Migration of Trivalent Praseodymium from Tombarthite Sewage by Microtubule Ultrafiltration Reactor with Organophosphorus in Fuel Oil.

A microtubule ultrafiltration reactor (MUFR), with an organophosphorus system containing a sewage section with buffer liquid acetic acid and an enrichment section with aqua fortis liquid and organophosphorus dissolved in fuel oil, has been studied for praseodymium(III) migration. Many factors of praseodymium(III) migration using MUFR need to be explored, including hydrogen ion molarity (or pH), cinit of praseodymium(III), the different ionic strengths of rare-earth mine sewage, the volume ratio of organophosphorus fuel oil and aqua fortis liquid (O/A), aqua fortis' molarity, organophosphorus' molarity, and the effects of different acid liquids in the enrichment section on praseodymium(III) migration with MUFR. The virtues of MUFR compared to conventional migration were explored. The effects of the hydrodynamic properties (stability and flow velocity) and UF system parameters (internal diameter of the microtubule, tubule shell thickness, void ratio), etc., on the mass migration performance of the MUFR process for praseodymium(III) migration were also studied. The experimental results show that the best migration prerequisites of praseodymium(III) were obtained as follows: an aqua fortis molarity of 4.00 mol/L, an organophosphorus molarity of 0.200 mol/L, an O/A of 0.6 in the enrichment section, and a pH value of 4.80 in the sewage section. The ionic strength of rare-earth mine sewage had no obvious effect on praseodymium(III) migration. When the cinit of praseodymium(III) molarity was 1.58 × 10-4 mol/L, the migration percentage of praseodymium(III) reached 95.2% in 160 min.

Hexameric to Trimeric Lanthanide-Included Selenotungstates and Their 2D Honeycomb Organic-Inorganic Hybrid Films Used for Detecting Ochratoxin A.

Two types of organic-inorganic hybrid structure-related lanthanide (Ln)-included selenotungstates (Ln-SeTs) [H2N(CH3)2]11Na7[Ce4(H2PTCA)2(H2O)12(HICA)]2[SeW4O17]2[W2O5]4[SeW9O33]4·64H2O (1, H3PTCA = 1,2,3-propanetricarboxylic acid, H2ICA = itaconic acid) and [H2N(CH3)2]6Na4[Ln4SeW8(H2O)14(H2PTCA)2O28] [SeW9O33]2·31H2O [Ln = Pr3+ (2), Nd3+ (3)] were obtained by Ln nature control. The primary frameworks of 1-3 are composed of trivacant Keggin-type [B-α-SeW9O33]8- and [SeW4Om]n- [Ln = Ce3+ (1), m = 17, n = 6; Ln = Pr3+ (2), Nd3+ (3), m = 18, n = 8] fragments bridged by organic ligands and Ln clusters. Intriguingly, Ln nature results in the degradation of hexameric 1 to trimeric 2-3. Besides, 1@DMDSA and 3@DMDSA composites (DMDSA·Cl = dimethyl distearylammonium chloride) were prepared through the cation exchange method, which were then reorganized to form two-dimensional (2D) honeycomb thin films by the breath figure method. Using these honeycomb thin films as electrode materials, the aptasensors were further established by utilizing methylene blue as an indicator and cDNA and Au nanoparticles as signal amplifiers to enhance the response signal so as to realize the purpose of ochratoxin A (OTA) detection. This work provides a new platform for detecting OTA and explores the application potential of POM-based composites in biological and clinical analyses.

Two new lanthanide complexes with 5-(Pyrazol-1-yl)nicotinic acid: Structures and their anti-cancer properties.

