Cranial Dislocation of Infrarenal Aortic Endoprostheses During Transcatheter Aortic Valve Replacement.

This report describes the complexity of transcatheter aortic valve replacement in which rare complications sometimes occur, even at experienced centers. This is a case of cranial migration of an infrarenal aortic aneurysm endograft while advancing the balloon-expandable prosthesis through the infrarenal aorta, which was subsequently successfully treated by deploying a thoracic endoprosthesis after deployment of the aortic valve bioprosthesis.

DNAzyme Cleavage of CAG Repeat RNA in Polyglutamine Diseases.

CAG repeat expansion is the genetic cause of nine incurable polyglutamine (polyQ) diseases with neurodegenerative features. Silencing repeat RNA holds great therapeutic value. Here, we developed a repeat-based RNA-cleaving DNAzyme that catalyzes the destruction of expanded CAG repeat RNA of six polyQ diseases with high potency. DNAzyme preferentially cleaved the expanded allele in spinocerebellar ataxia type 1 (SCA1) cells. While cleavage was non-allele-specific for spinocerebellar ataxia type 3 (SCA3) cells, treatment of DNAzyme leads to improved cell viability without affecting mitochondrial metabolism or p62-dependent aggresome formation. DNAzyme appears to be stable in mouse brain for at least 1 month, and an intermediate dosage of DNAzyme in a SCA3 mouse model leads to a significant reduction of high molecular weight ATXN3 proteins. Our data suggest that DNAzyme is an effective RNA silencing molecule for potential treatment of multiple polyQ diseases.

System of Psychological Support Based on Positive Suggestions to the Critically Ill Using ICU Doulas.

Surviving critical illness often creates a lasting psychological impact, including depression, anxiety, and post-traumatic stress. Memories of frightening and delusional experiences are the largest potentially modifiable risk factor, but currently, there is no proven intervention to improve these inciting factors. Psychological support based on positive suggestion is a psychotherapeutic approach that can be provided even to patients in altered cognitive states and is therefore a viable psychotherapy intervention throughout the ICU stay. Traditional ICU care team members have limited time and training to provide such psychological support to patients. Doulas are trained supportive companions who have been effectively used to provide patient advocacy and emotional support in other clinical settings and may address this need. Our aim was to train and implement a psychological support based on positive suggestion program for the critically ill using doulas, and measure acceptance of this intervention through stakeholder feedback. METHODS: Doula training included three objectives: an introduction to ICU practice structure and policies; education about fundamental aspects of critical care conditions and procedures; and didactic and hands-on learning experiences in effective use of psychological support based on positive suggestion in the critically ill. Doulas were evaluated at the end of their training and during subsequent clinical activities using competency-based assessments as well as through survey-based questions and interviews with key stakeholders. RESULTS: The ICU doulas performed psychological support based on positive suggestion on 43 critically ill patients in the ICU setting. Stakeholder feedback from nurses, patients, and patient families was positive. The majority (28/32) of surveyed bedside ICU nurses reported that the doulas' involvement was helpful for both patients and nurses alike. All interviewed family members offered positive comments about the ICU doula presence and of the 40 patients who recalled the intervention 37 found it comforting. CONCLUSIONS: Our program successfully trained two doulas to work effectively in the ICU setting performing patient-centered psychological support based on positive suggestion interventions. Their training improved their skill sets and was reported as beneficial by patients, families, and critical care nursing. This training program offers a proof of concept that could be applied in other medical centers, bringing doulas more commonly into the ICU practice to help humanize the experience for patients, families, and medical teams.

Improved Oxidative C-C Bond Formation Reactivity of High-Valent Pd Complexes Supported by a Pseudo-Tridentate Ligand.

