Unexpected Formation of Metallofulleroids from Multicomponent Reactions, with Crystallographic and Computational Studies of the Cluster Motion.

New multicomponent reactions involving an isocyanide, terminal or internal alkynes, and endohedral metallofullerene (EMF) Lu3 N@C80 yield metallofulleroids which are characterized by mass-spectrometry, HPLC, and multiple 1D and 2D NMR techniques. Single crystal studies revealed one ketenimine metallofulleroid has ordered Lu3 N cluster which is unusual for EMF monoadducts. Computational analysis, based on crystallographic data, confirm that the endohedral cluster motion is controlled by the position of the exohedral organic appendants. Our findings provide a new functionalization reaction for EMFs, and a potential facile approach to freeze the endohedral cluster motion at relatively high temperatures.

Ultrastable Zirconium-Based Cationic Metal-Organic Frameworks for Perrhenate Removal from Wastewater.

The effective removal of radioactive 99TcO4- anion from nuclear wastewater remains a very difficult unsolved problem. Functional adsorbent materials with high stability, anion-exchange capacity, excellent selectivity, and recyclability are much needed to solve this problem. In this work, we designed two stable cationic metal-organic frameworks (MOFs)-Zr-tcbp-Me and Zr-tcpp-Me-for possible use as adsorbent materials to remove 99TcO4-. Both compounds were synthesized by solvothermal reactions of the tetracarboxylate ligand with zirconium salt, followed by postsynthetic modification (N-methylation). The crystallinity of both zirconium-based MOFs can be well retained under harsh conditions, and they exhibit high adsorption capacity and selectivity toward ReO4- anion, a nonradioactive analogue of 99TcO4-. Zr-tcbp-Me and Zr-tcpp-Me demonstrate the highest framework stability toward acidity among all previously reported cationic MOFs that have been tested for perrhenate removal from wastewater.

Modeling the structure and infrared spectra of omega-3 fatty acid esters.

Omega-3 dietary supplements provide a rich source of the active moieties eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which exist in the form of triacylglycerols or ethyl esters. Infrared (IR) spectroscopy provides a rapid and quantitative tool to assess the quality of these products as specific normal modes, in particular the ester carbonyl stretch modes, exhibit characteristic spectral features for the two ester forms of omega-3 fatty acids. To uncover the origin of the observed spectra, in this work, we perform molecular dynamics simulations of EPA and DHA ethyl esters and triacylglycerols to characterize their conformation, packing, and dynamics in the liquid phase and use a mixed quantum/classical approach to calculate their IR absorption spectra in the ester carbonyl stretch region. We show that the ester liquids exhibit slow dynamics in spectral diffusion and translational and rotational motion, consistent with the diffusion ordered NMR spectroscopy measurements. We further demonstrate that the predicted IR spectra are in good agreement with experiments and reveal how a competition between intermolecular and intramolecular interactions gives rise to distinct absorption peaks for the fatty acid esters.

Highly Efficient Luminescent Metal-Organic Framework for the Simultaneous Detection and Removal of Heavy Metals from Water.

We have designed and synthesized an isoreticular series of luminescent metal-organic frameworks (LMOFs) by incorporating a strongly emissive molecular fluorophore and functionally diverse colinkers into Zn-based structures. The three-dimensional porous networks of LMOF-261, -262, and -263 represent a unique/new type of nets, classified as a 2-nodal, (4,4)-c net (mot-e type) with 4-fold, class IIIa interpenetration. All compounds crystallize in a body-centered tetragonal crystal system (space group I41/a). A systematic study has been implemented to analyze their interactions with heavy metals. LMOF-263 exhibits impressive water stability, high porosity, and strong luminescence, making it an excellent candidate as a fluorescent chemical sensor and adsorbent for aqueous contaminants. It is extremely responsive to toxic heavy metals at a parts per billion level (3.3 ppb Hg2+, 19.7 ppb Pb2+) and demonstrates high selectivity for heavy metals over light metals, with detection ratios of 167.4 and 209.5 for Hg2+/Ca2+ and Hg2+/Mg2+, respectively. Mixed-metal adsorption experiments also show that LMOF-263 selectively adsorbs Hg2+ over other heavy metal ions in addition to light metals. The Pb2+ KSV value for LMOF-263 (55,017 M-1) is the highest among LMOFs reported to date, and the Hg2+ KSV value is the second highest (459,446 M-1). LMOF-263 exhibits a maximum adsorption capacity of 380 mg Hg2+/g. The Hg2+ adsorption process follows pseudo-second-order kinetics, removing 99.1% of the metal within 30 min. An in situ XPS study provides insight to help understand the interaction mechanism between Hg2+ and LMOF-263. No other MOFs have demonstrated such a high performance in both the detection and the capture of Hg2+ from aqueous solution.

A study of the interactions between carboplatin and blood plasma proteins using size exclusion chromatography coupled to inductively coupled plasma mass spectrometry.