Two new lanthanide complexes [PrL2(EA)2]NO3 (complex 1) and [SmL2(EA)2]NO3 (complex 2) (H2L = 5-(Pyrazol-1-yl)nicotinic acid, EA = CH3CH2OH) were synthesized. The structures were characterized by single crystal X-ray and elemental analysis. The interaction between the complex and fish sperm DNA(FS-DNA) was monitored using ultraviolet and fluorescence spectroscopy, and the binding constants were determined. Both complexes showed the ability to effectively bind DNA, and the molecular docking technology was used to simulate the binding of the complex and DNA. In addition, through the annexin V-Fluorescein Isothiocyanate(FITC)/ Propidium Iodide (PI) test experiment, tetrazollium [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide(MTT) in vitro test, and cell morphology apoptosis studies, it was shown that the complex can effectively induce HeLa tumor cell apoptosis. Compared with cisplatin and complex, complex 1 shows significant cancer cell inhibition, and we hope that this new type of complex will open up new ways for the next generation of drugs in biomedical applications.

Praseodymium selective fluorescence recognition based on GdPO4: Tb3+ probe via energy transfer from Tb3+ to Pr3+ ions.

A novel strategy is proposed based on the efficient energy transfer from Tb3+ to Pr3+ for the sensitive and selective discrimination of praseodymium ions due to the matched energy levels of 5D4 (Tb3+) and 3P0 (Pr3+). The electron of Tb3+ transfers from the ground state to the excited state under the excitation of ultraviolet light and relaxes to the 5D4 level. In the presence of Pr3+ the electron has no time to return to the ground state, thus it transfers to the 3P0 level of Pr3+ resulting in the quenching of Tb3+ luminescence. In the case of GdPO4: Tb3+ nanowire, its fluorescence intensity at 545 nm linearly decreased when Pr3+ concentration ranged from 1 × 10-7 to 1 × 10-5 M, and the detection limit was 75 nM. To further investigate the sensing mechanism, CePO4: Tb3+, YPO4: Tb3+, and YBO3: Tb3+ nanoparticles were also synthesized for Pr3+ ion detection. For all materials, similar fluorescence quenching by Pr3+ ions occurred, which confirmed the efficient energy transfer from Tb3+ to Pr3+ ions. Utilizing the matched energy levels of 5D4 (Tb3+) and 3P0 (Pr3+), for the first time, we proposed a novel strategy (taking GdPO4: Tb3+ probe as the example) based on the efficient energy transfer from Tb3+ to Pr3+ for the sensitive and selective discrimination of praseodymium ions.

Synthesis and Characterization of Pyrochlore-Type Praseodymium Stannate Nanoparticles: An Effective Electrocatalyst for Detection of Nitrofurazone Drug in Biological Samples.

Apart from perovskites, the development of different types of pyrochlore oxides is highly focused on various electrochemical applications in recent times. Based on this, we have synthesized pyrochlore-type praseodymium stannate nanoparticles (Pr2Sn2O7 NPs) by using a coprecipitation method and further investigated by different analytical and spectroscopic techniques such as X-ray diffraction, Raman spectroscopy, field emission-scanning electron microscopy, high resolution-transmission electron microscopy, and X-ray photoelectron spectroscopy analysis. Followed by this, we have designed a unique and novel electrochemical sensor for nitrofurazone detection, by modifying the glassy carbon electrode (GCE) with the prepared Pr2Sn2O7 NPs. For that, the electrochemical experiments were performed by using cyclic voltammetry and differential pulse voltammetry techniques. The Pr2Sn2O7 NPs modified GCE exhibits high sensitivity (2.11 µA µM-1 cm-2), selectivity, dynamic linear ranges (0.01-24 µM and 32-332 µM), and lower detection limit (4 nM). Furthermore, the Pr2Sn2O7 NPs demonstrated promising real sample analysis with good recovery results in biological samples (human urine and blood serum) which showed better results than the noble metal catalysts. Based on these results, the present work gives clear evidence that the pyrochlore oxides are highly suitable electrode materials for performing outstanding catalytic activity toward electrochemical sensors.

Nanotized praseodymium oxide collagen 3-D pro-vasculogenic biomatrix for soft tissue engineering.

