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Transcription factors are key regulators in both normal and pathological cell processes. Affecting the activity of these proteins is a promising strategy for understanding gene regulation and developing effective therapeutics. CoIII Schiff base complexes ([Co(acacen)(L)2]+ where L=labile axial ligands) have been shown to be potent inhibitors of a number of zinc metalloproteins including Cys2His2 zinc finger transcription factors. Inhibition by [Co(acacen)(L)2]+ of the target protein is believed to occur through a dissociative exchange of the labile axial ligands for histidine (His) residues essential for function. Here, we report a series of spectroscopic investigations with model peptides of zinc fingers that elucidate the interaction between [Co(acacen)(L)2]+ complexes and zinc finger transcription factors. Observed changes in NMR chemical shifts and 2D 1H-1H NOESY NMR spectra demonstrate the preference of [Co(acacen)(L)2]+ complexes to coordinate His residues over other amino acids. The conformation of [Co(acacen)(L)2]+ upon His coordination was characterized by 1H NMR spectroscopy, near-UV CD, and electronic absorption. These studies reveal that the resulting His-coordinated [Co(acacen)(L)2]+ complex possesses an octahedral structure. The effects of [Co(acacen)(L)2]+ complexes on the zinc-finger structure were assessed by the degree of hydrogen bonding (probed by 2D NMR spectroscopy) and secondary-structure profiles measured by far-UV CD. These structural studies demonstrate the ability of [Co(acacen)(L)2]+ complexes to disrupt the ββα structure of zinc fingers, resulting in primarily random-coil conformations. A mechanism is described wherein [Co(acacen)(L)2]+ complexes inhibit zinc finger transcription factor activity through selectively coordinating His residues in the zinc finger by dissociative ligand exchange and disrupting the ββα structural motif required for gene regulation. [ABSTRACT FROM AUTHOR]

Purpose: To minimize feature loss in T1- and T2-weighted MRI by merging multiple MR images acquired at different TR and TE to generate an image with increased dynamic range. Materials and Methods: High Dynamic Range (HDR) processing techniques from the field of photography were applied to a series of acquired MR images. Specifically, a method to parameterize the algorithm for MRI data was developed and tested. T1- and T2-weighted images of a number of contrast agent phantoms and a live mouse were acquired with varying TR and TE parameters. The images were computationally merged to produce HDR-MR images. All acquisitions were performed on a 7.05 T Bruker PharmaScan with a multi-echo spin echo pulse sequence. Results: HDR-MRI delineated bright and dark features that were either saturated or indistinguishable from background in standard T1- and T2-weighted MRI. The increased dynamic range preserved intensity gradation over a larger range of T1 and T2 in phantoms and revealed more anatomical features in vivo. Conclusions: We have developed and tested a method to apply HDR processing to MR images. The increased dynamic range of HDR-MR images as compared to standard T1- and T2-weighted images minimizes feature loss caused by magnetization recovery or low SNR. [ABSTRACT FROM AUTHOR]

A polymer‐caged nanobin (PCN) theranostic platform with a doxorubicin (DXR)‐loaded liposomal core and an acid‐sensitive polymer shell that is functionalized with herceptin and GdIII‐based magnetic resonance imaging (MRI) contrast agents is reported. In vitro testing reveals an 120‐fold improvement in cellular GdIII uptake in comparison with clinically approved DOTA‐GdIII, leading to significant T1 MRI contrast enhancement. [ABSTRACT FROM AUTHOR]

