Facile synthesis of manganese-hafnium nanocomposites for multimodal MRI/CT imaging and in vitro photodynamic therapy of colon cancer

Precise diagnosis of complex and soft tumors is challenging, which limits appropriate treatment options to achieve desired therapeutic outcomes. However, multifunctional nano-sized contrast enhancement agents based on nanoparticles improve the diagnosis accuracy of various diseases such as cancer. Herein, a facile manganese-hafnium nanocomposites (Mn3O4-HfO2 NCs) system was designed for bimodal magnetic resonance imaging (MRI)/computed tomography (CT) contrast enhancement with a complimentary function of photodynamic therapy. The solvothermal method was used to fabricate NCs, and the average size of Mn3O4 NPs and Mn3O4-HfO2 NCs was about 7 nm and 15 nm, respectively, as estimated by TEM. Dynamic light scattering results showed good dispersion and high negative (-33 eV) zeta potential, indicating excellent stability in an aqueous medium. Mn3O4-HfO2 NCs revealed negligible toxic effects on the NCTC clone 929 (L929) and mouse colon cancer cell line (CT26), demonstrating promising biocompatibility. The synthesized Mn3O4-HfO2 NCs exhibit significant enhancement in T1-weighted magnetic resonance imaging (MRI) and X-ray computed tomography (CT), indicating the appropriateness for dual-modal MRI/CT molecular imaging probes. Moreover, ultra-small Mn3O4-HfO2 NCs show good relaxivities for MRI/CT. These nanoprobes Mn3O4-HfO2 NCs further possessed outstanding reactive oxygen species (ROS) generation ability under minute ultraviolet light (6 mW·cm-2) to ablate the colon cancer cells in vitro. Therefore, the designed multifunctional Mn3O4-HfO2 NCs were ideal candidates for cancer diagnosis and photodynamic therapy.

Fluorinated Hafnium and Zirconium Coenable the Tunable Biodegradability of Core-Multishell Heterogeneous Nanocrystals for Bioimaging

Upconversion (UC)/downconversion (DC)-luminescent lanthanide-doped nanocrystals (LDNCs) with near-infrared (NIR, 650-1700 nm) excitation have been gaining increasing popularity in bioimaging. However, conventional NIR-excited LDNCs cannot be degraded and eliminated eventually in vivo owing to intrinsic "rigid" lattices, thus constraining clinical applications. A biodegradability-tunable heterogeneous core-shell-shell luminescent LDNC of Na3HfF7:Yb,Er@Na3ZrF7:Yb,Er@CaF2:Yb,Zr (abbreviated as HZC) was developed and modified with oxidized sodium alginate (OSA) for multimode bioimaging. The dynamic "soft" lattice-Na3Hf(Zr)F7 host and the varying Zr4+ doping content in the outmoster CaF2 shell endowed HZC with tunable degradability. Through elaborated core-shell-shell coating, Yb3+/Er3+-coupled UC red and green and DC second near-infrared (NIR-II) emissions were, respectively, enhanced by 31.23-, 150.60-, and 19.42-fold when compared with core nanocrystals. HZC generated computed tomography (CT) imaging contrast effects, thus enabling NIR-II/CT/UC trimodal imaging. OSA modification not only ensured the exemplary biocompatibility of HZC but also enabled tumor-specific diagnosis. The findings would benefit the clinical imaging translation of LDNCs.

An Immunocompetent Hafnium Oxide-Based STING Nanoagonist for Cancer Radio-immunotherapy

cGAS-STING signaling plays a critical role in radiotherapy (RT)-mediated immunomodulation. However, RT alone is insufficient to sustain STING activation in tumors under a safe X-ray dose. Here, we propose a radiosensitization cooperated with cGAS stimulation strategy by engineering a core-shell structured nanosized radiosensitizer-based cGAS-STING agonist, which is constituted with the hafnium oxide (HfO2) core and the manganese oxide (MnO2) shell. HfO2-mediated radiosensitization enhances immunogenic cell death to afford tumor associated antigens and adequate cytosolic dsDNA, while the GSH-degradable MnO2 sustainably releases Mn2+ in tumors to improve the recognition sensitization of cGAS. The synchronization of sustained Mn2+ supply with cumulative cytosolic dsDNA damage synergistically augments the cGAS-STING activation in irradiated tumors, thereby enhancing RT-triggered local and system effects when combined with an immune checkpoint inhibitor. Therefore, the synchronous radiosensitization with sustained STING activation is demonstrated as a potent immunostimulation strategy to optimize cancer radio-immuotherapy.