The current study explores development of highly vascularizable biomatrix scaffold containing rare-earth metal praseodymium oxide nanoadditives for angiogenic and soft tissue regenerative applications. The therapeutic potential of praseodymium oxide nanoparticles rendered excellent endothelial cell differentiation for inducing pro angiogenic microenvironment by eliciting VE-Cadherin expression in the biomatrix scaffold. The nanoparticles were incorporated into bio-macromolecule collagen which aided in stabilization of collagen by maintaining the structural integrity of collagen and showed less susceptibility towards protease enzymes, high cyto-compatibility and high hemo-compatibility. The scaffold provided 3-dimensional micro-environments for the proliferation of endothelial cells and fibroblast cells promoting the wound healing process in an orchestrated fashion. Biological signal modulatory property of rare earth metal is the unexplored domains that can essentially bring significant therapeutic advancement in engineering advanced biological materials. This study opens potential use of nano-scaled rare earth metals in biomaterial application for tissue regeneration by modulating the pro-angiogenesis and anti-proteolysis properties.

Apatite matrix substituted with biologically essential rare earth elements as an artificial hard tissue substitute: Systematic physicochemical and biological evaluation.

Hydroxyapatite (HAP) forms the main inorganic component of natural bone and hence has been widely use in implant applications. Ionic substitutions in apatite also gains enormous interest during the recent years due to the crucial role played by these elements in the biological process. In this context, the least investigated elements namely lanthanum (La3+ ) and praseodymium (Pr3+ ) have been selected as a potential substitutions in apatite. The results from the analytical techniques confirm the phase purity of the HAP and its ability holds the substitutions at its lattice. Morphological analysis unveils the presence of agglomerated spheroids notwithstanding the ion concentration of substituents. EDX spectra affirm the presence of La and Pr alongside the determined Ca/P atomic ratio of 1.67. La3+ and Pr3+ presence envisaged the good antibacterial efficiency against the tested microbes and further demonstrated the biocompatibility nature from the cytotoxicity analysis.

Evaluating the potential risk by probing the site-selective binding of rutin-Pr(III) complex to human serum albumin.

Having reported that rare earth elements displayed potential toxicity in vivo, often be found in soil, plants and etc., which might be easily chelated with the natural functional molecule rutin to form rutin metal complexes, ultimately entering the human body by means of food chain. However, few reports paid the attention on the toxicology of the complexes consisting of rutin with rare earth ions. Here, we focused on the potential toxicity by probing the site-selective binding of the rutin-rare earth ions complexes to human serum albumin (HSA). As a proof-of-concept, we selected Pr3+ as the representative to conjugate with rutin to form rutin-Pr(III) complex, which was further applied to interact with HSA in aqueous solution. The results exhibited that the rutin-Pr(III) complex primary bound to the hydrophobic cavity at site II (subdomain IIIA) of HSA through hydrogen bonding and van der Waals force. Through the thermomechanical analysis, we found this binding process was spontaneous because of the negative ΔG. We believe that this work may offer a new insight into understanding the physiological effects (e.g. toxicology) of rutin and rare earth ions, which could be helpful to guide their rational use in the agriculture and environment-related industries.

One-pot synthesis of cerium and praseodymium co-doped carbon quantum dots as enhanced antioxidant for hydroxyl radical scavenging.

The antioxidant activity of ceria nanoparticles is tightly regulated by size distribution and heteroatom doping. Inspired by this rule, cerium and praseodymium codoped carbon quantum dots (Ce/Pr-CQDs) were synthesized through the one-pot hydrothermal carbonization method. Taking intrinsic advantage of CQDs, the resultant Ce/Pr-CQDs exhibited uniform and ultra-small morphology with an average size of 2.8 nm, which led to an increased proportion of Ce3+. In addition, the doping of Pr into Ce-CQDs improved the redox properties. As we expected, the Ce/Pr-CQDs possessed enhanced hydroxyl radical scavenging properties compared with the cerium-doped carbon quantum dots (Ce-CQDs). Furthermore, Ce/Pr-CQDs with favorable biocompatibility and negligible cytotoxicity are readily internalized into cytoplasm, decreasing the level of reactive oxygen species (ROS). Taken together, the resultant Ce/Pr-CQDs displayed great potential for applications relating to oxidative-stress-associated disease.

