Evidence for an intrinsic binding force between dodecaborate dianions and receptors with hydrophobic binding pockets

A gas phase binding study revealed strong intrinsic intermolecular interactions between dianionic halogenated closo-dodecaborates [B12X12](2-) and several neutral organic receptors. Oxidation of a tetrathiafulvalene host allowed switching between two host-guest binding modes in a supramolecular complex. Complexes of β-cyclodextrin with [B12F12](2-) show remarkable stability in the gas phase and were successfully tested as carriers for the delivery of boron clusters into cancer cells.

Identification of a neutral loss from precursor ions with nearly Gaussian-shaped isotopic patterns via inverted isotopic patterns of product ions

RATIONALE

Direct atomic composition determination of ions with very broad Gaussian-shaped isotopic patterns is challenging because no monoisotopic peak is available for high accurate mass determination and no characteristic shapes in isotopic patterns are visible.

METHODS

Isolation and fragmentation of the ions corresponding to one peak (one nominal mass) in the center of the broad Gaussian-shaped isotopic pattern lead to a mass spectrum with the product ion signal showing the inverted full isotopic profile of the neutral fragment.

RESULTS

We have introduced a convenient method for the fast and straightforward identification of a neutral loss for molecular ions with broad isotopic patterns. The theoretical considerations underlying this method are explained and its practical limitations are considered. The benefits of this method are exemplified by guiding a reader through the analysis of a complex mixture of bridged carborate clusters, compounds with very broad isotopic patterns.

CONCLUSIONS

The presented method can be efficiently used for the determination of atomic compositions of compounds with broad isotopic patterns by their fragmentation using mass spectrometry. This method should significantly facilitate the mass spectrometric analysis of compounds containing several atoms with broad isotopic distributions, such as Ge, Sn, Mo, Ru and Hg, and, thus, can considerably broaden the use of mass spectrometry as an analytical method in inorganic and organometallic chemistry. Copyright © 2016 John Wiley & Sons, Ltd.

Evaluating new processes and concepts for energy and resource recovery from municipal wastewater with life cycle assessment

Energy and resource recovery from municipal wastewater is a pre-requisite for an efficient and sustainable water management in cities of the future. However, a sound evaluation of available processes and pathways is required to identify opportunities and short-comings of the different options and reveal synergies and potentials for optimization. For evaluating environmental impacts in a holistic view, the tool of life cycle assessment (LCA, ISO 14040/44) is suitable to characterize and quantify the direct and indirect effects of new processes and concepts. This paper gives an overview of four new processes and concepts for upgrading existing wastewater treatment plants towards energy positive and resource efficient wastewater treatment, based upon an evaluation of their environmental impacts with LCA using data from pilot and full-scale assessments of the considered processes.

Protic anions [H(B12X12)]- (X = F, Cl, Br, I) that act as Brønsted acids in the gas phase

The acidity of protic cations and neutral molecules has been studied extensively in the gas phase, and the gas-phase acidity has been established previously as a very useful measure of the intrinsic acidity of neutral and cationic compounds. However, no data for any anionic acids were available prior to this study. The protic anions [H(B12X12)](-) (X = F, Cl, Br, I) are expected to be the most acidic anions known to date. Therefore, they were investigated in this study with respect to their ability to protonate neutral molecules in the gas phase by using a combination of mass spectrometry and quantum-chemical calculations. For the first time it was shown that in the gas phase protic anions are also able to protonate neutral molecules and thus act as Brønsted acids. According to theoretical calculations, [H(B12I12)](-) is the most acidic gas-phase anion, whereas in actual protonation experiments [H(B12Cl12)](-) is the most potent gas-phase acidic anion for the protonation of neutral molecules. This discrepancy is explained by ion pairing and kinetic effects.

The effect of particle size and ligand configuration on the asymmetric catalytic properties of proline-functionalized Pt-nanoparticles

Particle size alters activity but not stereoselectivity of ligand-functionalized nanoparticles suggesting that stereoselectivity is primarily determined by the ligand–reactant combination.

1-Naphthylamine functionalized Pt nanoparticles: electrochemical activity and redox chemistry occurring on one surface

Platinum nanoparticles functionalized with oligomerized 1-naphthylamine form a material where the organic ligand exhibits electrochemical activity and the metal surface catalytic activity.

Acetone and the precursor ligand acetylacetone: distinctly different electron beam induced decomposition?