Hafnium (Hf)-Chelating Porphyrin-Decorated Gold Nanosensitizers for Enhanced Radio-Radiodynamic Therapy of Colon Carcinoma

X-ray-induced radiodynamic therapy (RDT) that can significantly reduce radiation dose with an improved anticancer effect has emerged as an attractive and promising therapeutic modality for tumors. However, it is highly significant to develop safe and efficient radiosensitizing agents for tumor radiation therapy. Herein, we present a smart nanotheranostic system FA-Au-CH that consists of gold nanoradiosensitizers, photosensitizer chlorin e6 (Ce6), and folic acid (FA) as a folate-receptor-targeting ligand for improved tumor specificity. FA-Au-CH nanoparticles have been demonstrated to be able to simultaneously serve as radiosensitizers and RDT agents for enhanced computed tomography (CT) imaging-guided radiotherapy (RT) of colon carcinoma, owing to the strong X-ray attenuation capability of high-Z elements Au and Hf, as well as the characteristics of Hf that can transfer radiation energy to Ce6 to generate ROS from Ce6 under X-ray irradiation. The integration of RT and RDT in this study demonstrates great efficacy and offers a promising therapeutic modality for the treatment of malignant tumors.

Hafnium carbide nanoparticles for noninflammatory photothermal cancer therapy

Photothermal therapy (PTT) effectively suppresses tumor growth with high selectivity. Nevertheless, PTT may cause an inflammatory response that leads to tumor recurrence and treatment resistance, which are the main disadvantages of PTT. Herein, monodisperse hafnium carbide nanoparticles (HfC NPs) were successfully prepared for noninflammatory PTT of cancer. HfC NPs possessed satisfactory near-infrared (NIR) absorption, good photothermal conversion efficiency (PTCE, 36.8 %) and photothermal stability. Furthermore, holding large surface areas and intrinsic redox-active sites, HfC NPs exhibited excellent anti-inflammatory properties due to their antioxidant and superoxide dismutase (SOD) enzymatic activities. In vitro and in vivo experiments confirmed that HfC NPs converted light energy into heat energy upon NIR laser irradiation to kill cancer cells through PTT and achieved a better therapeutic effect by anti-inflammatory effects after PTT. This work highlights that multifunctional HfC NPs can be applied in noninflammatory PTT with outstanding safety and efficacy.

Construction of type-II scheme SnO@HfC photocatalyst for bisphenol A degradation via peroxymonosulfate activation; DFT and self-cleaning analysis

In this study, novel stannous oxide@hafnium carbide (SnO@HfC) nanocomposite was successfully manufactured by an appropriate hydrothermal scheme which was utilized for the photocatalytic degradation of BPA by stimulation of peroxymonosulfate (PMS) and self-cleaning application. Numerous methods were applied for the characterization of photocatalyst and demonstrated the successful preparation of SnO@HfC nanocomposite. The crystal structures, band structures and density of states for SnO and HfC were explored by DFT analysis. The amazing PMS stimulation performance of SnO@HfC nanocomposite originated from the establishment of a heterojunction, which led to the enhancement of the light response aptitude and the electron conduction competence of the composite. BPA was degraded by 0.75 g/L PMS and SnO@HfC at neutral pH during the period of 60 min. In order to identify active groups in the reaction procedure, quenching experiments and electron paramagnetic resonance (EPR) approaches were also used. In the subsequent active species scavenging assays, where sulfate radicals, hydroxyl radicals, holes, and superoxide radicals were engaged in the degradation of BPA. While, liquid phase mass spectrometry (LC-MS) was used to pinpoint the intermediate metabolites in the course of degradation. SnO@HfC/PMS/light system delivered excellent TOC removal efficiency and less ions leaching. The SnO@HfC nanocomposite proved good durability and reusability in continuous cycle tests along with excellent self-cleaning function on the glass substrate. The SnO@HfC nanocomposite performs admirably in terms of self-cleaning application. The SnO@HfC nanocomposite is expected to be used in the future for the treatment of wastewater that contains pharmaceuticals due to its superior stability and reusability after five consecutive cycles.

