(VI) – batch and column experiments

The use of agricultural byproducts and industrial biowaste materials has been shown to be an attractive technique for removing Cr(VI) from contaminated waste waters. In this study, used brewers draff, peat moss, sawdust, grape stalks and husks were investigated as novel biosorbents for Cr(VI). The material was tested in two different modifications. The material was dried, cut and sieved and part of it was subjected to acid (2 M H2 SO4 ) and alkali (0.5 M NaOH) pre-treatments to remove starch, proteins and sugars. Fourier transform infrared rays analysis on solid phase (FTIR-ATR) was used to determine the main functional groups that might control the metal uptake. Batch experiments were performed at different pH values (3, 4.5, 6) and at various initial concentration of Cr(VI) (25–2012;250 mg L−1 ). Two equilibrium empirical models, Langmuir and Freundlich, were used to describe Cr(VI) adsorption. In order to identify possible reduction processes, ion exchange separation on the AG1-X8 resin was used to separate the anionic Cr(VI) and the reduced cationic Cr(III) from the aqueous phase after biosorption. As expected, Cr(VI) removal was pH-dependent and fitted well both the Langmuir and Freundlich isotherm models. The ion exchange separation showed that Cr(VI) reduction had occurred in the solution during biosorption. The efficiency of draff as a biosorbent was comparable (or even higher) to highly organic materials (e.g., composted peat) showing its potential application for Cr(VI) decontamination.

A method for dating small amounts of uranium

In this study we describe a method for uranium dating (i.e. determination of the date of the last chemical purification undergone by the material) by measurement of the 230Th/234U ratio, applicable to sub-microgram quantities. The chosen protocol (AG1x8 resin in hydrochloric acid medium) has been tested on separation microcolumns (100 μl). This ‘microchemistry’ technique considerably limits the risks of contamination by reagents or the environment. Thorium extraction efficiencies were greater than 90 % and reproducible. The quantities of 230Th introduced by the chemical purification procedure were negligible. Using an ultra-sensitive inductively coupled plasma mass spectrometry measurement technique, detection limits of the order of femtograms (10−15 g) of 230Th were obtained. The complete procedure, chemical separation and isotope measurement, was successfully tested and validated on a few micrograms of uranium.

Chemical separation of enriched cadmium target from copper backing in cyclotron production of radioisotope 111In

A radiochemical purification procedure was developed for the separation of enriched cadmium (111Cd and 112Cd) from natural copper that used as backing; and was based upon the chromatographic adsorption. The separation of copper from cadmium was studied in this work. The ions were selectively separated from aqueous solution. Ion-exchange chromatography was employed as a column (1.5 cm i.d. and 15 cm length) with AG1-X8 resin (chloride form, 100–200 mesh) and a flow rate of 1–2 ml/min throughout the separation. 6 M HCl media was used for the adsorption of Cd and Cu on the resin. Then, Cu was eluted by 2 M HCl and Cd by 100 ml 0.5 M HNO3. The amount of Cu and Cd ions in the final solution (0.5 M HNO3) were measured by pulse polarographic method and the concentration of Cu was found to be <0.1 ppm. The Cd was quantitatively recovered and the recovery yield from ion-exchange chromatography was greater than 96 %.

A fit-for purpose procedure for lead isotopic ratio determination in crude oil, asphaltene and kerogen samples by MC-ICPMS

Lead isotopic ratios have been used extensively in geological, geochronological, and archaeological studies. However, the classical anion exchange method for Pb isolation/purification using AG1-X8 resin cannot be directly adopted for high content organic samples such as crude oils, due to the fact that the sample matrices probably interact with the active sites in the resin. This results in low percentages of Pb being recovered during column separation and low-level sample purity, therefore affecting the precision of the MC-ICPMS isotopic ratio. For Pb isolation/purification from crude oil samples, at least 0.5 mL of the resin AG1-X8 is required to obtain high Pb recovery without fractioning during the analysis of crude oil. After evaluation of 5 different mass bias correction methods, the combination of Tl normalisation (exponential law) and standard bracketing was selected, providing a precision of 0.0039, 0.0014 and 0.0012 and accuracies (‰) of 0.001, 0.001 and 0.004 for 208/204Pb, 207/204Pb and 206/204Pb isotope ratios, respectively, in the analysis of a solution of 10 ng mL−1 SRM NIST 981 (n = 18). The proposed procedure allows the reliable determination of Pb isotope ratio in crude oil, asphaltene and kerogen samples, important in geochronological studies.