There is a large interest in developing oxidative transformations catalyzed by palladium complexes that employ environmentally friendly and economical oxidizing reagents such as dioxygen. Recently, we have reported the isolation and characterization of various mononuclear PdIII and PdIV complexes supported by the tetradentate ligands N,N'-dialkyl-2,11-diaza[3.3](2,6)pyridinophane (RN4, R = tBu, iPr, Me), and the aerobically induced C-C and C-heteroatom bond formation reactivity was investigated in detail. Given that the steric and electronic properties of the multidentate ligands were shown to tune the stability and reactivity of the corresponding high-valent Pd complexes, herein we report the use of an asymmetric N4 ligand, N-mehtyl-N'-tosyl-2,11-diaza[3.3](2,6)pyridinophane (TsMeN4), in which one amine N atom contains a tosyl group. The N-Ts donor atom exhibits a markedly reduced donating ability, which led to the formation of transiently stable PdIII and PdIV complexes, and consequently the corresponding O2 oxidation reactivity and the subsequent C-C bond formation were improved significantly.

Coordination Chemistry of Bifunctional Chemical Agents Designed for Applications in 64Cu PET Imaging for Alzheimer's Disease.

Positron emission tomography (PET) is emerging as one of the most important diagnostic tools for brain imaging, yet the most commonly used radioisotopes in PET imaging, 11C and 18F, have short half-lives, and their usage is thus somewhat limited. By comparison, the 64Cu radionuclide has a half-life of 12.7 h, which is ideal for administering and imaging purposes. In spite of appreciable research efforts, high-affinity copper chelators suitable for brain imaging applications are still lacking. Herein, we present the synthesis and characterization of a series of bifunctional compounds (BFCs) based on macrocyclic 1,4,7-triazacyclononane and 2,11-diaza[3.3](2,6)pyridinophane ligand frameworks that exhibit a high affinity for Cu2+ ions. In addition, these BFCs contain a 2-phenylbenzothiazole fragment that is known to interact tightly with amyloid ß fibrillar aggregates. Determination of the protonation constants (pKa values) and stability constants (log ß values) of these BFCs, as well as characterization of the isolated copper complexes using X-ray crystallography, electron paramagnetic resonance spectroscopy, and electrochemical studies, suggests that these BFCs exhibit desirable properties for the development of novel 64Cu PET imaging agents for Alzheimer's disease.

Improved synthesis of symmetrically & asymmetrically N-substituted pyridinophane derivatives.

The N,N'-di(toluenesulfonyl)-2,11-diaza[3,3](2,6)pyridinophane (TsN4) precursor was sought after as a starting point for the preparation of various symmetric and asymmetric pyridinophane-derived ligands. Various procedures to synthesize TsN4 had been published, but the crucial problem had been the purification of TsN4 from the larger 18- and 24-membered azamacrocycles. Most commonly, column chromatography or other laborious methods have been utilized for this separation, yet we have found an alternate selective dissolution method upon protonation which allows for multi-gram scale output of TsN4·HCl. This optimized synthesis of TsN4 also led to the development of symmetric RN4 derivatives as well as the asymmetric derivative N-(tosyl)-2,11-diaza[3,3](2,6)pyridinophane (TsHN4). Using this TsHN4 precursor, different N-substituents can be added to create a library of asymmetric RR'N4 macrocyclic ligands. These asymmetric RR'N4 derivatives expand the utility of the RN4 framework in coordination chemistry and the ability to study the electronic, steric, and denticity effects of these pyridinophane ligands on the metal center.

Evaluation of 64Cu-Based Radiopharmaceuticals that Target Aß Peptide Aggregates as Diagnostic Tools for Alzheimer's Disease.

Positron emission tomography (PET) imaging agents that detect amyloid plaques containing amyloid beta (Aß) peptide aggregates in the brain of Alzheimer's disease (AD) patients have been successfully developed and recently approved by the FDA for clinical use. However, the short half-lives of the currently used radionuclides 11C (20.4 min) and 18F (109.8 min) may limit the widespread use of these imaging agents. Therefore, we have begun to evaluate novel AD diagnostic agents that can be radiolabeled with 64Cu, a radionuclide with a half-life of 12.7 h, ideal for PET imaging. Described herein are a series of bifunctional chelators (BFCs), L1-L5, that were designed to tightly bind 64Cu and shown to interact with Aß aggregates both in vitro and in transgenic AD mouse brain sections. Importantly, biodistribution studies show that these compounds exhibit promising brain uptake and rapid clearance in wild-type mice, and initial microPET imaging studies of transgenic AD mice suggest that these compounds could serve as lead compounds for the development of improved diagnostic agents for AD.