Synthesis of Nano-Praseodymium Oxide for Cataluminescence Sensing of Acetophenone in Exhaled Breath.

In this work, we successfully developed a novel and sensitive gas sensor for the determination of trace acetophenone based on its cataluminescence (CTL) emission on the surface of nano-praseodymium oxide (nano-Pr6O11). The effects of working conditions such as temperature, flow rate, and detecting wavelength on the CTL sensing were investigated in detail. Under the optimized conditions, the sensor exhibited linear response to the acetophenone in the range of 15-280 mg/m3 (2.8-52 ppm), with a correlation coefficient (R2) of 0.9968 and a limit of detection (S/N = 3) of 4 mg/m3 (0.7 ppm). The selectivity of the sensor was also investigated, no or weak response to other compounds, such as alcohols (methanol, ethanol, n-propanol, iso-propanol, n-butanol), aldehyde (formaldehyde and acetaldehyde), benzenes (toluene, o-xylene, m-xylene, p-xylene), n-pentane, ethyl acetate, ammonia, carbon monoxide, carbon dioxide. Finally, the present sensor was applied to the determination of acetophenone in human exhaled breath samples. The results showed that the sensor has promising application in clinical breath analysis.

Toxicity response of highly colloidal, bioactive, monodisperse SiO2@ Pr(OH)3 hollow microspheres.

In a facile synthesis, highly colloidal, bioactive Pr(OH)3-encapsulated silica microspheres (PSMSs) with an average diameter of 500-700 nm were successfully prepared via a sol-gel process followed by heat treatment. The phase formation, morphology, surface and optical properties of the as-synthesized PSMSs were characterized by various techniques including X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscope (SEM), transmission electron microscope (TEM), N2-adsorption-desorption, energy dispersive X-ray (EDX) analysis, Fourier transform infrared (FTIR) and UV/vis spectroscopy. The PSMSs were semi-amorphous or ultra-small in size, highly dispersible in water, mesoporous, irregular in size and spherical in shape. The SEM images show a well-ordered broad nanoporous structure which is preserved after coating with Pr(OH)3 molecules, demonstrating interaction between the optically active Pr3+ ion and silanol (Si-OH) groups via hydrogen bonding. Optical spectra show well-resolved weak intensity 4f-4f absorption transitions in the visible region of the Pr3+ ion, indicating successful grafting of the Pr(OH)3 layer. Toxicity was measured by MTT and NRU assays to determine potential toxicity. Cell viability was suppressed with increasing dosage of PSMSs, but showed greater than 55% cell viability at a concentration of 200 µg/mL, resulting in low toxicity. Due to its high aqueous dispersibility, optical activity, excellent biocompatibility and low toxic nature, it could be a favorable material for biomedical and drug delivery applications.

Photo-assisted SCR removal of NO by upconversion CeO2/Pr3+/attapulgite nanocatalyst.

The emission of nitrogen oxides has caused severe harm to the ecosystem; thus, the development of low-cost and high-efficiency denitrification catalysts and new methods are of great significance. In this work, a co-precipitation method was employed to prepare Pr-doped CeO2/attapulgite (CeO2/Pr3+/ATP) nanocomposites. X-ray diffraction (XRD), photoluminance spectroscopy (PL), ultraviolet-visible diffuse reflectance (UV-Vis), Fourier transform infrared (FT-IR), and high-resolution transmission electron microscopy (HRTEM) were utilized to characterize the products. Results showed that the CeO2/Pr3+ nanoparticles were uniformly coated on the surface of ATP and demonstrated outstanding upconversion effect which converted the visible light to ultraviolet light. The upconversion luminescence of CeO2/Pr3+/ATP was strongest when the molar doping amount of Pr was 1 mol%, and the photo-SCR denitrification achieved the highest of 90% conversion and 95% selectivity when the loading amount of CeO2/Pr3+ was 40 wt%. The ATP and CeO2/Pr3+ constructed an indirect Z-type heterojunction structure mediated by oxygen vacancy which benefited the separation of charge carriers and enhanced the reduction-oxidation potentials, both are responsible for the remarkable denitrification performance.