In focused electron beam induced deposition (FEBID) acetylacetone plays a role as a ligand in metal acetylacetonate complexes. As part of a larger effort to understand the chemical processes in FEBID, the electron-induced reactions of acetylacetone were studied both in condensed layers and in the gas phase and compared to those of acetone. X-ray photoelectron spectroscopy (XPS) shows that the electron-induced decomposition of condensed acetone layers yields a non-volatile hydrocarbon residue while electron irradiation of acetylacetone films produces a non-volatile residue that contains not only much larger amounts of carbon but also significant amounts of oxygen. Electron-stimulated desorption (ESD) and thermal desorption spectrometry (TDS) measurements reveal striking differences in the decay kinetics of the layers. In particular, intact acetylacetone suppresses the desorption of volatile products. Gas-phase studies of dissociative electron attachment and electron impact ionization suggest that this effect cannot be traced back to differences in the initial fragmentation reactions of the isolated molecules but is due to subsequent dissociation processes and to an efficient reaction of released methyl radicals with adjacent acetylacetone molecules. These results could explain the incorporation of large amounts of ligand material in deposits fabricated by FEBID processes using acetylacetonate complexes.

Predictive role of imaging in sentinel lymph node dissection for melanoma

A retrospective study of 67 patients with metastatic melanoma was performed to evaluate if imaging from lymphoscintigraphy could predict a higher miss rate if only the most radioactive node were removed. Following protocol for sentinel node biopsy, the surgeon resected all lymph nodes containing radioactivity > 10% of the most radioactive node. A correlation was performed between the radioactive counts of the lymph nodes and the presence of metastases. The percentage of cases in which the most radioactive node was negative for metastasis on pathology was calculated. Two nuclear medicine physicians read the images from lymphoscintigraphy specifically to determine if the first lymph node visualized became less intense than other nodes on later images. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated. In 13 of 67 (19%) patients, the most radioactive lymph node was negative for metastasis while a less radioactive node contained metastatic disease. Consensus reading by the nuclear medicine physicians determined that in 9 cases, the first lymph node visualized became less intense than another lymph node on later images. Of the 9 cases, 4 were true positive and 5 were false positive when correlated with intraoperative count rate and pathology. Of the cases where the most radioactive node was not positive on histopathology (n = 13), the consensus reading by the nuclear medicine physicians reported 4 of them (31%). Imaging by lymphoscintigram had a sensitivity 31%, specificity 91%, positive predictive value 44%, and negative predictive value 85% for predicting whether the most radioactive lymph node at surgery would be negative for metastasis at pathology. We conclude that in patients with melanoma, lymphoscintigraphy has high specificity and negative predictive value but modest sensitivity and positive predictive value for detecting when the sentinel node will not be the most radioactive lymph node during sentinel lymph node dissection. These findings support that dynamic imaging by lymphoscintigraphy has a role in surgical planning but that the imaging protocol could benefit from further optimization.

Relative substituent orientation in the structure of cis-3-chloro-1,3-dimethyl-N-(4-nitro-phen-yl)-2-oxo-cyclo-pentane-1-carboxamide

The crystal structure of the title compound allowed the cis substituent orientation on the cyclo­penta­none ring to be established. The mol­ecular conformation and crystal packing are governed by a network of hydrogen bonds and by π–π stacking.

The structure of the title compound, C₁₄H₁₅ClN₂O₄, prepared by reaction of a methacryloyl dimer with nitro­aniline, was determined to establish the relative substituent orientation on the cyclo­penta­none ring. In agreement with an earlier proposed reaction mechanism, the amide group and the methyl group adjacent to the chloro substituent adopt equatorial positions and relative cis orientation, whereas the Cl substituent itself and the methyl group adjacent to the amide have axial orientations relative to the mean plane of the five-membered ring. The conformation of the mol­ecule is stabilized by one classical N—H⋯O (2.18 Å) and one non-classical C—H⋯O (2.23 Å) hydrogen bond, each possessing an S(6) graph-set motif. The crystal packing is defined by several non-classical intra­molecular hydrogen bonds, as well as by partial stacking of the aromatic rings.

Control of chemical reactions and synthesis by low-energy electrons

Controlling the outcome of reactions is a central issue of chemical research. Physical tools can achieve this if they are able to precisely dissociate specific bonds of a molecule. However, to control synthesis, such tools must induce the formation of new bonds between two reactants to yield a more complex product. In the ideal case of an atom efficient synthesis, this product would contain all or at least most of the initial material. An electron beam is a physical tool that is capable of preparing molecules in reactive states or, at low electron energies, of initiating highly selective bond dissociation. The resulting fragments in turn can react with other molecules to yield stable products. This tutorial review focuses in particular on such low-energy electron-initiated molecular syntheses and their applications in the modification of surfaces. It thus emphasizes strategies towards the controlled and predictable formation of more complex products from small reactants initiated by interaction with low-energy electrons either through selective bond dissociation or formation of specific reactive molecular species. However, selective bond dissociation is not always desirable. This is briefly illustrated by the case of electron beam induced deposition where additional strategies may be required to control product formation.