Isolated Organometallic Nickel(III) and Nickel(IV) Complexes Relevant to Carbon-Carbon Bond Formation Reactions.

Nickel-catalyzed cross-coupling reactions are experiencing a dramatic resurgence in recent years given their ability to employ a wider range of electrophiles as well as promote stereospecific or stereoselective transformations. In contrast to the extensively studied Pd catalysts that generally employ diamagnetic intermediates, Ni systems can more easily access various oxidation states including odd-electron configurations. For example, organometallic NiIII intermediates with aryl and/or alkyl ligands are commonly proposed as the active intermediates in cross-coupling reactions. Herein, we report the first isolated NiIII-dialkyl complex and show that this species is involved in stoichiometric and catalytic C-C bond formation reactions. Interestingly, the rate of C-C bond formation from a NiIII center is enhanced in the presence of an oxidant, suggesting the involvement of transient NiIV species. Indeed, such a NiIV species was observed and characterized spectroscopically for a nickelacycle system. Overall, these studies suggest that both NiIII and NiIV species could play an important role in a range of Ni-catalyzed cross-coupling reactions, especially those involving alkyl substrates.

Facile Preparation of Stable Antibody-Gold Conjugates and Application to Affinity-Capture Self-Interaction Nanoparticle Spectroscopy.

Protein-nanoparticle conjugates are widely used for conventional applications such as immunohistochemistry and biomolecular detection as well as emerging applications such as therapeutics and advanced materials. Nevertheless, it remains challenging to reproducibly prepare stable protein-nanoparticle conjugates with highly similar optical properties. Here we report an improved physisorption method for reproducibly preparing stable antibody-gold conjugates at acidic pH using polyclonal antibodies from a wide range of species (human, goat, rabbit, mouse, and rat). We find that gold particles synthesized using citrate alone or in combination with tannic acid are similar in size but display variable colloidal stability when conjugated to polyclonal antibodies. The variability in conjugate stability is due to differences in the pH and composition of the original gold colloid, which prevents reproducible preparation of stable antibody conjugates without additional purification of the particles prior to conjugation. Sedimentation-based purification of gold particles synthesized using different methods enabled reproducible generation of antibody-gold conjugates with high stability and similar plasmon wavelengths. We also find that antibody conjugates prepared using our improved procedure display excellent performance when applied to a high-throughput immunogold assay (affinity-capture self-interaction nanoparticle spectroscopy, AC-SINS) for identifying monoclonal antibodies with low self-association, high solubility, and low viscosity. The stable antibody conjugates prepared with various types of gold colloid result in robust and reproducible AC-SINS measurements of antibody self-association using extremely dilute (microgram per mL) and unpurified antibody solutions. We expect that this improved methodology will be useful for reproducibly preparing stable antibody-gold conjugates for diverse applications.

Evidence for a cysteine-mediated mechanism of excitation energy regulation in a photosynthetic antenna complex.

Light-harvesting antenna complexes not only aid in the capture of solar energy for photosynthesis, but regulate the quantity of transferred energy as well. Light-harvesting regulation is important for protecting reaction center complexes from overexcitation, generation of reactive oxygen species, and metabolic overload. Usually, this regulation is controlled by the association of light-harvesting antennas with accessory quenchers such as carotenoids. One antenna complex, the Fenna-Matthews-Olson (FMO) antenna protein from green sulfur bacteria, completely lacks carotenoids and other known accessory quenchers. Nonetheless, the FMO protein is able to quench energy transfer in aerobic conditions effectively, indicating a previously unidentified type of regulatory mechanism. Through de novo sequencing MS, chemical modification, and mutagenesis, we have pinpointed the source of the quenching action to cysteine residues (Cys49 and Cys353) situated near two low-energy bacteriochlorophylls in the FMO protein from Chlorobaculum tepidum Removal of these cysteines (particularly removal of the completely conserved Cys353) through N-ethylmaleimide modification or mutagenesis to alanine abolishes the aerobic quenching effect. Electrochemical analysis and electron paramagnetic resonance spectra suggest that in aerobic conditions the cysteine thiols are converted to thiyl radicals which then are capable of quenching bacteriochlorophyll excited states through electron transfer photochemistry. This simple mechanism has implications for the design of bio-inspired light-harvesting antennas and the redesign of natural photosynthetic systems.