A novel optical approach for determination of prolactin based on Pr-MOF nanofibers.

The analytical quantification and follow-up of the hormone prolactin is very important in clinical diagnosis (e.g., in cases of breast cancer), treatment, and the medical laboratory. The development of a new simple, fast, and less costly method is of considerable importance. Novel praseodymium metal-organic framework nanofibers (Pr-MOF-NFs) were synthesized by a facile and simple method for the determination of human prolactin in serum samples. The Pr-MOF-NFs were well characterized with several spectroscopic tools, such as mass spectrometry, Fourier transform IR spectroscopy, UV-vis spectroscopy, elemental analysis, X-ray diffraction, field-emission scanning electron microscopy combined with energy-dispersive X-ray spectroscopy, and high-resolution transmission electron microscopy. The photoluminescence of Pr-MOF-NFs was investigated, and the results revealed that Pr-MOF-NFs could be used as a sensitive and selective nanofiber optical sensor for the detection of human prolactin. The calibration graph was studied over a wide prolactin concentration range of 0-200 ng/mL, with limits of detection and quantitation of 0.276 and 0.838 ng/mL, respectively, lower than the values mentioned in previous reports. The correlation coefficient was 0.9792. Moreover, the Pr-MOF-NFs were applied successfully for the detection of serum human prolactin at clinically applicable concentrations without interference from several types of hormones and various interfering analytes. Graphical abstract.

Praseodymium Vanadate-Decorated Sulfur-Doped Carbon Nitride Hybrid Nanocomposite: The Role of a Synergistic Electrocatalyst for the Detection of Metronidazole.

The construction of efficient and superior nanostructured materials for the precise determination of contaminants that are hazardous to the environment has gained significant attention by the scientific community. In this regard, we fabricated a nanocomposite consisting of praseodymium vanadate (PrVO4; PrV) anchored to sulfur-doped carbon nitride (PrV/SCN) and applied it to the electrochemical detection of the antibiotic drug metronidazole (MTZ). The structural and crystalline features of the as-prepared PrV/SCN nanocomposite were characterized by various analytical and spectroscopic methods. More distinctly, the PrV/SCN nanocomposite-modified glassy carbon electrode (GCE) exhibits an outstanding linear range (0.001-2444 µM), high sensitivity (1.386 µA/µM cm2), low detection limit (0.8 nM), good reproducibility, and strong anti-interference ability. Notably, the PrV/SCN sensor can determine MTZ in spiked urine and water samples with high recoveries, suggesting its feasibility for real-time applications. Our findings establish PrV/SCN as a robust and promising platform for electrochemical detection. This promotes innovative design for the synthesis of novel functional nanocomposites.

Electronic and fluorescent studies on the interaction of DNA and BSA with a new ternary praseodymium complex containing 2,9-dimethyl 1,10-phenanthroline and antibacterial activities testing.