Surgical resection for stage IV melanoma: A Southwest Oncology Group trial (S9430)

8019

Background: Surgery is the treatment of choice for isolated distant metastases of melanoma. Based on a number of retrospective reports, patients (pts) who have undergone complete resection of metastatic disease can have an excellent survival. Methods: In SWOG, we prospectively evaluated surgical resection for stage IV melanoma. Pts enrolled prior to surgery; treatment following resection was at the discretion of the treating physician. Resected specimens were collected, whenever possible, for future molecular analyses. Results: Over a 9 year period from 1996 to 2005, 77 pts were enrolled from 18 centers, with 7 centers accruing ≥4 pts. Of 77 pts, 10 were incompletely resected and 5 had no evidence of stage IV disease. Therefore, 62 pts (81%) felt to have resectable stage IV actually did, and were included in the analysis. Pts characteristics were: median age 54 yrs (range 23–81); M:F 69%:31%; PS 0–1 100%; prior adjuvant IFN 45%. Resected sites included skin/soft tissue 40%; distant LN 21%; lung 13%; liver 8%; CNS 5%; bone 2%; other visceral sites 27%. Post-surgical complications included 1 grade IV pulmonary embolus and 1 grade III liver toxicity. Following surgery but prior to any further recurrence, 18 pts received adjuvant treatment including 8 with IFN and 7 with radiotherapy. After surgery, median progression-free survival (PFS) was 6 mos (95% CI 3–7 mos) with 9 patients (15%) remaining progression-free. Median overall survival (OS) was 21 mos (95% CI 15–28 mos); 3- and 4-yr OS was 33% and 29%, respectively. Conclusions: These results provide an estimate of prognosis for resected stage IV disease from a diverse patient base. They illustrate the potential for prolonged OS even with a short PFS. In some cases, pts can be repeatedly resected for long-term control of their disease. Pts with resectable stage IV melanoma are appropriate candidates for inclusion in adjuvant therapy trials.

No significant financial relationships to disclose.

The stress-response proteins poly(ADP-ribose) polymerase and NF-kappaB protect against bile salt-induced apoptosis

Bile salts induce apoptosis and are implicated as promoters of colon cancer. The mechanisms by which bile salts produce these effects are poorly understood. We report that the cytotoxic bile salt, sodium deoxycholate (NaDOC), activates the key stress response proteins, NF-kappaB and poly(ADP-ribose) polymerase (PARP). The activation of NF-kappaB and PARP, respectively, indicates that bile salts induce oxidative stress and DNA damage. The pre-treatment of cells with specific inhibitors of these proteins [pyrrolidine dithiocarbamate (NF-kappaB inhibitor) and 3-aminobenzamide (PARP inhibitor)] sensitizes cells to the induction of apoptosis by NaDOC, indicating that these stress response pathways are protective in nature. Colon cancer risk has been reported to be associated with resistance to apoptosis. We found an increase in activated NF-kappaB at the base of human colon crypts that exhibit apoptosis resistance. This provides a link between an increased stress response and colon cancer risk. The implications of these findings with respect to apoptosis and to colon carcinogenesis are discussed.

Chromosomal and genetic alterations of 7,12-dimethylbenz[a]anthracene-induced melanoma from TP-ras transgenic mice

The TP-ras transgenic mouse line expresses an activated human T24 Ha-ras gene with a mutation in codon 12, regulated by a mouse tyrosinase promoter. The transgene is expressed in melanocytes of the skin, eyes, and brain. The mice develop cutaneous melanoma when treated with 7,12-dimethylbenz[a]anthracene. Cell lines have been generated from the cutaneous tumors and metastatic lesions. By using fluorescence in situ hybridization with mouse whole chromosome paints, the cell lines were characterized for chromosomal abnormalities. Key findings in the tumor cells included translocations of chromosome 4 and alterations in chromosome 6. One tumor cell line contained a double translocation involving chromosomes 3 and 6. To extend the results of the chromosome 4 painting, Southern analysis of the p15INK4B, p16INK4A, and p19INK4D genes was performed. Our data indicated that there were homozygous and partial allelic deletions and polymorphisms in the region of chromosome 4 containing these genes, resulting in the absence or reduced expression of the p16 product. These findings are similar to those reported for human melanoma, and the TP-ras transgenic mouse may therefore be a valuable model for studying novel strategies for melanoma prevention and treatment.