Perturbation of the O-U-O Angle in Uranyl by Coordination to a 12-Membered Macrocycle.

Reaction of [UO2Cl2(THF)2]2 (THF = tetrahydrofuran) with 2 equiv of (H)N4 ((H)N4 = 2,11-diaza[3,3](2,6) pyridinophane) or (Me)N4 ((Me)N4 = N,N'-dimethyl-2,11-diaza[3,3](2,6) pyridinophane), in MeCN, results in the formation of UO2Cl2((R)N4) (R = H; 1; Me, 2), which were isolated as yellow-orange solids in good yields. Similarly, reaction of UO2(OTf)2(THF)3 with (H)N4 in MeCN results in the formation of UO2(OTf)2((H)N4) (3), as an orange powder in 76% yield. Finally, reaction of UO2(OTf)2(THF)3 with (Me)N4 in THF results in the formation of [UO2(OTf)(THF)((H)N4)][OTf] (4), as an orange powder in 73% yield. Complexes 1-4 were fully characterized, including characterization by X-ray crystallography. These complexes exhibit the smallest O-U-O bond angles measured to date, ranging from 168.2(3)° (for 2) to 161.7(5)° (for 4), a consequence of an unfavorable steric interaction between the oxo ligands and the macrocycle backbone. A Raman spectroscopic study of 1-4 reveals no correlation between O-U-O angle and the U═O νsym mode. However, complexes 1 and 2 do feature lower U═O νsym modes than complexes 3 and 4, which can be rationalized by the stronger donor strength of Cl(-) versus OTf(-). This observation suggests that the identity of the equatorial ligands has a greater effect on the U═O νsym frequency than does a change in O-U-O angle, at least when the changes in the O-U-O angles are small.

Aromatic Cyanoalkylation through Double C-H Activation Mediated by Ni(III).

Herein we report an atom- and step-economic aromatic cyanoalkylation reaction that employs nitriles as building blocks and proceeds through Csp(2)-H and Csp(3)-H bond activation steps mediated by Ni(III). In addition to cyanomethylation with MeCN, regioselective α-cyanoalkylation was observed with various nitrile substrates to generate secondary and tertiary nitriles. Importantly, to the best of our knowledge these are the first examples of C-H bond activation reactions occurring at a Ni(III) center, which may exhibit different reactivity and selectivity profiles than those corresponding to analogous Ni(II) centers. These studies provide guiding principles to design catalytic C-H activation and functionalization reactions involving high-valent Ni species.

Discovery of highly soluble antibodies prior to purification using affinity-capture self-interaction nanoparticle spectroscopy.

Self-association of monoclonal antibodies (mAbs) at high concentrations can result in developability challenges such as poor solubility, aggregation, opalescence and high viscosity. There is a significant unmet need for methods that can evaluate self-association propensities of concentrated mAbs at the earliest stages in antibody discovery to avoid downstream issues. We have previously developed a method (affinity-capture self-interaction nanoparticle spectroscopy, AC-SINS) that is capable of detecting weak antibody self-interactions using unusually dilute mAb solutions (tens of µg/ml). Here we optimize and implement this assay for characterization of unpurified and highly dilute mAbs directly in cell culture media. This assay was applied to screen 87 mAbs obtained via immunization. Our measurements reveal a wide range of self-associative propensities for mAbs that bind to the same antigen and which differ mainly in their complementarity-determining regions. The least associative mAbs identified by AC-SINS were confirmed to be highly soluble when purified and concentrated by three to five orders of magnitude. This approach represents a key advance in screening mAb variants using unpurified antibody samples, and it holds significant potential to both improve initial candidate selection as well as to guide protein engineering efforts to improve the properties of specific mAb candidates.

Aromatic Methoxylation and Hydroxylation by Organometallic High-Valent Nickel Complexes.