Signal "On-Amplified-Off" Strategy Based on Hafnium Dioxide Nanomaterials as Electrochemiluminescence Emitters for Progesterone Detection

When consumed, excess progesterone (P4)─found in food and the environment─can lead to severe illnesses in humans. Therefore, quantitative analysis of P4 is critical for identifying its hazardous levels. In this study, a novel signal "on-amplified-off" P4 detection mode was proposed, which was based on the utilization of hafnium oxide (HfO2) as a unique electrochemiluminescence (ECL) emitter, produced by calcining UiO-66(Hf). This is the first time that HfO2 has been used as an ECL emitter. HfO2 displayed excellent conductivity and a high specific surface area, allowing it to connect with numerous aptamers and produce a "signal-on" effect. Ni-doped ZnO (Ni-ZnO) acted as a coreaction accelerator, enhancing the ECL strength of HfO2 by generating more tripropylamine radicals. cDNA was labeled with Ni-ZnO, and Ni-ZnO was linked to the aptamer via base complementary pairing, affording "signal-amplified". The presence of the target molecule P4 instigated a specific binding process with the aptamer, triggering the shedding of cDNA-Ni-ZnO and resulting in "signal-off". This novel "on-amplified-off" strategy effectively improved the sensitivity and specificity of P4 analysis, introducing a practical method for detecting biomolecules beyond the scope of this study, which holds immense potential for future applications.

Synthesis and X-ray structure analysis of cytotoxic heptacoordinated Salan hafnium(IV) complexes stabilized with 2,6-dipicolinic acid

Four novel Salan Hf^(IV) complexes stabilized by 2,6-dipicolinic acid (Dipic) were synthesized and characterized by ¹H, ¹³C NMR and X-ray diffraction spectroscopy. These Hf^(IV)bis-chelates could be obtained in good to excellent yields (88%-91%) and demonstrated rather good stability in aqueous media and on silica gel. [L₂Hf^(IV)Dipic^4-H,Cl] containing steric bulk L₂ were stable in about 10% H₂O (H₂O/THF (v/v)), however, [L₁Hf^(IV)Dipic^4-H,Cl] with non-steric L₁ could slowly dissociate and release nontoxic L₁. [L_1-2Hf^(IV)Dipic^4-Cl] showed excellent anti-tumoral activity in the range of cisplatin (Hela S3: IC₅₀ = 3.5 ± 0.4 μM, Hep G2: IC₅₀ = 11.2 ± 2.1 μM). In addition, the cellular uptake and apoptosis investigation of [L₁Hf^(IV)Dipic^4-Cl] suggested a fast cellular uptake process against Hela S3 cells with an almost exclusive induced apoptosis cell death path.

Electrodissolution-Coupled Hafnium Alkoxide Synthesis with High Environmental and Economic Benefits

The conventional thermal method of preparing hafnium alkoxides [Hf(OR)₄ , R=alkyl] - excellent precursors for gate-dielectric HfO₂ on semiconductors - is severely hindered by its unsatisfactory environmental and economic burdens. Herein, we propose a promising electrodissolution-coupled Hf(OR)₄ synthesis (EHS) system for green and efficient electrosynthesis of Hf(OR)₄ . The operational principle of the electrically driven system consists of two simultaneous heterogeneous reactions of Hf dissolution and alcohol dehydrogenation, plus a spontaneous solution-based combination reaction. In applying ethanol as solvent and Hf metal as electrodissolution medium, we achieved waste-free production of high-purity hafnium ethoxide [Hf(OEt)₄ ] with an equivalent "a concomitant" reduction in CO₂ emission of 187.33 g CO₂ per kg Hf(OEt)₄ and a high net profit of 30 477 USD per kg Hf(OEt)₄ . This system is very competitive with the thermal process, which unavoidably releases substantial waste and CO₂ for a net profit of 27 700 USD per kg Hf(OEt)₄ . We anticipate that the environmental and economic benefits of the EHS process could pave the way for its practical application.

Wafer-Scale 2D Hafnium Diselenide Based Memristor Crossbar Array for Energy-Efficient Neural Network Hardware

Memristor crossbar with programmable conductance could overcome the energy consumption and speed limitations of neural networks when executing core computing tasks in image processing. However, the implementation of crossbar array (CBA) based on ultrathin 2D materials is hindered by challenges associated with large-scale material synthesis and device integration. Here, a memristor CBA is demonstrated using wafer-scale (2-inch) polycrystalline hafnium diselenide (HfSe₂ ) grown by molecular beam epitaxy, and a metal-assisted van der Waals transfer technique. The memristor exhibits small switching voltage (0.6 V), low switching energy (0.82 pJ), and simultaneously achieves emulation of synaptic weight plasticity. Furthermore, the CBA enables artificial neural network with a high recognition accuracy of 93.34%. Hardware multiply-and-accumulate (MAC) operation with a narrow error distribution of 0.29% is also demonstrated, and a high power efficiency of greater than 8-trillion operations per second per Watt is achieved. Based on the MAC results, hardware convolution image processing can be performed using programmable kernels (i.e., soft, horizontal, and vertical edge enhancement), which constitutes a vital function for neural network hardware.