Interspin distances between 0.8 nm and 2.0 nm can be measured through the dipolar broadening of the continuous wave (cw) EPR spectrum of nitroxide spin labels at X-band (9.4 GHz, 0.35 T). We introduce Gd3+ as a promising alternative spin label for distance measurements by cw EPR above 7 Tesla, where the ☋−1/2〉 to ☋1/2〉 transition narrows below 1 mT and becomes extremely sensitive to dipolar broadening. To estimate the distance limits of cw EPR with Gd3+, we have measured spectra of frozen solutions of GdCl3 at 8.6 T (240 GHz) and 10 K at concentrations ranging from 50 mM to 0.1 mM, covering a range of average interspin distances. These experiments show substantial dipolar broadening at distances where line broadening cannot be observed with nitroxides at X-band. This data, and its agreement with calculated dipolar-broadened lineshapes, show Gd3+ to be sensitive to distances as long as ∼3.8 nm. Further, the linewidth of a bis-Gd3+ complex with a flexible ∼1.6 nm bridge is strongly broadened as compared to the mono-Gd3+ complex, demonstrating the potential for application to pairwise distances. Gd-DOTA-based chelates that can be functionalized to protein surfaces display linewidths narrower than aqueous GdCl3, implying they should be even more sensitive to dipolar broadening. Therefore, we suggest that the combination of tailored Gd3+ labels and high magnetic fields can extend the longest interspin distances measurable by cw EPR from 2.0 nm to 3.8 nm. cw EPR data at 260 K demonstrate that the line broadening remains clear out to similar average interspin distances, offering Gd3+ probes as promising distance rulers at temperatures higher than possible with conventional pulsed EPR distance measurements. [ABSTRACT FROM AUTHOR]

Objectives Patients with rheumatoid arthritis (RA) have a reduced life expectancy due to increased cardiovascular disease. The lack of a suitable animal model resembling both RA and atherosclerosis has hindered studies demonstrating a direct link between systemic infl ammation in RA and the development of atherosclerosis. Our objective was to overcome this barrier by generating an animal model (K/BxAg7) that spontaneously develops both RA-like disease and atherosclerosis. Methods Arthritis severity was evaluated using clinical indices and immunohistochemical staining of ankle joint specimens. Aortic atherosclerosis was delineated via Sudan IV staining and immunohistochemical analysis. Serum cholesterol and lipoprotein levels were measured using enzymatic assays. Serum levels of cytokines, chemokines and adipokines were determined by Luminex assays. Results K/BxAg7 mice developed a destructive arthropathy followed by prominent aortic atherosclerosis. These animals also displayed dyslipidaemia, characterised by reduced serum levels of total cholesterol and highdensity lipoprotein, and increased low-density lipoprotein (LDL)/vLDL compared with control mice. Further, there were higher levels of circulating infl ammatory mediators, such as interleukin-6, sRANKL and CCL5 in atherosclerotic K/BxAg7 mice compared with controls. Treatment with etanercept reduced arthritis and atherosclerosis development in K/BxAg7 mice. Conclusions K/BxAg7 mice recapitulate the same sequence of events occurring in patients with RA, namely an erosive, infl ammatory arthritis followed by atherosclerosis. These data suggest that the K/BxAg7 mouse is a novel system for investigating the interplay between systemic infl ammation occurring in RA and the development of atherosclerosis. [ABSTRACT FROM AUTHOR]

The article discusses a study on the role of magnetic resonance imaging (MRI) in synthesizing ferritin-coated polystyrene beads. The researchers examined particles that are useful to study the effects of ferritin distribution, particle size and bead fraction on proton relaxation. Study revealed that ferritin-coated polystyrene beads were synthesized and characterized as long-term synthetic ferritin or hemosiderin mimics.

Despite recent advances in tissue engineering to regenerate biological function by combining cells with material supports, development is hindered by inadequate techniques for characterizing biomaterials in vivo. Magnetic resonance imaging is a tomographic technique with high temporal and spatial resolution and represents an excellent imaging modality for longitudinal noninvasive assessment of biomaterials in vivo. To distinguish biomaterials from surrounding tissues for magnetic resonance imaging, protein polymer contrast agents were developed and incorporated into hydrogels. In vitro and in vivo images of protein polymer hydrogels, with and without covalently incorporated protein polymer contrast agents, were acquired by magnetic resonance imaging. T1 values of the labeled gels were consistently lower when protein polymer contrast agents were included. As a result, the protein polymer contrast agent hydrogels facilitated fate tracking, quantification of degradation, and detection of immune response in vivo. For the duration of the in vivo study, the protein polymer contrast agent-containing hydrogels could be distinguished from adjacent tissues and from the foreign body response surrounding the gels. The hydrogels containing protein polymer contrast agent have a contrast-to-noise ratio 2-fold greater than hydrogels without protein polymer contrast agent. In the absence of the protein polymer contrast agent, hydrogels cannot be distinguished by the end of the gel lifetime. Magn Reson Med, 2010. © 2010 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