To study the carboplatin-protein interaction, a sensitive method using size exclusion chromatography coupled to inductively coupled plasma mass spectrometry (SEC-ICP-MS) was developed. The complexes formed between plasma proteins and carboplatin were monitored and identified with this method. Composite blood plasma samples from patients who were undergoing chemotherapy were analyzed, and carboplatin was found to bind plasma proteins. In addition, blank plasma samples were spiked with carboplatin and were analyzed as a time course study, and the results confirmed that carboplatin formed complexes with plasma proteins, primarily albumin and gamma-globulin. To further substantiate the study, these two proteins were incubated with carboplatin. The binding between carboplatin and these proteins was then characterized qualitatively and quantitatively. In addition to a one-to-one binding of Pt to protein, protein aggregation was observed. The kinetics of the binding process of carboplatin to albumin and gamma-globulin was also studied. The initial reaction rate constant of carboplatin binding to albumin was determined to be 0.74 M(-1) min(-1), while that for gamma-globulin was 1.01 M(-1) min(-1), which are both lower than the rate constant of the cisplatin-albumin reaction previously reported.

Insight into the molecular arrangement of high-density polyethylene polymer chains in blends of polystyrene/highdensity polyethylene from differential scanning calorimetry and Raman techniques.

Polystyrene/high-density polyethylene (PS/HDPE) blends were synthesized by melt blending in a single screw extruder. Co-continuity measurements using solvent extraction and scanning electron (SEM) micrographs showed that co-continuity was obtained around 35% PS. Thermal analyses measurements revealed a reduction in crystallinity of the HDPE phase around the co-continuous composition. Raman analyses across the entire composition range of these blends showed an increase in the normalized integral intensities of the 1128 cm(-1) and 1061 cm(-1) stretching vibrations of the HDPE molecules. The presence of all-trans HDPE chains that are not packed into an orthorhombic structure is used to explain the simultaneous occurrence of reduced crystallinity and increased intensity of all-trans HDPE stretch vibrations.

Arsenic speciation analysis of human urine using ion exchange chromatography coupled to inductively coupled plasma mass spectrometry.

A sensitive and robust method for the determination of seven inorganic and organic arsenic species was developed using ion exchange chromatography combined with inductively coupled plasma mass spectrometry (IC-ICP-MS). Both anion and cation exchange columns were used in a complementary fashion. Arsenite (As(III)), arsenate (As(V)), monomethylarsonic acid (MMA(V)) and dimethylarsinic acid (DMA(V)) were selectively separated by an anion exchange column using sodium hydroxide (NaOH) gradient elution, while monomethylarsonous acid (MMA(III)), dimethylarsinous acid (DMA(III)) and arsenobetaine (AsB) were separated by a cation exchange column using 70 mM nitric acid as the mobile phase. Baseline separation, high repeatability and low detection limits (0.10-0.75 ng mL(-1)) were achieved. The spiked urine samples were analyzed with this method to evaluate the matrix effect on the method. The results suggest 1-10 dilutions should be made to urine samples before sample injection for the anion exchange analysis to minimize the matrix effect. To validate the method, a new standard reference material (NIST SRM-2670a) was also analyzed. The arsenic species in NIST SRM-2670a were determined by this method, and the sum of their concentrations agreed well with the total arsenic content certified for NIST SRM-2670a. Moreover, this method was applied to measure arsenic species in urine samples from one subject living in New Jersey who drank well water contaminated with arsenic. By this method, two key arsenic metabolites, MMA(III) and DMA(III), were found to be present in these urine samples, which has previously been rarely reported.

Comparative stability determination of oligonucleotide duplexes in gas and solution phase.

The relative stability of RNA duplexes were determined in both solution and gas phase. Solution stability as determined by a spectrophotometric method indicated that the Watson-Crick duplexes were more stable than duplexes containing one GA mismatch or two tandem GA mismatches. Gas phase stability was determined using ESI-MS through variation of the collision energy in an ion trap. Stability curves similar to the melting curves obtained in solution were observed. The relative stability in gas phase differed, however, from that in solution. The duplexes with two tandem GA mismatches were found to be more stable than the Watson-Crick and single GA mismatch duplexes. The different trends observed in solution versus gas phase can be attributed to the primary means of interaction. In solution, stacking is expected to be the dominant interaction mode. In the gas phase, hydrogen bonding is expected to be the dominant interaction mode. Duplexes with tandem GA mismatches have the potential to undergo additional hydrogen bonding relative to the other duplexes which could account for their increased stability in the gas phase.

Lead in breast milk and maternal bone turnover.

OBJECTIVE: Our purpose was to determine whether breast milk lead (Pb) levels are correlated with maternal blood Pb levels, bone loss, or bone turnover during reproduction. STUDY DESIGN: Data were collected prospectively at 0, 1.5, 3, 6, and 12 months after delivery in 15 lactating and 30 bottle-feeding women. Variables included breast milk Pb (inductively coupled mass spectrometry), maternal blood Pb (atomic absorption spectrophotometry), osteocalcin (radioimmunoassay), and bone mineral density change (dual-energy x-ray absorptiometry). RESULTS: Mean Pb breast milk concentrations were 6.1, 5.6, 5.9, and 4.3 ng/mL at the 1.5, 3, 6, and 12 months post partum, whereas mean maternal blood Pb concentrations were 1.4, 1.6, 1.7, and 1.4 microg/dL at 0, 3, 6, and 12 months post partum. The 5.6% bone loss and significant bone turnover were related to breast milk Pb levels but not to postpartum maternal blood Pb levels. Maternal and breast milk Pb values were modestly correlated at 1 to 2 months. CONCLUSIONS: Bone loss and bone turnover were related to breast milk Pb levels. In these women, there was no evidence that either high maternal blood or breast milk Pb concentrations are a major public health concern.