Accumulation of scandium, cerium, europium, hafnium, and tantalum in oats and barley grown in soils that differ in their characteristics and level of contamination

Up to now, information about biogeochemistry of many trace elements is scarce. Meanwhile, all the elements are always present in soil and plants. It may be suggested that the trace elements also play certain role in the biogeochemical processes. The aim of the research was to study bioaccumulation of poorly investigated trace elements (scandium, cerium, europium, hafnium, and tantalum) and well-known elements (chromium, iron, cobalt, zinc, and arsenic) in two crops, oats and barley, and examine how these elements interact with each other as they absorbed by plants. The plants were grown in the soils that differed in their parameters and in level of contamination. Although oats and barley are botanically similar and were grown under the same conditions, the plants differed in the ability to accumulate many elements. The uptake of the elements by the plants also depended on type of soil. For example, concentrations of Cr, Fe, Co, As, Sc, Ce, Eu, Hf, and Ta in roots of the oats grown in slightly contaminated soil were much higher as compared to the concentrations of the elements in roots of the barley grown in the same soil. In leaves of the oats grown in moderately contaminated soil, the concentrations of Cr, As, Ce, Eu, and Ta were statistically significantly higher than those in leaves of the barley grown in the soil. In soils and in plants, relationships between elements were both similar and different. A statistically significant correlation was found between the poorly investigated trace elements and well-studied elements.

Wide range modulation of synaptic weight in thin-film transistors with hafnium oxide gate insulator and indium-zinc oxide channel layer for artificial synapse application

Wide range synaptic weight modulation with a tunable drain current was demonstrated in thin-film transistors (TFTs) with a hafnium oxide (HfO2-x) gate insulator and an indium-zinc oxide (IZO) channel layer for application to artificial synapses in neuromorphic systems. The drain current in these TFTs was reduced significantly by four orders of magnitude on application of a negative gate bias, then could be restored to its original value by applying a positive bias. The reduced drain current under negative biasing is interpreted as being caused by voltage-driven oxygen ion migration from the HfO2-x gate insulator to the IZO channel, which reduces the oxygen vacancy concentration in the IZO channel. In addition to emulating the analog-type potentiation and depression motions in artificial synapses, the tunable drain current presents paired-pulse facilitation and short-term and long-term plasticity behaviors. These wide-ranging and nonvolatile synaptic behaviors with tunable drain currents are indicative of the potential of the proposed TFTs for artificial synapse applications.

Stimuli-Responsive Small-on-Large Nanoradiosensitizer for Enhanced Tumor Penetration and Radiotherapy Sensitization

Development of an efficient nanoradiosensitization system that enhances the radiation doses in cancer cells to sensitize radiotherapy (RT) while sparing normal tissues is highly desirable. Here, we construct a tumor microenvironment (TME)-responsive disassembled small-on-large molybdenum disulfide/hafnium dioxide (MoS₂/HfO₂) dextran (M/H-D) nanoradiosensitizer. The M/H-D can degrade and release the HfO₂ nanoparticles (NPs) in TME to enhance tumor penetration of the HfO₂ NPs upon near-infrared (NIR) exposure, which can solve the bottleneck of insufficient internalization of the HfO₂ NPs. Simultaneously, the NIR photothermal therapy increased peroxidase-like catalytic efficiency of the M/H-D nanoradiosensitizer in TME, which selectively catalyzed intratumorally overexpressed H₂O₂ into highly oxidized hydroxyl radicals (·OH). The heat induced by PTT also relieved the intratumoral hypoxia to sensitize RT. Consequently, this TME-responsive precise nanoradiosensitization achieved improved irradiation effectiveness, potent oxygenation in tumor, and efficient suppression to tumor, which can be real-time monitored by computed tomography and photoacoustic imaging.