Separation of platinum(IV) and rhodium(III) from acidic chloride solution by ion exchange with anion resins

Ion exchange experiments have been done to separate Pt(IV) and Rh(III) from chloride solution. Loading of the two metals into anion exchange resins, such as AG1-x2, AG1-x8 and AGMP-1 resin, was investigated in the HCl concentration range from 0.1 to 5M. The concentration ratio of Pt and Rh in the chloride solution was fixed at 10:1. It was found that the loading of Pt into the resins followed Langmuir isotherm. The resins employed in this study had selectivity for Pt over Rh. The concentration of HCl had a pronounced effect on the loading of the two metals and Pt was effectively separated from Rh at low concentration of HCl. Batch experiments indicated that AG1-x8 resin was the most effective in separating Pt and Rh in our range. Continuous experiments with AG1-x8 resin verified that complete separation of Pt from Rh was possible. The loaded AG1-x8 resin was successfully regenerated by elution with thiourea.

Separation of Pt from hydrochloric acid leaching solution of spent catalysts by solvent extraction and ion exchange

Leaching of spent catalysts (Pt/Al2O3) with a mixture of HCl and H2O2 results in a mixed chloride solution containing Pt(IV), Fe(III), Al(III), Ni(II), and silicon. Separation of Pt(IV) from the synthetic chloride solution containing Fe(III) and Al(III) has been performed by solvent extraction and ion exchange. Effects of extraction and sorption conditions on the separation of Pt were investigated in the HCl concentration range from 1 to 9M. In solvent extraction experiments, amines (Alamine304-1, Alamine308, Alamine336, Aliquat336), TBP and TOPO were tested, while AG1-x8 resin was employed in ion exchange experiments. Solvent extraction experiments indicated that it was difficult to separate Pt from Fe and Al by amines and solvating extractants in our tested range. In ion exchange by using AG1-x8 resin, only Pt was loaded from the synthetic solution when HCl concentration was lower than 1M, while Fe and Al remained in the solution. Continuous experiments with AG1-x8 resin indicated that most of Pt was loaded onto the resin from 0.5M HCl solution, leaving Fe and Al in the effluent and complete separation of Pt was possible.

The Fifth Transmembrane Domain of Angiotensin II Type 1 Receptor Participates in the Formation of the Ligand-binding Pocket and Undergoes a Counterclockwise Rotation upon Receptor Activation

The octapeptide hormone angiotensin II exerts a wide variety of cardiovascular effects through the activation of the angiotensin II Type 1 (AT(1)) receptor, which belongs to the G protein-coupled receptor superfamily. Like other G protein- coupled receptors, the AT(1) receptor possesses seven transmembrane domains that provide structural support for the formation of the ligand-binding pocket. The role of the fifth transmembrane domain (TMD5) was investigated using the substituted cysteine accessibility method. All of the residues within Thr-190 to Leu-217 region were mutated one at a time to cysteine, and after expression in COS-7 cells, the mutant receptors were treated with the sulfhydryl-specific alkylating agent methanethiosulfonate-ethylammonium (MTSEA). MTSEA reacts selectively with water-accessible, free sulfhydryl groups of endogenous or introduced point mutation cysteines. If a cysteine is found in the binding pocket, the covalent modification will affect the binding kinetics of the ligand. MTSEA substantially decreased the binding affinity of L197C-AT(1), N200C-AT(1), I201C-AT(1), G203C-AT(1), and F204C-AT(1) mutant receptors, which suggests that these residues orient themselves within the water-accessible binding pocket of the AT(1) receptor. Interestingly, this pattern of acquired MTSEA sensitivity was altered for TMD5 reporter cysteines engineered in a constitutively active N111G-AT(1) receptor background. Indeed, mutant I201C-N111G-AT(1) became more sensitive to MTSEA, whereas mutant G203C-N111G-AT(1) lost some sensitivity. Our results suggest that constitutive activation of AT(1) receptor causes an apparent counterclockwise rotation of TMD5 as viewed from the extracellular side.

Separation of the no-carrier-added 109Cd from Ag, Cu and 65Zn by use of a precipitation and AG1-X8 resin

The 109Cd radionuclide was produced in the cyclotron via natAg(p,n)109Cd reaction. The radiochemical separation of 109Cd from silver and non-isotopic impurities comprised of two stages. The optimum conditions of the 109Cd separation methods were: Ag precipitation with 0.015 M HCl and Cu and 65Zn by use of 0.015 M HCl on AG1-X8 strong anion-exchange resin. Chemical and radionuclidic purity of 109Cd were measured by ICP-AES and gamma-ray spectrometry respectively. Recovery yield and radionuclidic purity were obtained 99.7% and 99%, respectively.