Herein we report the synthesis and reactivity of several organometallic Ni(III) complexes stabilized by a modified tetradentate pyridinophane ligand containing one phenyl group. A room temperature stable dicationic Ni(III)-disolvento complex was also isolated, and the presence of two available cis coordination sites in this complex offers an opportunity to probe the C-heteroatom bond formation reactivity of high-valent Ni centers. Interestingly, the Ni(III)-dihydroxide and Ni(III)-dimethoxide species can be synthesized, and they undergo aryl methoxylation and hydroxylation that is favored by addition of oxidant, which also limits the ß-hydride elimination side reaction. Overall, these results provide strong evidence for the involvement of high-valent organometallic Ni species, possibly both Ni(III) and Ni(IV) species, in oxidatively induced C-heteroatom bond formation reactions.

Early safety and efficacy of percutaneous left atrial appendage suture ligation: results from the U.S. transcatheter LAA ligation consortium.

BACKGROUND: Transcatheter left atrial appendage (LAA) ligation may represent an alternative to oral anticoagulation for stroke prevention in atrial fibrillation. OBJECTIVES: This study sought to assess the early safety and efficacy of transcatheter ligation of the LAA for stroke prevention in atrial fibrillation. METHODS: This was a retrospective, multicenter study of consecutive patients undergoing LAA ligation with the Lariat device at 8 U.S. sites. The primary endpoint was procedural success, defined as device success (suture deployment and <5 mm leak by post-procedure transesophageal echocardiography), and no major complication at discharge (death, myocardial infarction, stroke, Bleeding Academic Research Consortium bleeding type 3 or greater, or cardiac surgery). Post-discharge management was per operator discretion. RESULTS: A total of 154 patients were enrolled. Median CHADS2 score (congestive heart failure, hypertension, age ≥ 75 years, diabetes mellitus, prior stroke, transient ischemic attack, or thromboembolism [doubled]) was 3 (interquartile range: 2 to 4). Device success was 94%, and procedural success was 86%. A major complication occurred in 15 patients (9.7%). There were 14 major bleeds (9.1%), driven by the need for transfusion (4.5%). Significant pericardial effusion occurred in 16 patients (10.4%). Follow-up was available in 134 patients at a median of 112 days (interquartile range: 50 to 270 days): Death, myocardial infarction, or stroke occurred in 4 patients (2.9%). Among 63 patients with acute closure and transesophageal echocardiography follow-up, there were 3 thrombi (4.8%) and 13 (20%) with residual leak. CONCLUSIONS: In this initial multicenter experience of LAA ligation with the Lariat device, the rate of acute closure was high, but procedural success was limited by bleeding. A prospective randomized trial is required to adequately define clinical efficacy, optimal post-procedure medical therapy, and the effect of operator experience on procedural safety.

Cardiac platypnea-orthodeoxia syndrome: an often unrecognized malady.

Platypnea-orthodeoxia syndrome (POS) is a rare but clinically important form of dyspnea. The syndrome is characterized by dyspnea and arterial oxygen desaturation that occurs in the upright position and improves with recumbency. In cardiac POS, an atrial septal defect or patent foramen ovale allows communication between the right- and left-sided circulations. A second defect, such as a dilated aorta, prominent eustachian valve, or pneumonectomy, then contributes to right-to-left shunting through the interatrial connection. Diagnosis is made through pulse oximetry to confirm orthodeoxia and through transesophageal echocardiography with bubble study to visualize the shunt. Although data are limited for this rare syndrome, percutaneous closure has thus far proven safe and effective.

Organometallic nickel(III) complexes relevant to cross-coupling and carbon-heteroatom bond formation reactions.

Nickel complexes have been widely employed as catalysts in C-C and C-heteroatom bond formation reactions. In addition to Ni(0) and Ni(II) intermediates, several Ni-catalyzed reactions are proposed to also involve odd-electron Ni(I) and Ni(III) oxidation states. We report herein the isolation, structural and spectroscopic characterization, and organometallic reactivity of Ni(III) complexes containing aryl and alkyl ligands. These Ni(III) species undergo transmetalation and/or reductive elimination reactions to form new C-C or C-heteroatom bonds and are also competent catalysts for Kumada and Negishi cross-coupling reactions. Overall, these results provide strong evidence for the direct involvement of organometallic Ni(III) species in cross-coupling reactions and oxidatively induced C-heteroatom bond formation reactions.