Synthesis and Characterization of Gd3+ Doped HfO₂ Nanoparticles for Radiotherapy Applications

Synthesis of pure Hafnium Oxide (HfO₂), and HfO₂ doped with Gadolinium (1, 3, 5 and 7 mol%) nanoparticles (NPs) had been carried out by Precipitation and co-precipitation method using the precursor solution of Hafnium (IV) chloride (HfCl₄) and Gadolinium(III) chloride hexahydrate (GdCl₃·6H₂O) with Sodium hydroxide (NaOH) which was dissolved in deionized water. The synthesized compound was characterized and analyzed by X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Energy dispersive X-ray analysis (EDX), UV-visible spectrophotometer, Photoluminescence (PL), Fourier Transform infrared spectroscopy (FTIR) and Raman spectroscopy. The result from X-ray diffraction showed that the Gd³⁺ concentration for 7 mol% had attended directly crystalline phase of Cubic HfO₂ structure. Morphology and element analysis of the samples were analyzed using FESEM and EDX, which indicated cluster formation, fluffy and voids with highly agglomerated particles and EDX exhibited no extra peaks with other than constituent elements present in extrinsic HfO₂. From UV Spectra it was observed that the optical band gap of both Intrinsic and extrinsic of HfO2 NPs were found to be 5.74 eV, 3.62 eV, 3.69 eV, 3.78 eV and 4.19 eV. The Photoluminescence Spectra showed the 313 nm emission line which might be due to ⁶P_7/2→⁸S_7/2 transition and the Raman Spectra clearly represented the monoclinic structure by showing the presence of A_g and B_g Modes and cubic structure because of the presence of F_2g mode.

Hafnia (HfO2) nanoparticles as an X-ray contrast agent and mid-infrared biosensor

The interaction of hafnium oxide (HfO2) nanoparticles (NPs) with X-ray and mid-infrared radiation was investigated to assess the potential as a multifunctional diagnostic probe for X-ray computed tomography (CT) and/or mid-infrared biosensing. HfO2 NPs of controlled size were prepared by a sol-gel process and surface functionalized with polyvinylpyrrolidone, resulting in relatively spherical and monodispersed NPs with a tunable mean diameter in the range of ∼7-31 nm. The X-ray attenuation of HfO2 NPs was measured over 0.5-50 mM concentration and compared with Au NPs and iodine, which are the most prominent X-ray contrast agents currently used in research and clinical diagnostic imaging, respectively. At clinical CT tube potentials >80 kVp, HfO2 NPs exhibited superior or similar X-ray contrast compared to Au NPs, while both exhibited significantly greater X-ray contrast compared to iodine, due to the favorable location of the k-shell absorption edge for hafnium and gold. Moreover, energy-dependent differences in X-ray attenuation enabled simultaneous quantitative molecular imaging of each agent using photon-counting spectral (multi-energy) CT. HfO2 NPs also exhibited a strong mid-infrared absorption in the Reststrahlen band from ∼250-800 cm(-1) and negative permittivity below 695 cm(-1), which can enable development of mid-infrared biosensors and contrast agents, leveraging surface enhanced mid-infrared and/or phonon polariton absorption.

Is titanium tetrafluoride (TiF4) effective to prevent carious and erosive lesions? A review of the literature

The present review summarises the effects of titanium tetrafluoride (TiF(4)) on the development and progression of carious and erosive lesions. The mode of action of TiF(4) is due to the formation of an acid-stable surface layer, which provides mechanical protection to the surface, and to an increased fluoride uptake, which might chemically reduce demineralisation of dental hard tissues. Most in vitro studies showed that TiF(4) is effective in reducing the formation of carious and erosive enamel and dentine lesions. Thereby, TiF(4) was equally or more effective than sodium fluoride (NaF), amine fluoride (AmF) or stannous fluoride (SnF(2)). While clinical data confirm the caries-preventive effect, clinical trials analysing the anti-erosive effect of TiF(4) are lacking. Few data available from in situ studies revealed conflicting results by showing either no effect or a beneficial effect of TiF(4) on enamel erosion. Even though research focused on TiF(4), there is also evidence to show that other metal fluorides, such as zirconium and hafnium tetrafluorides, affect enamel and dentine demineralisation.

CONCLUSION

The potential of TiF(4) to prevent acid demineralisation requires further research to confirm the promising in vitro results obtained by in situ studies and clinical trials.