In this study, fluorescence emission spectra, UV-vis absorption spectra, ethidium bromide (EB)-competition experiment, and iodide quenching experiment were used for the interaction study of the Fish salmon DNA (FS-DNA) with [Pr(dmp)2Cl3(OH2)] where dmp is 2,9-dimethyl 1,10-phenanthroline. The binding constant and the number of binding sites of the complex with FS-DNA were 6.09 ± 0.04 M-1 and 1.18, respectively. The free energy, enthalpy, and entropy changes (ΔG°, ΔH°, and ΔS°) in the binding process of the Pr(III) complex with FS-DNA were -8.02 kcal mol-1, +39.44 kcal mol-1, and +159.56 cal mol-1 K-1, respectively. Based on these results, the interaction process between FS-DNA with [Pr(dmp)2Cl3(OH2)] was spontaneous and the main binding interaction force was groove binding mode. Also, Fluorescence and electronic absorption spectroscopy were used in order to evaluate the binding characteristics, stoichiometry, and interaction mode of praseodymium(III) (Pr(III)) complex with bovine serum albumin (BSA). Title complex showed good binding propensity to BSA presenting moderately high Kb values. The fluorescence quenching of BSA by Pr(III) complex has been observed to be the static process. The positive ΔH° and ΔS° values showed that the hydrophobic interaction is the main force in the binding of Pr(III) complex and BSA. Eventually, the average aggregation number, , of BSA potentially induced by title complex confirmed the 1:1 stoichiometry for title complex-BSA adducts. In vitro, antimicrobial activity of title complex was indicated that the complex is more active against both Escherichia coli and Enterococcus faecalis bacterial strains than Staphylococcus aureus, and Pseudomonas aeruginosa. Communicated by Ramaswamy H. Sarma.

Schiff base rare earth metal complexes: Studies on functional, optical and thermal properties and assessment of antibacterial activity.

We used the condensation chemistry with anthracene­9­carbaldehyde and 3,4­diaminopyridine to form Schiff base (SB) ligand, N2,N3­bis (anthracen­9­ylmethylene) pyridine­3,4­diamine incorporating Er, Pr and Yb rare earth metals to form a series of SB complexes. Surface, structure, thermal, and optical properties of the resulting complexes were investigated using a variety of tools. The characteristic luminescence properties were observed after rare earth metal inclusions in SB. Antibacterial studies were performed against Bacillus subtilis, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa in terms of zone of inhibition for SB complexes. The SB-Pr complexes showed better immune behavior against all the pathogens than the other SB metal complexes.

Dual-photosensitizer coupled nanoscintillator capable of producing type I and type II ROS for next generation photodynamic therapy.

The current photodynamic therapy (PDT) is majorly hindered by the shallow penetration depth and oxygen dependency, limiting its application to deep-seated solid hypoxic tumors. Thus, it is meaningful to develop efficient X-ray mediated PDT system capable of generating reactive oxygen species (ROS) under both the normoxic and hypoxic conditions. Herein, we report the synthesis and characterization of nanocomposite, YAG:Pr@ZnO@PpIX with an amalgamation of UV-emitting Y2.99Pr0.01Al5O12 (YAG:Pr) nanoscintillator, and zinc oxide (ZnO) and protoporphyrin IX (PpIX) as photosensitizers. YAG:Pr surface was coated with a ZnO layer (∼10 nm) by atomic layer deposition, and then PpIX was covalently conjugated via a linker to give YAG:Pr@ZnO@PpIX. The photo- and cathodoluminescence analyses gave the evidences of efficient energy transfer from YAG:Pr to ZnO at ∼320 nm, and YAG:Pr@ZnO to PpIX at Soret region (350-450 nm). The nanohybrid was able to produce both, Type I and Type II ROS upon direct and indirect photoactivation with UV365nm and UV290nm, respectively. In vitro cytotoxicity of non-activated YAG:Pr@ZnO@PpIX in mouse melanoma cells revealed low toxicity, which significantly enhanced upon photoactivation with UV365nm indicating the photokilling property of the nanohybrid. Overall, our preliminary studies successfully demonstrate the potential of YAG:Pr@ZnO@PpIX to overcome the limited penetration and oxygen-dependency of traditional PDT.

Tunable luminescent properties of BaGd2 O4 :Eu3+ scintillating phosphors by Pr3+ -codoping.