A chiral porphyrazine (pz), H2[pz(trans-A2B2)) (247), has been prepared that exhibits preferential in vivo accumulation inthe cells of tumors. Pz 247 exhibits near-infrared (NIR) emission with λ > 700 nm in the required wavelength range for maximum tissue penetration. When MDA-MB-231 breast tumor cells are treated with 247, the agent shows strong intracellular fluorescence with an emission maximum, 704 nm, which indicates that it localizes within a hydrophobic microenvironment. Pz 247 is shown to associate with the lipophilic core of LDL and undergo cellular entry primarily through receptor-mediated endocytosis accumulating in lysosomes. Preliminary in vivo studies show that 247 exhibits preferential accumulation and retention in the cells of MDA-MB231 tumors subcutaneously implanted in mice, thereby enabling NIR optical imaging with excellent contrast between tumor and surrounding tissue. The intensity of fluorescence from 247 within the tumor increases over time up to 48 h after injection presumably due to the sequestration of circulating 247/LDL complex by the tumor tissue. As the need for cholesterol, and thus LDL, is elevated in highly proliferative tumor cells over nontumorigenic cells, 247 has potential application for all such tumors. [ABSTRACT FROM AUTHOR]

A transition metal complex targeted for the inhibition of a subset of zinc finger transcription factors has been synthesized and tested in Xenopus Iaevis. A Co(lll) Schiff base complex modified with a 17-bp DNA sequence is designed to selectively inhibit Snail family transcription factors. The oligonucleotide-conjugated Co(lll) complex prevents Slug, Snail, and Sipi from binding their DNA targets whereas other transcription factors are still able to interact with their target DNA. The attachment of the oligonucleotide to the Co(lll) complex increases specificity 150-fold over the unconjugated complex. Studies demonstrate that neither the oligo, or the Co(lll) Schiff base complex alone, are sufficient for inactivation of Slug at concentrations that the conjugated complex mediates inhibition. Slug, Snail, and Sipi have been implicated in the regulation of epithelial-to-mesenchymal transition in development and cancer. A complex targeted to inactivate their transcriptional activity could prove valuable as an experimental tool and a cancer therapeutic. [ABSTRACT FROM AUTHOR]

We report the synthesis and characterization of polyvinyl alcohol (PVA) embolic particles modified with a clinically approved magnetic resonance (MR) contrast agent. PVA particles are used during transcatheter arterial embolization (TAE) procedures and this minimally invasive technique is a widely employed treatment for inoperable tumors. The PVA particles are injected into tumor vessels and prevent blood flow which results in tumor attenuation. An accurate assessment of the endpoint of embolization is critical to successful TAE procedures. Recent reports suggest that 20% of endpoint determination of TAE procedures by angiographic techniques are erroneous. Real time, in vivo imaging of the embolic particles would overcome this limitation. The contrast-modified PVA particles described here show an 80% decrease in T1 relaxation times compared to unmodified particles. Images of particles in capillary tubes of similar size to catheters used in TAE procedures are clearly visible by MRI. Magn Reson Med 59:898-902, 2008. © 2008 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Zinc(II) plays a vital role in normal cellular function as an essential component of numerous enzymes, transcription factors, and synaptic vesicles. While zinc can be linked to a variety of physiological processes, the mechanisms of its cellular actions are less discernible. Here, we have synthesized and tested a Zn(II)-activated magnetic resonance imaging (MRI) contrast agent in which the coordination geometry of the complex rearranges upon binding of Zn(II). In the absence of Zn(II) water is restricted from binding to a chelated Gd(III) ion by coordinating acetate arms resulting in a low relaxivity of 2.33 mM-1·s-1 at 60 MHz. Upon addition of Zn(II) the relaxivity of the Gd(III)-Zn(II) complex increases to 5.07 mM-1·s-1 and is consistent with one water molecule bound to Gd(III). These results were confirmed by nuclear magnetic relaxation dispersion analysis. There was no observed change in relaxivity of the Gd(III) complex when physiologically competing cations Ca(II) and Mg(II) were added. A competitive binding assay gave a dissociation constant of 2.38 × 10-4 M for the Gd(III)-Zn(II) complex. In vitro magnetic resonance images confirm that Zn(II) concentrations as low as 100 µM can be detected by using this contrast agent. [ABSTRACT FROM AUTHOR]