Microstructural and auger microanalytical characterization of Cu-Hf and Cu-Ti catalysts

Degradation processes occurring at the surface and in the bulk of Cu-based amorphous alloys during cathodic hydrogen charging were used for promoting the catalytic activity of such alloys. These processes modifying the structure, composition, and morphology of the substrate proved to be useful methods for transforming Cu-Hf and inactive Cu-Ti amorphous alloy precursors into active and durable catalysts. Indeed, their catalytic activity for dehydrogenation of 2-propanol increased up to a conversion level of approximately 60% at selectivities to acetone of about 99% for Cu-Ti and to conversion of approximately 90% at selectivities of approximately 95% for Cu-Hf. Previous attempts carried out by aging in air or hydrogen charging from the gas phase resulted in a maximum conversion level up to 15% for Cu-Hf and up to 3% for Cu-Ti. High resolution Auger spectroscopy allowed changes occurring during the activation process to be identified, namely, the formation of small Cu particles on the HfO2 surface and the formation of highly porous particles containing mostly Cu and some Ti and O (Cu-Ti-O) on a Cu-Ti substrate. Differences in the chemistry and structure of both catalysts are discussed, and the implications for catalytic function are considered. A probable configuration of active sites on the Cu-Ti-O/Ti-O-Cu catalyst for dehydrogenation of 2-propanol is proposed.

Mechanical properties of cast Ti-Hf alloys

This study examined the mechanical properties of a series of Ti-Hf alloys. Titanium alloys with 10 to 40 mass % Hf were made with titanium and hafnium sponge in an argon-arc melting furnace. Specimens cast into magnesia-based investment molds were tested for yield strength, tensile strength, percentage elongation, and modulus of elasticity. Vickers microhardness was determined at 25 to 600 microm from the cast surface. X-ray diffractometry was also performed. Commercially pure Ti (CP Ti) and pure Ti prepared from titanium sponge were used as controls. The data (n = 5) were analyzed with a one-way ANOVA and the Student-Newman-Keuls test (alpha = 0.05). The diffraction peaks of all the metals matched those for alpha Ti; no beta phase peaks were found. Alloys with Hf > or = 25% had significantly (p < 0.05) higher yield and tensile strength compared to the CP Ti and pure Ti. There were no significant differences (p > 0.05) in elongation among all the Ti-Hf alloys and CP Ti, whereas the elongation of alloys with Hf > or = 30% was significantly (p < 0.05) lower than that of the pure Ti. The cast Ti-Hf alloys tested can be considered viable alternatives to CP Ti because they were stronger than CP Ti and had similar elongation.

[Determination of trace niobium and tantalum in rock sample by atomic emission spectrometry]

This paper describes the determination of trace Nb and Ta in sample using carbon powder and hafnium oxide as buffer by atomic emission spectrometry (AES). Hafnium has been selected as internal standard, since it has scinilar evaporation curve as those of Nb and Ta. Samples can be analyzed without chemical pretreatment. The sample was directly loaded onto the ordinary electrode. The method is simple, rapid and accurate. The range of determination for Nb and Ta are 0%-0.25% and 0%-0.125% respectively, and the detection limits are found to be 0.003% and 0.001%, respectively. Satisfactory results are obtained.

Influence of protein dynamics on the metal-sites of ovotransferrin

Using the perturbed angular correlations (PAC) technique, the formation of hafnium-ovotransferrin complexes has been studied. Two binding configurations at each of the two specific binding-sites of the protein have been observed. They are characterized by well-defined electric quadrupole frequencies. Information about the dynamics of the protein was derived from temperature dependent measurements of the relaxation constant. The well-resolved spectra taken with fast BaF2-detectors allow a precise determination of the relaxation behaviour of the protein. The results are compared with the predictions from a hydrodynamic model for the reorientation of macromolecules. Thus the hydrodynamic volume of ovotransferrin and its N-terminal half-molecule were determined. The ovotransferrin volume is in agreement with a value derived for human serum transferrin from small angle neutron scattering. From experiments with immobilized protein material there is evidence for internal protein dynamics which is probed by the Hf-ion bound to the specific metal-sites.

Scintigraphic imaging with tantalum-178 and the Anger scintillation camera: concise communication

Tantalum-178 is a short-liver radionuclide (T 1/2 = 9.3 min.) and emits primarily 56- to 64-keV characteristic x-rays. We have determined the imaging characteristics with this radionuclide and a large-field-of-view Anger camera. With a pinhole collimator, good spatial resolution is possible with Ta-178, although the image quality is superior with Tc-99m under comparable conditions. Spatial resolution with parallel-hole or converging collimators was much less satisfactory with Ta-178 because of septal penetration by high-energy photons. Pulmonary perfusion and liver-spleen images of excellent quality were obtained in the rabbit using the pinhole collimator and Ta-178-labeled agents.