BaGd2 O4 :Eu3+ scintillating phosphors by Pr3+ -codoping were synthesized at 1300°C in air using a solid-state reaction method. The as-synthesized phosphors were characterized by X-ray diffraction (XRD), photoluminescence (PL) including excitation and emission spectra, radioluminescence (RL) spectra excited by X-ray and thermoluminescence (TL) spectra. Both the PL and RL spectra are composed of the featured trivalent europium (Eu3+ ) without any praseodymium (Pr3+ ) ions, and the PL and RL intensities as well as the lifetimes of BaGd2 O4 :Eu3+ scintillating phosphors decrease dramatically with an increasing concentration of Pr3+ ions. Finally, the TL spectra reveal the trap concentration of the existing defects decrease with an increasing concentration of Pr3+ ions, while the relative TL intensity ratio of the high temperature band to the low temperature one increases with an increasing concentration of Pr3+ ions, which results in the afterglow suppression of BaGd2 O4 :Eu3+ scintillating phosphors.

Electron transfer dissociation mass spectrometry of acidic phosphorylated peptides cationized with trivalent praseodymium.

The lanthanide ion praseodymium, Pr(III), was employed to study metallated ion formation and electron transfer dissociation (ETD) of 27 biological and model highly acidic phosphopeptides. All phosphopeptides investigated form metallated ions by electrospray ionization (ESI) that can be studied by ETD to yield abundant sequence information. The ions formed are [M + Pr - H]2+ , [M + Pr]3+ , and [M + Pr + H]4+ . All biological phosphopeptides with a chain length of seven or more residues generate [M + Pr]3+ . For biological phosphopeptides, [M + Pr]3+ undergoes more backbone cleavage by ETD than [M + Pr - H]2+ and, in some cases, full sequence coverage occurs. Acidic model phosphorylated hexa-peptides and octa-peptides, composed of alanine residues and one phosphorylated residue, form exclusively [M + Pr - H]2+ by ESI. Limited sequence information is obtained by ETD of [M + Pr - H]2+ with only metallated product ions being generated. For two biological phosphopeptides, [M + Pr + H]4+ is observed and may be due to the presence of at least one residue with a highly basic side chain that facilitates the addition of an extra proton. For the model phosphopeptides, more sequence coverage occurs when the phosphorylated residue is in the middle of the sequence than at either the N- or C-terminus. ETD of the metallated precursor ions formed by ESI generates exclusively metallated and nonmetallated c- and z-ions for the biological phosphopeptides, while metallated c-ions, z-ions, and a few y-ions form for the model phosphopeptides. Most of the product ions contain the phosphorylated residue indicating that the metal ion binds predominantly at the deprotonated phosphate group. The results of this study indicate that ETD is a promising tool for sequencing highly acidic phosphorylated peptides by metal adduction with Pr (III) and, by extension, all nonradioactive lanthanide metal ions.

Luminescence and structural characterization on praseodymium (Pr3+) doped potassium bromide (KBr) single crystals.

The luminescence properties of praseodymium (Pr3+ ) ion in potassium bromide (KBr) host have been investigated. The excitation bands observed in the region 220-300 nm are attributed to the transitions from 4f level to the 5d crystal field splitting levels of Pr3+ ion. Emission bands originated due to transition of 3 P2 →3 H6 (564 nm), 3 P0 →3 H6 (604 nm), 1 D2 →3 P4 (721 nm) and 3 P0 →3 F2 (659 nm) have been observed. Optical absorption, photoluminescence (PL) and thermoluminescence (TL) studies confirms the trivalent state of Pr3+ ion in KBr host. Trap parameters for the TL glow curve have been calculated and the values are tabulated by using Chen's peak shape method. The lattice cell parameters of Pr3+ doped KBr single crystals are a = b = c = 6.596 Å, α = ß = Î³ = 90°. From the scanning electron microscopy (SEM) micrograph analysis, the particle size ranges from a few micrometres to 5 µm. Electron paramagnetic resonance (EPR) spectrum exhibits two resonance signals at magnetic fields of 2895 and 3106 gauss with g-values of 2.32 and 2.16, respectively, calculated using Lande's formula.