The in vivo monitoring of cell survival and migration will be essential to the translation of cell-based therapies from the laboratory to clinical studies. The pre-labeling of cells with magnetic resonance imaging (MRI) contrast agents renders them visible in vivo for serial cellular imaging. However, little is known about the impact of the presence of these metal particles inside transplanted cells. The use of the bimodal contrast agent GRID made it possible to demonstrate by means of fluorescent microscopy and inductively coupled plasma mass spectrometry (ICP-MS) that, after 16 h of incubation (without the use of a transfection agent), neural stem cells (NSCs) were saturated and no longer incorporated particles. With this maximal uptake, no significant effect on cell viability was observed. However, a significant decrease in proliferation was evident in cells that underwent 24 h of labeling. A significant increase in reactive oxygen species was observed for all GRID labeling, with a very significant increase with 24 h of labeling. GRID labeling did not affect cell motility in comparison with PKH26-labeled NSCs in a glioma-based migration assay and also allowed differentiation into all major cell types of the brain. GRID-labeled cells induced a signal change of 47% on T2 measurements and allows a detection of cell clusters of ∼220 cells/µl. Further in vivo testing will be required to ensure that cell labeling with gadolinium-based MRI contrast agents does not impair their ability to repair. Copyright © 2006 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Magnetic resonance imaging is a noninvasive, volume rendering diagnostic technique that uses lanthanide complexes to enhance proton relaxation. Magnetic resonance imaging is not limited by light scattering as optical microscopic techniques are, and allows imaging of whole animals. Clinical contrast agents are nonspecific and report solely on anatomy, whereas contrast agents that can be activated can be tailored to report on the physiological status or metabolic activity of biological systems. These new classes of magnetic resonance contrast agents represent a substantial leap in the type of information that can be derived from imaging experiments, and are the focus of this review. [Copyright &y& Elsevier]

Incorporation of metalated nucleosides into DNA through covalent modification is crucial to measurement of thermal electron-transfer rates and the dependence of these rates with structure, distance, and position. Here, we report the first synthesis of an electron donor-acceptor pair of 5' metallonucleosides and their subsequent incorporation into oligonucleotides using solid-phase DNA synthesis techniques. Large-scale syntheses of metal-containing oligonucleotides are achieved using 5' modified phosporamidites containing [Ru(acac)[sub 2](IMPy)][sup 2+] (acac is acetylacetonato; IMPy is 2'-iminomethylpyridyl-2'-deoxyuridine) (3) and [Ru(bpy)[sub 2](IMPy)][sup 2+] (bpy is 2,2'-bipyridine; IMPy is 2'-iminomethylpyridyl-2'-deoxyuridine) (4). Duplexes formed with the metal-containing oligonucleotides exhibit thermal stability comparable to the corresponding unmetalated duplexes (T[sub m] of modified duplex = 49 °C vs T[sub m] of unmodified duplex = 47 °C). Electrochemical (3, E[sub ½] = -0.04 V vs NHE; 4, E[sub 1/2] = 1.12 V vs NHE), absorption (3, λ[sub max] = 568, 369 nm; 4, λ[sub max] = 480 nm), and emission (4, λ[sub max] = 720 nm, τ = 55 ns, φ = 1.2 &times 10[sup -4]) data for the ruthenium-modified nucleosides and otigonucleotides indicate that incorporation into an oligonucleotide does not perturb the electronic properties of the ruthenium complex or the DNA significantly. In addition, the absence of any change in the emission properties upon metalated duplex formation suggests that the [Ru(bpy)[sub 2](IMPy)][sup 2+][Ru(acac)[sub 2](IMPy)][sup 2+] pair will provide a valuable probe for DNA-mediated electron-transfer studies. [ABSTRACT FROM AUTHOR]

Focuses on a study which developed novel contrast agents in magnetic resonance imaging (MRI) and their potential roles in biomedical research. Elements of MR image formation; Contrast enhancement; Challenges and future prospects.